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1. or to set up configuration for multiple workers you can omit specifying a sender when you connect from celery signals import celeryd_init celeryd_init connect def configure_workers sender None conf None kwargs if sender in workerl example com worker2 example com conf CELERY_DEFAULT_RATE_LIMIT 10 m if sender worker3 example com conf CELERYD_PREFETCH_MULTIPLIER 0 Provides arguments e sender Hostname of the worker e instance This is the celery apps worker Worker instance to be initialized Note that only the app and hostname attributes have been set so far and the rest of __ init __ has not been executed e conf The configuration of the current app worker_init Dispatched before the worker is started worker_ready Dispatched when the worker is ready to accept work worker_process_init Dispatched by each new pool worker process when it starts worker_shutdown Dispatched when the worker is about to shut down Celerybeat Signals beat_init Dispatched when celerybeat starts either standalone or embedded Sender is the celery beat Service instance beat_embedded_init Dispatched in addition to the beat__init signal when celerybeat is started as an embedded process Sender is the celery beat Service instance Evenilet Signals eventlet_pool_started Sent when the eventlet pool has been started Sender is the
2. See also The API reference for Task States Celery can keep track of the tasks current state The state also contains the result of a successful task or the exception and traceback information of a failed task There are several result backends to choose from and they all have different strengths and weaknesses see Result Backends During its lifetime a task will transition through several possible states and each state may have arbitrary metadata attached to it When a task moves into a new state the previous state is forgotten about but some transitions can be deducted e g a task now in the FAILED state is implied to have been in the STARTED state at some point T There are also sets of states like the set of FAILURE_STATES and the set of READY_STATES The client uses the membership of these sets to decide whether the exception should be re raised PROPAGATE_STATES or whether the state can be cached it can if the task is ready You can also define Custom states Result Backends Celery needs to store or send the states somewhere There are several built in backends to choose from SQLAIchemy Django ORM Memcached RabbitMQ amqp MongoDB and Redis or you can define your own No backend works well for every use case You should read about the strengths and weaknesses of each backend and choose the most appropriate for your needs See also Task resul
3. If the old behavior is wanted the setting can be set to False or the new no execv to celery worker Deprecated module celery conf has been removed The CELERY_TIMEZONE now always require the pyt z library to be installed exept if the timezone is set to UTC 2 10 What s new in Celery 3 0 Chiastic Slide 195 Celery Documeniation Release 3 0 25 e The Tokyo Tyrant backend has been removed and is no longer supported e Now uses maybe_declare to cache queue declarations e There is no longer a global default for the CELERYBEAT_MAX_LOOP_INTERVAL setting it is instead set by individual schedulers e Worker now truncates very long message bodies in error reports e No longer deepcopies exceptions when trying to serialize errors e CELERY_BENCH environment variable will now also list memory usage statistics at worker shutdown e Worker now only ever use a single timer for all timing needs and instead set different priorities e An exceptions arguments are now safely pickled Contributed by Matt Long e Worker Celerybeat no longer logs the startup banner Previously it would be logged with severity warning now it s only written to stdout e The contrib directory in the distribution has been renamed to ext ra e New signal task_revoked e celery contrib migrate Many improvements including filtering queue migration and support for acking m
4. oracle BROKER_URL sqlatoracle scott tiger 127 0 0 1 1521 sidname Results To store results in the database as well you should configure the result backend See Database backend settings Limitations The SQLAIchemy database transport does not currently support e Remote control commands celeryev broadcast e Events including the Django Admin monitor e Using more than a few workers can lead to messages being executed multiple times Using the Django Database Installation Configuration The database transport uses the Django DATABASE_ settings for database configuration values 1 Set your broker transport BROKER_URL django 2 Add kombu transport django to INSTALLED_APPS 14 Chapter 2 Contents Celery Documeniation Release 3 0 25 INSTALLED_APPS kombu transport django 3 Sync your database schema S python manage py syncdb Limitations The Django database transport does not currently support e Remote control commands celeryev broadcast e Events including the Django Admin monitor e Using more than a few workers can lead to messages being executed multiple times Using MongoDB Installation For the MongoDB support you have to install additional dependencies You can install both Celery and these dependencies in one go using either the celery with mongodb or the django celery with mongodb bundles pip install U celery with mongodb C
5. T celery conf CEL celery conf CE RY_ALWAYS_EAGER True ERY ALWAYS _EAGER True Controlling workers gt gt gt gt gt gt celery control inspect active celery control rate_limit add name celery control broadcast shutdown celery control discard_all 100 m gt gt gt gt gt gt Other interesting attributes Establish broker connection gt gt gt celery broker_connection AMQP Specific features gt gt gt celery amqp gt gt gt celery amgp Router 2 14 Internals 315 Celery Documentation Release 3 0 25 gt gt gt celery amgqp get_queues gt gt gt celery amgp get_task_consumer Loader gt gt gt celery loader Default backend gt gt gt celery backend As you can probably see this really opens up another dimension of customization abilities Deprecations e celery task ping celery task PingTask Inferior to the ping remote control command Will be removed in Celery 2 3 Removed deprecations e celery utils timedelta_seconds Use celery utils timeutils timedelta_seconds e celery utils defaultdict Use celery utils compat defaultdict e celery utils all Use celery utils compat all e celery task apply_async Use app send_task e celery task tasks Use celery registry tasks Aliases Pending deprecation e celery task base Task gt app create_task_cls e celery task
6. Let s look at some examples that work and one that doesn t OK class HttpError Exception pass BAD class HttpError Exception def init self status_code self status_code status_code OK class HttpError Exception def init self status_code self status_code status_code Exception __init__ self status_code lt REQUIRED So the rule is For any exception that supports custom arguments xargs Exception __init__ self xargs must be used There is no special support for keyword arguments so if you want to preserve keyword arguments when the exception is unpickled you have to pass them as regular args 2 3 User Guide 51 Celery Documentation Release 3 0 25 class HttpError Exception def init__ self status_code headers None body None self status_code status_code self headers headers self body body super HttpError self __init__ status_code headers body Custom task classes All tasks inherit from the celery Task class The run method becomes the task body As an example the following code celery task def add x y return x y will do roughly this behind the scenes celery task class AddTask Task def run self x y return x y add registry tasks AddTask name Instantiation A task is not instantiated for every request but is registered in the task registry as a global instance This means that t
7. Pool Pool map_asyne func iterable chunksize None callback None er ror_callback None Asynchronous equivalent of map method Pool Pool restart Pool Pool shrink n Pool Pool starmap func iterable chunksize None Like map method but the elements of the iterable are expected to be iterables as well and will be unpacked as arguments Hence func and a b becomes func a b 342 Chapter 2 Contents Celery Documeniation Release 3 0 25 as as as as as as as as as as as as as as as as as K K K K K K K K TaskPool Pool starmap_asyne func iterable chunksize None callback None er ror_callback None Asynchronous version of starmap method TaskPool Pool terminate TaskPool Pool terminate_Job pid sig None Pool did_start_ok Pool grow n Pool handle_timeouts Pool init_callbacks kwargs Pool num_processes Pool on_close Pool on_start Run the task pool Will pre fork all workers so they re ready to accept tasks Pool on_stop Gracefully stop the pool Pool on_terminate Force terminate the pool Pool readers Pool requires_mediator True Pool restart Pool shrink n Pool terminate_job pid signal None Pool timers Pool uses_semaphore True Pool writers celery concurrency processes WORKER_SIGIGNORE frozenset
8. CELERY_TASK_PUBLISH_RETRY_POLICY New in version 2 2 Defines the default policy when retrying publishing a task message in the case of connection loss or other connection errors See Message Sending Retry for more information CELERY_DEFAULT_RATE_LIMIT The global default rate limit for tasks This value is used for tasks that does not have a custom rate limit The default is no rate limit CELERY_DISABLE_RATE_LIMITS Disable all rate limits even if tasks has explicit rate limits set CELERY_ACKS_LATE Late ack means the task messages will be acknowledged after the task has been executed not just before which is the default behavior See also FAQ Should I use retry or acks_late Worker celeryd CELERY_IMPORTS A sequence of modules to import when the worker starts 140 Chapter 2 Contents Celery Documeniation Release 3 0 25 This is used to specify the task modules to import but also to import signal handlers and additional remote control commands etc The modules will be imported in the original order CELERY_INCLUDE Exact same semantics as CELERY_IMPORTS but can be used as a means to have different import categories The modules in this setting are imported after the modules in CELERY_IMPORTS CELERYD_FORCE_EXECV On Unix the processes pool will fork so that child processes start with the same memory as the parent process This can cause problems as there is a kn
9. The exc method is used to pass exception information that is used in logs and when storing task results Both the exception and the traceback will be available in the task state if a result backend is enabled If the task has amax_retries value the current exception will be re raised if the max number of retries has been exceeded but this will not happen if e An exc argument was not given In this case the celery exceptions MaxRetriesExceeded exception will be raised e There is no current exception If there s no original exception to re raise the exc argument will be used instead so send_twitter_status retry exc Twitter LoginError will raise the exc argument given Using a custom retry delay When a task is to be retried it can wait for a given amount of time before doing so and the default delay is defined by the default_retry_delay attribute By default this is set to 3 minutes Note that the unit for setting the delay is in seconds int or float You can also provide the countdown argument to ret ry to override this default celery task default_retry_delay 30 60 retry in 30 minutes def add x y try except Exception exc raise add retry exc exc countdown 60 override t in List of Options The task decorator can take a number of options that change the way the task behaves for example you can set the rate limit for a task using the rate_limit option Any keyword argu
10. worker2 example com pong f t 1 worker3 example com pong ping also supports the destination argument so you can specify which workers to ping gt gt gt ping worker2 example com worker3 example com w r l orker2 example c rker3 example Enable disable events You can enable disable events by using the enable_events disable_events commands This is useful to temporarily monitor a worker using celery events celerymon gt gt gt celery control enable_events gt gt gt celery control disable_events Writing your own remote control commands Remote control commands are registered in the control panel and they take a single argument the current ControlDispatch instance From there you have access to the active Consumer if needed Here s an example control command that restarts the broker connection 90 Chapter 2 Contents Celery Documeniation Release 3 0 25 from celery worker control import Panel Panel register def reset_connection panel panel consumer reset_connection return ok connection reset 2 3 6 Periodic Tasks e Introduction e Time Zones e Entries Available Fields e Crontab schedules e Starting the Scheduler Using custom scheduler classes Introduction celery beat is a scheduler It kicks off tasks at regular intervals which are then executed by the worker nodes avail
11. 100 Chapter 2 Contents Celery Documeniation Release 3 0 25 Parameters e passive Passive means the exchange won t be created but you can use this to check if the exchange already exists e durable Durable exchanges are persistent That is they survive a broker restart e auto_delete This means the queue will be deleted by the broker when there are no more queues using it queue declare queue_name passive durable exclusive auto_delete Declares a queue by name Exclusive queues can only be consumed from by the current connection Exclusive also implies auto_delete queue bind queue_name exchange_name routing_key Binds a queue to an exchange with a routing key Unbound queues will not receive messages so this is necessary queue delete name if_unused False if_empty False Deletes a queue and its binding exchange delete name if_unused False Deletes an exchange Note Declaring does not necessarily mean create When you declare you assert that the entity exists and that it s operable There is no rule as to whom should initially create the exchange queue binding whether consumer or producer Usually the first one to need it will be the one to create it Hands on with the API Celery comes with a tool called celery amqp that is used for command line access to the AMQP API enabling access to administration tasks like creating deleting queues and exchanges purging queues o
12. S celery worker loglevel INFO concurrency 10 n workerl example com S celery worker loglevel INFO concurrency 10 n worker2 example com S celery worker loglevel INFO concurrency 10 n worker3 example com Stopping the worker Shutdown should be accomplished using the TERM signal When shutdown is initiated the worker will finish all currently executing tasks before it actually terminates so if these tasks are important you should wait for it to finish before doing anything drastic like sending the KILL signal If the worker won t shutdown after considerate time for example because of tasks stuck in an infinite loop you can use the KILL signal to force terminate the worker but be aware that currently executing tasks will be lost unless the tasks have the acks_late option set Also as processes can t override the KILL signal the worker will not be able to reap its children so make sure to do so manually This command usually does the trick ps auxww grep celery worker awk print 2 xargs kill 9 Restarting the worker Other than stopping then starting the worker to restart you can also restart the worker using the HUP signal kill HUP Spid The worker will then replace itself with a new instance using the same arguments as it was started with Note Restarting by HUP only works if the worker is running in the background as a daemon it does not have a controlling terminal HUP is disabled
13. celery utils functional is_list l Returns true if object is list like but not a dict or string celery utils functional mattrgetter attrs Like operator itemgetter but returns None on missing attributes instead of raising AttributeError celery utils functional maybe_list l Returns list of one element if 1 is a scalar celery utils functional memoize maxsize None Cache lt class cel ery utils functional LRUCache at 0x7fb768d58870 gt class celery utils functional mpromise fun args kwargs Memoized promise The function is only evaluated once every subsequent access will return the same value evaluated Set to to True after the promise has been evaluated evaluate evaluated False celery utils functional noop args kwargs No operation Takes any arguments keyword arguments and does nothing celery utils functional padlist container size default None Pad list with default elements Examples gt gt gt first last city padlist George Costanza NYC 3 George Costanza NYC gt gt gt first last city padlist George Costanza 3 George Costanza None gt gt gt first last city planet padlist George Costanza nNyC 4 default Earth 378 Chapter 2 Contents Celery Documeniation Release 3 0 25 celery utils functional regen it Reg
14. celery worker SHUTDOWN_SOCKET_TIMEOUT 5 0 Default socket timeout at shutdown class celery worker StateDB w kwargs This component sets up the workers state db if enabled create w name state db namespace worker class celery worker Timers parent kwargs This component initializes the internal timers used by the worker create w include_if w name timers namespace worker 320 Chapter 2 Contents Celery Documeniation Release 3 0 25 on_timer_error exc on_timer_tick delay requires pool class celery worker WorkController loglevel None hostname None ready_callback lt function noop at 0x7fb768d6c848 gt queues None app None pid file None use_eventloop None kwargs Unmanaged worker instance CLOSE 2 RUN 1 TERMINATE 3 app None autoreloader_cls None autoscaler_cls None concurrency None consumer_cls None disable_rate_limits None force_execv None logfile None loglevel 40 max_tasks_per_child None mediator_cls None pool_cls None pool_putlocks None pool_restarts None prefetch_multiplier None process_task req Process task by sending it to the pool of workers process_task_sem req reload modules None reload False reloader None schedule_filename None scheduler_cls None send_events None should_use_eventloop Signal_consumer_close start Starts the workers main loop
15. e celeryev Now works on Windows but the curses monitor won t work without having curses e Unit test output no longer emits non standard characters e celeryd The broadcast consumer is now closed if the connection is reset e celeryd Now properly handles errors occurring while trying to acknowledge the message TaskRequest on_failure now encodes traceback using the current filesystem encoding Issue 286 e EagerResult can now be pickled Issue 288 Documentation e Adding Contributing e Added Optimizing 424 Chapter 2 Contents Celery Documeniation Release 3 0 25 e Added Security section to the FAQ 2 1 3 release date 2010 11 09 05 00 P M CEST e Fixed deadlocks in timer2 which could lead to djcelerymon celeryev c hanging e EventReceiver now sends heartbeat request to find workers This means celeryev and friends finds workers immediately at startup e celeryev cursesmon Set screen_delay to 10ms so the screen refreshes more often e Fixed pickling errors when pickling AsyncResult on older Python versions e celeryd prefetch count was decremented by eta tasks even if there were no active prefetch limits 2 1 2 release data TBA Fixes e celeryd Now sends the task ret ried event for retried tasks e celeryd Now honors ignore result for WorkerLostError and timeout errors e celerybeat Fixed UnboundLocalError in celerybeat logging when using logging setup signals e cele
16. Parameters e state State from event e timestamp Timestamp from event fields Event data class celery events state Worker fields Worker State alive expire window 200 heartbeat_expires heartbeat_max 4 on_heartbeat timestamp None kwargs Callback for the worker heartbeat event on_offline kwargs Callback for the worker offline event on_online timestamp None kwargs Callback for the worker online event celery events state heartbeat_expires timestamp freq 60 expire_window 200 2 13 33 celery apps worker e celery apps worker j celery apps worker This module is the program version of celery worker It does everything necessary to run that module as an actual application like installing signal handlers platform tweaks and so on class celery apps worker Worker hostname None purge False beat False queues None in clude None app None pidfile None autoscale None au toreload False no_execv False no_color None kwargs class WorkCont roller loglevel None hostname None ready_callback lt function noop at Ox7fb768d6c848 gt queues None app None __ pidfile None use_eventloop None kwargs Unmanaged worker instance 282 Chapter 2 Contents Celery Documeniation Release 3 0 25 CLOSE 2 RUN 1 TERMINATE 3 app None autoreloader_cls None autoscaler_cls None concurrency None consumer_cls None disable_rate_limi
17. Why aren t my tasks processed Answer With RabbitMQ you can see how many consumers are currently receiving tasks by running the following command rabbitmqctl list_queues p lt myvhost gt name messages consumers Listing queues celery 2891 2 This shows that there s 2891 messages waiting to be processed in the task queue and there are two consumers pro cessing them One reason that the queue is never emptied could be that you have a stale worker process taking the messages hostage This could happen if celeryd wasn t properly shut down When a message is received by a worker the broker waits for it to be acknowledged before marking the message as processed The broker will not re send that message to another consumer until the consumer is shut down properly If you hit this problem you have to kill all workers manually and restart them ps auxww grep celeryd awk print 2 xargs kill You might have to wait a while until all workers have finished the work they re doing If it s still hanging after a long time you can kill them by force with ps auxww grep celeryd awk print 2 xargs kill 9 2 9 Frequently Asked Questions 177 Celery Documeniation Release 3 0 25 Why won t my Task run Answer There might be syntax errors preventing the tasks module being imported You can find out if Celery is able to run the task by executing the task manually gt gt gt from myapp tas
18. celery task base OtherTask def add x y return x y To create a custom task class you should inherit from the neutral base class celery Task from celery import Task class DebugTask Task abstract True def call self xargs x xkwargs print TASK STARTING s s self name self request id return self run xargs xkwargs The neutral base class is special because it s not bound to any specific app yet Concrete subclasses of this class will be bound so you should always mark generic base classes as abstract 2 3 User Guide 41 Celery Documentation Release 3 0 25 Once a task is bound to an app it will read configuration to set default values and so on It s also possible to change the default base class for an application by changing its Celery Task attribute gt gt gt from celery import Celery Task gt gt gt celery Celery gt gt gt class MyBaseTask Task abstract True send_error_emails True gt gt gt celery Task MyBaseTask gt gt gt celery Task lt unbound MyBaseTask gt gt gt gt x task def add x y return x y lt task main__ add gt gt gt add __class__ mro AC y __main__ 0x1012b4410 gt gt 2 3 2 Tasks Tasks are the building blocks of Celery applications A task is a class that can be created out of any callable It performs dual roles in that it defines both what happens when a task is called sends
19. class celery worker autoscale WorkerComponent w kwargs create w create_ev w create_threaded w name autoscaler namespace worker on_poll_init scaler hub requires pool celery worker bootsteps e celery worker bootsteps celery worker bootsteps The boot step components class celery worker bootsteps Component parent kwargs A component The __init___ method is called when the component is bound to a parent object and can as such be used to initialize attributes in the parent object at parent instantiation time abstract None if set the component will not be registered but can be used as a component base class create parent Create the component enabled True This provides the default for include_if include parent include_if parent An optional predicate that decided whether this component should be created instantiate qualname args kwargs 338 Chapter 2 Contents Celery Documeniation Release 3 0 25 last False This flag is reserved for the workers Consumer since it is required to always be started last There can only be one object marked with Isat in every namespace name None The name of the component or the namespace and the name of the component separated by dot namespace None can be used to specify the namespace if the name does not include it obj None Optional obj created by the create method T
20. from celery import task task def add x y print My task id is r add request id Task attributes The task attributes queue e exchange e exchange_type e routing_key e delivery_mode priority is deprecated and must be set by CELERY_ROUTES instead celery result e BaseAsyncResult gt AsyncResult TaskSetResult gt GroupResult e TaskSetResult total gt len GroupResult e TaskSetResult taskset_id gt GroupResult id Apply to AsyncResult EagerResult Result wait gt Result get e Result task_id gt Result id e Result status gt Result state 2 14 Internals 309 Celery Documeniation Release 3 0 25 celery loader e current_loader gt current_app loader e load_settings gt current_app conf Modules to Remove e cel xecut Ler y This module only contains send_task which must be replaced with celery send_task instead e cel e cel Settings lery decorators See Compat Task Modules ler Ler ler ler ler Use y Use Ye Use lery log U y registry U task con se celery log instead y messaging Use celery amqp instead se celery app registry instead trol celery control instead task sch edules celery schedules instead task cho rds celery chord instead BROKER Settings BROKI REDIS Resul
21. kwargs callback None ac cept_callback None pid None timeout None timeout_callback None rest celery concurrency base e celery concurrency base j celery concurrency base TaskPool interface class celery concurrency base BasePool limit None putlocks True forking_enable True call backs_propagate options CLOSE 2 RUN 1 TERMINATE 3 class Timer schedule None on_error None on_tick None max_interval None kwargs class Entry fun args None kwargs None args cancel cancelled fun kwargs tref class BasePool Timer Schedule max_interval None on_error None kwargs ETA scheduler class Entry fun args None kwargs None args cancel cancelled fun kwargs tref 346 Chapter 2 Contents Celery Documeniation Release 3 0 25 Base Base Base Base Base Base Base Base Base Base Base Base Base Base Base Base Base Base Base Base Base Base Base Base Base Base Base Base Base Pool Pool Pool Pool Pool Pool Pool Pool Pool Pool Pool Pool Pool Pool T Pool T Pool T Pool 1 Pool imer Schedule apply_after msecs fun args kwargs prior ity 0 imer Schedule apply_at eta fun args kwargs priority 0 imer Schedule apply entry entry imer Schedule apply_ interval msecs fun args kwargs priority 0
22. tate_limit gt app control rate_limit ping gt app control ping revoke gt app control revoke discard_all gt app control discard_all inspect gt app control inspect celery utils info humanize_seconds gt celery utils timeutils humanize_seconds textindent gt celery utils textindent get_broker_info gt app amqp get_broker_info format_broker_info gt app amqp format_broker_info format_queues gt app amqp format_queues Default App Usage To be backward compatible it must be possible to use all the classes functions without passing an explicit app instance This is achieved by having all app dependent objects use de fault_app if the app instance is missing 2 14 Internals 317 Celery Documentation Release 3 0 25 from celery app import app_or_default class SomeClass object def _ init__ self app None self app app_or_default app The problem with this approach is that there is a chance that the app instance is lost along the way and everything seems to be working normally Testing app instance leaks is hard The environment variable CELERY_TRACE_APP can be used when this is enabled celery app app_or_default will raise an exception whenever it has to go back to the default app instance App Dependency Tree e app celery loaders base BaseLoader celery backends base BaseBackend app TaskSet ce
23. 15 for every quarter or minute 1 13 30 45 50 59 2 hour eA list of integers from 0 23 that represent the hours of a day of when execution should occur or eA string representing a crontab pattern This may get pretty advanced like hour 3 for every three hours or hour 0 8 17 2 at midnight and every two hours during office hours day_of week eA list of integers from 0 6 where Sunday 0 and Saturday 6 that represent the days of a week that execution should occur eA string representing a crontab pattern This may get pretty advanced like day_of_week mon fri for weekdays only Beware that day_of_week 2 does not literally mean every two days but every day that is divisible by two day_of_month eA list of integers from 1 31 that represents the days of the month that execution should occur eA string representing a crontab pattern This may get pretty advanced such as day_of_month 2 30 3 for every even numbered day or day_of_month I 7 15 21 for the first and third weeks of the month month_of_year eA list of integers from 1 12 that represents the months of the year during which execution can occur A string representing a crontab pattern This may get pretty advanced such as month_of_year 3 for the first month of every quarter or month_of_year 2 12 2 for every even numbered month It is important to realize that any day o
24. Celery Documeniation Release 3 0 25 A chord is a task that only executes after all of the tasks in a taskset have finished executing Let s calculate the sum of the expression 1 1 2 2 3 3 n n up to a hundred digits First you need two tasks add and tsum sum is already a standard function celery task def add x y return x y celery task def tsum numbers return sum numbers Now you can use a chord to calculate each addition step in parallel and then get the sum of the resulting numbers gt gt gt from celery import chord gt gt gt from tasks import add tsum gt gt gt chord add s i i for i in xrange 100 tsum s get 9900 This is obviously a very contrived example the overhead of messaging and synchronization makes this a lot slower than its Python counterpart sum i i for i in xrange 100 The synchronization step is costly so you should avoid using chords as much as possible Still the chord is a powerful primitive to have in your toolbox as synchronization is a required step for many parallel algorithms Let s break the chord expression down gt gt gt callback tsum subtask gt gt gt header add subtask i i for i in xrange 100 gt gt gt result chord header callback gt gt gt result get 9900 Remember the callback can only be executed after all of the tasks in the header have returned Each step in the header is execute
25. Examples gt gt gt from celery platforms import signals gt gt gt signals INT my_handler gt gt gt signals INT 1andler gt gt gt signals supported INT gt gt gt signals signum INT gt gt gt signals ignore USR1 gt gt gt signals USR1 signals ignored 392 Chapter 2 Contents Celery Documeniation Release 3 0 25 True gt gt gt signals reset USR1 gt gt gt signals USR1 signals default rrue gt gt gt signals update INT exit_handler ERM exit_handler UP hup_handler H T default 0 ignore signal_names Ignore signal using SIG_IGN Does nothing if the platform doesn t support signals or the specified signal in particular ignored 1 reset signal_names Reset signals to the default signal handler Does nothing if the platform doesn t support signals or the specified signal in particular signum signal_name Get signal number from signal name supported signal_name Returns true value if signal_name exists on this platform update _d_ None sigmap Set signal handlers from a mapping celery platforms close_open_fds keep None celery platforms create_pidlock pidfile Create and verify pidfile If the pidfile already exists the program exits with an error message however if the process it refers to is not running anymore the pidfile is deleted and the pr
26. If you broke something and need to update new versions of the bundles then you can use up load_bundles_fix 2 7 Community Resources This is a list of external blog posts tutorials and slides related to Celery If you have a link that s missing from this list please contact the mailing list or submit a patch e Resources Who s using Celery Wiki Celery questions on Stack Overflow Mailing list Archive celery users e News 2 1 Resources Who s using Celery http wiki github com celery celery using Wiki http wiki github com celery celery Celery questions on Stack Overflow http stackoverflow com search q celery amp tab newest Mailing list Archive celery users http blog gmane org gmane comp python amap celery user 2 7 Community Resources 165 Celery Documentation Release 3 0 25 2 7 2 News This section has moved to the Celery homepage http celeryproject org community 2 8 Tutorials Release 3 0 Date July 10 2014 2 8 1 Running the worker as a daemon Celery does not daemonize itself please use one of the following daemonization tools e Generic init scripts Init script celeryd x Example configuration x Example Django configuration x Example Django configuration Using Virtualenv x Available options Init script celerybeat x Example configuration x Example Django configuration x Available options Troubleshooting e supervisord e launchd O
27. as as as K K K K K K K K K K K K body handle_event args handle _ timeouts on_hard_timeout job on_soft_timeout job TaskPool Pool apply func args kwds Equivalent of func args kwargs askPool Pool apply_asynce func args kwds callback None er ror_callback None accept_callback None timeout_callback None waitforslot None soft_timeout None timeout None lost_worker_timeout None callbacks_propagate Asynchronous equivalent of apply method Callback is called when the functions return value is ready The accept callback is called when the job is accepted to be executed Simplified the flow is like this gt gt gt if accept_callback js accept_callback gt gt gt retval func args xxkwds gt gt gt if callback callback retval Pool Pool close Pool Pool did_start_ok Pool Pool grow n Pool Pool imap func iterable chunksize 1 lost_worker_timeout None Equivalent of map can be MUCH slower than Pool map Pool Pool imap_unordered func iterable chunksize 1 lost_worker_timeout None Like imap method but ordering of results is arbitrary Pool Pool Jjoin Pool Pool maintain_pool args kwargs Pool Pool map func iterable chunksize None Apply func to each element in iterable collecting the results in a list that is returned
28. cel cel ery app builtins add_chunk_task app ery app builtins add_group_task app ery app builtins add_map_task app ery app builtins add_starmap_task app ery app builtins add_unlock_chord_task app The unlock chord task is used by result backends that doesn t have native chord support It creates a task chain polling the header for completion ery app builtins load_shared_tasks app Loads the built in tasks for an app instance ery app builtins shared_task constructor Decorator that specifies that the decorated function is a function that generates a built in task The function will then be called for every new app instance created lazily so more exactly when the task registry for that app is needed 2 13 9 celery app log e celery app log j celery app log The Celery instances logging section Celery log Sets up logging for the worker and other programs redirects stdouts colors log output patches logging related com patibility fixes and so on class celery app log Logging app colored logfile None enabled None get_default_logger name celery kwargs redirect_stdouts_to_logger logger loglevel None stdout True stderr True Redirect sys stdout and sys stderr to a logging instance Parameters e logger The logging Logger instance to redirect to e loglevel The loglevel redirected messages will be logged as setup loglevel None logfile None
29. celery A proj events when you re finished monitoring you can disable events again celery A proj control disable_events The celery status command also uses remote control commands and shows a list of online workers in the cluster S celery A proj status You can read more about the celery command and monitoring in the Monitoring Guide 2 2 Getting Started 33 Celery Documentation Release 3 0 25 Timezone All times and dates internally and in messages uses the UTC timezone When the worker receives a message for example with a countdown set it converts that UTC time to local time If you wish to use a different timezone than the system timezone then you must configure that using the CELERY_TIMEZONE setting To use custom timezones you also have to install the pyt z library S pip install pytz Setting a custom timezone celery conf CELERY_TIMEZONE Europe London Optimization The default configuration is not optimized for throughput by default it tries to walk the middle way between many short tasks and fewer long tasks a compromise between throughput and fair scheduling If you have strict fair scheduling requirements or want to optimize for throughput then you should read the Optimizing Guide If you re using RabbitMQ then you should install the Librabbitmq module which is an AMQP client implemented in C pip install librabbitmq What to d
30. state state_db None 2 14 Internals 321 Celery Documentation Release 3 0 25 stop in_sighandler False Graceful shutdown of the worker server task_soft_time_limit None task_time_limit None terminate in_sighandler False Not so graceful shutdown of the worker server timer_cls None timer_precision None worker lost_wait None celery worker consumer e celery worker consumer I celery worker consumer This module contains the component responsible for consuming messages from the broker processing the messages and keeping the broker connections up and running e start is an infinite loop which only iterates again if the connection is lost For each iteration at start or if the connection is lost it calls reset_connection and starts the consumer by calling consume_messages e reset_connection clears the internal queues establishes a new connection to the broker sets up the task consumer QoS and the broadcast remote control command consumer Also if events are enabled it configures the event dispatcher and starts up the heartbeat thread e Finally it can consume messages consume_messages is simply an infinite loop waiting for events on the AMQP channels Both the task consumer and the broadcast consumer uses the same callback receive_message e So for each message received the receive_message method is called this checks the payload of the message for
31. update_bucket_for_type fask_name class celery worker buckets TokenBucketQueue fill_rate queue None capacity 1 Queue with rate limited get operations This uses the token bucket algorithm to rate limit the queue on get operations Parameters e fill_rate The rate in tokens second that the bucket will be refilled e capacity Maximum number of tokens in the bucket Default is 1 exception RateLimitExceeded The token buckets rate limit has been exceeded TokenBucket Queue clear Delete all data in the queue okenBucketQueue empty Returns True if the queue is empty TokenBucketQueue expected_time tokens 1 Returns the expected time in seconds of when a new token should be available TokenBucket Queue get block True Remove and return an item from the queue Raises 330 Chapter 2 Contents Celery Documeniation Release 3 0 25 e RateLimitExceeded If a token could not be consumed from the token bucket consuming from the queue too fast e Queue Empty If an item is not immediately available TokenBucket Queue get_nowait Remove and return an item from the queue without blocking Raises e RateLimitExceeded If a token could not be consumed from the token bucket consuming from the queue too fast e Queue Empty If an item is not immediately available TokenBucketQueue items Underlying data Do not modify TokenBucket Queue put item block True
32. where you can set configuration values directly ITru ue gt gt gt celery conf CELERY_ENABLE_UTC or you can update several keys at once by using the update method gt gt gt celery conf update CELERY_ENABLE_UTC True CELERY_TIMEZONE Europe London The configuration object consists of multiple dictionaries that are consulted in order 1 Changes made at runtime 2 The configuration module if any 3 The default configuration celery app defaults See also Go to the Configuration reference for a complete listing of all the available settings and their default values config_from_object Timezones amp pytz Setting a time zone other than UTC requires the pytz library to be installed see the CELERY_TIMEZONE setting for more information 2 3 User Guide 37 Celery Documentation Release 3 0 25 The Celery config_from_object method loads configuration from a configuration object This can be a configuration module or any object with configuration attributes Note that any configuration that was previous set will be reset when config_from_object is called If you want to set additional configuration you should do so after Example 1 Using the name of a module from celery import Celery celery Celery celery config_from_object celeryconfig The celeryconfig module may then look like thi
33. Celery Documentation Release 3 0 25 2 12 24 3 0 2 release date 2012 07 20 04 00 P M BST by Ask Solem A bug caused the following task options to not take defaults from the configuration Issue 867 Issue 858 The following settings were affected CELERY_IGNORE_RESULT CELERYD_SEND_TASK_ERROR_EMATILS CELERY_TRACK_STARTED a CELERY_STORE_ERRORS_ T iVEN_IF_IGNORED Fix contributed by John Watson e Task Request delivery info is now passed through as is Issue 807 e The eta argument now supports datetime s with a timezone set Issue 855 e The worker s banner displayed the autoscale settings in the wrong order Issue 859 e Extension commands are now loaded after concurrency is set up so that they don t interfere with e g eventlet patching e Fixed bug in the threaded pool Issue 863 e The task failure handler mixed up the fields in sys exc_info Fix contributed by Rinat Shigapov e Fixed typos and wording in the docs Fix contributed by Paul McMillan e New setting CELERY_WORKER_DIRECT If enabled each worker will consume from their own dedicated queue which can be used to route tasks to specific workers e Fixed several edge case bugs in the add consumer remote control command e migrate Can now filter and move tasks to specific
34. Celery also defines a group of bundles that can be used to install Celery and the dependencies for a given feature The following bundles are available celery with redis for using Redis as a broker celery with mongodb for using MongoDB as a broker django celery with redis for Django and using Redis as a broker django celery with mongodb for Django and using MongoDB as a broker Downloading and installing from source Download the latest version of Celery from http pypi python org pypi celery You can install it by doing the following tar xvfz celery 0 0 0 tar gz cd celery 0 0 0 python setup py build python setup py install The last command must be executed as a privileged user if you are not currently using a virtualenv Using the development version You can clone the repository by doing the following git clone https github com celery celery cd celery S python setup py develop The development version will usually also depend on the development version of kombu the messaging framework Celery uses to send and receive messages so you should also install that from git git clone https github com celery kombu cd kombu python setup py develop 2 2 2 Brokers Release 3 0 Date July 10 2014 Celery supports several message transport alternatives 10 Chapter 2 Contents Celery Documeniation Release 3 0 25 Broker Instructions Using RabbitMQ e Installation amp Configura
35. Fixed several typos in the documentation Contributed by Marius Gedminas Batches Now works when using the eventlet pool Fix contributed by Thomas Grainger Batches Added example sending results to celery contrib batches Contributed by Thomas Grainger Mongodb backend Connection max_pool_size can now be set in CELERY _MONGODB_ BACKEND _ SETTINGS 216 Chapter 2 Contents Celery Documeniation Release 3 0 25 Contributed by Craig Younkins e Fixed problem when using earlier versions of pyt z Fix contributed by Vlad e Docs updated to include the default value for the CELERY_TASK_RESULT_EXPIRES setting Improvements to the django celery tutorial Contributed by Locker537 e The add_consumer control command did not properly persist the addition of new queues so that they survived connection failure Issue 1079 2 12 14 3 0 12 release date 2012 11 06 02 00 P M UTC e Now depends on kombu 2 4 8 Redis New and improved fair queue cycle algorithm Kevin McCarthy Redis Now uses a Redis based mutex when restoring messages Redis Number of messages that can be restored in one interval is no longer limited but can be set using the unacked_restore_limit transport option Heartbeat value can be specified in broker URLs Mher Movsisyan Fixed problem with msgpack on Python 3 Jasper Bryant Greene e Now depends on billiard 2 7 3 18 e Celery
36. REVOKED SUCCESS exception TimeoutError The operation timed out BaseBackend UNREADY_STATES frozenset STARTED RECEIVED RETRY PENDING BaseBackend cleanup Backend cleanup Is run by celery task DeleteExpiredTaskMetaTask BaseBackend current_task_children BaseBackend decode payload BaseBackend delete_group group_id BaseBackend encode data BaseBackend encode_result result status 352 Chapter 2 Contents Celery Documeniation Release 3 0 25 BaseBacke nd exception_to_python exc Convert serialized exception to Python exception BaseBacke BaseBacke BaseBacke BaseBacke BaseBacke Get the BaseBacke Get the BaseBacke Get the BaseBacke BaseBacke nd fail_from_current_stack task_id exc None nd fallback_chord_unlock group_id body result None countdown 1 kwargs nd forget task_id nd get_children task_id nd get_result task_id result of a task nd get_status fask_id status of a task nd get_traceback fask_id traceback for a failed task nd is_ cached task_id nd mark_as_done task_id result Mark task as successfully executed BaseBacke nd mark_as_failure task_id exc traceback None Mark task as executed with failure Stores the execption BaseBacke nd mark_as_retry task_id exc traceback None Mark task as being retries Stores the current exception if any BaseBacke Ba
37. TaskRegistry filter_types type TaskRegistry periodic TaskRegistry register task Register a task in the task registry The task will be automatically instantiated if not already an instance TaskRegistry regular TaskRegistry unregister name Unregister task by name Parameters name name of the task to unregister ora celery task base Task with a valid name attribute Raises celery exceptions NotRegistered_ if the task has not been registered 2 13 8 celery app builtins e celery app builtins j celery app builtins Built in tasks that are always available in all app instances E g chord group and xmap celery app builtins add_backend_cleanup_task app The backend cleanup task can be used to clean up the default result backend This task is also added do the periodic task schedule so that it is run every day at midnight but celerybeat must be running for this to be effective Note that not all backends do anything for this what needs to be done at cleanup is up to each backend and some backends may even clean up in realtime so that a periodic cleanup is not necessary celery app builtins add_chain_task app celery app builtins add_chord_task app Every chord is executed in a dedicated task so that the chord can be used as a subtask and this generates the task responsible for that 246 Chapter 2 Contents Celery Documeniation Release 3 0 25 cel cel cel cel cel
38. def route_for_task self task args None kwargs None if task celery ping return default route_for_task may return a string or a dict A string then means it s a queue name in CELERY_QUEUES a dict means it s a custom route When sending tasks the routers are consulted in order The first router that doesn t return None is the route to use The message options is then merged with the found route settings where the routers settings have priority Example if apply_async has these arguments gt gt gt Task apply_async immediate False exchange video routing_key video compress and a router returns immediate True exchange urgent the final message options will be immediate True exchange urgent routing_key video compress and any default message options defined in the Task class New Task handler called after the task returns after_return ExceptionInfo now passed to on_retry on_failure as einfo keyword argument celeryd Added CELERYD_MAX_TASKS_PER_CHILD maxtasksperchild Defines the maximum number of tasks a pool worker can process before the process is terminated and replaced by a new one Revoked tasks now marked with state REVOKED and result get will now raise TaskRevokedError celery task control ping now works as expected apply throw True CELERY_EAGER_PROPAGATES_EXCEPTIONS Makes eager execut
39. e celery amap previously camqadm The old programs are still available celeryd celerybeat etc but you are discouraged from using them Now depends on billiard Billiard is a fork of the multiprocessing containing the no execv patch by sbt http bugs python org issue8713 and also contains the pool improvements previously located in Celery This fork was necessary as changes to the C extension code was required for the no execv patch to work e Issue 625 e Issue 627 e Issue 640 e django celery 122 lt http github com celery django celery issues 122 e django celery 124 lt http github com celery django celery issues 122 celery app task no longer a package The celery app task module is now a module instead of a package The setup py install script will try to remove the old package but if that doesn t work for some reason you have to remove it manually This command helps rm r dirname python c import celery print celery __file__ app task If you experience an error like ImportError cannot import name _unpickle_task you just have to remove the old package and everything is fine 186 Chapter 2 Contents Celery Documeniation Release 3 0 25 Last version to support Python 2 5 The 3 0 series will be last version to support Python 2 5 and starting from 3 1 Python 2 6 and later will be required With several other distributions taking the step to discontinue Python 2 5 support we f
40. gt gt gt result ready True gt gt gt result result 4 8 16 e Refactored the task metadata cache and database backends and added a new backend for Tokyo Tyrant You can set the backend in your django settings file E g CELERY_RESULT_BACKEND database CELERY_RESULT_BACKEND cache CELERY_RESULT_BACKEND tyrant HOST localhost Hostname for _PORT 6657 Port of the Tokyo Tyrant 0 1 11 release date 2009 05 12 02 08 P M CET e The logging system was leaking file descriptors resulting in servers stopping with the EMFILES too many open files error fixed 472 Chapter 2 Contents Celery Documeniation Release 3 0 25 0 1 10 release date 2009 05 11 12 46 PM CET e Tasks now supports both positional arguments and keyword arguments e Requires carrot 0 3 8 e The daemon now tries to reconnect if the connection is lost 0 1 8 release date 2009 05 07 12 27 P M CET e Better test coverage e More documentation e celeryd doesn t emit Queue is empty message if settings CELERYD_EMPTY_MSG_EMIT_EVERY is 0 0 1 7 release date 2009 04 30 01 50 PM CET Added some unit tests Can now use the database for task metadata like if the task has been executed or not Set set tings CELERY_TASK_META Can now run python setup py test to run the unit tests from within the tests project e Can set the AMQP exchange routing key qu
41. leryd n image myhost c 10 leryd n video myhost c 3 celeryd n data myhost c 3 sk GGG A G QqQaqqaqQqaqQq nh ranges and lists of workers in options is also allowed c 1 3 can also be written as c 1 2 3 celeryd multi start 5 c 3 c 1 3 10 leryd multi n celerydl myhost c 10 leryd multi n celeryd2 myhost c 10 leryd multi n celeryd3 myhost c 10 leryd multi n celeryd4 myhost c 3 leryd multi n celeryd5 myhost c 3 lists also works with named workers celeryd multi start foo bar baz xuzzy c 3 c foo bar baz 10 leryd multi n foo myhost c 10 leryd multi n bar myhost c 10 leryd multi n baz myhost c 10 leryd multi n xuzzy myhost c 3 e The worker now calls the result backends process_cleanup method after task execution instead of before e AMQP result backend now supports Pika 2 15 7 Change history for Celery 1 0 448 Chapter 2 Contents Celery Documeniation Release 3 0 25 e 1 0 6 e 1 0 5 Critical Changes e 1 0 4 e 1 0 3 Important notes News Remote control commands Fixes e 1 0 2 1 0 1 e 1 0 0 Backward incompatible changes Deprecations News Changes Bugs Documentation e 0 8 4 e 0 8 3 e 0 8 2 e 0 8 1 Very important note Important changes Changes e 0 8 0 Backward incompatible changes Important changes News e 0 6 0 Important changes
42. project_id token you must remember to include the at the end The login credentials can also be set using the environment variables IRON_TOKEN and IRON_PROJECT_ID which are set automatically if you use the IronMQ Heroku add on And in this case the broker url may only be ironma 18 Chapter 2 Contents Celery Documeniation Release 3 0 25 Clouds The default cloud region is AWS us east 1 You can choose the IronMQ Rackspace ORD cloud by changing the URL to ironmg project_id token mq rackspace ord iron io Results You can store results in IronCache with the same Iron io credentials just set the results URL with the same syntax as the broker URL but changing the start to i roncache ironcache project_id token This will default to a cache named Celery if you want to change that ironcache project_id token awesomecache More Information You can find more information in the iron_celery README http github com iron io iron_celery Broker Overview This is comparison table of the different transports supports more information can be found in the documentation for each individual transport see Broker Instructions Name Status Monitoring Remote Control RabbitMQ Stable Yes Yes Redis Stable Yes Yes Mongo DB Experimental Yes Yes Beanstalk Experimental No No Amazon SQS Experimental No No Couch DB Experimental No No Zookeeper Experimental No No Django DB
43. return subtask callback delay taskset join raise unlock_chord retry countdown interval max_retries max_retries This is used by all result backends except Redis and Memcached which increment a counter after each task in the header then applying the callback when the counter exceeds the number of tasks in the set Note chords do not properly work with Redis before version 2 2 you will need to upgrade to at least 2 2 to use them The Redis and Memcached approach is a much better solution but not easily implemented in other backends sugges tions welcome Note If you are using chords with the Redis result backend and also overriding the Task after_return method you need to make sure to call the super method or else the chord callback will not be applied def after_return self xargs xkwargs do_something super MyTask self after_return xargs xxkwargs 78 Chapter 2 Contents Celery Documeniation Release 3 0 25 Map amp Starmap map and starmap are built in tasks that calls the task for every element in a sequence They differ from group in that e only one task message is sent e the operation is sequential For example using map gt gt gt from proj tasks import add gt gt gt xsum map range 10 range 100 45 4950 is the same as having a task doing celery task def temp return xsum range 10 xsum range 100 and using starmap gt gt gt add starmap zip
44. returns True if the task has finished processing False gt gt gt result result task is not ready so no return value yet None gt gt gt result get Waits until the task is done and returns the retval gt gt gt result result direct access to result doesn t re raise errors gt gt gt result successful returns True if the task didn t end in failure True If the task raises an exception the return value of result successful willbe False and result result will contain the exception instance raised by the task Where to go from here To learn more you should read the Celery User Guide and the Celery Documentation in general 2 5 2 Unit Testing Testing with Django The first problem you ll run in to when trying to write a test that runs a task is that Django s test runner doesn t use the same database as your celery daemon is using If you re using the database backend this means that your tombstones won t show up in your test database and you won t be able to get the return value or check the status of your tasks There are two ways to get around this You can either take advantage of CELERY_ALWAYS_EAGER True to skip the daemon or you can avoid testing anything that needs to check the status or result of a task Using a custom test runner to test with celery If you re going the CELERY_ALWAYS_EAGER route which is probably better than just never testing some pa
45. started status can be useful for when there are long running tasks and there is a need to report which task is currently running The global default can be overridden by the CELERY_TRACK_STARTED setting e User Guide New section Tips and Best Practices Contributions welcome 452 Chapter 2 Contents Celery Documeniation Release 3 0 25 Remote control commands e Remote control commands can now send replies back to the caller Existing commands has been improved to send replies and the client interface in celery task control has new keyword arguments reply timeout and limit Where reply means it will wait for replies timeout is the time in seconds to stop waiting for replies and limit is the maximum number of replies to get By default it will wait for as many replies as possible for one second rate_limit task_name destination all reply False timeout 1 limit 0 Worker returns ok message on success or failure message on failure gt gt gt from celery task control import rate_limit gt gt gt rate_limit tasks add 10 s workerl E ok new r limit f l f Li worker2 ok new rat limit ping destination all reply False timeout 1 limit 0 Worker returns the simple message pong gt gt gt from celery task control import ping gt gt gt ping reply True workerl pong worker2 po
46. How to call manage py celeryd_multi CELERYD_MULTI SCELERYD_CHDIR manage py celeryd_multi How to call manage py celeryctl CELERYCTL CELERYD_CHDIR manage py celeryctl Extra arguments to celeryd CELERYD_OPTS time limit 300 concurrency 8 sn will be replaced with the nodename CELERYD_LOG_FILE var log celery n log CELERYD_PID_FILE var run celery n pid Workers should run as an unprivileged user CELERYD_USER celery CELERYD_GROUP celery Name of the projects settings module export DJANGO_SETTINGS_MODULE MyProject settings Example Django configuration Using Virtualenv In case you are using virtualenv you should add the path to your environment s python interpreter Name of nodes to start here we have a single node CELERYD_NODES w1 or we could have three nodes 2 8 Tutorials 167 Celery Documentation Release 3 0 25 ERYD_NODES wl w2 w3 here to chdir at start ELERYD_CHDIR opt Myproject Python interpreter from environment ENV PYTHON SCELERYD_CHDIR env bin python How to call manage py celeryd_multi CELE RYD_MULTI SENV_PYTHON SCELERYD_CHDIR manage py celeryd_multi H ow to call manage py celeryctli CELE RYCTL SENV_PYTHON SCELERYD_CHDIR manage py celeryctl ry E
47. News e 0 4 1 e 0 4 0 e 0 3 20 0 3 7 0 3 3 0 3 2 e 0 3 1 e 0 3 0 e 0 2 0 e 0 2 0 pre3 e 0 2 0 pre2 e 0 2 0 pre1 e OLIS e 0 1 14 e 0 1 13 0 1 12 0 1 11 e 0 1 10 e 0 1 8 e 0 1 7 e 0 1 6 e 0 1 0 2 15 History 449 Celery Documentation Release 3 0 25 1 0 6 1 0 5 release date 2010 06 30 09 57 A M CEST RabbitMQ 1 8 0 has extended their exchange equivalence tests to include auto_delete and durable This broke the AMQP backend If you ve already used the AMQP backend this means you have to delete the previous definitions camqadm exchange delete celeryresults or python manage py camqadm exchange delete celeryresults release date 2010 06 01 02 36 PM CEST Critical SIGINT Ctrl C killed the pool abruptly terminating the currently executing tasks Fixed by making the pool worker processes ignore SIGINT Should not close the consumers before the pool is terminated just cancel the consumers See issue 122 Now depends on billiard gt 0 3 1 celeryd Previously exceptions raised by worker components could stall startup now it correctly logs the excep tions and shuts down celeryd Prefetch counts was set too late QoS is now set as early as possible so celeryd can t slurp in all the messages at start up Changes celery contrib abortable Abortable tasks Tasks that defines steps of execution the task can then be aborted after each step has comp
48. Release 3 0 25 celery worker buckets e celery worker buckets j celery worker buckets This module implements the rate limiting of tasks by having a token bucket queue for each task type When a task is allowed to be processed it s moved over the the ready_queue The celery worker mediator is then responsible for moving tasks from the ready_queue to the worker pool class celery worker buckets AsyncTaskBucket task_registry callback None worker None add_bucket_for_type name clear cont request bucket tokens get args kwargs put request refresh class celery worker buckets FastQueue maxsize 0 Queue Queue supporting the interface of TokenBucketQueue clear expected_time tokens 1 items wait block True exception celery worker buckets RateLimitExceeded The token buckets rate limit has been exceeded class celery worker buckets TaskBucket task_registry callback None worker None This is a collection of token buckets each task type having its own token bucket If the task type doesn t have a rate limit it will have a plain Queue object instead of a TokenBucket Queue The put operation forwards the task to its appropriate bucket while the get operation iterates over the buckets and retrieves the first available item Say we have three types of tasks in the registry twitter update feed refresh and video compress the TaskBucket will consist of the following item
49. Run the program program run logfile var log app log celery platforms fileno f celery platforms get_errno n Get errno for string e g ENOENT celery platforms get_fdmax default None Returns the maximum number of open file descriptors on this system Parameters default Value returned if there s no file descriptor limit celery platforms ignore_errno args kwds Context manager to ignore specific POSIX error codes Takes a list of error codes to ignore which can be either the name of the code or the code integer itself gt gt gt with ignore_errno ENOENT with open foo r return r read gt gt gt with ignore_errno errno ENOENT errno EPERM pass Parameters types A tuple of exceptions to ignore when the errno matches defaults to Exception celery platforms initgroups uid gid Compat version of os initgroups which was first added to Python 2 7 celery platforms maybe_drop_privileges uid None gid None Change process privileges to new user group If UID and GID is specified the real user group is changed If only UID is specified the real user is changed and the group is changed to the users primary group If only GID is specified only the group is changed celery platforms maybe_fileno f Get object fileno or None if not defined celery platforms maybe_patch_con
50. Some examples 2 3 User Guide 93 Celery Documentation Release 3 0 25 Example crontab crontab minute 0 hour 0 crontab minute 0 hour 3 crontab minute 0 hour 0 3 6 9 12 15 18 21 crontab minute 15 crontab day_of_week sunday crontab minute hour x day_of_week sun crontab minute 10 hour 3 17 22 day_of_week thu fri crontab minute 0 hour 2 3 crontab minute 0 hour 5 crontab minute 0 hour 3 8 17 crontab day_of_month 2 crontab day_of_month 2 30 3 crontab day_of_month 1 7 15 21 crontab day _of month 11 month_of_year 5 crontab month_of_year 3 Meaning Execute every minute Execute daily at midnight Execute every three hours 3am 6am 9am noon 3pm 6pm 9pm Same as previous Execute every 15 minutes Execute every minute at Sundays Same as previous Execute every ten minutes but only between 3 4 am 5 6 pm and 10 11 pm on Thursdays or Fridays Execute every even hour and every hour divisible by three This means at every hour except lam 5am 7am llam lpm 5pm 7pm 11pm Execute hour divisible by 5 This means that it is trig gered at 3pm not 5pm since 3pm equals the 24 hour clock value of 15 which is divisible by 5 Execute every hour divisible by 3 and every hour during o
51. celery CASSANDRA_COLUMN_FAMILY task_results CASSANDRA_READ_ CONSISTENCY ONE CASSANDRA_WRITE_CONSISTENCY ONE CASSANDRA DETAILED MODE True CASSANDRA OPTIONS timeout 300 max_retries 10 lIronCache backend settings Note The Cassandra backend requires the iron_celery library http pypi python org pypi iron_celery To install the iron_celery package use pip or easy_install pip install iron_celery IronCache is configured via the URL provided in CELERY_RESULT_BACKEND for example CELERY_RESULT_BACKEND ironcache project_id token Or to change the cache name ironcache project_id token awesomecach For more information see https github com iron io iron_celery Message Routing CELERY_QUEUES The mapping of queues the worker consumes from This is a dictionary of queue name options See Routing Tasks for more information The default is a queue exchange binding key of celery with exchange type direct 134 Chapter 2 Contents Celery Documeniation Release 3 0 25 You don t have to care about this unless you want custom routing facilities CELERY_ROUTES A list of routers or a single router used to route tasks to queues When deciding the final destination of a task the routers are consulted in order See Routers for more information CELERY_QUEUE_HA_POLICY brokers Ra
52. celery utils imports qualname obj celery utils imports reload_from_ewd module reloader None celery utils log e celery utils log j celery utils log Logging utilities class celery utils log ColorFormatter fmt None use_color True COLORS blue lt bound method colored blue of gt black lt bound method colored black of gt yellow lt bound me Loglevel gt Color mapping colors DEBUG lt bound method colored blue of gt CRITICAL lt bound method colored magenta of gt WARN format record 2 14 Internals 387 Celery Documentation Release 3 0 25 formatException ei class celery utils log LoggingProxy logger loglevel None ce ce ce ce ce ce ce Forward file object to Logging Logger instance Parameters e logger The logging Logger instance to forward to e loglevel Loglevel to use when writing messages close When the object is closed no write requests are forwarded to the logging object anymore closed False flush This object is not buffered so any flush requests are ignored isatty Always returns False Just here for file support loglevel 40 mode w name None write data Write message to logging object writelines sequence writelines sequence_of_strings gt None Write the strings to the file The sequence can be any iterable object producing strin
53. cmd node_alive pid note msg newline True restart argv cmd retcode 0 say m newline True show argv cmd shutdown_nodes nodes sig 15 retry None callback None 2 13 API Reference 301 Celery Documentation Release 3 0 25 signal_node nodename pid sig splash start argv cmd stop argv cmd retry None callback None stop_verify argv cmd stopwait argv cmd usage waitexec argv path home docs checkouts readthedocs org user_builds celery envs 3 0 bin python with_detacher_default_options p class celery bin celeryd_multi NamespacedOptionParser args cel add_option name value short False ns None optmerge ns defaults None parse process_long_opt arg value None process_short_opt arg value None ery bin cel cel ery bin cel cel ery abits cel cel bin cel cel ery ery bin cel cel ery bin cel cel ery bin cel eryd eryd eryd eryd eryd eryd m m m eryd 2 14 Internals Release 3 0 Date July 10 2014 u u u u u u u LEi Tei lti LEL lti Lei TET abbreviations mapping findsig args default 15 format_opt opt value main multi_args p cmd celeryd append prefix parse_ns_range ns ranges False quote v 2 14 1 Contributors Guid
54. fri sat Examples from celery schedules import crontab from celery decorators import periodic_task periodic_task run_every crontab hour 7 minute 30 def every _morning print Runs every morning at 7 30a m periodic_task run_every crontab hour 7 minute 30 day_of_week mon def every_monday_ morning print Run every monday morning at 7 30a m periodic_task run_every crontab minutes 30 def every_hour print URunsMeviesy hour on shemclock eg IS0F O Sa s0Neren Note This a late addition While we have unittests due to the nature of this feature we haven t been able to completely test this in practice so consider this experimental e TaskPool apply_async Now supports the accept_callback argument e apply_async Now raises ValueError if task args is not a list or kwargs is not a tuple Issue 95 e Task max_retries can now be None which means it will retry forever e Celerybeat Now reuses the same connection when publishing large sets of tasks e Modified the task locking example in the documentation to use cache add for atomic locking e Added experimental support for a started status on tasks If Task track_started is enabled the task will report its status as started when the task is executed by a worker The default value is False as the normal behaviour is to not report that level of granularity Tasks are either pending finished or waiting to be retried Having a
55. minutes or hours by appending s m or h to the value Example 00 m hundred tasks a minute Default is the CELERY_DEFAULT_RATE_LIMIT setting which if not specified means rate limiting for tasks is disabled by default Task time_limit The hard time limit for this task If not set then the workers default will be used Task soft_time_limit The soft time limit for this task If not set then the workers default will be used Task ignore_result Don t store task state Note that this means you can t use AsyncResulLt to check if the task is ready or get its return value Task store_errors_even_if_ignored If True errors will be stored even if the task is configured to ignore results Task send_error_emails Send an email whenever a task of this type fails Defaults to the CELERY_SEND_TASK_ERROR_EMAITLS setting See Error E Mails for more information Task ErrorMail If the sending of error emails is enabled for this task then this is the class defining the logic to send error mails Task serializer A string identifying the default serialization method to use Defaults to the CELERY_TASK_SERIALIZER setting Can be pickle json yaml or any custom serialization methods that have been registered with kombu serialization registry Please see Serializers for more information Task compression A string identifying the default compression s
56. namespace celery Default configuration namespace on_concurrency_setup option_list List of options without preload options parse_doc doc parse_options prog_name arguments Parse the available options parse_preload_options args preload_options lt Option at 0x7fb762fd3248 A app gt lt Option at 0x7fb762bfebd8 b broker gt lt Option at 0x7 List of options to parse before parsing other options prepare_args options args prepare_parser parser process_cmdline_config argv respects_app_option True run args options This is the body of the command called by handle_argv 2 13 API Reference 287 Celery Documentation Release 3 0 25 run_from_argv prog_name argv None setup_app_from_commandline argv supports_args True If false the parser will raise an exception if positional args are provided symbol _by name name usage command Returns the command line usage string for this app version 3 0 25 Chiastic Slide Application version with_pool_option argv Returns tuple of short_opts long_opts if the command supports a pool argument and used to monkey patch eventlet gevent environments as early as possible E g has_pool_option P pool class celery bin base HelpFormatter indent_increment 2 max_help_position 24 width None short_first 1 format_description description format_epilog epilog celery b
57. retry_policy None publisher send type fields Send event Parameters e type Kind of event e fields Event arguments class celery events EventReceiver connection handlers None routing_key node_id None app None queue_prefix celeryev Capture events Parameters connection Connection to the broker handlers Event handlers handlers is a dict of event types and their handlers the special handler captures all events that doesn t have a handler app None capture limit None timeout None wakeup True Open up a consumer capturing events This has to run in the main process and it will never stop unless forced via KeyboardInterrupt or SystemExit consumer args kwds Create event consumer drain_events kwargs 2 13 API Reference 279 Celery Documentation Release 3 0 25 handlers itercapture limit None timeout None wakeup True process type event Process the received event by dispatching it to the appropriate handler wakeup_workers channel None class celery events Events app None Dispatcher Receiver State default_dispatcher args kwds celery events get_exchange conn 2 13 32 celery events state s celery events state j celery events state This module implements a datastructure used to keep track of the state of a cluster of workers and the tasks it is working on by consuming events For
58. return x y The first argument to Celery is the name of the current module this is needed so that names can be automatically generated the second argument is the broker keyword argument which specifies the URL of the message broker you want to use using RabbitMQ here which is already the default option See Choosing a Broker above for more choices e g for Redis you can use redis localhost or MongoDB mongodb localhost You defined a single task called add which returns the sum of two numbers Running the celery worker server You now run the worker by executing our program with the worker argument 2 2 Getting Started 21 Celery Documentation Release 3 0 25 celery A tasks worker loglevel info In production you will want to run the worker in the background as a daemon To do this you need to use the tools provided by your platform or something like supervisord see Running the worker as a daemon for more information For a complete listing of the command line options available do celery worker help There also several other commands available and help is also available S celery help Calling the task To call our task you can use the delay method This is a handy shortcut to the apply_async method which gives greater control of the task execution see Calling Tasks gt gt gt from tasks import add gt gt gt add delay 4 4 The task has now been processed by the worker you start
59. see for example Ensuring a task is only executed one at a time Available Fields e task The name of the task to execute e schedule The frequency of execution This can be the number of seconds as an integer at imedelta ora crontab You can also define your own custom schedule types by extending the interface of schedule e args Positional arguments list or tuple e kwargs Keyword arguments dict options 92 Chapter 2 Contents Celery Documeniation Release 3 0 25 Execution options dict This can be any argument supported by apply_async e g exchange routing_key expires and so on e relative By default timedelta schedules are scheduled by the clock This means the frequency is rounded to the nearest second minute hour or day depending on the period of the timedelta If relative is true the frequency is not rounded and will be relative to the time when celery beat was started Crontab schedules If you want more control over when the task is executed for example a particular time of day or day of the week you can use the crontab schedule type from celery schedules import crontab CELERYBEAT SCHEDULE Executes every Monday morning at 7 30 A M add every monday morning task tasks aadi schedule crontab hour 7 minute 30 day_of_week 1 fangs 16 16 br The syntax of these crontab expressions are very flexible
60. the cluster state is written to the TaskState and WorkerState models e Periodic tasks When the database backed schedule is used the periodic task schedule is taken from the PeriodicTask model there are also several other helper tables IntervalSchedule CrontabSchedule PeriodicTasks e Task results The database result backend is enabled by default when using django celery this is for historical reasons and thus for backward compatibility The results are stored in the TaskMeta and TaskSetMeta models these tables are not created if another result backend is configured 2 9 9 Windows The B beat option to celeryd doesn t work Answer That s right Run celerybeat and celeryd as separate services instead 2 10 What s new in Celery 3 0 Chiastic Slide Celery is a simple flexible and reliable distributed system to process vast amounts of messages while providing operations with the tools required to maintain such a system It s a task queue with focus on real time processing while also supporting task scheduling Celery has a large and diverse community of users and contributors you should come join us on IRC or our mailing list To read more about Celery you should go read the introduction While this version is backward compatible with previous versions it s important that you read the following section 184 Chapter 2 Contents Celery Documeniation Release 3 0 25 If you use Celery in co
61. to your broker See Security for more Example using serializer name CELERY_ACCEPT_CONTENT json or the actual content type MIME CELERY_ACCEPT_CONTENT application json BROKER_TRANSPORT Aliases BROKER_BACKEND Deprecated aliases CARROT_BACKEND 136 Chapter 2 Contents Celery Documeniation Release 3 0 25 BROKER_URL Default broker URL This must be an URL in the form of transport userid password hostname port virtual_host Only the scheme part transport is required the rest is optional and defaults to the specific transports default values The transport part is the broker implementation to use and the default is amqp which uses 1ibrabbitmg by default or falls back to pyamap if that is not installed Also there are many other choices including redis beanstalk sqlalchemy django mongodb couchdb It can also be a fully qualified path to your own transport implemen tation See URLs in the Kombu documentation for more information BROKER_HEARTBEAT transports supported pyamap It s not always possible to detect connection loss in a timely manner using TCP IP alone so AMQP defines something called heartbeats that s is used both by the client and the broker to detect if a connection was closed Hartbeats are disabled by default If the heartbeat value is 10 seconds then the heartbeat will be monitored at the interval specifie
62. zip range 100 range 100 10 apply_async You can also convert chunks to a group gt gt gt group add chunks zip range 100 range 100 10 group and with the group skew the countdown of each task by increments of one gt gt gt group skew start 1 stop 10 which means that the first task will have a countdown of 1 the second a countdown of 2 and so on 2 3 5 Workers Guide e Starting the worker e Stopping the worker e Restarting the worker e Process Signals e Concurrency e Remote control e Revoking tasks e Time Limits e Rate Limits e Max tasks per child setting e Autoscaling e Queues e Autoreloading e Inspecting workers e Additional Commands e Writing your own remote control commands Starting the worker Daemonizing You probably want to use a daemonization tool to start in the background See Running the worker as a daemon for help detaching the worker using popular daemonization tools You can start the worker in the foreground by executing the command S celery worker app app 1 info 80 Chapter 2 Contents Celery Documeniation Release 3 0 25 For a full list of available command line options see ce leryd or simply do celery worker help You can also start multiple workers on the same machine If you do so be sure to give a unique name to each individual worker by specifying a host name with the hostname n argument
63. 0 united states license the Celery software is offered under the less restrictive BSD License 3 Clause 2 2 Getting Started Release 3 0 Date July 10 2014 2 2 1 Introduction to Celery What is a Task Queue What do I need Get Started Celery is Features Framework Integration Quickjump Installation Celery Documentation Release 3 0 25 What is a Task Queue Task queues are used as a mechanism to distribute work across threads or machines A task queue s input is a unit of work called a task dedicated worker processes then constantly monitor the queue for new work to perform Celery communicates via messages using a broker to mediate between clients and workers To initiate a task a client puts a message on the queue the broker then delivers the message to a worker A Celery system can consist of multiple workers and brokers giving way to high availability and horizontal scaling Celery is written in Python but the protocol can be implemented in any language So far there s RCelery for the Ruby programming language and a PHP client but language interoperability can also be achieved by using webhooks What do need Version Requirements Celery version 3 0 runs on Python 2 5 2 6 2 7 3 2 3 3 PyPy 1 8 1 9 e Jython 2 5 2 7 This is the last version to support Python 2 5 and from the next version Python 2 6 or newer is required The last version to support Python 2 4 was Cel
64. 13 16 00 P M BST e New signals after_setup_logger and after_setup_task_logger These signals can be used to augment logging configuration after Celery has set up logging e Redis result backend now works with Redis 2 4 4 e celeryd_multi The gid option now works correctly e celeryd Retry wrongfully used the repr of the traceback instead of the string representation e App config_from_object Now loads module not attribute of module 410 Chapter 2 Contents Celery Documeniation Release 3 0 25 e Fixed issue where logging of objects would give lt Unrepresentable gt 2 2 6 release date 2011 04 15 16 00 Important Notes e Now depends on Kombu 1 1 2 e Dependency lists now explicitly py3k gt P M CEST specifies that we don t want python dateutil 2 x as this version only supports If you have installed dateutil 2 0 by accident you should downgrade to the 1 5 0 version pip install U python dateutil 1 5 0 or by easy_install easy_install U python dateutil 1 5 0 Fixes Sending emails did not work on Beat Adds method Schedule The new Wat chedFileHandler broke Python 2 5 support Issue 367 Task Don t use app main if the task name is set explicitly Python 2 5 due to a bug in the version detection code Issue 378 This method can be overri We no longer propagate errors Entry _default_now dden to change the default value of last_run_at An error o
65. 2 2 Note that if you open a regular python shell by simply running python you will need to import your Django applica tion s settings by running Replace myproject with your project s name gt gt gt from myproject import settings The delay method used above is a handy shortcut to the apply_async method which enables you to have greater control of the task execution To read more about calling tasks including specifying the time at which the task should be processed see Calling Tasks 2 5 Django 149 Celery Documeniation Release 3 0 25 Note Tasks need to be stored in a real module they can t be defined in the python shell or Python bpython This is because the worker server must be able to import the task function The task should now be processed by the worker you started earlier and you can verify that by looking at the worker s console output Calling a task returns an AsyncResult instance which can be used to check the state of the task wait for the task to finish or get its return value or if the task failed the exception and traceback By default django celery stores this state in the Django database You may consider choosing an alternate result backend or disabling states alltogether see Result Backends To demonstrate how the results work call the task again but this time keep the result instance returned gt gt gt result add delay 4 4 gt gt gt result ready
66. 25 Canvas Designing Workflows Routing Tasks e celeryd Standard out error is now being redirected to the log file e billiard has been moved back to the celery repository Module name celery equivalent billiard pool celery concurrency processes pool billiard serialization celery serialization billiard utils functional celery utils functional The billiard distribution may be maintained depending on interest e now depends on carrot gt 0 10 5 e now depends on pyparsing e celeryd Added purge as an alias to discard e celeryd Ctrl C SIGINT once does warm shutdown hitting Ctrl C twice forces termination e Added support for using complex crontab expressions in periodic tasks For example you can now use gt gt gt crontab minute 15 or even gt gt gt crontab minute 30 hour 8 17 1 2 day_of_week thu fri See Periodic Tasks e celeryd Now waits for available pool processes before applying new tasks to the pool This means it doesn t have to wait for dozens of tasks to finish at shutdown because it has applied prefetched tasks without having any pool processes available to immediately accept them See issue 122 e New built in way to do task callbacks using subt ask See Canvas Designing Workflows for more information e TaskSets can now contain several types of tasks TaskSet has been refactored to use a new syntax please see Canvas Designing Workflows for m
67. 269 task base 250 task http 95 task trace 366 tils 376 tils compat 381 tils debug 263 tils dispatch 389 tils dispatch saferef 390 tils dispatch signal 389 tils functional 377 tils imports 387 tils log 387 CG CG G G G G G G 479 Celery Documentation Release 3 0 25 ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce lery lery lery lery lery lery lery lery lery lery lery lery lery lery lery lery lery lery lery lery tils tils mail 264 serialization 381 tils tils tils tils Gcaoagcagsa tils worker worker worker worker worker worker worker worker worker worker worker worker worker term 379 text 388 threads 383 timer2 384 timeutils 380 319 autoreload 336 autoscale 337 boot steps 338 buckets 329 consumer 322 control 333 heartbeat 331 hub 331 job 326 mediator 328 state 334 strategy 335 480 Python Module Index
68. 30 PM BST Now depends on Kombu 2 5 13 Now depends on billiard 2 7 3 32 Fixed bug with monthly and yearly crontabs Issue 1465 Fix contributed by Guillaume Gauvrit Fixed memory leak caused by time limits Issue 1129 Issue 1427 Worker will now sleep if being restarted more than 5 times in one second to avoid spamming with worker online events Includes documentation fixes Contributed by Ken Fromm Andreas Savwvides Alex Kiriukha Michael Fladischer 2 5 3 0 21 release date 2013 07 05 16 30 PM BST e Now depends on billiard 2 7 3 31 This version fixed a bug when running without the billiard C extension e 3 0 20 broke eventlet gevent support worker not starting e Fixed memory leak problem when MongoDB result backend was used with the gevent pool Fix contributed by Ross Lawley 2 6 3 0 20 release date 2013 06 28 16 00 PM BST Contains workaround for deadlock problems A better solution will be part of Celery 3 1 Now depends on Kombu 2 5 12 Now depends on billiard 2 7 3 30 loader argument no longer supported importing loaders from the current directory Worker Fixed memory leak when restarting after connection lost Issue 1325 Worker Fixed UnicodeDecodeError at startup Issue 1373 Fix contributed by Jessica Tallon Worker Now properly rewrites unpickleable exceptions again Fixed possible race condition when evicting items from the revoked task set e generic init d Fi
69. Celery uses the standard Python logger library for which documentation can be found in the Logging module You can also simply use print as anything written to standard out err will be redirected to the workers logs by default see CELERY_REDIRECT_STDOUTS Retrying retry can be used to re execute the task for example in the event of recoverable errors When you call ret ry it will send a new message using the same task id and it will take care to make sure the message is delivered to the same queue as the originating task When a task is retried this is also recorded as a task state so that you can track the progress of the task using the result instance see States Here s an example using retry celery task def send_twitter_status oauth tweet try twitter Twitter oauth twitter update_status tweet except Twitter FailWhaleError Twitter LoginError exc raise send_twitter_status retry exc exc Note The retry call will raise an exception so any code after the retry will not be reached This is the RetryTaskError exception it is not handled as an error but rather as a semi predicate to signify to the worker that the task is to be retried so that it can store the correct state when a result backend is enabled This is normal operation and always happens unless the throw argument to retry is set to False 46 Chapter 2 Contents Celery Documeniation Release 3 0 25
70. Contributed by Chris Adams celeryd_multi now supports a stop_verify command to wait for processes to shutdown Cache backend did not work if the cache key was unicode Issue 504 Fix contributed by Neil Chintomby New setting CELERY_RESULT_DB_SHORT_LIVED_SESSIONS added which if enabled will disable the caching of SQLAIchemy sessions Issue 449 Contributed by Leo Dirac All result backends now implements __ reduce__ so that they can be pickled Issue 441 Fix contributed by Remy Noel 2 15 History 403 Celery Documentation Release 3 0 25 celeryd multi did not work on Windows Issue 472 New style CELERY_REDIS__ settings now takes precedence over the old REDIS_ configuration keys Issue 508 Fix contributed by Joshua Ginsberg Generic celerybeat init script no longer sets bash e Issue 510 Fix contributed by Roger Hu Documented that Chords do not work well with redis server versions before 2 2 Contributed by Dan McGee The CELERYBEAT_MAX_LOOP_INTERVAL setting was not respected inspect registered_tasks renamed to inspect registered for naming consistency The previous name is still available as an alias Contributed by Mher Movsisyan Worker logged the string representation of args and kwargs without safe guards Issue 480 RHEL init script Changed celeryd startup priority The default start stop priorities for MySQL on RHEL
71. M CET e Fixed a syntax error in the TaskSet class No such variable TimeOutError 0 1 13 release date 2009 05 19 12 36 P M CET e Forgot to add yadayada to install requirements e Now deletes all expired task results not just those marked as done 2 15 History 471 Celery Documeniation Release 3 0 25 e Able to load the Tokyo Tyrant backend class without django configuration can specify tyrant settings directly in the class constructor e Improved API documentation e Now using the Sphinx documentation system you can build the html documentation by doing cd docs make html and the result will be in docs build html 0 1 12 release date 2009 05 18 04 38 P M CET e delay_task etc now returns celery task AsyncResult object which lets you check the result and any failure that might have happened It kind of works like the multiprocessing AsyncResult class returned by multiprocess ing Pool map_async e Added dmap and dmap_async This works like the multiprocessing Pool versions except they are tasks distributed to the celery server Example gt gt gt from celery task import dmap import operator dmap operator add 4 8 16 gt gt gt gt gt gt 2 2 4 4 gt gt gt gt gt gt gt gt gt from celery task import dmap_async import operator result dmap_async operator add result ready gt gt gt 2 gt gt gt False gt gt gt time sleep 1
72. None run redirect_stdouts_level None run_worker set_process_ status info setup_logging colorize None startup_info Worker tasklist include_builtins True sep n int_ celery lery apps lery apps lery apps lery apps lery apps lery apps lery apps wor wor wor wor wor wor wor Ker Ker Ker Ker Ker Ker Ker active_thread_count install_HUP_not_supported_handler worker sig SIGHUP install_cry handler install_rdb_handler envvar CELERY_RDBSIG sig SIGUSR2 install_worker_restart_handler worker sig SIGHUP on_SIGINT worker safe_say msg 2 13 34 celery apps beat e celery apps beat j 284 Chapter 2 Contents Celery Documeniation Release 3 0 25 celery apps beat This module is the program version of celery beat It does everything necessary to run that module as an actual application like installing signal handlers and so on class celery apps beat Beat max_interval None app None socket_timeout 30 pidfile None no_color None kwargs class Service max_interval None schedule_filename None scheduler_cls None app None get_scheduler lazy False scheduler scheduler_cls alias of PersistentScheduler start embedded_process False stop wait False sync Beat app None Beat init_loader Beat install_sync_handler beat Instal
73. None default Redis password None port 6379 default Redis server port 6379 redis None redis py client module set key value supports_autoexpire True supports_native_join True celery backends cassandra celery backends cassandra Apache Cassandra result store backend class celery backends cassandra CassandraBackend servers None column_family None cas sandra_options None de tailed_mode False kwargs Highly fault tolerant Cassandra backend servers List of Cassandra servers with format hostname port e celery backends cassandra j keyspace None Raises celery exceptions ImproperlyConfigured if module pycassa is not available column_family None detailed_mode False keyspace None process_cleanup servers supports_autoexpire True 2 14 Internals 365 Celery Documentation Release 3 0 25 celery task trace e celery task trace j celery task trace This module defines how the task execution is traced errors are recorded handlers are applied and so on class celery task trace TraceInfo state retval None handle_error_state task eager False handle_failure task store_errors True Handle exception handle_retry task store_errors True Handle retry exception retval state celery task trace build_tracer name task loader None hostname None store_errors True Info lt class celery task trace Tracelnfo gt eager Fa
74. Release 3 0 25 r maxrate Camera Optional shutter rate limit e g 10 m 1 loglevel Logging level choose between DEBUG INFO WARNING ERROR CRITICAL or FATAL Default is INFO class celery bin celeryev EvCommand app None get_app None doc n nThe program celery events command n n program celery events n n seealso n n See ref preload opt get_options run dump False camera None frequency 1 0 maxrate None __loglevel INFO log file None prog_name celeryev pidfile None uid None gid None umask None work ing_directory None detach False kwargs run_evcam camera logfile None pidfile None uid None gid None umask None work ing_directory None detach False kwargs run_evdump run_evtop set_process_status prog info supports_args False celery bin celeryev main 2 13 39 celery bin celery The celery umbrella command class celery bin celery CeleryCommand app None get_app None commands control lt class celery bin celery control gt status lt class celery bin celery status gt multi lt class cele enable_config_from_cmdline True execute command argv None execute_from_commandline argv None classmethod get_command_info command indent 0 color None handle_argv prog_name argv classmethod 1ist_commands indent 0 on_concurrency_setup prog_name celery remove_op
75. See the Kombu 2 3 changelog for more information e Delivery info is no longer passed directly through It was discovered that the SQS transport adds objects that can t be pickled to the delivery info mapping so we had to go back to using the whitelist again Fixing this bug also means that the SQS transport is now working again e The semaphore was not properly released when a task was revoked Issue 877 This could lead to tasks being swallowed and not released until a worker restart Thanks to Hynek Schlawack for debugging the issue e Retrying a task now also forwards any linked tasks This means that if a task is part of a chain or linked in some other way and that even if the task is retried then the next task in the chain will be executed when the retry succeeds e Chords Now supports setting the interval and other keyword arguments to the chord unlock task The interval can now be set as part of the chord subtasks kwargs chord header body interval 10 0 In addition the chord unlock task now honors the Task default_retry_delay option used when none is specified which also means that the default interval can also be changed using annotations 224 Chapter 2 Contents Celery Documeniation Release 3 0 25 Q H ERY_ANNOTATIONS celery chord_unlock default_retry_delay 10 0 e New Celery add_defaults method can add new default configuration dicts to the ap
76. Terminating a task now works if the task has been sent to the pool but not yet acknowledged by a pool process Issue 1007 Fix contributed by Alexey Zatelepin Terminating a task now properly updates the state of the task to revoked and sends a task revoked event Generic worker init script now waits for workers to shutdown by default Multi No longer parses app option Issue 1008 Multi stop_verify command renamed to stopwait 218 Chapter 2 Contents Celery Documeniation Release 3 0 25 e Daemonization Now delays trying to create pidfile logfile until after the working directory has been changed into e celery worker and celery beat commands now respects the no color option Issue 999 e Fixed typos in eventlet examples Issue 1000 Fix contributed by Bryan Bishop Congratulations on opening bug 1000 e Tasks that raise Ignore are now acknowledged e Beat Now shows the name of the entry in sending due task logs 2 12 16 3 0 10 release date 2012 09 20 05 30 PM BST e Now depends on kombu 2 4 7 e Now depends on billiard 2 7 3 14 Fixes crash at startup when using Django and pre 1 4 projects setup_environ Hard time limits now sends the KILL signal shortly after TERM to terminate processes that have signal handlers blocked by C extensions Billiard now installs even if the C extension cannot be built It s still recommended to build the C extension if you are using a transport other tha
77. The name of the logfile e format The log format string e colorize Specify if log messages are colored or not after_setup_task_logger Sent after the setup of every single task logger Used to augment logging configuration Provides arguments e logger The logger object e loglevel The level of the logging object e logfile The name of the logfile 126 Chapter 2 Contents Celery Documeniation Release 3 0 25 e format The log format string e colorize Specify if log messages are colored or not 2 4 Configuration and defaults This document describes the configuration options available If you re using the default loader you must create the celeryconfig py module and make sure it is available on the Python path e Example configuration file e Configuration Directives Time and date settings Task settings Concurrency settings Task result backend settings Database backend settings AMQP backend settings Cache backend settings Redis backend settings MongoDB backend settings Cassandra backend settings IronCache backend settings Message Routing Broker Settings Task execution settings Worker celeryd Error E Mails Events Broadcast Commands Logging Security Custom Component Classes advanced Periodic Task Server celerybeat Monitor Server celerymon 2 4 1 Example configuration file This is an example configu
78. Timer Schedule cancel tref imer Schedule clear Timer Schedule empty Is the schedule empty Timer Schedule enter entry eta None priority 0 Enter function into the scheduler Parameters Pool T Pool T PooOL lt T Pool T Pool Snap Pool T Pool T Pool T Pool T Pool T Pool T imer Timer Timer Timer imer imer imer imer imer imer imer Timer Timer Timer e entry Item to enter e eta Scheduled time as a datetime datetime object e priority Unused imer Schedule enter_after msecs entry priority 0 time lt built in function time gt imer Schedule handle_error exc_info imer Schedule info imer Schedule on_error None Timer Schedule queue shot of underlying datastructure imer Schedule schedule imer Schedule stop apply after args kwargs apply_at args kwargs apply interval args kwargs cancel tref clear empty ensure_started enter entry eta priority None enter_after args kwargs exit_after msecs priority 10 next on_tick None queue run 2 14 Internals 347 Celery Documentation Release 3 0 25 BasePool Timer running False BasePool Timer stop BasePool active BasePool apply_asynce target args kwargs options Equivalent of the apply built in function Callbacks should optimally return as soon as poss
79. a list of tasks that should be applied in parallel e chain The chain primitive lets us link together subtasks so that one is called after the other essentially forming a chain of callbacks chord A chord is just like a group but with a callback A chord consists of a header group and a body where the body is a task that should execute after all of the tasks in the header are complete e map The map primitive works like the built in map function but creates a temporary task where a list of arguments is applied to the task E g task map 1 2 results in a single task being called applying the arguments in order to the task function so that the result is res task 1 task 2 e starmap Works exactly like map except the arguments are applied as xargs For example add starmap 2 2 4 4 results ina single task calling res add 2 2 add 4 4 e chunks Chunking splits a long list of arguments into parts e g the operation gt gt gt add chunks zip xrange 1000 xrange 1000 10 will create 10 tasks that apply 100 items each The primitives are also subtasks themselves so that they can be combined in any number of ways to compose complex workflows Here s some examples e Simple chain Here s a simple chain the first task executes passing its return value to the next task in the chain and so on gt gt gt from celery import chain gt gt gt res chain add s 2 2 add s 4 ad
80. a message and what happens when a worker receives that message Every task class has a unique name and this name is referenced in messages so that the worker can find the right function to execute A task message does not disappear until the message has been acknowledged by a worker A worker can reserve many messages in advance and even if the worker is killed caused by power failure or otherwise the message will be redelivered to another worker Ideally task functions should be idempotent which means that the function will not cause unintented effects even if called multiple times with the same arguments Since the worker cannot detect if your tasks are idempotent the default behavior is to acknowledge the message in advance before it s executed so that a task that has already been started is never executed again If your task is idempotent you can set the acks_late option to have the worker acknowledge the message after the task returns instead See also the FAQ entry Should I use retry or acks_late In this chapter you will learn all about defining tasks and this is the table of contents 42 Chapter 2 Contents Celery Documeniation Release 3 0 25 e Basics e Names e Context e Logging e Retrying e List of Options e States e Custom task classes e How it works e Tips and Best Practices e Performance and Strategies e Example Basics You can easily create a task from any callable by usi
81. advanced features After you have finished this tutorial it s a good idea to browse the rest of the documentation for example the Next Steps tutorial which will showcase Celery s capabilities e Choosing a Broker RabbitMQ Redis Using a database Other brokers e Installing Celery e Application e Running the celery worker server e Calling the task e Keeping Results e Configuration e Where to go from here Choosing a Broker Celery requires a solution to send and receive messages usually this comes in the form of a separate service called a message broker There are several choices available including RabbitMQ RabbitMQ is feature complete stable durable and easy to install It s an excellent choice for a production environ ment Detailed information about using RabbitMQ with Celery Using RabbitMQ If you are using Ubuntu or Debian install RabbitMQ by executing this command sudo apt get install rabbitmq server When the command completes the broker is already running in the background ready to move messages for you Starting rabbitmq server SUCCESS And don t worry if you re not running Ubuntu or Debian you can go to this website to find similarly simple installation instructions for other platforms including Microsoft Windows http www rabbitmq com download html Redis Redis is also feature complete but is more susceptible to data loss in the event of abrupt termination or power
82. against force upgrading to Kombu 2 2 0 e Version parity with django celery 2 5 3 release date 2012 04 16 07 00 P M BST by Ask Solem k e A bug causes messages to be sent with UTC timestamps even though CELERY_ENABLE_UTC was not enabled Issue 636 e celerybeat No longer crashes if an entry s args is set to None Issue 657 e Autoreload did not work if a module s___ file____ attribute was set to the modules pyc file Issue 647 396 Chapter 2 Contents Celery Documeniation Release 3 0 25 e Fixes early 2 5 compatibility where __package__ does not exist Issue 638 2 5 2 release date 2012 04 13 04 30 PM GMT by Ask Solem News e Now depends on Kombu 2 1 5 e Django documentation has been moved to the main Celery docs See Django e New celeryd_init signal can be used to configure workers by hostname e Signal connect can now be used as a decorator Example from celery signals import task_sent task_sent connect def on_task_sent xkwargs print sent task r kwargs e Invalid task messages are now rejected instead of acked This means that they will be moved to the dead letter queue introduced in the latest RabbitMQ version but must be enabled manually consult the RabbitMQ documentation e Internal logging calls has been cleaned up to work better with tools like Sentry Contributed by David Cramer e New method subtask clone can be used to clone
83. and cancel_consumer Queues Adding consumers The add_consumer control command will tell one or more workers to start consuming from a queue This operation is idempotent To tell all workers in the cluster to start consuming from a queue named foo you can use the celery control program S celery control add_consumer foo gt workerl local OK started consuming from u foo If you want to specify a specific worker you can use the dest ination argument celery control add_consumer foo d workerl local The same can be accomplished dynamically using the celery control add_consumer method gt gt gt myapp control add_consumer foo reply True u workerl local u ok u already consuming from u foo gt gt gt myapp control add_consumer foo reply True destination workerl local J u ok u already consuming from u foo u workerl local By now I have only shown examples using automatic queues If you need more control you can also specify the exchange routing _key and even other options gt gt gt myapp control add_consumer queue baz exchange ex xchange_type topic routing_key media x options queue_durable False exchange_durable False reply True destination workerl local worker2 local Queues Cancelling consumers You can cancel a consumer by queue name using t
84. and the task is applied while executing an other task then the result will be appended to the parent tasks request children attribute e publisher Deprecated alias to producer Also supports all keyword arguments supported by kombu messaging Producer publish Note If the CELERY_ALWAYS_EAGER setting is set it will be replaced by a local apply call instead ask autoregister True If disabled this task won t be registered automatically Task backend lt celery backends cache CacheBackend object at 0x7fb767118c10 gt The result store backend used for this task ask chunks it n Creates a chunks task for this task Task default_retry_delay 180 Default time in seconds before a retry of the task should be executed 3 minutes by default ask delay args kwargs Star argument version of apply_async Does not support the extra options enabled by apply_async Parameters e args positional arguments passed on to the task e kwargs keyword arguments passed on to the task returns celery result AsyncResult Task expires None Default task expiry time Task ignore_result False If enabled the worker will not store task state and return values for this task Defaults to the CELERY_IGNORE_RESULT setting Task map it Creates a xmap task from it Task max_retries 3 Maximum number of retries before giving up If set to None
85. are chkconfig 64 36 Therefore if Celery is using a database as a broker message store it should be started after the database is up and running otherwise errors will ensue This commit changes the priority in the init script to chkconfig 85 15 which are the default recommended settings for 3 rd party applications and assure that Celery will be started after the database service amp shut down before it terminates Contributed by Yury V Zaytsev Key ValueStoreBackend get_many did not respect the timeout argument Issue 512 celerybeat celeryev s workdir option did not chdir before after configuration was attempted Issue 506 After deprecating 2 4 support we can now name modules correctly since we can take use of absolute imports Therefore the following internal modules have been renamed celery concurrency evlet gt celery concurrency eventlet celery concurrency evg gt cel ery concutrency gevent AUTHORS file is now sorted alphabetically Also as you may have noticed the contributors of new features fixes are now mentioned in the Changelog 2 15 3 Change history for Celery 2 3 404 Chapter 2 Contents Celery Documeniation Release 3 0 25 e 2 3 4 Security Fixes Fixes 233 23 2 News Fixes e 2 3 1 Fixes e 2 3 0 Important Notes News Fixes 2 3 4 release date 2011 11 25 16 00 P M GMT by Ask Solem Security Fixes e Security CE
86. awesome rst S vim celery worker awesome rst y schedules to vim index rst Add celery worker awesome to the index Add the file to git S git add celery worker awesome rst S git add index rst S git commit celery worker awesome rst index rst m Adds reference for celery worker awesome 2 6 8 Coding Style You should probably be able to pick up the coding style from surrounding code but it is a good idea to be aware of the following conventions e All Python code must follow the PEP 8 guidelines pep8 py is an utility you can use to verify that your code is following the conventions e Docstrings must follow the PEP 257 conventions and use the following style Do this 2 6 Contributing 159 Celery Documentation Release 3 0 25 def method self arg WuM Short description More details ww or def method self arg Un hort ClSeieieay oe ationg ly WWI but not this def method self arg ww Short description e Lines should not exceed 78 columns You can enforce this in vim by setting the textwidth option set textwidth 78 If adhering to this limit makes the code less readable you have one more character to go on which means 78 is a soft limit and 79 is the hard limit e Import order Python standard library import xxx Python standard library from xxx import Third party packages Other modules from the current package or in case of cod
87. backends backends backends beat 349 base 285 camqadm 297 bin celery 291 bin bin cel ery ery erybeat 290 bin celeryd 288 ery ery bin celeryd_multi 299 bin celeryev 290 lery lery lery lery lery concurrency 340 concurrency base 346 concurrency eventlet 343 concurrency gevent 345 concurrency processes 340 ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce cel cel cel ce ce ce ce ce ce ce ce cel ce ce ce ce ce ce ce ce cel ce ce ce Lery Lery Lery Lery Lery Lery concurrency threads 349 Lery Lery Lery Lery Lery Lery events 278 Lery events dumper 374 Lery events state 280 Lery Lery Lery Lery Lery Lery Lery Lery Lery Lery Lery Lery Lery Lery Lery task 249 Lery Lery Lery Lery Lery Lery Lery Lery Lery Lery Lery Lery concurrency solo 340 contrib abortable 270 contrib batches 272 contrib methods 277 contrib migrate 274 contrib rdb 276 datastructures 370 events cursesmon 373 events snapshot 372 exceptions 265 loaders 266 loaders app 267 loaders base 267 loaders default 267 platforms 391 result 251 schedules 259 security 262 security certificate 368 security key 369 security serialization 369 security utils 369 signals 262 states
88. be timing delays between nodes starting If there are 3 offline nodes and one active node all messages will be delivered to the active node 4 This is the concurrency setting CELERYD_CONCURRENCY or the c option to celeryd 120 Chapter 2 Contents Celery Documeniation Release 3 0 25 2 3 12 Concurrency Release 3 0 Date July 10 2014 Concurrency with Eventlet Introduction The Eventlet homepage describes it as A concurrent networking library for Python that allows you to change how you run your code not how you write it e It uses epoll 4 or libevent for highly scalable non blocking I O e Coroutines ensure that the developer uses a blocking style of programming that is similar to threading but provide the benefits of non blocking I O e The event dispatch is implicit which means you can easily use Eventlet from the Python interpreter or as a small part of a larger application Celery supports Eventlet as an alternative execution pool implementation It is in some cases superior to multiprocess ing but you need to ensure your tasks do not perform blocking calls as this will halt all other operations in the worker until the blocking call returns The multiprocessing pool can take use of multiple processes but how many is often limited to a few processes per CPU With Eventlet you can efficiently spawn hundreds or thousands of green threads In an informal test with a feed hub system the Eventlet pool could fetch
89. been revoked 2 15 History 455 Celery Documentation Release 3 0 25 1 0 1 management commands camqadm Fixed typo camgpadm gt camqadm Issue 83 PeriodicTask delta_resolution Was not working for days and hours now fixed by rounding to the nearest day hour Fixed a potential infinite loop in BaseAsyncResult __eq__ although there is no evidence that it has ever been triggered celeryd Now handles messages with encoding problems by acking them and emitting an error message release date 2010 02 24 07 05 PM CET Tasks are now acknowledged early instead of late This is done because messages can only be acknowledged within the same connection channel so if the connection is lost we would have to refetch the message again to acknowledge it This might or might not affect you but mostly those running tasks with a really long execution time are affected as all tasks that has made it all the way into the pool needs to be executed before the worker can safely terminate this is at most the number of pool workers multiplied by the CELERYD_PREFETCH_MULTIPLIER setting We multiply the prefetch count by default to increase the performance at times with bursts of tasks with a short execution time If this doesn t apply to your use case you should be able to set the prefetch multiplier to zero without sacrificing performance Note A patch to multiprocessing is currently being worked on this patch would enable us to
90. being applied as a callback of the previous task If called with only one argument then that argument must be an iterable of tasks to chain Example gt gt gt res chain add s 2 2 add s 4 apply_async is effectively 2 2 4 2 13 API Reference 231 Celery Documentation Release 3 0 25 gt gt gt res get Calling a chain will return the result of the last task in the chain You can get to the other tasks by following the result parent s gt gt gt res parent get 4 class celery chord header body A chord consists of a header and a body The header is a group of tasks that must complete before the callback is called A chord is essentially a callback for a group of tasks Example gt gt gt res chord add s 2 2 add s 4 4 sum_task s is effectively H 2 2 4 4 gt gt gt res get The body is applied with the return values of all the header tasks as a list class celery subtask fask None args kwargs options Describes the arguments and execution options for a single task invocation Used as the parts in a group or to safely pass tasks around as callbacks Subtasks can also be created from tasks gt gt gt add subtask args kwargs options or the s shortcut gt gt gt add s xargs xkwargs Parameters e task Either a task class instance or the name of a task e args Positional arguments to apply
91. belongs to it uses the main module name to generate the beginning of the task name This is only a problem in a limited set of use cases 1 If the module that the task is defined in is run as a program 2 If the application is created in the Python shell REPL For example here where the tasks module is also used to start a worker tasks py from celery import Celery celery Celery celery task def add x y return x y if name main__ celery worker_main When this module is executed the tasks will be named starting with ___main__ but when it the module is imported by another process say to call a task the tasks will be named starting with tasks the real name of the module gt gt gt from tasks import add gt gt gt add name tasks add 36 Chapter 2 Contents Celery Documeniation Release 3 0 25 You can specify another name for the main module gt gt gt celery Celery tasks gt gt gt celery main tasks gt gt gt celery task def add x y return x y gt gt gt add name tasks add See also Names Configuration There are lots of different options you can set that will change how Celery work These options can be set on the app instance directly or you can use a dedicated configuration module The configuration is available as Celery conf gt gt gt celery conf CELERY_TIMEZONE Europe London
92. can look up the name in its task registry to find the execution code This means that your workers should always be updated with the same software as the client This is a drawback but the alternative is a technical challenge that has yet to be solved Tips and Best Practices Ignore results you don t want If you don t care about the results of a task be sure to set the ignore_result option as storing results wastes time and resources celery task ignore_result True def mytask something Results can even be disabled globally using the CELERY_IGNORE_RESULT setting Disable rate limits if they re not used Disabling rate limits altogether is recommended if you don t have any tasks using them This is because the rate limit subsystem introduces quite a lot of complexity Set the CELERY_DISABLE_ RATE_LIMITS setting to globally disable rate limits CELERY _DISABLE_RATE LIMITS True You find additional optimization tips in the Optimizing Guide Avoid launching synchronous subtasks Having a task wait for the result of another task is really inefficient and may even cause a deadlock if the worker pool is exhausted Make your design asynchronous instead for example by using callbacks Bad celery task def update_page_info url page fetch_page delay url get info parse_page delay url page get store_page_info delay url i
93. can now be used with static analysis tools like PyDev PyCharm pylint etc e Development documentation has moved to Read The Docs The new URL is http docs celeryproject org en master e New CELERY_QUEUE_HA_ POLICY setting used to set the default HA policy for queues when using Rab bitMQ e New method Task subtask_from_request returns a subtask using the current request e Results get_many method did not respect timeout argument Fix contributed by Remigiusz Modrzejewski generic_init d scripts now support setting CELERY_CREATE_DIRS to always create log and pid directories Issue 1045 This can be set in your etc default celeryd e Fixed strange kombu import problem on Python 3 2 Issue 1034 e Worker ETA scheduler now uses millisecond precision Issue 1040 e The config argument to programs is now supported by all loaders e The CASSANDRA_OPTIONS setting has now been documented Contributed by Jared Biel e Task methods celery contrib methods cannot be used with the old task base class the task decorator in that module now inherits from the new e An optimization was too eager and caused some logging messages to never emit 2 12 Change history 217 Celery Documentation Release 3 0 25 celery contrib batches now works again Fixed missing whitespace in bdist_rpm requirements Issue 1046 Event state s tasks_by_name applied limit before filtering by name Fix contr
94. can use to avoid overflowing its queues or otherwise finding itself receiving more messages than it can process The peer that receives a request to stop sending content will finish sending the current content if any and then wait until flow is reactivated no_ack None on_decode_error None on_message None purge Purge messages from all queues Warning This will delete all ready messages there is no undo operation qos prefetch_size 0 prefetch_count 0 apply_global False Specify quality of service The client can request that messages should be sent in advance so that when the client finishes processing a message the following message is already held locally rather than needing to be sent down the channel Prefetching gives a performance improvement The prefetch window is Ignored if the no_ack option is set Parameters e prefetch_size Specify the prefetch window in octets The server will send a message in advance if it is equal to or smaller in size than the available prefetch size and also falls within other prefetch limits May be set to zero meaning no specific limit although other prefetch limits may still apply e prefetch_count Specify the prefetch window in terms of whole mes sages e apply_global Apply new settings globally on all channels Currently not supported by RabbitMQ queues None receive body message Method called when a message is received This dispatches
95. celery concurrency eventlet TaskPool instance eventlet_pool_preshutdown Sent when the worker shutdown just before the eventlet pool is requested to wait for remaining workers Sender is the celery concurrency eventlet TaskPool instance 2 3 User Guide 125 Celery Documentation Release 3 0 25 eventlet_pool_postshutdown Sent when the pool has been joined and the worker is ready to shutdown Sender is the celery concurrency eventlet TaskPool instance eventlet_pool_apply Sent whenever a task is applied to the pool Sender is the celery concurrency eventlet TaskPool instance Provides arguments e target The target function e args Positional arguments e kwargs Keyword arguments Logging Signals setup_logging Celery won t configure the loggers if this signal is connected so you can use this to completely override the logging configuration with your own If you would like to augment the logging configuration setup by Celery then you can use the after_setup_logger and after_setup_task_logger signals Provides arguments e loglevel The level of the logging object e logfile The name of the logfile e format The log format string e colorize Specify if log messages are colored or not after_setup_logger Sent after the setup of every global logger not task loggers Used to augment logging config uration Provides arguments e logger The logger object e loglevel The level of the logging object e logfile
96. celery events C mod attr F 1 0 detach maxrate 100 m 1 info Command celery bin celeryev EvCommand sortpri 10 class celery bin celery help app None no_color False stdout lt open file lt stdout gt mode w at Ox7fb76c556150 gt stderr lt open file lt stderr gt mode w at Ox7fb76c5561e0 gt show_reply True Show help screen and exit run args kwargs sortpri 0 usage command class celery bin celery inspect app None no_color False stdout lt open file lt stdout gt mode w at Ox7fb76c556150 gt stderr lt open file lt stderr gt mode w at 0x7fb76c5561e0 gt show_reply True Inspect the worker at runtime Availability RabbitMQ amqp Redis and MongoDB transports Examples celery inspect active timeout 5 celery inspect scheduled d workerl example com celery inspect revoked d wl e com w2 e com call method args options choices scheduled 1 0 dump scheduled tasks eta countdown retry active_queues 1 0 dump queues being 294 Chapter 2 Contents Celery Documeniation Release 3 0 25 name inspect sortpri 0 class celery bin celery 1list_ app None no_color False stdout lt open file lt stdout gt mode w at 0x7fb76c556150 gt stderr lt open file lt stderr gt mode w at Ox7fb76c5561e0 gt show_reply True Get info from broker E
97. celery utils serialization Utilities for safely pickling exceptions exception celery utils serialization UnpickleableExceptionWrapper exc_module exc_cls_name exc_args text None Wraps unpickleable exceptions Parameters e exc_module see exc_module e exc_cls_name see exc_cls_name e exc_args see exc_args Example gt gt gt try something_raising_unpickleable_exc gt gt gt except Exception e exc UnpickleableException e __class__ __module__ e __class__ __name__ e args pickle dumps exc Works fine exc_args None The arguments for the original exception exc_cls_name None The name of the original exception class exc_module None The module of the original exception classmethod from_exception exc restore celery utils serialization create_exception_cls name module parent None Dynamically create an exception class celery utils serialization find_nearest_pickleable_exception exc loads lt built in function loads gt dumps lt built in function dumps gt With an exception instance iterate over its super classes by mro and find the first super exception that is pickleable It does not go below Exception ie it skips Exception BaseException and object If that happens you should use UnpickleableException instead Parameters exc An exception instance Returns the nearest exception if it s not Exception or below if it is it returns Non
98. class Scheduler object def init__ self app None self app app_or_default app In development you can set the CELERY_TRACE_APP environment variable to raise an exception if the app chain breaks CELERY_TRACE_APP 1 celery worker 1 info 40 Chapter 2 Contents Celery Documeniation Release 3 0 25 Evolving the API Celery has changed a lot in the 3 years since it was initially created For example in the beginning it was possible to use any callable as a task def hello to return hello s to gt gt gt from celery execute import apply_async gt gt gt apply_async hello world or you could also create a Task class to set certain options or override other behavior from celery task import Task from celery registry import tasks class Hello Task send_error_emails Tru def run self to return hello s to tasks register Hello gt gt gt Hello delay world Later it was decided that passing arbitrary call ables was an anti pattern since it makes it very hard to use serializers other than pickle and the feature was removed in 2 0 replaced by task decorators from celery task import task task send_error_emails True def hello x return hello s to Abstract Tasks All tasks created using the task decorator will inherit from the applications base Task class You can specify a different base class with the base argument
99. d5OwMr This means those who created their celery tables via syncdb or celeryinit with picklefield versions gt 0 1 5 has to alter their tables to allow the result field to be NULL manually MySQL ALTER TABLE celery_taskmeta MODIFY result TEXT NULL PostgreSQL ALTER TABLE celery_taskmeta ALTER COLUMN result DROP NOT NULL e Removed Task rate_limit_queue_type as it was not really useful and made it harder to refactor some parts e Now depends on carrot gt 0 10 4 e Now depends on billiard gt 0 3 0 News e AMQP backend Added timeout support for result get result wait e New task option Task acks_late default CELERY_ACKS_LATE 2 15 History 451 Celery Documeniation Release 3 0 25 Late ack means the task messages will be acknowledged after the task has been executed not just before which is the default behavior Note This means the tasks may be executed twice if the worker crashes in mid execution Not acceptable for most applications but desirable for others e Added crontab like scheduling to periodic tasks Like a cron job you can specify units of time of when you would like the task to execute While not a full implementation of cron s features it should provide a fair degree of common scheduling needs You can specify a minute 0 59 an hour 0 23 and or a day of the week 0 6 where 0 is Sunday or by names sun mon tue wed thu
100. data video O celery3 pi local Crs 4 13826 0 images data video O celery4 pi local Crp 1 1989 0 data celery5 pi local Cr 1 1983 0 data O celery6 pi local 3 2245 3 celery7 pi local Crp 3 2283 3 celery data O celery8 pi local Online 3 2279 3 celery celery9 pi local CID 3 2287 3 celery More screenshots Usage You can use pip to install Flower pip install flower Running the flower command will start a web server that you can visit celery flower The default port is http localhost 5555 but you can change this using the port argument celery flower port 5555 Broker URL can also be passed through the broker argument celery flower broker amqp guest guest localhost 5672 or celery flower broker redis guest guest localhost 6379 0 Then you can visit flower in your web browser open http localhost 5555 108 Chapter 2 Contents Celery Documeniation Release 3 0 25 e060 H Celery Flower x Wal 5 CLF localhost 5555 monitor kann S Celery Flower Workers Tasks Monitor Docs About Succeeded tasks Mon 13 Aug 2012 14 12 28 GMT 600 v BD colery9 pi iocal v E colery6 pi iocal v colery2 pi iocal v colery7 pi iocal v colery8 pi local v colory5 pi local w E colory3 pi local v BD colory4 pi local v G colery1 pi iocal celery3 pi local 135 00 celery events Curses Monitor New in version 2 0 celery events is a simple cu
101. default ConfigurationView class celery datastructures ConfigurationView changes defaults A view over an applications configuration dicts If the key does not exist in changes the defaults dicts are consulted Parameters 370 Chapter 2 Contents Celery Documeniation Release 3 0 25 e changes Dict containing changes to the configuration e defaults List of dicts containing the default configuration add_defaults d changes None defaults None first keys get key default None items iteritems iterkeys itervalues keys setdefault key default update args kwargs values ExceptionInfo class celery datastructures ExceptionInfo exc_info None internal False Exception wrapping an exception and its traceback Parameters exc_info The exception info tuple as returned by sys exc_info exception None Exception instance internal False Set to true if this is an internal error tb None Pickleable traceback instance for use with t raceback traceback None String representation of the traceback type None Exception type LimitedSet class celery datastructures LimitedSet maxlen None Kind of Set with limitations expires None data None Good for when you need to test for membership a in set but the list might become to big so you want to limit it so it doesn t consume too much resources Parameters e maxlen Maximu
102. either a task key or a control key If the message is a task it verifies the validity of the message converts it to a celery worker job Request and sends it to on_task If the message is a control command the message is passed to on_control which in turn dispatches the control command using the control dispatcher It also tries to handle malformed or invalid messages properly so the worker doesn t choke on them and die Any invalid messages are acknowledged immediately and logged so the message is not resent again and again e If the task has an ETA countdown the task is moved to the timer so the timer2 Timer can schedule it at its deadline Tasks without an eta are moved immediately to the ready_queue so they can be picked up by the Mediator to be sent to the pool e When a task with an ETA is received the QoS prefetch count is also incremented so another message can be reserved When the ETA is met the prefetch count is decremented again though this cannot happen immediately because most broker clients don t support doing broker requests across threads Instead the current prefetch 322 Chapter 2 Contents Celery Documeniation Release 3 0 25 count is kept as a shared counter so as soon as consume_messages detects that the value has changed it will send out the actual QoS event to the broker Notice that when the connection is lost all internal queues are cleared because we can no longer ack the messages rese
103. error if the program is not executable Does not modify CELERYD when using django with virtualenv 1 0 0 release date 2010 02 10 04 00 P M CET Backward incompatible changes e Celery does not support detaching anymore so you have to use the tools available on your platform or something like Supervisord to make celeryd celerybeat celerymon into background processes We ve had too many problems with celeryd daemonizing itself so it was decided it has to be re moved Example startup scripts has been added to the extra directory Debian Ubuntu start stop daemon extra debian init d celeryd extra debian init d celerybeat Mac OS X launchd extra mac org celeryq celeryd plist extra mac org celeryq celerybeat plist ex tra mac org celeryq celerymon plist Supervisord http supervisord org extra supervisord supervisord conf In addition to detach the following program arguments has been removed uid gid workdir chroot pidfile umask All good daemonization tools should support equivalent functionality so don t worry Also the following configuration keys has been removed CELERYD_PID_FILE CELERY BEAT_PID_FILE CELERYMON_PID_FILE e Default celeryd loglevel is now WARN to enable the previous log level start celeryd with loglevel INFO e Tasks are automatically registered This means you no longer have to register your tasks manually You don t have to change your old code right awa
104. extract_response raw_response loads lt function loads at 0x7fb768fc0848 gt Extract the response text from a raw JSON response celery task http maybe_ut 8 value Encode to utf 8 only if the value is Unicode celery task http utf8dict tup With a dict s items tuple return a new dict with any utf 8 keys values encoded 2 13 15 celery schedules e celery schedules j celery schedules Schedules define the intervals at which periodic tasks should run exception celery schedules ParseException Raised by crontab_parser when the input can t be parsed celery schedules cronfield s class celery schedules crontab minute hour day_of_week day_of_month month_of_year nowfun None A crontab can be used as the run_every value of a PeriodicTask to add cron like scheduling Like a cron job you can specify units of time of when you would like the task to execute It is a reasonably complete implementation of cron s features so it should provide a fair degree of scheduling needs You can specify a minute an hour a day of the week a day of the month and or a month in the year in any of the following formats minute 2 13 API Reference 259 Celery Documentation Release 3 0 25 eA list of integers from 0 59 that represent the minutes of an hour of when execution should occur or eA string representing a crontab pattern This may get pretty advanced like minute
105. failures Detailed information about using Redis Using Redis 20 Chapter 2 Contents Celery Documeniation Release 3 0 25 Using a database Using a database as a message queue is not recommended but can be sufficient for very small installations Your options include e Using SQLAlchemy e Using the Django Database If you re already using a Django database for example using it as your message broker can be convenient while developing even if you use a more robust system in production Other brokers In addition to the above there are other experimental transport implementations to choose from including Amazon SQS Using MongoDB and IronMQ See Broker Overview Installing Celery Celery is on the Python Package Index PyPI so it can be installed with standard Python tools like pip or easy_install pip install celery Application The first thing you need is a Celery instance this is called the celery application or just app in short Since this instance is used as the entry point for everything you want to do in Celery like creating tasks and managing workers it must be possible for other modules to import it In this tutorial you will keep everything contained in a single module but for larger projects you want to create a dedicated module Let s create the file tasks py from celery import Celery celery Celery tasks broker amqp guest localhost celery task def add x y
106. file system changes to all imported task modules imported and also any non task modules added to the CELERY_IMPORTS setting or the I include option This is an experimental feature intended for use in development only using auto reload in production is discouraged as the behavior of reloading a module in Python is undefined and may cause hard to diagnose bugs and crashes Celery uses the same approach as the auto reloader found in e g the Django runserver command When auto reload is enabled the worker starts an additional thread that watches for changes in the file system New modules are imported and already imported modules are reloaded whenever a change is detected and if the processes pool is used the child processes will finish the work they are doing and exit so that they can be replaced by fresh processes effectively reloading the code File system notification backends are pluggable and it comes with three implementations e inotify Linux Used if the pyinotify library is installed If you are running on Linux this is the recommended implementation to install the pyinotify library you have to run the following command S pip install pyinotify e kqueue OS X BSD 2 3 User Guide 87 Celery Documeniation Release 3 0 25 e stat The fallback implementation simply polls the files using st at and is very expensive You can force an implementation by setting the CELERYD_FSNOTIFY environment variabl
107. for delivery sent but not received messages_unacknowledged is the number of messages that has been received by a worker but not acknowledged yet meaning it is in progress or has been reserved messages is the sum of ready and unacknowledged messages Finding the number of workers currently consuming from a queue rabbitmqctl list_queues name consumers Finding the amount of memory allocated to a queue rabbitmgqctl list_queues name memory Tip Adding the q option to rabbitmqctl 1 makes the output easier to parse Redis If you re using Redis as the broker you can monitor the Celery cluster using the redis cli 1 command to list lengths of queues Inspecting queues Finding the number of tasks in a queue redis cli h HOST p PORT n DATABASE NUMBER llen QUEUE_NAME The default queue is named celery To get all available queues invoke redis cli h HOST p PORT n DATABASE_NUMBER keys Note Queue keys only exists when there are tasks in them so if a key does not exist it simply means there are no messages in that queue This is because in Redis a list with no elements in it is automatically removed and hence it won t show up in the keys command output and llen for that list returns 0 Also if you re using Redis for other purposes the output of the keys command will include unrelated values stored in the database The recommended way around this is to use a de
108. for historical reasons Now you can start server z to only process the feeds queue like this user z S celery worker Q feeds You can specify as many queues as you want so you can make this server process the default queue as well user z S celery worker Q feeds celery Changing the name of the default queue You can change the name of the default queue by using the following configuration 2 3 User Guide 97 Celery Documentation Release 3 0 25 from kombu import Exchange Queue CELERY_DEFAULT_QUEUE default CELERY_QUEUES Queue default Exchange default routing_key default How the queues are defined The point with this feature is to hide the complex AMQP protocol for users with only basic needs However you may still be interested in how these queues are declared A queue named video will be created with the following settings exchange video exchange_type direct routing_key videod The non AMQP backends like ghettog does not support exchanges so they require the exchange to have the same name as the queue Using this design ensures it will work for them as well Manual routing Say you have two servers x and y that handles regular tasks and one server z that only handles feed related tasks you can use this configuration from kombu import Queue CE
109. for new greenlets Eventlet gevent Fixed a bug where the worker could not recover from connection loss Issue 959 Also because of a suspected bug in gevent the BROKER_CONNECTION_TIMEOUT setting has been disabled when using gevent 2 12 17 3 0 9 release date 2012 08 31 06 00 PM BST Important note for users of Django and the database scheduler Recently a timezone issue has been fixed for periodic tasks but erroneous timezones could have already been stored in the database so for the fix to work you need to reset the last_run_at fields You can do this by executing the following command 220 Chapter 2 Contents Celery Documeniation Release 3 0 25 S python manage py shell gt gt gt from djcelery models import PeriodicTask gt gt gt PeriodicTask objects update last_run_at None You also have to do this if you change the timezone or CELERY_ENABLE_UTC setting Note about the CELERY_ENABLE_UTC setting If you previously disabled this just to force periodic tasks to work with your timezone then you are now encouraged to re enable it Now depends on Kombu 2 4 5 which fixes PyPy Jython installation Fixed bug with timezones when CELERY_ENABLE_UTC is disabled Issue 952 Fixed a typo in the celerybeat upgrade mechanism Issue 951 Make sure the exc_info argument to logging is resolved Issue 899 Fixed problem with Python 3 2 and thre
110. from remote workers celery inspect report Module celery log moved to celery app log Module celery task control moved to celery app control New signal task_revoked Sent in the main process when the task is revoked or terminated AsyncResult task_idrenamed to AsyncResult id TasksetResult taskset_idrenamed to id xmap task sequence and xstarmap task sequence Returns a list of the results applying the task function to every item in the sequence Example gt gt gt from celery import xstarmap gt gt gt xstarmap add zip range 10 range 10 apply_async 0 2 4 6 8 10 12 14 16 18 chunks task sequence chunksize group skew start stop step Skew will skew the countdown for the individual tasks in a group e g with a group gt gt gt g group add s i i for i in xrange 10 Skewing the tasks from 0 seconds to 10 seconds gt gt gt g skew stop 10 Will have the first task execute in 0 seconds the second in 1 second the third in 2 seconds and so on 99 test Coverage CELERY_QUEUES can now be a list tuple of Queue instances Internally celery amqp queues is now a mapping of name Queue instances instead of con verting on the fly Can now specify connection for celery control inspect from kombu import Connection i celery control inspect connection Connection redis i active_queues CELERY_FORCE_EXECV is now enabled by default
111. function and a list of keyword arguments returns arguments in the list which the function takes If the object has an argspec attribute that is used instead of using the inspect getargspec introspection Parameters e fun The function to inspect arguments of e kwlist The list of keyword arguments Examples 376 Chapter 2 Contents Celery Documeniation Release 3 0 25 gt gt gt def foo self x y logfile None loglevel None ai return x y gt gt gt fun_takes_kwargs foo logfile loglevel task_id logfile loglevel gt gt gt def foo self x y xkwargs gt gt gt fun_takes_kwargs foo logfile loglevel task_id logfile loglevel task_id celery utils gen_task_name app name module_name celery utils is_iterable obj celery utils isatty fh celery utils jsonify obj Transforms object making it suitable for json serialization celery utils lpmerge L R In place left precedent dictionary merge Keeps values from L if the value in R is None celery utils maybe_reraise Reraise if an exception is currently being handled or return otherwise celery utils strtobool term table l True 0 False false False no False off False yes True on True true True celery utils warn_deprecated description None deprecation None removal None altern
112. guide to the codebase e Versions e Branches master branch Maintenance branches Archived branches Feature branches e Tags e Working on Features amp Patches Forking and setting up the repository Running the unit test suite Creating pull requests x Calculating test coverage x Running the tests on all supported Python versions Building the documentation Verifying your contribution pyflakes amp PEP8 x API reference e Coding Style e Contacts Committers x Ask Solem x Mher Movsisyan Steeve Morin Website Mauro Rocco x Jan Henrik Helmers e Packages celery kombu billiard librabbitmq celerymon django celery cl cyme Deprecated e Release Procedure Updating the version number Releasing Updating bundles 152 Chapter 2 Contents Celery Documeniation Release 3 0 25 2 6 1 Community Code of Conduct The goal is to maintain a diverse community that is pleasant for everyone That is why we would greatly appreciate it if everyone contributing to and interacting with the community also followed this Code of Conduct The Code of Conduct covers our behavior as members of the community in any forum mailing list wiki website Internet relay chat IRC public meeting or private correspondence The Code of Conduct is heavily based on the Ubuntu Code of Conduct and the Pylons Code of Conduct Be considerate Your work will be used by o
113. higher level interfaces using broadcast in the background like rate_limit andping Sending the rate_1imit command and keyword arguments gt gt gt celery control broadcast rate_limit arguments task_name myapp mytask Crawemlsuminey Y2i0 0 mes This will send the command asynchronously without waiting for a reply To request a reply you have to use the reply argument gt gt gt celery control broadcast rate_limit task_name myapp mytask rate_limit 200 m reply True workerl example com New rat cces K limit se successfully r 82 Chapter 2 Contents Celery Documeniation Release 3 0 25 Using the destination argument you can specify a list of workers to receive the command gt gt gt celery control broadcast rate_limit task_name myapp mytask rate_limit 200 m reply True destination workerl example com workerl example com New rate limit set suc sfully Of course using the higher level interface to set rate limits is much more convenient but there are commands that can only be requested using broadcast Revoking tasks pool support all broker support amgp redis mongodb All worker nodes keeps a memory of revoked task ids either in memory or persistent on disk see Persistent revokes When a worker receives a revoke request it will skip executing the t
114. is not included in the Python Standard Library Task settings CELERY_ANNOTATIONS This setting can be used to rewrite any task attribute from the configuration The setting can be a dict or a list of annotation objects that filter for tasks and return a map of attributes to change This will change the rate_limit attribute for the tasks add task CELERY_ANNOTATIONS tasks add rate_limit 10 s or change the same for all tasks CELERY_ANNOTATIONS x rate_limit 10 s You can change methods too for example the on_failure handler def my_on_failure self exc task_id args kwargs einfo o print Oh no Task failed r exc CELERY_ANNOTATIONS x on_failure my_on_failure If you need more flexibility then you can use objects instead of a dict to choose which tasks to annotate 128 Chapter 2 Contents Celery Documeniation Release 3 0 25 class MyAnnotate object def annotate self task if task name startswith tasks return cate limitet Mil0i 7 si CELERY_ANNOTATIONS MyAnnotate Concurrency settings CELERYD_CONCURRENCY The number of concurrent worker processes threads green threads executing tasks If you re doing mostly I O you can have more processes but if mostly CPU bound try to keep it close to the number of CPUs on your machine If not set the number of CPUs cores on the hos
115. is now always initialized to ensure calling the task function directly works even if it actively uses the request context 2 15 History 413 Celery Documentation Release 3 0 25 2 2 e Exception occuring when iterating over the result from TaskSet apply fixed e eventlet Now properly schedules tasks with an ETA in the past 4 release date 2011 02 19 12 00 AM CET Fixes 2 2 e celeryd 2 2 3 broke error logging resulting in tracebacks not being logged AMQP result backend Polling task states did not work properly if there were more than one result message in the queue TaskSet apply_async and TaskSet apply now supports an optional taskset_id keyword argument Issue 331 The current taskset id if any is now available in the task context as request taskset Issue 329 SQLAlchemy result backend date_done was no longer part of the results as it had been accidentally removed It is now available again Issue 325 SQLAlchemy result backend Added unique constraint on Task id and TaskSet taskset_id Tables needs to be recreated for this to take effect Fixed exception raised when iterating on the result of TaskSet apply Tasks Userguide Added section on choosing a result backend 3 release date 2011 02 12 04 00 PM CET Fixes Now depends on Kombu 1 0 3 Task retry now supports amax_retries argument used to change the default value multiprocessing cpu_count may raise Not Imp lem
116. its eta is e g a week into the future The task_id argument is now respected even if the task is executed eagerly either using apply or CELERY_ALWAYS_EAGER The internal queues are now cleared if the connection is reset New magic keyword argument delivery_info Used by retry to resend the task to its original destination using the same exchange routing_key Events Fields was not passed by send fixes the UUID key errors in celerymon Added schedule s option to celeryd so it is possible to specify a custom schedule filename when using an embedded celerybeat server the B beat option Better Python 2 4 compatibility The test suite now passes task decorators Now preserve docstring as cls __doc__ was previously copied to cls run __doc__ 2 15 History 457 Celery Documentation Release 3 0 25 e The festproj directory has been renamed to fests and we re now using nose django nose for test discovery and unittest2 for test cases e New pip requirements files available in requirements e TaskPublisher Declarations are now done once per process e Added Task delivery_mode and the CELERY_DEFAULT_DELIVERY_MODE setting These can be used to mark messages non persistent i e so they are lost if the broker is restarted e Now have our own ImproperlyConfigured exception instead of using the Django one e Improvements to the Debian init scripts Shows an
117. key used to route the task to a worker server If in combination with a queue argument only used to specify custom routing keys to topic exchanges e queue The queue to route the task to This must be a key present in CELERY_QUEUES or CELERY_CREATE_MISSING_QUEUES must be enabled See Routing Tasks for more information e exchange Named custom exchange to send the task to Usually not used in combi nation with the queue argument e priority The task priority a number between 0 and 9 Defaults to the priority attribute e serializer A string identifying the default serialization method to use Can be pickle json yaml msgpack or any custom serialization method that has been registered with kombu serialization registry Defaults to the serializer attribute e compression A string identifying the compression method to use Can be one of zlib bzip2 or any custom compression methods reg istered with kombu compression register Defaults to the CELERY_MESSAGE_COMPRESSION setting 236 Chapter 2 Contents Celery Documeniation Release 3 0 25 e link A single or a list of subtasks to apply if the task exits successfully e link_error A single or a list of subtasks to apply if an error occurs while executing the task e producer class amgqp TaskProducer instance to use e add_to_parent If set to True default
118. make up for the time you lose upgrading so be sure to read the News section Quite a lot of potential users have been upset about the Django dependency so maybe this is a chance to get wider adoption by the Python community as well Big thanks to all contributors testers and users Upgrading for Django users Django integration has been moved to a separate package django celery e To upgrade you need to install the django celery module and change 2 15 History 439 Celery Documentation Release 3 0 25 INSTALLED_APPS celery to INSTALLED_APPS djcelery e If you use mod_wsgi you need to add the following line to your wsgi file import os os environ CELERY_LOADER django e The following modules has been moved to django celery Module name Replace with celery models djcelery models celery managers djcelery managers celery views djcelery views celery urls djcelery urls celery management djcelery management celery loaders djangoapp djcelery loaders celery backends database djcelery backends database celery backends cache djcelery backends cache Importing djcelery will automatically setup Celery to use Django loader loader It does this by setting the CELERY_LOADER environment variable to django it won t change it if a loader is already set When the Django loader is used the database and cache result backend aliases will point
119. manual Thanks to Honza Kral and Anton Tsigularov for this solution celeryd is not doing anything just hanging Answer See MySQL is throwing deadlock errors what can I do or Why is Task delay apply just hanging 176 Chapter 2 Contents Celery Documeniation Release 3 0 25 Task results aren t reliably returning Answer If you re using the database backend for results and in particular using MySQL see MySQL is throwing deadlock errors what can I do Why is Task delay apply celeryd just hanging Answer There is a bug in some AMQP clients that will make it hang if it s not able to authenticate the current user the password doesn t match or the user does not have access to the virtual host specified Be sure to check your broker logs for RabbitMQ that is var log rabbitmq rabbit 1log on most systems it usually contains a message describing the reason Does it work on FreeBSD Answer The multiprocessing pool requires a working POSIX semaphore implementation which isn t enabled in FreeBSD by default You have to enable POSIX semaphores in the kernel and manually recompile multiprocessing Luckily Viktor Petersson has written a tutorial to get you started with Celery on FreeBSD here http www playingwithwire com 2009 10 how to get celeryd to work on freebsd I m having IntegrityError Duplicate Key errors Why Answer See MySQL is throwing deadlock errors what can I do Thanks to howsthedotcom
120. module The avail able configuration options and their types can now be introspected e Remote control commands are now provided by kombu pidbox the generic process mailbox 2 15 History 419 Celery Documentation Release 3 0 25 e Internal module celery worker listener has been renamed to celery worker consumer and CarrotListener is now Consumer e Previously deprecated modules celery models and celery management commands have now been removed as per the deprecation timeline Security Low severity Removed celery task RemoteExecuteTask and accompanying functions dmap_async and execute_remote Executing arbitrary code using pickle is a potential security issue if someone gains unrestricted access to the message broker If you really need this functionality then you would have to add this to your own project e Security Low severity The stats command no longer transmits the broker password One would have needed an authenticated broker connection to receive this password in the first place but sniffing the password at the wire level would have been possible if using unencrypted communication News e The internal module celery task builtins has been removed e The module celery task schedules is deprecated and celery schedules should be used instead For example if you have from celery task schedules import crontab You should replace that with from celery schedules import crontab The module
121. needs to be renamed because it must be possible to import schedules without importing the celery task module e The following functions have been deprecated and is scheduled for removal in version 2 3 celery execute apply_async Use task apply_async instead celery execute apply Jse task apply instead celery execute delay_task Use registry tasks name delay instead e Importing TaskSet from celery task base is now deprecated You should use gt gt gt from celery task import TaskSet instead e New remote control commands active_queues 420 Chapter 2 Contents Celery Documeniation Release 3 0 25 Returns the queue declarations a worker is currently consuming from e Added the ability to retry publishing the task message in the event of connection loss or failure This is disabled by default but can be enabled using the CELERY_TASK_PUBLISH_RETRY set ting and tweaked by the CELERY_TASK_PUBLISH_RI ETRY_POLICY setting In addition retry and retry_policy keyword arguments have been added to Task apply_async Note Using the retry argument to apply_async requires you to handle the publisher connection manually e Periodic Task classes periodic_task PeriodicTask will not be deprecated as previously indicated in the source code But you are encouraged to use the more flexible CELERYBEAT_SCHEDULE setting
122. on OS X because of a limitation on that platform Process Signals The worker s main process overrides the following signals TERM Warm shutdown wait for tasks to complete QUIT Cold shutdown terminate ASAP USR1 Dump traceback for all active threads USR2 Remote debug see celery contrib rdb Concurrency By default multiprocessing is used to perform concurrent execution of tasks but you can also use Eventlet The number of worker processes threads can be changed using the concurrency argument and defaults to the number of CPUs available on the machine 2 3 User Guide 81 Celery Documentation Release 3 0 25 Number of processes multiprocessing More pool processes are usually better but there s a cut off point where adding more pool processes affects perfor mance in negative ways There is even some evidence to support that having multiple worker instances running may perform better than having a single worker For example 3 workers with 10 pool processes each You need to exper iment to find the numbers that works best for you as this varies based on application work load task run times and other factors Remote control New in version 2 0 The celery command The celery program is used to execute remote control commands from the command line It supports all of the commands listed below See celery Command Line Management Utility for more information pool suppor
123. option only affects the database backend Example configuration CELERY_RESULT_BACKEND database CELERY_RESULT_DBURI mysql user password host dbname AMQP backend settings Note The AMQP backend requires RabbitMQ 1 1 0 or higher to automatically expire results If you are running an older version of RabbitmQ you should disable result expiration like this CELERY_TASK_RESULT_EXPIRES None CELERY_RESULT_EXCHANGE Name of the exchange to publish results in Default is celeryresults 130 Chapter 2 Contents Celery Documeniation Release 3 0 25 CELERY_RESULT_EXCHANGE_TYPE The exchange type of the result exchange Default is to use a direct exchange CELERY_RESULT_PERSISTENT If set to True result messages will be persistent This means the messages will not be lost after a broker restart The default is for the results to be transient Example configuration Q Hi ELERY_RESULT_BACKEND amqp IERY_TASK_RESULT_EXPIRES 18000 5 hours Q iiri Cache backend settings Note The cache backend supports the pylibmc and python memcached libraries The latter is used only if pylibmc is not installed CELERY_CACHE_BACKEND Using a single memcached server CELERY_CACHE_BACKEND memcached 127 0 0 1 11211 Using multiple memcached servers CELERY_RESULT_BACKEND cache CELERY_CACH
124. perfor mance it is the only safe option for older Python versions News e celeryev Curses Celery Monitor and Event Viewer This is a simple monitor allowing you to see what tasks are executing in real time and investigate tracebacks and results of ready tasks It also enables you to set new rate limits and revoke tasks Screenshot If you run celeryev with the d switch it will act as an event dumper simply dumping the events it receives to standard out S celeryev d gt celeryev starting capture casper local 2010 06 04 10 42 07 020000 heartbeat casper local 2010 06 04 10 42 14 750000 task received tasks add 61a68756 27 4 4879 b816 3cf815672b0e args 2 2 kwargs eta 2010 06 04T10 42 16 669290 retries 0 casper local 2010 06 04 10 42 17 230000 task started tasks add 61a68756 27 4 4879 b816 3cf815672b0e args 2 2 kwargs casper local 2010 06 04 10 42 17 960000 task succeeded tasks add 61a68756 27f 4 4879 b816 3cf815672b0e args 2 2 kwargs result 4 runtime 0 782663106918 The fields here are in order xsender hostnamex xtimestamp xevent type and xadditional event fields e AMQP result backend Now supports ready successful result status and even responds to changes in task state e New user guides Workers Guide 442 Chapter 2 Contents Celery Documeniation Release 3 0 25 2 15 History 443 Celery Documentation Release 3 0
125. purge the queue of waiting tasks you have to stop all the workers and then purge the tasks using celery control purge 2 9 4 Results How do get the result of a task if have the ID that points there Answer Use task AsyncResult gt gt gt result my_task AsyncResult task_id gt gt gt result get 178 Chapter 2 Contents Celery Documeniation Release 3 0 25 This will give you a AsyncResulLt instance using the tasks current result backend If you need to specify a custom result backend or you want to use the current application s default backend you can use Celery AsyncResult gt gt gt result app AsyncResult task_id gt gt gt result get 2 9 5 Security Isn t using pickle a security concern Answer Yes indeed it is You are right to have a security concern as this can indeed be a real issue It is essential that you protect against unauthorized access to your broker databases and other services transmitting pickled data For the task messages you can set the CELERY_TASK_SERIALIZER setting to json or yaml instead of pickle There is currently no alternative solution for task results but writing a custom result backend using JSON is a simple task Note that this is not just something you should be aware of with Celery for example also Django uses pickle for its cache client Can messages be encrypted Answer Some AMQP brokers supports using SSL
126. rabbit node should now be rabbit myhost as verified by rabbitmactl sudo rabbitmqcetl status Status of node rabbit myhost running_applications rabbit RabbitMO 1 7 1 mnesia MNESIA CXC 138 12 4 4 12 fos_mon GPO EIES Ye sasl EAS MG XC PC CmeInIA S stdlib YEN Ee ee T kernel KERTO Re C Eee LETA E nodes rabbit myhost running_nodes rabbit myhost sre done This is especially important if your DHCP server gives you a host name starting with an IP address e g 23 10 112 31 comcast net because then RabbitMQ will try to use rabbit 23 which is an illegal host name Starting Stopping the RabbitMQ server To start the server sudo rabbitmq server you can also run it in the background by adding the detached option note only one dash sudo rabbitmq server detached Never use kill to stop the RabbitMQ server but rather use the rabbitmqctl command sudo rabbitmqctl stop When the server is running you can continue reading Setting up RabbitMQ 12 Chapter 2 Contents Celery Documeniation Release 3 0 25 Using Redis Installation For the Redis support you have to install additional dependencies You can install both Celery and these dependencies in one go using either the celery with redis or the django celery with redis bundles pip install U celery with redis Configuration Configuration is easy just configure the location of your R
127. range 10 range 10 0 2 4 6 8 10 12 14 16 18 is the same as having a task doing celery task def temp return add i i for i in range 10 Both map and st armap are subtasks so they can be used as other subtasks and combined in groups etc for example to call the starmap after 10 seconds gt gt gt add starmap zip range 10 range 10 apply_async countdown 10 Chunks Chunking lets you divide an iterable of work into pieces so that if you have one million objects you can create 10 tasks with hundred thousand objects each Some may worry that chunking your tasks results in a degradation of parallelism but this is rarely true for a busy cluster and in practice since you are avoiding the overhead of messaging it may considerably increase performance To create a chunks subtask you can use celery Task chunks gt gt gt add chunks zip range 100 range 100 10 As with group the act of calling the chunks will call the tasks in the current process gt gt gt from proj tasks import add gt gt gt res add chunks zip range 100 range 100 10 gt gt gt res get Ll Oy 2y 44 6 By 10 12 14 1b 1813 20 22 24 26 28 30 3 4 30 40 42 44 46 48 50 2 3 User Guide 79 Celery Documentation Release 3 0 25 while calling apply_async will create a dedicated task so that the individual tasks are applied in a worker instead gt gt gt add chunks
128. retry for the worker by using the celeryd_after_setup signal from celery signals import celeryd_after_setup celeryd_after_setup connect def configure_worker instance conf xkwargs conf CELERY_ TASK PUBLISH RETRY POLICY max_retries 100 Cimeecrviciuastartrteu 0 Pimtcnvciamaxa 1 interval_step 0 2 e Worker Will now properly display message body in error messages even if the body is a buffer instance e 3 0 18 broke the MongoDB result backend Issue 1303 2 12 Change history 209 Celery Documentation Release 3 0 25 2 12 8 3 0 18 release date 2013 04 12 05 00 00 P M BST Now depends on kombu 2 5 10 See the kombu changelog Now depends on billiard 2 7 3 27 Can now specify a whitelist of accepted serializers using the new CELERY_ACCEPT_CONTENT setting This means that you can force the worker to discard messages serialized with pickle and other untrusted serializers For example to only allow JSON serialized messages use CELERY_ACCEPT_CONTENT json you can also specify MIME types in the whitelist CELERY_ACCEPT_CONTENT application json Fixed deadlock in multiprocessing s pool caused by the semaphore not being released when terminated by signal Processes Pool It s now possible to debug pool processes using GDB celery report now censors possibly secret settings like
129. run celery n pid logfile var log celery n log You need to add the same arguments when you restart as these are not persisted anywhere S celeryd multi restart Lesli E pidfile var run celery n pid logfile var run celery n log To stop the node you need to specify the same pidfile S celeryd multi stop Lesli pidfile var run celery n pid 3 workers with 3 processes each S celeryd multi start 3 c 3 celeryd n celerydl myhost c 3 celeryd n celeryd2 myhost c 3 celeryd n celeryd3 myhost c 3 start 3 named workers S celeryd multi start image video data c 3 celeryd n image myhost c 3 celeryd n video myhost c 3 celeryd n data myhost c 3 Aa QAU V H H VN QA QA Q UO H specify custom hostname celeryd multi start 2 n worker example com c 3 leryd n celerydl worker example com c 3 leryd n celeryd2 worker example com c 3 Advanced example starting 10 workers in the background x Three of the workers processes the images and video queue x Two of the workers processes the data queue with loglevel DEBUG x the rest processes the default queue celeryd multi start 10 1 INFO Q 1 3 images video Q 4 5 data Q default L 4 5 DEBUG You can show the commands necessary to start the workers with the show command celeryd multi show 10 1 INFO Q 1 3 images video Q 4 5 data Q default L 4 5 DEBUG Additional options are a
130. s retry exc s Format string used to log task retry revoked If revoked skip task and mark state send_event type fields 2 14 Internals 327 Celery Documentation Release 3 0 25 shortinfo store_errors success_msg Task name s id s succeeded in runtime ss return_value s n Format string used to log task success task task_id task_name terminate pool signal None time_start tzlocal utc worker pid class celery worker job TaskRequest name id args kwargs eta None expires None options celery worker mediator e celery worker mediator j celery worker mediator The mediator is an internal thread that moves tasks from an internal Queue to the worker pool This is only used if rate limits are enabled as it moves messages from the rate limited queue which holds tasks that are allowed to be processed to the pool Disabling rate limits will also disable this machinery and can improve performance class celery worker mediator Mediator ready_queue callback app None kw Mediator thread body callback None Callback called when a task is obtained ready_queue None The task queue a Queue instance class celery worker mediator WorkerComponent w kwargs create w include_if w name mediator namespace worker requires pool queues 328 Chapter 2 Contents Celery Documeniation
131. s 8 gt gt gt res c2 gt gt gt res get 352 Chaining a group together with another task will automatically upgrade it to be a chord xsum s gt gt gt c3 group add s i i for i in xrange 10 gt gt gt res c3 gt gt gt res get 90 Groups and chords accepts partial arguments too so in a chain the return value of the previous task is forwarded to all tasks in the group gt gt gt new_user_workflow create_user s group import_contacts s send_welcome_email s new_user_workflow delay username artv first Art last Vandelay email art vandelay com If you don t want to forward arguments to the group then you can make the subtasks in the group immutable gt gt gt res add s 4 4 group add si i i for i in xrange 10 gt gt gt res get lt GroupResult bc01831b 94 gt gt gt res parent get 72 Chapter 2 Contents Celery Documeniation Release 3 0 25 Chains New in version 3 0 Tasks can be linked together which in practice means adding a callback task gt gt gt res add apply_async 2 2 link mul s 16 gt gt gt res get 4 The linked task will be applied with the result of its parent task as the first argument which in the above case will resultin mul 4 16 since the result is 4 The results will keep track of what subtasks a task applies and this can be accessed from th
132. s now outputs how the sequence would like imperatively gt gt gt from celery import chord i for i in xrange 10 gt gt gt chord add s i xsum s pow s 2 New remote control commands These commands were previously experimental but they have proven stable and is now documented as part of the offical API e add_consumer cancel_consumer Tells workers to consume from a new queue or cancel consuming from a queue This command has also been changed so that the worker remembers the queues added so that the change will persist even if the connection is re connected These commands are available programmatically as celery control add_consumer celery control cancel_consumer gt gt gt celery control add_consumer queue_name destination wl example com gt gt gt celery control cancel_consumer queue_name destination wl example com or using the celery control command 190 Chapter 2 Contents Celery Documeniation Release 3 0 25 S celery control d wl example com add_consumer queue S celery control d wl example com cancel_consumer queue Note Remember that a control command without destination will be sent to all workers autoscale Tells workers with autoscale enabled to change autoscale max min concurrency settings This command is available programmatically as celery control autoscale gt gt gt celery control autoscale max 10 min 5 destinat
133. serialization e celery security serialization celery security serialization Secure serializer class celery security serialization SecureSerializer key None cert None cert_store None digest shal serializer json deserialize data deserialize data structure from string serialize data serialize data structure into string celery security serialization b64decode s celery security serialization b64encode s celery security serialization register_auth key None cert None store None di gest shal serializer json register security serializer celery security utils e celery security utils j 2 14 Internals 369 Celery Documentation Release 3 0 25 celery security utils Utilities used by the message signing serializer celery security utils reraise_errors args kwds celery datastructures Custom types and data structures e AttributeDict e DictAttribute e ConfigurationView e ExceptionInfo e LimitedSet e LRUCache AttributeDict class celery datastructures AttributeDict Dict subclass with attribute access class celery datastructures AttributeDictMixin Adds attribute access to mappings d key gt d key DictAttribute class celery datastructures DictAttribute obj Dict interface to attributes obj k gt obj k get key default None items iteritems iterkeys keys obj None setdefault key
134. sets TaskSet gt app TaskSet e celery decorators celery task task gt app task e celery execute e celery log apply_async gt task apply_async apply gt task apply send_task gt app send_task delay_task gt no alternative get_default_logger gt app log get_default_logger setup_logger gt app log setup_logger get_task_logger gt app log get_task_logger setup_task_logger gt app log setup_task_logger 316 Chapter 2 Contents Celery Documeniation Release 3 0 25 setup_logging subsystem gt app log setup_logging subsystem redirect_stdouts_to_logger gt app log redirect_stdouts_to_logger celery messaging establish_connection gt app broker_connection with_connection gt app with_connection get_consumer_set gt app amqp get_task_consumer TaskPublisher gt app amqp TaskPublisher TaskConsumer gt app amqp TaskConsumer ConsumerSet gt app amqp ConsumerSet e celery conf gt app conf NOTE All configuration keys are now named the same as in the configuration So the key CEL ERY ALWAYS _EAGER is accessed as gt gt gt app conf CELERY_ALWAYS_EAGER instead of gt gt gt from celery import conf gt gt gt conf ALWAYS_EAGER get_queues gt app amqp get_queues e celery task control broadcast gt app control broadcast
135. setting current provides the currently executing task In Other News e Fixes 2 11 1 Important Notes Broker connection pool now enabled by default The default limit is 10 connections if you have many threads green threads using connections at the same time you may want to tweak this limit to avoid contention See the BROKER_POOL_LIMIT setting for more information 198 Chapter 2 Contents Celery Documeniation Release 3 0 25 Also note that publishing tasks will be retried by default to change this default or the default retry policy see CELERY_TASK_PUBLISH_RETRY and CELERY_TASK_PUBLISH_RETRY_POLICY Rabbit Result Backend Exchange is no longer auto delete The exchange used for results in the Rabbit AMQP result backend used to have the auto_delete flag set which could result in a race condition leading to an annoying warning For RabbitMQ users Old exchanges created with the auto_delete flag enabled has to be removed The camqadm command can be used to delete the previous exchange camqadm exchange delete celeryresults As an alternative to deleting the old exchange you can configure a new name for the exchange CELERY_RESULT_EXCHANGE celeryresults2 But you have to make sure that all clients and workers use this new setting so they are updated to use the same exchange name Solution for hanging workers but m
136. setup using syslog see also syslog ng and rsyslog Celery uses the Logging library and already has support for using syslog A tip for the paranoid is to send logs using UDP and cut the transmit part of the logging server s network cable Tripwire Tripwire is a now commercial data integrity tool with several open source implementations used to keep crypto graphic hashes of files in the file system so that administrators can be alerted when they change This way when the damage is done and your system has been compromised you can tell exactly what files intruders have changed password files logs backdoors rootkits and so on Often this is the only way you will be able to detect an intrusion Some open source implementations include e OSSEC 118 Chapter 2 Contents Celery Documeniation Release 3 0 25 e Samhain e Open Source Tripwire e AIDE Also the ZFS file system comes with built in integrity checks that can be used 2 3 11 Optimizing Introduction The default configuration makes a lot of compromises It s not optimal for any single case but works well enough for most situations There are optimizations that can be applied based on specific use cases Optimizations can apply to different properties of the running environment be it the time tasks take to execute the amount of memory used or responsiveness at times of high load Ensuring Operations In the book Programming Pearls Jon Bentley pr
137. simply be ignored so make sure you re running a version that supports it CELERY_ACCEPT_CONTENT json This accepts a list of serializer names and content types so you could also specify the content type for json CELERY_ACCEPT_CONTENT application json Celery also comes with a special auth serializer that validates communication between Celery clients and workers making sure that messages originates from trusted sources Using Public key cryptography the auth serializer can verify the authenticity of senders to enable this read Message Signing for more information 1 http nadiana com python pickle insecure 2 3 User Guide 117 Celery Documeniation Release 3 0 25 Message Signing Celery can use the pyOpenSSL library to sign message using Public key cryptography where messages sent by clients are signed using a private key and then later verified by the worker using a public certificate Optimally certificates should be signed by an official Certificate Authority but they can also be self signed To enable this you should configure the CELERY_TASK_SERIALIZER setting to use the auth serializer Also required is configuring the paths used to locate private keys and certificates on the _ file system the CELERY SECURITY_KEY CELERY _SECURITY_CERTIFICATE and CELERY_SECURITY_CERT_STORE settings respectively With these configured it is als
138. t have any way to handle the errors that might happen which may even be database dependent See http bit ly 94fwdd e celeryd The worker components are now configurable CELERYD_POOL CELERYD_CONSUMER CE L ERYD_MEDIATOR and CELERYD_ETA_SCHEDULER The default configuration is as follows ERYD_POOL celery concurrency processes TaskPool ERYD_MEDIATOR celery worker controllers Mediator ERYD_ETA_SCHEDULER celery worker controllers ScheduleController ERYD_CONSUMER celery worker consumer Consumer Oe OE OO The CELERYD_POOL setting makes it easy to swap out the multiprocessing pool with a threaded pool or how about a twisted eventlet pool Consider the competition for the first pool plug in started e Debian init scripts Use a not amp amp Issue 82 e Debian init scripts Now always preserves CELERYD_OPTS from the etc default celeryd and etc default celerybeat e celery beat Scheduler Fixed a bug where the schedule was not properly flushed to disk if the schedule had not been properly initialized e celerybeat Now syncs the schedule to disk when receiving the SIGTERM and SIGINT signals e Control commands Make sure keywords arguments are not in Unicode e ETA scheduler Was missing a logger object so the scheduler crashed when trying to log that a task had
139. task trace setup_worker_optimizations app 366 Chapter 2 Contents Celery Documeniation Release 3 0 25 celery task trace task_has_custom task attr Returns true if the task or one of its bases defines att r excluding the one in BaseTask celery task trace trace_task task uuid args kwargs request opts celery task trace trace_task_ret name uuid args kwargs request opts celery app abstract e celery app abstract j celery app abstract Abstract class that takes default attribute values from the configuration class celery app abstract configurated confopts_as_dict setup_defaults kwargs namespace celery class celery app abstract from_config key None get_key atir celery app annotations e celery app annotations j celery app annotations Annotations is a nice term for moneky patching task classes in the configuration This prepares and performs the annotations in the CELERY_ANNOTATIONS setting class celery app annotations MapAnnotation annotate task annotate_any celery app annotations prepare annotations Expands the CELERY_ANNOTATIONS setting celery app annotations resolve_all anno task 2 14 Internals 367 Celery Documentation Release 3 0 25 celery app routes g celery routes j celery routes 7 Contains utilities for working with task routers CELERY_ROUTES class c
140. the log AMQP Backend No longer deletes the result queue after successful poll as this should be handled by the CELERY_AMOP_TASK_RESULT_EXPIRES setting instead AMQP Backend Now ensures queues are declared before polling results Windows celeryd Show error if running with B option Running celerybeat embedded is known not to work on Windows so users are encouraged to run celerybeat as a separate service instead Windows Utilities no longer output ANSI color codes on Windows camqadm Now properly handles Ctrl C by simply exiting instead of showing confusing traceback Windows All tests are now passing on Windows Remove bin directory and scripts section from setup py This means we now rely completely on setuptools entrypoints Experimental e Jython celeryd now runs on Jython using the threaded pool All tests pass but there may still be bugs lurking around the corners e PyPy celeryd now runs on PyPy It runs without any pool so to get parallel execution you must start multiple instances e g using celeryd multi Sadly an initial benchmark seems to show a 30 performance decrease on pypy 1 4 1 JIT We would like to find out why this is so stay tuned e PublisherPool Experimental pool of task publishers and connections to be used with the retry argument to apply_async The example code below will re use connections and channels and retry sending of the task message if the connectio
141. the new USE_TZ setting introduced in Django 1 4 2 3 User Guide 91 Celery Documeniation Release 3 0 25 For Django users the time zone specified in the TIME_ZONE setting will be used or you can specify a custom time zone for Celery alone by using the CELERY_TIMEZONE setting The database scheduler will not reset when timezone related settings change so you must do this manually S python manage py shell gt gt gt from djcelery models import PeriodicTask gt gt gt PeriodicTask objects update last_run_at None Entries To schedule a task periodically you have to add an entry to the CELERYBEAT_SCHEDULE setting Example Run the tasks add task every 30 seconds from datetime import timedelta CELERYBEAT SCHEDULE add every 30 seconds aSk tasks edo schedule timedelta seconds 30 wewagcm 16 16 br CELERY_TIMEZONE UTC Using a timedelta for the schedule means the task will be sent in 30 second intervals the first task will be sent 30 seconds after celery beat starts and then every 30 seconds after the last run A crontab like schedule also exists see the section on Crontab schedules Like with cron the tasks may overlap if the first task does not complete before the next If that is a concern you should use a locking strategy to ensure only one instance can run at a time
142. the real time Celery monitor which you can read about in the Monitoring and Management guide Queues is the list of queues that the worker will consume tasks from The worker can be told to consume from several queues at once and this is used to route messages to specific workers as a means for Quality of Service separation of concerns and emulating priorities all described in the Routing Guide You can get a complete list of command line arguments by passing in the help flag celery worker help These options are described in more detailed in the Workers Guide Stopping the worker To stop the worker simply hit Ctrl C A list of signals supported by the worker is detailed in the Workers Guide In the background In production you will want to run the worker in the background this is described in detail in the daemonization tutorial The daemonization scripts uses the celery multi command to start one or more workers in the background celery multi start wl A proj 1l info celeryd multi v3 0 0 Chiastic Slide gt Starting nodes gt wl halcyon local OK You can restart it too celery multi restart wl A proj 1 info celeryd multi v3 0 0 Chiastic Slide gt Stopping nodes gt wl halcyon local TERM gt 64024 gt Waiting for 1 node gt wl halcyon local OK gt Restarting node wl halcyon local OK celeryd multi v3 0 0 Chiastic Slide gt Stopping nodes gt wl halcyon local TERM gt
143. then tasks will not be able to call sudo when celeryd is running as a daemon If you want to enable that then you need to remove the line from sudoers See http timelordz com wiki Apache_Sudo_Commands Why do workers delete tasks from the queue if they are unable to process them Answer The worker rejects unknown tasks messages with encoding errors and messages that doesn t contain the proper fields as per the task message protocol If it did not reject them they could be redelivered again and again causing a loop Recent versions of RabbitMQ has the ability to configure a dead letter queue for exchange so that rejected messages is moved there 180 Chapter 2 Contents Celery Documeniation Release 3 0 25 Can I call a task by name Answer Yes Use celery execute send_task You can also call a task by name from any language that has an AMQP client gt gt gt from celery execute import send_task gt gt gt send_task tasks add args 2 2 kwargs lt AsyncResult 373550e8 b9a0 4666 bc61 ace0lfa4f9ld gt How can get the task id of the current task Answer The current id and more is available in the task request celery task def mytask cache set mytask request id Running For more information see Context Can I specify a custom task_id Answer Yes Use the task_id argument to Task apply_async gt gt gt task apply_async args kwargs task_id Can use d
144. these are all equal celery app proj S celery app proj celery S celery app proj celery celery Calling Tasks You can call a task using the delay method gt gt gt add delay 2 2 This method is actually a star argument shortcut to another method called apply_async gt gt gt add apply_async 2 2 The latter enables you to specify execution options like the time to run countdown the queue it should be sent to and so on gt gt gt add apply_async 2 2 queue lopri countdown 10 In the above example the task will be sent to a queue named lopri and the task will execute at the earliest 10 seconds after the message was sent Applying the task directly will execute the task in the current process so that no message is sent gt gt gt add 2 2 These three methods delay apply_async and applying call which are also used for subtasks represents the Celery calling API A more detailed overview of the Calling API can be found in the Calling User Guide Every task invocation will be given a unique identifier an UUID this is the task id The delay and apply_async methods return an AsyncResul1t instance which can be used to keep track of the tasks execution state But for this you need to enable a result backend so that the state can be stored somewhere Results are disabled by default because of the fact that there is no result backend that suits every application
145. to WorkController celery datastructures TaskProcess Queue is now renamed to celery pool TaskPool The pool algorithm has been refactored for greater performance and stability 470 Chapter 2 Contents Celery Documeniation Release 3 0 25 0 2 0 release date 2009 05 20 05 14 P M CET e Final release of 0 2 0 e Compatible with carrot version 0 4 0 e Fixes some syntax errors related to fetching results from the database backend 0 2 0 pre3 release date 2009 05 20 05 14 P M CET e Internal release Improved handling of unpickleable exceptions get_result now tries to recreate something looking like the original exception 0 2 0 pre2 release date 2009 05 20 01 56 P M CET e Now handles unpickleable exceptions like the dynamically generated subclasses of django core exception MultipleObjectsReturned 0 2 0 pre1 release date 2009 05 20 12 33 P M CET e It s getting quite stable with a lot of new features so bump version to 0 2 This is a pre release e celery task mark_as_read and _ celery task mark_as_failure has been removed Use cel ery backends default_backend mark_as_read and celery backends default_backend mark_as_failure instead 0 1 15 release date 2009 05 19 04 13 P M CET e The celery daemon was leaking AMQP connections this should be fixed if you have any problems with too many files open like emfile errors in rabbit log please contact us 0 1 14 release date 2009 05 19 01 08 P
146. to the BROKER_TRANSPORT setting returns kombu connection Connection connection_or_acquire connection None For use within a with statement to get a connection from the pool if one is not already provided Parameters connection If not provided then a connection will be acquired from the con nection pool producer_or_acquire producer None For use within a with statement to get a producer from the pool if one is not already provided Parameters producer If not provided then a producer will be acquired from the producer pool mail_admins subject body fail_silently False Sends an email to the admins in the ADMINS setting select_queues queues Select a subset of queues where queues must be a list of queue names to keep now Returns the current time and date as a datetime object set_current Makes this the current app for this thread finalize Finalizes the app by loading built in tasks and evaluating pending task decorators Pickler Helper class used to pickle this application Grouping Tasks class celery group task1 task2 task3 ae taskN Creates a group of tasks to be executed in parallel Example gt gt gt res group add s 2 2 add s 4 4 apply_async gt gt gt res get 4 bp The apply_async method returns GroupResult class celery chain task1 task2 task3 ae taskN Chains tasks together so that each tasks follows each other by
147. to the registered callbacks 358 Chapter 2 Contents Celery Documeniation Release 3 0 25 Parameters e body The decoded message body e message The Message instance Raises NotImplementedError If no consumer callbacks have been registered recover requeue False Redeliver unacknowledged messages Asks the broker to redeliver all unacknowledged messages on the specified channel Parameters requeue By default the messages will be redelivered to the original re cipient With requeue set to true the server will attempt to requeue the message potentially then delivering it to an alternative subscriber register_callback callback Register a new callback to be called when a message is received The signature of the callback needs to accept two arguments body message which is the decoded message body and the Message instance a subclass of Message revive channel Revive consumer after connection loss class AMOPBackend Exchange name type channel None kwargs An Exchange declaration Parameters e name See name e type See type e channel See channel e durable See durable e auto_delete See auto_delete e delivery_mode See delivery_mode e arguments See arguments name Name of the exchange Default is no name the default exchange type AMQP defines four default exchange types routing algorithms that covers most of the common messaging use cases An AMQ
148. tree master e 3 0 devel http github com celery celery tree 3 0 devel You can see the state of any branch by looking at the Changelog https github com celery celery blob master Changelog If the branch is in active development the topmost version info should contain metadata like release date TBA status DEVELOPMENT branch master The status field can be one of e PLANNING The branch is currently experimental and in the planning stage e DEVELOPMENT The branch is in active development but the test suite should be passing and the product should be working and possible for users to test e FROZEN The branch is frozen and no more features will be accepted When a branch is frozen the focus is on testing the version as much as possible before it is released master branch The master branch is where development of the next version happens Maintenance branches Maintenance branches are named after the version e g the maintenance branch for the 2 2 x series is named 2 2 Previously these were named releaseXX maint The versions we currently maintain is e 2 3 This is the current series 2 6 Contributing 155 Celery Documeniation Release 3 0 25 e 2 2 This is the previous series and the last version to support Python 2 4 2 1 This is the last version to use the carrot AMQP framework Recent versions use kombu Archived branches Archived branches are kept for p
149. untrusted serializers and if configured to use the auth serializer will register the auth serializer with the provided settings into the Kombu serializer registry Parameters e allowed_serializers List of serializer names or content_types that should be exempt from being disabled e key Name of private key file to use Defaults to the CELERY_SECURITY_KEY setting 262 Chapter 2 Contents Celery Documeniation Release 3 0 25 cert Name of certificate file to use Defaults to the CELERY_SECURITY_CERTIFICATE setting store Directory containing certificates Defaults to the CELERY_SECURITY_CERT_STORE setting digest Digest algorithm used when signing messages Default is shal serializer Serializer used to encode messages after they have been signed See CELERY_TASK_SERIALIZER for the serializers supported Default is json 2 13 18 celery utils debug e Sampling Memory Usage e API Reference celery utils debug Sampling Memory Usage This module can be used to diagnose and sample the memory usage used by parts of your application E g to sample the memory usage of calling tasks you can do this from celery utils debug import sample_mem memdump from tasks import add try for i in range 100 for j in range 100 add delay i j sample_mem finally memdump API Reference celery uti
150. using manage py S python manage py celeryd Thanks to Gr goire Cachet Added support for message priorities topic exchanges custom routing keys for tasks This means we have introduced celery task apply_async a new way of executing tasks You can use celery task delay and celery Task delay like usual but if you want greater control over the message sent you want celery task apply_async and celery Task apply_async This also means the AMQP configuration has changed Some settings has been renamed while others are new ERY_AMOP_ EXCHANGE ERY_AMOP_PUBLISHER_ROUTING_KEY ERY_AMOP_CONSUMER_ROUTING_KEY ERY_AMQP_CONSUMER_QUEUE ERY_AMOP_EXCHANGE_TYPE OQ O Onoe See the entry Can I send some tasks to only some servers in the FAQ for more information Task errors are now logged using log level ERROR instead of INFO and stacktraces are dumped Thanks to Gr goire Cachet Make every new worker process re establish it s Django DB connection this solving the MySQL connection died exceptions Thanks to Vitaly Babiy and Jirka Vejrazka IMPORTANT Now using pickle to encode task arguments This means you now can pass complex python objects to tasks as arguments Removed dependency to yadayada Added a FAQ see docs faq rst Now converts any Unicode keys in task kwargs to regular strings Thanks Vitaly Babiy Renamed the TaskDaemon
151. which is the situation with the amqp and redis broker transports e Chord exception behavior defined Issue 1172 From Celery 3 1 the chord callback will change state to FAILURE when a task part of a chord raises an exception It was never documented what happens in this case and the actual behavior was very unsatisfactory indeed it will just forward the exception value to the chord callback For backward compatibility reasons we do not change to the new behavior in a bugfix re lease even if the current behavior was never documented Instead you can enable the CELERY_CHORD_PROPAGAT ery 3 1 See more at Error handling ES setting to get the new behavior that will be default from Cel e worker Fixes bug with ignored and retried tasks The on_chord_part_return and Task after_return callbacks nor the task_postrun signal should be called when the task was retried ignored Fix contributed by Vlad e GroupResult join_native now respects the propagate argument e subtask id added as an alias to subtask options id gt gt gt task_ gt gt gt s add s 2 2 gt gt gt s id my id gt gt gt s options sk s id ia id my id e worker Fixed error Could not start worker processes occurring when restarting after connection failure Issue 1118 e Adds new signal task ret ried Issue 1169 e celery events dumper now h
152. workers if CELERY_WORKER_DIRECT is enabled Among other improvements the following functions have been added e default move_direct filterfun xopts move_direct_by_id task_id worker_hostname xopts move_direct_by_idmap task_id worker_hostname xopts move_direct_by_taskmap task_name worker_hostname xxopts connection now accepts a pool argument that if set to false causes a new connection to be created instead of acquiring one from the pool e New signal celeryd_after_setup e Default loader now keeps lowercase attributes from the configuration module 226 Chapter 2 Contents Celery Documeniation Release 3 0 25 2 12 25 3 0 1 release date 2012 07 10 06 00 P M BST by Ask Solem Now depends on kombu 2 2 5 inspect now supports limit argument myapp control inspect limit 1 ping Beat now works with timezone aware datetime s Task classes inheriting from celery import Task mistakingly enabled accept_magic_kwargs Fixed bug in inspect scheduled Issue 829 Beat Now resets the schedule to upgrade to UTC The celery worker command now works with eventlet gevent Previously it would not patch the environment early enough The celery command now supports extension commands using setuptools entry points Libraries can add additional commands to the celery command by adding an entry point like setup entry_points celery commands foo my modu
153. worth it in the end See also The book Art of Concurrency has a section dedicated to the topic of task granularity AOC 1 Data locality The worker processing the task should be as close to the data as possible The best would be to have a copy in memory the worst would be a full transfer from another continent 56 Chapter 2 Contents Celery Documeniation Release 3 0 25 If the data is far away you could try to run another worker at location or if that s not possible cache often used data or preload data you know is going to be used The easiest way to share data between workers is to use a distributed cache system like memcached See also The paper Distributed Computing Economics by Jim Gray is an excellent introduction to the topic of data locality State Since celery is a distributed system you can t know in which process or on what machine the task will be executed You can t even know if the task will run in a timely manner The ancient async sayings tells us that asserting the world is the responsibility of the task What this means is that the world view may have changed since the task was requested so the task is responsible for making sure the world is how it should be If you have a task that re indexes a search engine and the search engine should only be re indexed at maximum every 5 minutes then it must be the tasks responsibility to assert that not the callers Another gotcha is Djan
154. you have to install additional dependencies You can install both Celery and these dependencies in one go using either the celery with beanstalk or the django celery with beanstalk bundles pip install U celery with beanstalk Configuration Configuration is easy set the transport and configure the location of your Beanstalk database BROKER_URL beanstalk localhost 11300 Where the URL is in the format of beanstalk hostname port The host name will default to Localhost and the port to 11300 and so they are optional Results Using Beanstalk to store task state and results is currently not supported Limitations The Beanstalk message transport does not currently support e Remote control commands celeryctl broadcast e Authentication Using lronMQ Installation For IronMQ support you ll need the iron_celery http github com iron io iron_celery library pip install iron_celery As well as an Iron io account http www iron io Sign up for free at iron io http www iron io Configuration First you ll need to import the iron_celery library right after you import Celery for example from celery import Celery import iron_celery celery Celery mytasks broker ironmq backend ironcache You have to specify IronMQ in the broker URL BROKER_URL ironmq ABCDEFGHIJKLMNOPORST ZYXK7NiynG1TogH8Nj P 9n1E73sq3 where the URL format is ironmgq
155. 0 14 This setting defines what happens when a task part of a chord raises an exception e If propagate is True the chord callback will change state to FAILURE with the exception value set to a ChordError instance containing information about the error and the task that failed This is the default behavior in Celery 3 1 e If propagate is False the exception value will instead be forwarded to the chord callback This was the default behavior before version 3 1 CELERY_TRACK_STARTED If True the task will report its status as started when the task is executed by a worker The default value is False as the normal behaviour is to not report that level of granularity Tasks are either pending finished or waiting to be retried Having a started state can be useful for when there are long running tasks and there is a need to report which task is currently running 2 4 Configuration and defaults 139 Celery Documeniation Release 3 0 25 CELERY_TASK_SERIALIZER A string identifying the default serialization method to use Can be pickle default json yaml msgpack or any custom serialization methods that have been registered with kombu serialization registry See also Serializers CELERY_TASK_PUBLISH_RETRY New in version 2 2 Decides if publishing task messages will be retried in the case of connection loss or other connection errors See also CELERY_TASK_PUBLISH_RETRY_POLICY Enabled by default
156. 1 for node_name reply in stats CeleryStats objects update_stat node_name stats and here s the same using Celery app objects 2 14 Internals 305 Celery Documentation Release 3 0 25 from celery import celery from models import CeleryStats celery task def write_stats_to_db stats celery control inspect stats timeout 1 for node_name reply in stats CeleryStats objects update_stat node_name stats In the example above the actual application instance is imported from a module in the project this module could look something like this from celery import Celery celery Celery celery config_from_object BROKER_URL amqp Module Overview e celery app This is the core of Celery the entry point for all functionality e celery loaders Every app must have a loader The loader decides how configuration is read what happens when the worker starts when a task starts and ends and so on The loaders included are app Custom celery app instances uses this loader by default default single mode uses this loader by default Extension loaders also exist like django celery celery pylons and so on e celery worker This is the worker implementation e celery backends Task result backends live here e celery apps Major user applications celeryd and celerybeat e celery bin Command line applications setup py creates setuptools entrypoints for these e celery concur
157. 1211 B example com To use the cache backend you must either have the pylibmc or python memcached library installed of which the former is regarded as the best choice The support backend types are memcached and memory we haven t felt the need to support any of the other backends provided by Django Backward incompatible changes e Default python loader now prints warning on missing celeryconfig py instead of raising ImportError celeryd raises ImproperlyConfiguredif the configuration is not set up This makes it possible to use help etc without having a working configuration Also this makes it possible to use the client side of celery without being configured gt gt gt from carrot connection import BrokerConnection gt gt gt conn BrokerConnection localhost guest guest gt gt gt from celery execute import send_task gt gt gt r send_task celery ping args kwargs connection conn gt gt gt from celery backends amqp import AMOPBackend gt gt gt r backend AMOPBackend connection conn gt gt gt r get pong e The following deprecated settings has been removed as scheduled by the Celery Deprecation Timeline Setting name Replace with CELERY_AMQP_CONSUMER_QUEUES CELERY_AMQP_EXCHANGE CELERY_AMQP_EXCHANGE_TYPE CELERY_AMQP_CONSUMER_ROUTING_KEY CELERY_AMQP_PUBLISHER_ROUTING_KEY CELERY_QUEUES CELERY_DEFAULT_EXCHANGE CELERY_DEFAU
158. 5 e properties Additional message properties see AMQP spec release revive channel Revive the producer after connection loss routing_key serializer None AM PBackend Queue alias of NoCacheQueue AMQPBackend consume task_id timeout None 10 PBackend delete_group group_id D 10 PBackend drain_events connection consumer timeout None now lt built in function time gt PBackend get_many task_ids timeout None kwargs PBackend get_task_meta task_id backlog_limit 1000 PBackend poll task_id backlog_limit 1000 D p pp p O O O 0 PBackend reload_group_result task_id Reload group result even if it has been previously fetched PBackend reload_task_result task_id PBackend restore_group group_id cache True PBackend retry_policy interval_start 0 interval_max 1 max_retries 20 interval_step 1 PBackend save_group group_id result PBackend supports_autoexpire True gt Pp p p p p PH Q Q Q QPBackend revive channel Q Q Q PBackend supports_native_join True AMQPBackend wait_for task_id timeout None cache True propagate True kwargs exception celery backends amqp BacklogLimitExceeded Too much state history to fast forward class celery backends amqp NoCacheQueue name exchange None routing_key chan nel None bindings None on_declared None kwargs can_cache_declaration Fals
159. 64052 or stop it celery multi stop wl A proj 1l info Note celery multi doesn t store information about workers so you need to use the same command line parameters when restarting Also the same pidfile and logfile arguments must be used when stopping killing By default it will create pid and log files in the current directory to protect against multiple workers launching on top of each other you are encouraged to put these in a dedicated directory mkdir p var run celery mkdir p var log celery celery multi start wl A proj l info pidfile var run celery n pid logfile var log celery n pid 2 2 Getting Started 27 Celery Documentation Release 3 0 25 With the multi command you can start multiple workers and there is a powerful command line syntax to specify arguments for different workers too e g celeryd multi start 10 A proj l info Q 1 3 images video Q 4 5 data Q default L 4 5 debug For more examples see the celeryd_multi module in the API reference About the app argument The app argument specifies the Celery app instance to use it must be in the form of module path celery where the part before the colon is the name of the module and the attribute name comes last If a package name is specified instead it will automatically try to find a celery module in that package and if the name is a module it will try to find a celery attribute in that module This means that
160. 8 C no color gt lt Option at 0x7fb7 run args kwargs sortpri 0 class celery bin celery worker args kwargs Start worker instance Examples celery worker app proj 1l info celery worker A proj l info Q hipri lopri celery worker A proj concurrency 4 celery worker A proj concurrency 1000 P eventlet celery worker autoscale 10 0 Command celery bin celeryd WorkerCommand sortpri 1 2 13 40 celery bin camqadm The celery amqp command class celery bin camqadm AMQPAdmin args kwargs The celery camqadm utility Shell alias of AMOShe1l1 connect conn None note m run class celery bin camqadm AMQPAdminCommand app None get_app None run args options class celery bin camqadm AMQShe11 args kwargs AMQP API Shell Parameters e connect Function used to connect to the server must return connection object e silent If True the commands won t have annoying output not relevant when running in non shell mode 2 13 API Reference 297 Celery Documentation Release 3 0 25 amqp Mapping of AMQP API commands and their Spec amqp queue declare lt celery bin camqadm Spec object at 0x7fb7635bc310 gt queue purge lt celery bin camqadm Sp builtins exit do_exit EOF do_exit help do_help chan None completenames text ignored Return all commands starting with text for ta
161. ACKEND Deprecated compat alias to BROKER_TRANSPORT BROKER_HOST BROKER_TRANSPORT CELERY_RESULT_BACKEND CELERY_TIMEZONE find_option name namespace celery Search for option by name Willreturn namespace option_name Option tuple e g gt gt gt celery conf find_option disable_rate_limits CELERY DISABLE _RATE_LIMITS 248 Chapter 2 Contents Celery Documeniation Release 3 0 25 ce ce Parameters e name Name of option cannot be partial e namespace Preferred namespace CELERY by default find_value_for_key name namespace celery Shortcut to get_by_parts find_option name 1 get_by_ parts parts Returns the current value for setting specified as a path Example gt gt gt celery conf get_by_parts CELERY DISABLE RATE LIMITS False humanize Returns a human readable string showing changes to the configuration without_defaults Returns the current configuration but without defaults lery app utils bugreport app Returns a string containing information useful in bug reports lery app utils filter_hidden_settings conf 2 13 11 celery task e celery task j celery task This is the old task module it should not be used anymore import from the main celery module instead If you re looking for the decorator implementation then that s in celery app
162. Also celery execute send_task has been introduced which can apply tasks using just the task name useful if the client does not have the destination task in its task registry Example gt gt gt from celery execute import send_task gt gt gt result send_task celery ping args kwargs gt gt gt result get pong camqadm This is a new utility for command line access to the AMQP API Excellent for deleting queues bindings exchanges experimentation and testing camgqadm 1 gt help Gives an interactive shell type help for a list of commands When using Django use the management command instead python manage py camgqadm 1 gt help Redis result backend To conform to recent Redis API changes the following settings has been deprecated REDIS_TIMEOUT REDIS_CONNECT_RETRY These will emit a DeprecationWarning if used A REDIS_PASSWORD setting has been added so you can use the new simple authentication mech anism in Redis The redis result backend no longer calls SAVE when disconnecting as this is apparently better handled by Redis itself If settings DEBUG is on celeryd now warns about the possible memory leak it can result in The ETA scheduler now sleeps at most two seconds between iterations The ETA scheduler now deletes any revoked tasks it might encounter As revokes are not yet persistent this is done to make sure the task is revoked even though it s currently being hold because
163. Celery Documentation Release 3 0 25 Ask Solem Contributors July 10 2014 Contents 1 Getting Started 3 2 Contents 5 ZA Copyfight 2 on 4260 Geo oe alee eee Ree aa eae OE ae eed ee el eae amp 5 22 Meine Stated spo as A eae ok Be eh AR ae a ga A ahaa E dog Bees 5 2 3 UserGuide oa a y ae a bee Pa bee bade tach E ee ao ed oat A 35 24 Configuration and defaults o sepo ee a ee A Oe eS Ee SO OS a ew 8 127 2 9 MDjaNGO ses ce Rew oe ee eA REA BARRA DE we eee Re ES 147 26 COntibUUNS syk ae 4 Ae Sete Sea eb we eae Shee ee Bale Hae bd Sw ie aie eS 151 27 Community Resources gs Kae ed gee Sk be be hoes Be ES ee pe bE ee 165 2 8 SWUOTMAlS ass ta 3 ok Sd bene hs bah ee eed hae Ee ale edt baw ba oh eS 166 29 Frequently Asked Questions e ouse 5 484 Soke ee WER eRe WE Sa ew Ge es 172 2 10 What s new in Celery 3 0 Chiastie Slide c a saie ti Axe eed BS BA aS a OR w Reed g 184 211 Whatsn w im Celery 2 5 J 4 65 Boa e e gaii a E kg a gd a aa es cg Bose 198 2 12 Change history eces oe Se a Re PA a Rae wa A ed eat 205 2 13 APT Referente soa Gels Ba Gok bh eee k Bow OK A BU ES Stes amp Geb Se SOS ad Bow E 227 2 44 UntermalsS 2 25 5602 Ne a poe eae ete ede been eee SE ee Pe ee a ee 302 DAD HISI seis ei eos ee RO A ae A BG GA Se ae He RS Bh es bk AS SS 396 2 16 Glossaty so 23Gb w bee Ebb bGA Oe eee ae Mae dee eb eae 474 3 Indices and tables 475 Bibliography 477 Python Module Index 479 Celery Documeniation R
164. Deprecated and scheduled for removal in v4 0 Task acks_late False When enabled messages for this task will be acknowledged after the task has been executed and not just before which is the default behavior Please note that this means the task may be executed twice if the worker crashes mid execution which may be acceptable for some applications The application default can be overridden with the CELERY_ACKS_LATE setting Task after_return status retval task_id args kwargs einfo Handler called after the task returns Parameters status Current task state retval Task return value exception task_id Unique id of the task args Original arguments for the task that failed kwargs Original keyword arguments for the task that failed einfo Except ionInfo instance containing the traceback if any The return value of this handler is ignored Task apply args None kwargs None link None link_error None options Execute this task locally by blocking until the task returns Parameters 2 13 API Reference 235 Celery Documentation Release 3 0 25 e args positional arguments passed on to the task e kwargs keyword arguments passed on to the task e throw Re raise task exceptions Defaults to the CELERY_EAGER_PROPAGATES_EXCEPTIONS setting rtype celery result EagerResult Task apply async args None kwar
165. EVENT setting is enabled task received signature task received uuid name args kwargs retries eta hostname timestamp Sent when the worker receives a task task started signature task started uuid hostname timestamp pid Sent just before the worker executes the task 114 Chapter 2 Contents Celery Documeniation Release 3 0 25 task succeeded signature task succeeded uuid result runtime hostname timestamp Sent if the task executed successfully Runtime is the time it took to execute the task using the pool Starting from the task is sent to the worker pool and ending when the pool result handler callback is called task failed signature task failed uuid exception traceback hostname timestamp Sent if the execution of the task failed task revoked signature task revoked uuid terminated signum expired Sent if the task has been revoked Note that this is likely to be sent by more than one worker e terminated is set to true if the task process was terminated and the signum field set to the signal used e expired is set to true if the task expired task retried signature task retried uuid exception traceback hostname timestamp Sent if the task failed but will be retried in the future Worker Events worker online signature worker online hostname timestamp freq sw_ident sw_ver sw_sys The worker has connected to the broker and is online e
166. E_BACKEND memcached 172 19 26 240 11211 172 19 26 242 11211 H The memory backend stores the cache in memory only CELERY_CACHE_BACKEND memory CELERY_CACHE_BACKEND_OPTIONS You can set pylibmc options using the CELERY_CACHE_BACKEND_OPTIONS setting CELERY_CACHE_BACKEND_OPTIONS binary True behaviors tcp_nodelay True Redis backend settings Configuring the backend URL Note The Redis backend requires the redis library http pypi python org pypi redis To install the redis package use pip or easy_install 2 4 Configuration and defaults 131 Celery Documeniation Release 3 0 25 pip install redis This backend requires the CELERY_RESULT_BACKEND setting to be set to a Redis URL CELERY_RESULT_BACKEND redis password host port db For example CELERY_RESULT_BACKEND redis localhost 0 which is the same as CELERY_RESULT_BACKEND redis The fields of the URL is defined as folows e host Host name or IP address of the Redis server e g localhost e port Port to the Redis server Default is 6379 e db Database number to use Default is 0 The db can include an optional leading slash e password Password used to connect to the database CELERY_REDIS_MAX_CONNECTIONS Maximum number of connect
167. Experimental No No SQLAIchemy Experimental No No Iron MQ 3rd party No No Experimental brokers may be functional but they do not have dedicated maintainers Missing monitor support means that the transport does not implement events and as such Flower celery events celerymon and other event based monitoring tools will not work Remote control means the ability to inspect and manage workers at runtime using the celery inspect and celery control commands and other tools using the remote control API 2 2 3 First Steps with Celery Celery is a task queue with batteries included It is easy to use so that you can get started without learning the full complexities of the problem it solves It is designed around best practices so that your product can scale and integrate with other languages and it comes with the tools and support you need to run such a system in production In this tutorial you will learn the absolute basics of using Celery You will learn about e Choosing and installing a message broker e Installing Celery and creating your first task e Starting the worker and calling tasks 2 2 Getting Started 19 Celery Documentation Release 3 0 25 e Keeping track of tasks as they transition through different states and inspecting return values Celery may seem daunting at first but don t worry this tutorial will get you started in no time It is deliberately kept simple so to not confuse you with
168. F_IGNORED If set the worker stores all task errors in the result store even if Task ignore_result is on CELERYD_STATE_DB Name of the file used to stores persistent worker state like revoked tasks Can be a relative or absolute path but be aware that the suffix db may be appended to the file name depending on Python version Can also be set via the st atedb argument to celeryd Not enabled by default CELERYD_TIMER_PRECISION Set the maximum time in seconds that the ETA scheduler can sleep between rechecking the schedule Default is 1 second Setting this value to 1 second means the schedulers precision will be 1 second If you need near millisecond precision you can set this to 0 1 Error E Mails CELERY_SEND_TASK_ERROR_EMAILS The default value for the Task send_error_emails attribute which if set to True means errors occurring during task execution will be sent to ADMINS by email Disabled by default ADMINS List of name email_address tuples for the administrators that should receive error emails SERVER_EMAIL The email address this worker sends emails from Default is celery localhost EMAIL_HOST The mail server to use Default is localhost 142 Chapter 2 Contents Celery Documeniation Release 3 0 25 EMAIL_HOST_USER User name if required to log on to the mail server with EMAIL_HOST_PASSWORD Password if required to log on to the mail server with EMAIL_PORT The port th
169. False stdout lt open file lt stdout gt mode w at 0x7fb76c556150 gt stderr lt open file lt stderr gt mode w at Ox7fb76c5561e0 gt show_reply True Erase all messages from all known task queues 2 13 API Reference 295 Celery Documentation Release 3 0 25 WARNING There is no undo operation for this command run args kwargs sortpri 0 class celery bin celery report app None no_color False stdout lt open file lt stdout gt mode w at 0x7fb76c556150 gt stderr lt open file lt stderr gt mode w at Ox7fb76c5561e0 gt show_reply True Shows information useful to include in bugreports run args kwargs sortpri 0 class celery bin celery result app None no_color False stdout lt open file lt stdout gt mode w at 0x7fb76c556150 gt stderr lt open file lt stderr gt mode w at Ox7fb76c5561e0 gt show_reply True Gives the return value for a given task id Examples celery result 8 511516 e2f5 4da4 9d2f 0fb83a86e500 celery result 8f 511516 e2f5 4da4 9d2f 0fb83a86e500 t tasks add celery result 8f 511516 e2f5 4da4 9d2f O0fb83a86e500 traceback args lt task_id gt option_list lt Option at 0x7fb762af2a70 q quiet gt lt Option at 0x7fb762af2098 C no color gt lt Option at 0x7fb7 run task_id args kwargs sortpri 0 class celery bin celery shel1l1 app None no_color Fals
170. Fixed error with error email and new task classes Issue 931 e BaseTask ___call__ is no longer optimized away if it has been monkey patched e Fixed shutdown issue when using gevent Issue 911 amp Issue 936 Fix contributed by Thomas Meson 2 12 19 3 0 7 release date 2012 08 24 05 00 PM BST Fixes several problems with periodic tasks and timezones Issue 937 Now depends on kombu 2 4 2 Redis Fixes a race condition crash Fixes an infinite loop that could happen when retrying establishing the broker connection Daemons now redirect standard file descriptors to dev null Though by default the standard outs are also redirected to the logger instead but you can disable this by changing the CELERY_REDIRECT_STDOUTS setting Fixes possible problems when eventlet gevent is patched too late LoggingProxy no longer defines fileno Issue 928 Results are now ignored for the chord unlock task Fix contributed by Steeve Morin Cassandra backend now works if result expiry is disabled Fix contributed by Steeve Morin The traceback object is now passed to signal handlers instead of the string representation Fix contributed by Adam DePue Celery command Extensions are now sorted by name A regression caused the task failed event to be sent with the exception object instead of its string repre sentation The worker daemon would try to create the pid file before daemonizing to catch e
171. Frequently Asked Questions 172 Chapter 2 Contents Celery Documeniation Release 3 0 25 e General What kinds of things should I use Celery for Misconceptions Does Celery really consist of 50 000 lines of code Does Celery have many dependencies celery django celery kombu Is Celery heavy weight Is Celery dependent on pickle Is Celery for Django only Do I have to use AMQP RabbitMQ Is Celery multilingual Troubleshooting MySQL is throwing deadlock errors what can I do celeryd is not doing anything just hanging Task results aren t reliably returning Why is Task delay apply celeryd just hanging Does it work on FreeBSD Im having IntegrityError Duplicate Key errors Why Why aren t my tasks processed Why won t my Task run Why won t my periodic task run How do I purge all waiting tasks I ve purged messages but there are still messages left in the queue e Results How do I get the result of a task if I have the ID that points there e Security Isn t using pickle a security concern Can messages be encrypted Is it safe to run celeryd as root e Brokers Why is RabbitMQ crashing Can I use Celery with Active MQ STOMP What features are not supported when not using an AMQP broker e Tasks How can I reuse the same connection when calling tasks Sudo ina subprocess returns None Why
172. GATES True While the traceback may be different depending on which result backend is being used you can see the error descrip tion includes the id of the task that failed and a string representation of the original exception You can also find the original traceback in result traceback Note that the rest of the tasks will still execute so the third task add s 8 8 is still executed even though the middle task failed Also the ChordError only shows the task that failed first in time it does not respect the ordering of the header group Important Notes Tasks used within a chord must not ignore their results In practice this means that you must enable a CELERY_RESULT_BACKEND in order to use chords Additionally if CELERY_IGNORE_RESULT is set to True in your configuration be sure that the individual tasks to be used within the chord are defined with ignore_result False This applies to both Task subclasses and decorated tasks Example Task subclass class MyTask Task abstract True ignore_result Fals Example decorated task celery task ignore_result False def another_task project do_something By default the synchronization step is implemented by having a recurring task poll the completion of the taskset every second calling the subtask when ready Example implementation def unlock _chord taskset callback interval 1 max_retries None if taskset ready
173. IONS tasks add rate_limit 10 s or change the same for all tasks CELERY_ANNOTATIONS rate_limit 10 s You can change methods too for example the on_failure handler 2 11 What s new in Celery 2 5 201 Celery Documentation Release 3 0 25 def my_on_failure self exc task_id args kwargs einfo o print Oh no Task failed tr exc CELERY_ANNOTATIONS on_failure my_on_failure If you need more flexibility then you can also create objects that filter for tasks to annotate class MyAnnotate object def annotate self task if task name startswith tasks return rate_limit 10 s CELERY_ANNOTATIONS MyAnnotate current provides the currently executing task The new celery task current proxy will always give the currently executing task Example from celery task import current task task def update _twitter_status auth message twitter Twitter auth try twitter update_status message except twitter FailWhale exc retry in 10 seconds current retry countdown 10 exc exc Previously you would have to type update_twitter_status retry here which can be annoying for long task names Note This will not work if the task function is called directly i e update_twitter_status a b For that to work apply must be used update_twi
174. If enabled an event will be sent with every task so monitors can track tasks before the workers receive them e celerybeat Now reuses the broker connection when calling scheduled tasks e The configuration module and loader to use can now be specified on the command line For example celeryd config celeryconfig py loader myloader Loader e Added signals beat_init and beat_embedded_init celery signals beat_init Dispatched when celerybeat starts either standalone or embedded Sender is the celery beat Service instance celery signals beat_embedded_init Dispatched in addition to the beat _init signal when celerybeat is started as an embedded process Sender is the celery beat Service instance e Redis result backend Removed deprecated settings REDIS_TIMEOUT and REDIS_CONNECT_RETRY e CentOS init script for celeryd now available in extra centos e Now depends on pyparsing version 1 5 0 or higher There have been reported issues using Celery with pyparsing 1 4 x so please upgrade to the latest version e Lots of new unit tests written now with a total coverage of 95 Fixes e celeryev Curses Monitor Improved resize handling and UI layout Issue 274 Issue 276 e AMQP Backend Exceptions occurring while sending task results are now propagated instead of silenced 422 Chapter 2 Contents Celery Documeniation Release 3 0 25 celeryd will then show the full traceback of these errors in
175. LERYSA 0001 Daemons would set effective id s rather than real id s when the uid gid arguments to celeryd multi celeryd_detach celerybeat and celeryev were used This means privileges weren t properly dropped and that it would be possible to regain supervisor privileges later Fixes e Backported fix for 455 from 2 4 to 2 3 e Statedb was not saved at shutdown e Fixes worker sometimes hanging when hard time limit exceeded 2 3 3 release date 2011 16 09 05 00 P M BST by Mher Movsisyan e Monkey patching sys stdout could result in the worker crashing if the replacing object did not define isatty Issue 477 e CELERYD option in etc default celeryd should not be used with generic init scripts 2 3 2 release date 2011 10 07 05 00 PM BST 2 15 History 405 Celery Documentation Release 3 0 25 News e Improved Contributing guide If you d like to contribute to Celery you should read the Contributing Gudie We are looking for contributors at all skill levels so don t hesitate e Now depends on Kombu 1 3 1 e Task request now contains the current worker host name Issue 460 Available as task request hostname e It is now easier for app subclasses to extend how they are pickled see celery app AppPickler Fixes e purge discard_all was not working correctly Issue 455 e The coloring of log messages didn t handle non ASCII data well Issue 427 e Windows the m
176. LERY_DEFAULT_QUEUE default CELERY_QUEUES Queue default routing_key task Queue feed_tasks routing_key feed ERY_DEFAULT_EXCHANGE tasks ERY_DEFAULT_EXCHANGE_TYPE topic ERY_DEFAULT_ROUTING_KEY task default TETE i H H H CELERY_QUEUES is a list of Queue instances If you don t set the exchange or exchange type values for a key these will be taken from the CELERY_DEFAULT_EXCHANGE and CELERY_DEFAULT_EXCHANGE_TYPE settings To route a task to the feed_tasks queue you can add an entry in the CELERY_ROUTES setting CELERY_ROUTES feeds tasks import_feed queue feed_tasks routing key feed import hy You can also override this using the routing_key argument to Task apply_async orsend_task gt gt gt from feeds tasks import import_feed gt gt gt import_feed apply_async args http cnn com rss queue feed_tasks routing_key feed import To make server z consume from the feed queue exclusively you can start it with the Q option 98 Chapter 2 Contents Celery Documeniation Release 3 0 25 user z celery worker Q feed_tasks hostname z example com Servers x and y must be configured to consume from the default queue user x S cele
177. LLED_APPS REET djcelery celerytest After the new app has been created and added to INSTALLED_APPS you can define your tasks by creating a new file called celerytest tasks py from celery import task task def add x y return x y Our example task is pretty pointless it just returns the sum of two arguments but it will do for demonstration and it is referred to in many parts of the Celery documentation Relative Imports You have to be consistent in how you import the task module e g if you have project app in INSTALLED_APPS then you also need to import the tasks from project app or else the names of the tasks will be different See Automatic naming and relative imports Starting the worker process In a production environment you will want to run the worker in the background as a daemon see Running the worker as a daemon but for testing and development it is useful to be able to start a worker instance by using the celery worker manage command much as you would use Django s runserver S python manage py celery worker loglevel info For a complete listing of the command line options available use the help command S python manage py celery help Calling our task Now that the worker is running open up a new python interactive shell with python manage py shell to actually call the task you defined gt gt gt from celerytest tasks import add gt gt gt add delay
178. LOOKUP RECEIVED 5 RETRY 6 REVOKED 3 SUCCESS 0 STARTED 4 Hash lookup of PRECEDENCE to index celery states precedence state Get the precedence index for state Lower index means higher precedence class celery states state State is a subclass of st r implementing comparison methods adhering to state precedence rules gt gt gt from celery states import state PENDING SUCCESS gt gt gt state PENDING lt state SUCCESS True Any custom state is considered to be lower than FAILURE and SUCCESS but higher than any of the other built in states gt gt gt state PROGRESS gt state STARTED rrue gt gt gt state PROGRESS gt state SUCCESS False 2 13 26 celery contrib abortable e Abortable tasks overview Usage example Abortable tasks overview For long running Task s it can be desirable to support aborting during execution Of course these tasks should be built to support abortion specifically The AbortableTask serves as a base class for all Task objects that should support abortion by producers e Producers may invoke the abort method on AbortableAsyncResult instances to request abortion e Consumers workers should periodically check and honor the is_aborted method at controlled points in their task s run method The more often the better The necessary intermediate communicati
179. LT_EXCHANGE_TYPE CELERY_QUEUES CELERY_DEFAULT_ROUTING_KEY e The celery task rest module has been removed use celery task http instead as scheduled by the Celery Deprecation Timeline e It s no longer allowed to skip the class name in loader names as scheduled by the Celery Deprecation Timeline Assuming the implicit Loader class name is no longer supported if you use e g Q H ERY_LOADER myapp loaders You need to include the loader class name like this Q H 1ERY_LOADER myapp loaders Loader e CELERY_TASK_RESULT_EXPIRES now defaults to 1 day 2 15 History 441 Celery Documeniation Release 3 0 25 Previous default setting was to expire in 5 days e AMQP backend Don t use different values for auto_delete This bug became visible with RabbitMQ 1 8 0 which no longer allows conflicting declarations for the auto_delete and durable settings If you ve already used celery with this backend chances are you have to delete the previous decla ration camqadm exchange delete celeryresults e Now uses pickle instead of cPickle on Python versions lt 2 5 cPickle is broken in Python lt 2 5 It unsafely and incorrectly uses relative instead of absolute imports so e g exceptions KeyError becomes celery exceptions KeyError Your best choice is to upgrade to Python 2 6 as while the pure pickle version has worse
180. MAIL_SIGNATURE_SEP body nTask name s with id id s raised exception n exc r n n nTask was called with args args s kwargs Format string used to generate error email content error whitelist None 264 Chapter 2 Contents Celery Documeniation Release 3 0 25 format_body context format_subJect context send context exc fail_silently True should_send context exc Returns true or false depending on if a task error mail should be sent for this type of error subject celery hostname s Error Task name s id s exc s n Format string used to generate error email subjects class celery utils mail Mailer host localhost port 0 user None password None timeout 2 use_ssl False use_tls False send message fail_silently False supports_timeout True class celery utils mail Message to None sender None subject None body None charset us ascii exception celery utils mail SendmailWarning Problem happened while sending the email message celery utils mail get_local_hostname 2 13 20 celery exceptions e celery exceptions j celery exceptions This module contains all exceptions used by the Celery API exception celery exceptions AlreadyRegistered The task is already registered exception celery exceptions AlwaysEagerIgnored send_task ignores CELERY_ALWAYS_EAGER option exception celery exceptions CDeprecationWarning exception cel
181. N_TIMEOUT The default timeout in seconds before we give up establishing a connection to the AMQP server Default is 4 seconds BROKER_CONNECTION_RETRY Automatically try to re establish the connection to the AMQP broker if lost The time between retries is increased for each retry and is not exhausted before BROKER_CONNECTION_MAX_RETRIES is exceeded This behavior is on by default BROKER_CONNECTION_MAX_RETRIES Maximum number of retries before we give up re establishing a connection to the AMQP broker If this is set to 0 or None we will retry forever Default is 100 retries BROKER_TRANSPORT_OPTIONS New in version 2 2 A dict of additional options passed to the underlying transport See your transport user manual for supported options if any Example setting the visibility timeout supported by Redis and SQS transports BROKER_TRANSPORT_OPTIONS visibility_timeout 18000 5 hours Task execution settings CELERY_ALWAYS_EAGER If this is True all tasks will be executed locally by blocking until the task returns apply_async and Task delay will return an EagerResult instance which emulates the API and behavior of AsyncResult except the result is already evaluated That is tasks will be executed locally instead of being sent to the queue CELERY_EAGER_PROPAGATES_EXCEPTIONS If this is True eagerly executed tasks applied by task apply or when the CELERY
182. OL_LIMIT 10 A limit of 10 means a maximum of 10 simultaneous connections can co exist Only a single con nection will ever be used in a single thread environment but in a concurrent environment threads greenlets etc but not processes when the limit has been exceeded any try to acquire a connec tion will block the thread and wait for a connection to be released This is something to take into consideration when choosing a limit A limit of None or 0 means no limit and connections will be established and closed every time e Introducing Chords taskset callbacks A chord is a task that only executes after all of the tasks in a taskset has finished executing It s a fancy term for taskset callbacks adopted from Cw 2 15 History 407 Celery Documentation Release 3 0 25 It works with all result backends but the best implementation is currently provided by the Redis result backend Here s an example chord gt gt gt chord add subtask i i for i in xrange 100 tsum subtask get 1900 Please read the Chords section in the user guide if you want to know more Time limits can now be set for individual tasks To set the soft and hard time limits for a task use the time_limit and soft_time_limit attributes import time task time_limit 60 soft_time_limit 30 def sleeptask seconds time sleep seconds If the attributes are not set then the workers default time limits will be
183. ON is supported in many programming languages is now a standard part of Python since 2 6 and is fairly fast to decode using the modern Python libraries such as cj son or simplejson The primary disadvantage to JSON is that it limits you to the following data types strings Unicode floats boolean dictionaries and lists Decimals and dates are notably missing Also binary data will be transferred using Base64 encoding which will cause the transferred data to be around 34 larger than an encoding which supports native binary types However if your data fits inside the above constraints and you need cross language support the default setting of JSON is probably your best choice See http json org for more information pickle If you have no desire to support any language other than Python then using the pickle encoding will gain you the support of all built in Python data types except class instances smaller messages when send ing binary files and a slight speedup over JSON processing See http docs python org library pickle html for more information yaml YAML has many of the same characteristics as json except that it natively supports more data types in cluding dates recursive references etc However the Python libraries for YAML are a good bit slower than the libraries for JSON If you need a more expressive set of data types and need to maintain cross language compatibility then YAML may be a better f
184. P broker can also define additional exchange types so see your broker manual for more information about available exchange types edirect default Direct match between the routing key in the message and the rout ing criteria used when a queue is bound to this exchange etopic Wildcard match between the routing key and the routing pattern specified in the exchange queue binding The routing key is treated as zero or more words delimited by and supports special wild card characters matches a single word and matches zero or more words efanout Queues are bound to this exchange with no arguments Hence any message sent to this exchange will be forwarded to all queues bound to this exchange eheaders 2 14 Internals 359 Celery Documentation Release 3 0 25 Queues are bound to this exchange with a table of arguments con taining headers and values optional A special argument named x match determines the matching algorithm where all implies an AND all pairs must match and any implies OR at least one pair must match arguments is used to specify the arguments This description of AMQP exchange types was shamelessly stolen from the blog post AMQP in 10 minutes Part 4 by Rajith Attapattu This article is recommended reading channel The channel the exchange is bound to if bound durable Durable exchanges remain active when a server restarts Non durable exchanges tr
185. PI Reference 273 Celery Documentation Release 3 0 25 args positional arguments delivery_info None message delivery information classmethod from_request request hostname None worker node name id None task id kwargs keyword arguments name None task name 2 13 28 celery contrib migrate celery contrib migrate Migration tools e celery contrib migrate j class celery contrib migrate State count 0 filtered 0 strtotal total_apx 0 exception celery contrib migrate StopFiltering celery contrib migrate expand_dest ret exchange routing_key celery contrib migrate filter_callback callback tasks celery contrib migrate filter_status state body message celery contrib migrate migrate_task producer body_ message queues None celery contrib migrate migrate_tasks source dest migrate lt function migrate_task at Ox7fb76261caa0 gt app None queues None kwargs celery contrib migrate move predicate connection None exchange None routing_key None source None app None callback None limit None trans form None kwargs Find tasks by filtering them and move the tasks to a new queue Parameters 274 Chapter 2 Contents Celery Documeniation Release 3 0 25 e predicate Filter function used to decide which messages to move Must accept the standard signature of body message used by Kombu consumer callbacks If the predicate wants the messag
186. Put an item onto the queue TokenBucket Queue put_nowait item Put an item into the queue without blocking Raises Queue Full If a free slot is not immediately available TokenBucket Queue qsize Returns the size of the queue TokenBucketQueue wait block False Wait until a token can be retrieved from the bucket and return the next item celery worker buckets chain_from_iterable chain from_iterable iterable gt chain object Alternate chain contructor taking a single iterable argument that evaluates lazily celery worker heartbeat e celery worker heartbeat j celery worker heartbeat This is the internal thread that sends heartbeat events at regular intervals class celery worker heartbeat Heart timer eventer interval None Timer sending heartbeats at regular intervals Parameters timer Timer instance e eventer Event dispatcher used to send the event interval Time in seconds between heartbeats Default is 30 seconds start stop celery worker hub e celery worker hub j 2 14 Internals 331 Celery Documentation Release 3 0 25 celery worker hub Event loop implementation class celery worker hub BoundedSemaphore value Asynchronous Bounded Semaphore Bounded means that the value will stay within the specified range even if it is released more times than it was acquired This type is not thread safe Example gt gt gt x Bo
187. S X e Windows e CentOS Generic init scripts See the extra generic init d directory Celery distribution This directory contains generic bash init scripts for celeryd that should run on Linux FreeBSD OpenBSD and other Unix platforms Init script celeryd Usage etc init d celeryd start stop restart status Configuration file etc default celeryd To configure celeryd you probably need to at least tell it where to change directory to when it starts to find your celeryconfig Example configuration This is an example configuration for a Python project etc default celeryd 166 Chapter 2 Contents Celery Documeniation Release 3 0 25 Or we Coulc CELERYD_NODES Where to chdir at start CELERYD_CHDIR opt Myproject Extra arguments to celeryd CELERYD_OPTS time limit 300 concurrency 8 Sn will be replaced with the nodename CELERYD_LOG_FILE var log celery n log CELERYD_PID_FILE var run celery n pid d user Workers should run as an unprivileg CELERYD_USER celery CELERYD_GROUP celery Example Django configuration This is an example configuration for those using django celery ame of nodes to start here we have a single node CELERYD_NODES w1 or we could have three nodes CELERYD_NODES wl w2 w3 Where to chdir at start CELERYD_CHDIR opt Myproject zj
188. SIGINT List of signals to ignore when a child process starts celery concurrency processes WORKER_SIGRESET frozenset SIGHUP SIGTERM SIGTTOU SIGTTIN lt List of signals to reset when a child process starts celery concurrency processes process_initializer app hostname Initializes the process so it can be used to process tasks celery concurrency eventlett experimental celery concurrency eventlet j 2 14 Internals 343 Celery Documentation Release 3 0 25 celery concurrency eventlet Eventlet pool implementation class c elery concurrency eventlet Schedule args kwargs clear queue class c elery concurrency eventlet TaskPool args kwargs class Timer schedule None on_error None on_tick None max_interval None kwargs class c class Schedule args kwargs clear queue TaskPool Timer cancel tref TaskPool Timer ensure_started TaskPool Timer start TaskPool Timer stop askPool is_green True askPool on_apply target args None kwargs None callback None accept_callback None kk O askPool on_start askPool on_stop askPool rlimit_safe False askPool signal_safe False elery concurrency eventlet Timer schedule None on_error None on_tick None max_interval None kwargs class Schedule args kwargs clear queue Timer canceli tref Timer ensure_
189. Thread 340 Chapter 2 Contents Celery Documeniation Release 3 0 25 authkey daemon exitcode Return exit code of process or None if it has yet to stop ident Return identifier PID of process or None if it has yet to start is_alive Return whether process is alive join timeout None Wait until child process terminates name pid Return identifier PID of process or None if it has yet to start run Method to be run in sub process can be overridden in sub class sentinel Return a file descriptor Unix or handle Windows suitable for waiting for process termina tion start Start child process terminate Terminate process sends SIGTERM signal or uses TerminateProcess class TaskPool Pool ResultHandler outqueue get cache poll join_exited_workers putlock restart_state check_timeouts body finish_at_shutdown handle_timeouts False handle_event args on_stop_not_started exception TaskPool Pool SoftTimeLimitExceeded The soft time limit has been exceeded This exception is raised to give the task a chance to clean up class TaskPool Pool Supervisor pool body class TaskPool Pool TaskHandler taskqueue put outqueue pool body on_stop_not_started tell_others class TaskPool Pool TimeoutHandler processes cache t_soft t_hard 2 14 Internals 341 Celery Documentation Release 3 0 25 as as as as as as as as as
190. URL amqp CELERY_RESULT_BACKEND amqp ELERY_TASK_SERIALIZER json Cc CELERY_RESULT_SERIALIZER json fe c T ELERY_TIMEZONE Europe Oslo ELERY_ ENABLE _UTC True To verify that your configuration file works properly and doesn t contain any syntax errors you can try to import it S python m celeryconfig For a complete reference of configuration options see Configuration and defaults To demonstrate the power of configuration files this how you would route a misbehaving task to a dedicated queue celeryconfig py CELERY_ROUTES Beasisseadda MlowopEtorriseyie Or instead of routing it you could rate limit the task instead so that only 10 tasks of this type can be processed in a minute 10 m celeryconfig py CELERY_ANNOTATIONS Beaskseadd Irate Emits aOy miZ If you are using RabbitMQ Redis or MongoDB as the broker then you can also direct the workers to set a new rate limit for the task at runtime celery control rate_limit tasks add 10 m worker example com OK new rate limit set successfully See Routing Tasks to read more about task routing and the CELERY_ANNOTATIONS setting for more about anno tations or Monitoring and Management Guide for more about remote control commands and how to monitor what your workers are d
191. What s new in Celery 2 5 199 Celery Documeniation Release 3 0 25 2 11 3 Deprecations Removals The old TaskSet signature of task_name list_of_tasks can no longer be used originally sched uled for removal in 2 4 The deprecated task_name and task attributes has also been removed e The functions celery execute delay_task celery execute apply and celery execute apply_async has been removed originally scheduled for removal in 2 3 The built in ping task has been removed originally scheduled for removal in 2 3 Please use the ping broadcast command instead It is no longer possible to import subtask and TaskSet from celery task base please import them from celery task instead originally scheduled for removal in 2 4 Deprecations e The celery decorators module has changed status from pending deprecation to deprecated and is sched uled for removal in version 4 0 The celery task module must be used instead 2 11 4 News Timezone support Celery can now be configured to treat all incoming and outgoing dates as UTC and the local timezone can be config ured This is not yet enabled by default since enabling time zone support means workers running versions pre 2 5 will be out of sync with upgraded workers To enable UTC you have to set CELERY_ENABLE_UTC CELERY_ENABLE UTC True When UTC is enabled dates and times in task messages will be converted to UTC and th
192. _ is now optimized away in the task tracer rather than when the task class is created This fixes a bug where a custom __call__ may mysteriously disappear Autoreload s inotify support has been improved Contributed by Mher Movsisyan The Django broker documentation has been improved Removed confusing warning at top of routing user guide release date 2012 03 01 01 00 P M GMT by Ask Solem Eventlet Gevent A small typo caused celeryd to hang when eventlet gevent was used this was because the environment was not monkey patched early enough Eventlet Gevent Another small typo caused the mediator to be started with eventlet gevent which would make celeryd sometimes hang at shutdown Mulitprocessing Fixed an error occurring if the pool was stopped before it was properly started Proxy objects now redirects ___ doc___ and___ name___ so he lp obj works 398 Chapter 2 Contents Celery Documeniation Release 3 0 25 e Internal timer timer2 now logs exceptions instead of swallowing them Issue 626 e celeryctl shell can now be started with vent let or gevent options to apply their monkey patches 2 5 0 release date 2012 02 24 04 00 PM GMT by Ask Solem See What s new in Celery 2 5 Since the changelog has gained considerable size we decided to do things differently this time by having separate what s new documents for major version changes Bugfix releases will still be found in the chang
193. _ALWAYS_EAGER setting is enabled will propagate exceptions It s the same as always running apply with throw True 138 Chapter 2 Contents Celery Documeniation Release 3 0 25 CELERY_IGNORE_RESULT Whether to store the task return values or not tombstones If you still want to store errors just not successful return values you can set CELERY_STORE_FRRORS_EVEN_IF_IGNORED CELERY_MESSAGE_COMPRESSION Default compression used for task messages Can be gzip bzip2 if available or any custom compression schemes registered in the Kombu compression registry The default is to send uncompressed messages CELERY_TASK_RESULT_EXPIRES Time in seconds or a t imedelta object for when after stored task tombstones will be deleted A built in periodic task will delete the results after this time celery task backend_cleanup A value of None or 0 means results will never expire depending on backend specifications Default is to expire after 1 day Note For the moment this only works with the amqp database cache redis and MongoDB backends When using the database or MongoDB backends celerybeat must be running for the results to be expired CELERY_MAX_CACHED_RESULTS Result backends caches ready results used by the client This is the total number of results to cache before older results are evicted The default is 5000 CELERY_CHORD_PROPAGATES New in version 3
194. _delay 10 screen_height screen_width selected_position 0 selected_str Selected selected_task None selection_info selection_rate_limit selection_result selection_traceback tasks win None workers class celery events cursesmon DisplayThread display run celery events cursesmon capture_events app state display celery events cursesmon evtop app None celery events dumper e celery events dumper j 374 Chapter 2 Contents Celery Documeniation Release 3 0 25 celery events dumper This is a simple program that dumps events to the console as they happen Think of it like a tcpdump for Celery events class celery events dumper Dumper out lt open file lt stdout gt mode w at Ox7fb76c556150 gt ce ce ce format_task_event hostname timestamp type task ev on_event ev say msg lt lery events dumper evdump app None out lt open file lt stdout gt mode w at 0x7fb76c556150 gt lery events dumper humanize_type type lery events dumper say msg out lt open file lt stdout gt mode w at 0x7fb76c556150 gt celery backends database models e celery backends database models j celery backends database models Database tables for the SQLAlchemy result store backend class celery backends database models Task task_id Task result status date_done id result status task_id to_dict tra
195. a tive None celery utils worker_direct hostname celery utils functional e celery utils functional j celery utils functional Utilities for functions class celery utils functional LRUCache limit None LRU Cache implementation using a doubly linked list to track access Parameters limit The maximum number of keys to keep in the cache When a new key is inserted and the limit has been exceeded the Least Recently Used key will be discarded from the cache incr key delta items iteritems itervalues keys update args kwargs 2 14 Internals 377 Celery Documentation Release 3 0 25 values celery utils functional chunks it n Split an iterator into chunks with n elements each Examples n 2 gt gt gt x chunks iter 0 1 2 3 4 5 6 7 8 9 10 2 gt gt gt list x 0 1 2 3 4 5 6 7 8 9 10 n 3 gt gt gt x chunks iter 0 1 2 3 4 5 6 7 8 9 10 3 gt gt gt list x 0 1 2 3 4 5 6 7 8 9 10 celery utils functional first predicate it Returns the first element in iterable that predicate returns a True value for If predicate is None it will return the first item that is not None celery utils functional firstmethod method Returns a function that with a list of instances finds the first instance that returns a value for the given method The list can also contain promises promise
196. able in the cluster By default the entries are taken from the CELERYBEAT_SCHEDULE setting but custom stores can also be used like storing the entries in an SQL database You have to ensure only a single scheduler is running for a schedule at a time otherwise you would end up with duplicate tasks Using a centralized approach means the schedule does not have to be synchronized and the service can operate without using locks Time Zones The periodic task schedules uses the UTC time zone by default but you can change the time zone used using the CELERY_TIMEZONE setting The pytz library is recommended when setting a default timezone If pytz is not installed it will fallback to the mod dateutil library which depends on a system timezone file being available for the timezone selected Timezone definitions change frequently so for the best results an up to date pyt z installation should be used S pip install U pytz An example time zone could be Europe London CELERY_TIMEZONE Europe London The default scheduler storing the schedule in the celerybeat schedule file will automatically detect that the time zone has changed and so will reset the schedule itself but other schedulers may not be so smart e g the Django database scheduler see below and in that case you will have to reset the schedule manually Django Users Celery recommends and is compatible with
197. ach Issue 447 ErrorMail with the implementation for The error mail class can be sub classed to gain complete control of when error messages are sent thus removing the need for a separate white list setting The CELERY TASK ERROR_WHIT completely in version 4 0 e Additional Deprecations ELIST setting has been deprecated and will be removed The following functions has been deprecated and is scheduled for removal in version 4 0 Old function Alternative celery loaders current_loader celery loaders load_settings celery execute apply celery execute apply_async celery execute delay_task celery current_app loader celery current_app conf Task apply Task apply_async celery execute send_task Old setting Alternative CELERYD_LOG_LEVEL celeryd loglevel CELERYD_LOG_FILE celeryd logfile CELERYBEAT_LOG_LEVEL celerybeat loglevel CELERYBEAT_LOG_FILE celerybeat logfile CELERYMON_LOG_LEVEL celerymon loglevel CELERYMON_LOG_FILE celerymon logfile The following settings has been deprecated and is scheduled for removal in version 4 0 402 Chapter 2 Contents Celery Documeniation Release 3 0 25 News e No longer depends on pyparsing e Now depends on Kombu 1 4 3 e CELERY_IMPORTS can now be a scalar value Issue 485 It is too easy to forget to add the comma after the sole element of a tuple and this is somethi
198. ad join timeout overflow Issue 796 A test case was occasionally broken for Python 2 5 Unit test suite now passes for PyPy 1 9 App instances now supports the with statement This calls the new close method at exit which cleans up after the app like closing pool con nections Note that this is only necessary when dynamically creating apps e g for temporary apps Support for piping a subtask to a chain For example pipe sometask s othertask s new_pipe mytask s pipe Contributed by Steve Morin Fixed problem with group results on non pickle serializers Fix contributed by Steeve Morin 2 12 18 3 0 8 release date 2012 08 29 05 00 PM BST Now depends on Kombu 2 4 4 Fixed problem with amaqplib and receiving larger message payloads Issue 922 The problem would manifest itself as either the worker hanging or occasionally a Framing error exception appearing Users of the new pyamaqp transport must upgrade to amqp 0 9 3 Beat Fixed another timezone bug with interval and crontab schedules Issue 943 Beat The schedule file is now automatically cleared if the timezone is changed The schedule is also cleared when you upgrade to 3 0 8 from an earlier version this to register the initial timezone info Events The worker heartbeat event now include processed and active count fields 2 12 Change history 221 Celery Documentation Release 3 0 25 Contributed by Mher Movsisyan e
199. add delay 4 4 The ready method returns whether the task has finished processing or not gt gt gt result ready False 22 Chapter 2 Contents Celery Documeniation Release 3 0 25 You can wait for the result to complete but this is rarely used since it turns the asynchronous call into a synchronous one gt gt gt result get timeout 1 In case the task raised an exception get will re raise the exception but you can override this by specifying the propagate argument gt gt gt result get propagate True If the task raised an exception you can also gain access to the original traceback gt gt gt result traceback See celery result for the complete result object reference Configuration Celery like a consumer appliance doesn t need much to be operated It has an input and an output where you must connect the input to a broker and maybe the output to a result backend if so wanted But if you look closely at the back there s a lid revealing loads of sliders dials and buttons this is the configuration The default configuration should be good enough for most uses but there s many things to tweak so Celery works just the way you want it to Reading about the options available is a good idea to get familiar with what can be configured You can read about the options in the the Configuration and defaults reference The configuration can be set on the app directly or by using a dedicated configu
200. ading utilities class celery util class celery util e celery utils threads j ls threads Local ls threads LocalManager locals None ident_func None Local objects cannot manage themselves For that you need a local manager You can pass a local manager multiple locals or add them later by appending them to manager locals Everytime the manager cleans up it will clean up all the data left in the locals for this context The ident_func cleanup parameter can be added to override the default ident function for the wrapped locals Manually clean up the data in the locals for this context Call this get_ident at the end of the request or use make_middleware Return the context identifier the local objects use internally for this context You cannot override this method to change the behavior but use it to link other context local objects such as SQLAIchemy s scoped sessions to the Werkzeug locals celery utils threads LocalStack alias of _LocalStack class celery utils threads bgThread name None kwargs body on_crash msg fmt kwargs run stop Graceful shutdown 2 14 Internals 383 Celery Documentation Release 3 0 25 celery utils threads release_local local Releases the contents of the local for the current context This makes it possible to use locals without a manager Example gt gt gt loc Local gt gt gt loc foo 42 gt g
201. ages False tasks None queues None call back None forever False on_declare_queue None consume_from None state None kwargs migrate task_id_eq task_id body message migrate task_id_in ids body message 2 13 29 celery contrib rdb Remote http snippets dzone com posts show 7248 Usage debugger for Celery tasks running in multiprocessing pool workers Inspired by from celery contrib import rdb from celery import task task def add x y result x rdb set_trace return result Y Environment Variables CELERY_RDB_HOST CELERY_RDB_PORT Hostname to bind to Default is 127 0 01 which means the socket will only be accessible from the local host Base port to bind to Default is 6899 The debugger will try to find an available port starting from the base port The selected port will be logged by the worker 276 Chapter 2 Contents Celery Documeniation Release 3 0 25 celery contrib rdb set_trace frame None Set breakpoint at current location or a specified frame celery contrib rdb debugger Returns the current debugger instance if any or creates a new one class celery contrib rdb Rdb host 127 0 0 1 port 6899 port_search_limit 100 port_skew 0 out lt open file lt stdout gt mode w at 0x7fb76c556150 gt 2 13 30 celery contrib methods Task decorator that supports creating tasks out of methods Examples from celery contrib methods i
202. ain app freq 1 0 state app events State with app connection as connection recv app events Receiver connection handlers with DumpCam state freq freq recv capture limit None timeout None if name main__ celery Celery broker amgp guest localhost main celery Real time processing To process events in real time you need the following e An event consumer this is the Receiver A set of handlers called when events come in x s state event You can have different handlers for each event type or a catch all handler can be used e State optional celery events State is a convenient in memory representation of tasks and workers in the cluster that is updated as events come in It encapsulates solutions for many common things like checking if a worker is still alive by verifying heart beats merging event fields together as events come in making sure timestamps are in sync and so on Combining these you can easily process events in real time from celery import Celery def monitor_events app state app events State def on_event event state event event lt updates in memory clus o print Workers online Sr Jjoin te r state worker for worker in state workers if worker alive with app connection as connection recv app events Receiver connection handlers x gt on_event recv cap
203. alance between calling it regularly for responsiveness but not too often for performance name celery contrib abortable AbortableTask rate_limit None request_stack lt celery utils threads _LocalStack object at 0x7fb76428db50 gt 2 13 27 celery contrib batches Experimental task class that buffers messages and processes them as a list Warning For this to work you have to set CELERYD_PREFETCH_MULTIPLIER to zero or some value where the final multiplied value is higher than flush_every In the future we hope to add the ability to direct batching tasks to a channel with different QoS requirements than the task channel Simple Example A click counter that flushes the buffer every 100 messages and every seconds Does not do anything with the data but can easily be modified to store it in a database sssages or 1U seconds app task base Batches lush_every 100 flush_interval 10 def count_click requests from collections import Counter count Counter request kwargs url for request in requests for url count in count items print P e eks Gas gt es url count Flush after 100 mess Then you can ask for a click to be counted by doing gt gt gt count_click delay http example com Example returning results An interface to the Web of Trust API that flushes the buffer every 100 messages and every 10 seconds 272 Chapter 2 Contents Ce
204. alled with the return value of the parent task as a partial argument ETA and countdown The ETA estimated time of arrival lets you set a specific date and time that is the earliest time at which your task will be executed countdown is a shortcut to set eta by seconds into the future gt gt gt result add apply_async 2 2 countdown 3 gt gt gt result get this akes at least 3 seconds to return The task is guaranteed to be executed at some time after the specified date and time but not necessarily at that exact time Possible reasons for broken deadlines may include many items waiting in the queue or heavy network latency To make sure your tasks are executed in a timely manner you should monitor the queue for congestion Use Munin or similar tools to receive alerts so appropriate action can be taken to ease the workload See Munin While countdown is an integer eta must be a dat et ime object specifying an exact date and time including mil lisecond precision and timezone information gt gt gt from datetime import datetime timedelta gt gt gt tomorrow datetime utcnow timedelta days 1 gt gt gt add apply_async 2 2 eta tomorrow 62 Chapter 2 Contents Celery Documeniation Release 3 0 25 Expiration The expires argument defines an optional expiry time either as seconds after task publish or a specific date and time using datetime gt gt gt Task expires after one minu
205. alse signal SIGTERM kwargs Tell all or specific workers to revoke a task by id If a task is revoked the workers will ignore the task and not execute it after all Parameters e task_id Id of the task to revoke e terminate Also terminate the process currently working on the task if any e signal Name of signal to send to process if terminate Default is TERM See broadcast for supported keyword arguments Control time_limit task_name soft None hard None kwargs Tell all or specific workers to set time limits for a task by type Parameters e task_name Name of task to change time limits for soft New soft time limit in seconds e hard New hard time limit in seconds Any additional keyword arguments are passed on to broadcast class celery app control Inspect destination None timeout 1 callback None connec tion None app None limit None active safe False active_queues app None conf ping registered taskinfoitems registered_tasks taskinfoitems report reserved safe False revoked scheduled safe False stats celery app control flatten_reply reply 2 13 API Reference 245 Celery Documentation Release 3 0 25 2 13 7 celery app registry e celery app registry j celery app registry Registry of available tasks class celery app registry TaskRegistry exception NotRegistered The task is not registered
206. ame Replace with CELERY_AMQP_CONSUMER_QUEUES CELERY_QUEUES CELERY_AMQP_CONSUMER_QUEUES CELERY_QUEUES CELERY_AMQP_EXCHANGE CELERY_DEFAULT_EXCHANGE CELERY_AMOQP_EXCHANGE_TYPE CELERY_DEFAULT_AMQP_EXCHANGE_TYPE CELERY_AMQP_CONSUMER_ROUTING_KEY CELERY_QUEUES CELERY_AMQP_PUBLISHER_ROUTING_KEY CELERY_DEFAULT_ROUTING_KEY e CELERY LOADER definitions without class name E g celery loaders default needs to include the class name celery loaders default Loader e TaskSet run Use celery task base TaskSet apply async instead e The module celery task rest use celery task http instead 2 14 3 Internals The worker e Introduction e Data structures ready_queue eta_schedule e Components Consumer ScheduleController Mediator TaskPool Introduction The worker consists of 4 main components the consumer the scheduler the mediator and the task pool All these components runs in parallel working with two data structures the ready queue and the ETA schedule 2 14 Internals 311 Celery Documentation Release 3 0 25 Data structures ready_queue The ready queue is either an instance of Queue Queue or celery buckets TaskBucket The latter if rate limiting is enabled eta_schedule The ETA schedule is a heap queue sorted by time Components Consumer Receives messages from the broker using Kombu When a message is received it s converted into a celery worker j
207. an existing subtask with augmented arguments options Example gt gt gt s add subtask 5 gt gt gt new s clone args 10 countdown 5 gt gt gt new args TO 3 gt gt gt new options countdown 5 e Chord callbacks are now triggered in eager mode Fixes e Programs now verifies that the pidfile is actually written correctly Issue 641 2 15 History 397 Celery Documentation Release 3 0 25 2 5 1 Fixes Hopefully this will crash the worker immediately if the system is out of space to store the complete pidfile In addition we now verify that existing pidfiles contain a new line so that a partially written pidfile is detected as broken as before doing echo n 1 gt celeryd pid would cause celeryd to think that an existing instance was already running init has pid 1 after all Fixed 2 5 compatibility issue with use of print_exception Fix contributed by Martin Melin Fixed 2 5 compatibility issue with imports Fix contributed by Iurii Kriachko All programs now fix up ___package__ when called as main This fixes compatibility with Python 2 5 Fix contributed by Martin Melin celeryctl can now be configured on the command line Like with celeryd it is now possible to configure celery settings on the command line for celeryctl celeryctl broker pool_limit 30 Version dependency for python dateutil fixed to be strict Fix contributed by Thomas Meson Task __call_
208. and process hundreds of feeds every second while the multiprocessing pool spent 14 seconds processing 100 feeds Note that is one of the applications evented I O is especially good at asynchronous HTTP requests You may want a mix of both Eventlet and multiprocessing workers and route tasks according to compatibility or what works best Enabling Eventlet You can enable the Eventlet pool by using the P option to celery worker celery worker P eventlet c 1000 Examples See the Eventlet examples directory in the Celery distribution for some examples taking use of Eventlet support 2 3 13 Signals 2 3 User Guide 121 Celery Documeniation Release 3 0 25 e Basics e Signals Task Signals x task sent task_prerun task_postrun task_success task_failure task_revoked Worker Signals x celeryd_after_setup celeryd_init worker_init worker_ready worker_process_init worker_shutdown Celerybeat Signals x beat_init x beat_embedded_init Eventlet Signals eventlet_pool_started eventlet_pool_preshutdown eventlet_pool_postshutdown eventlet_pool_apply Logging Signals setup_logging after_setup_logger x after_setup_task_logger l l l x o Signals allows decoupled applications to receive notifications when certain actions occur elsewhere in the application Celery ships with many signals that you application can hook into to augment behavior of certain actions Basics Sev
209. andles connection loss e Will now retry sending the task sent event in case of connection failure e amqp backend Now uses Message requeue instead of republishing the message after poll e New BROK ER H KARTB EAT CH ECKRAT E setting introduced to modify the rate at which broker connection heartbeats are monitored The default value was also changed from 3 0 to 2 0 e celery events state State is now pickleable Fix contributed by Mher Movsisyan 214 Chapter 2 Contents Celery Documeniation Release 3 0 25 celery datastructures LRUCache is now pickleable Fix contributed by Mher Movsisyan The stats broadcast command now includes the workers pid Contributed by Mher Movsisyan New conf remote control command to get a workers current configuration Contributed by Mher Movsisyan Adds the ability to modify the chord unlock task s countdown argument Issue 1146 Contributed by Jun Sakai beat The scheduler now uses the now method of the schedule so that schedules can provide a custom way to get the current date and time Contributed by Rapha l Slinckx Fixed pickling of configuration modules on Windows or when execv is used Issue 1126 Multiprocessing logger is now configured with loglevel ERROR by default Since 3 0 the multiprocessing loggers were disabled by default only configured when the MP_LOG environment variable was set 2 12 13 3 0 13 relea
210. ansient ex changes are purged when a server restarts Default is True auto_delete If set the exchange is deleted when all queues have finished using it Default is False delivery mode The default delivery mode used for messages The value is an integer or alias string e or transient The message is transient Which means it is stored in memory only and is lost if the server dies or restarts 2 or persistent default The message is persistent Which means the message is stored both in memory and on disk and therefore preserved if the server dies or restarts The default value is 2 persistent arguments Additional arguments to specify when the exchange is declared Message body delivery_mode None priority None content_type None con tent_encoding None properties None headers None Create message instance to be sent with publish Parameters body Message body delivery mode Set custom delivery mode Defaults to delivery_mode priority Message priority 0 to 9 currently not supported by Rab bitMQ content_type The messages content_type If content_type is set no serialization occurs as it is assumed this is either a binary object or you ve done your own serialization Leave blank if using built in serialization as our library properly sets content_type content_encoding The character set in which this object is encoded Use binary if sending in raw bina
211. apply_async this happens in a temporary task instead gt gt gt g group add s i i for i in xrange 10 gt gt gt g apply_async This is useful because you can e g specify a time for the messages in the group to be called gt gt gt g apply_async countdown 10 e Simple chord The chord primitive enables us to add callback to be called when all of the tasks in a group have finished executing which is often required for algorithms that aren t embarrassingly parallel gt gt gt from celery import chord gt gt gt res chord add s i i for i in xrange 10 xsum s gt gt gt res get The above example creates 10 task that all start in parallel and when all of them are complete the return values are combined into a list and sent to the xsum task The body of a chord can also be immutable so that the return value of the group is not passed on to the callback gt gt gt chord import_contact s c for c in contacts notify_complete si import_id apply_async 2 3 User Guide 71 Celery Documentation Release 3 0 25 Note the use of si above which creates an immutable subtask e Blow your mind by combining Chains can be partial too gt gt gt cl add s 4 mul s 8 16 4 gt 8 gt gt gt res cl1 16 gt gt gt res get 160 Which means that you can combine chains 4 16 2 4 x 8 gt gt gt c2 add s 4 16 mul s 2 add s 4 mul
212. apter 2 Contents Celery Documeniation Release 3 0 25 e logfile The logfile used by the task execute_using_pool pool kwargs Like execute but using a worker pool Parameters pool A celery concurrency base TaskPool instance Raises celery exceptions TaskRevokedError if the task was revoked and ignored expires extend_with_default_kwargs Extend the tasks keyword arguments with standard task arguments Currently these are logfile loglevel task_id task_name task_retries and delivery_info See celery task base Task run for more information Magic keyword arguments are deprecated and will be removed in version 4 0 classmethod from_message message body kwargs hostname id ignored_msg Task name s id s ignored n info safe False internal_error_msg Task name s id s INTERNAL ERROR exc s n Format string used to log internal error kwargs maybe_expire If expired mark the task as revoked name on_accepted pid time_accepted Handler called when task is accepted by worker pool on_ack on_failure exc_info Handler called if the task raised an exception on_retry exc_info Handler called if the task should be retried on_success ret_value now None Handler called if the task was successfully processed on_timeout soft timeout Handler called if the task times out repr_result result maxlen 46 request_dict retry_msg Task name s id
213. apter is available to read for free here The back of the envelope The book is a classic text Highly recommended 2 3 User Guide 119 Celery Documentation Release 3 0 25 Worker Settings Prefetch Limits Prefetch is a term inherited from AMQP that is often misunderstood by users The prefetch limit is a limit for the number of tasks messages a worker can reserve for itself If it is zero the worker will keep consuming messages not respecting that there may be other available worker nodes that may be able to process them sooner or that the messages may not even fit in memory The workers default prefetch count is the CELERYD_PREFETCH_MULTIPLIER setting multiplied by the number of child worker processes If you have many tasks with a long duration you want the multiplier value to be 1 which means it will only reserve one task per worker process at a time However If you have many short running tasks and throughput round trip latency is important to you this number should be large The worker is able to process more tasks per second if the messages have already been prefetched and is available in memory You may have to experiment to find the best value that works for you Values like 50 or 150 might make sense in these circumstances Say 64 or 128 If you have a combination of long and short running tasks the best option is to use two worker nodes that are configured separately and
214. ar e gevent Now supports autoscaling Issue 599 Contributed by Mark Lavin e multiprocessing Mediator thread is now always enabled even though rate limits are disabled as the pool semaphore is known to block the main thread causing broadcast commands and shutdown to depend on the semaphore being released 2 11 5 Fixes e Exceptions that are re raised with a new exception object now keeps the original stack trace e Windows Fixed the no handlers found for multiprocessing warning 204 Chapter 2 Contents Celery Documeniation Release 3 0 25 Windows The celeryd program can now be used Previously Windows users had to launch celeryd using python m celery bin celeryd Redis result backend Now uses SETEX command to set result key and expiry atomically Suggested by yaniv aknin celeryd Fixed a problem where shutdown hanged when Ctrl C was used to terminate celeryd No longer crashes when channel errors occur Fix contributed by Roger Hu Fixed memory leak in the eventlet pool caused by the use of greenlet getcurrent Fix contributed by Ignas Mikalajnas Cassandra backend No longer uses pycassa connect which is deprecated since pycassa 1 4 Fix contributed by Jeff Terrace Fixed unicode decode errors that could occur while sending error emails Fix contributed by Seong Wun Mun celery bin programs now always defines _ pack age___ as recommended by PEP 366 s
215. args print In task s kwargs task_id return x y And this will not use magic keyword arguments new style from celery task import task task def add x y print In task s add request id return x y In addition tasks can choose not to accept magic keyword arguments by setting the task accept_magic_kwargs attribute 416 Chapter 2 Contents Celery Documeniation Release 3 0 25 Deprecation Using the decorators in celery decorators emits a PendingDeprecationWarning with a helpful message urging you to change your code in version 2 4 this will be replaced with a DeprecationWarning and in version 4 0 the celery decorators module will be re moved and no longer exist Similarly the task accept_magic_kwargs attribute will no longer have any effect starting from ver sion 4 0 e The magic keyword arguments are now available as task request This is called the context Using thread local storage the context contains state that is related to the current request It is mutable and you can add custom attributes that will only be seen by the current task request The following context attributes are always available Magic Keyword Argument Replace with kwargs task_id self request id kwargs delivery_info self request delivery_info kwargs task_retries self request retries kwargs logfile self request logfile kwargs loglevel self request logle
216. args None Keyword arguments to apply last_run_at None The time and date of when this task was last scheduled name None The task name next last_run_at None Returns a new instance of the same class but with its date and count fields updated options None Task execution options schedule None The schedule run_every crontab total_run_count 0 Total number of times this task has been scheduled update other Update values from another entry Does only update editable fields task schedule args kwargs options class celery beat Scheduler schedule None max_interval None app None Publisher None lazy False kwargs Scheduler for periodic tasks Parameters e schedule see schedule e max_interval see max_interval Entry alias of ScheduleEntry add kwargs apply async entry publisher None kwargs 350 Chapter 2 Contents Celery Documeniation Release 3 0 25 close connection get_schedule info install_default_entries data logger lt celery utils log SigSafeLogger object at 0x7fb7655e1150 gt max_interval 300 Maximum time to sleep between re checking the schedule maybe_due entry publisher None merge_inplace b publisher reserve entry schedule The schedule dict shelve send_task args kwargs set_schedule schedule setup_schedule should_sync sync sync_every 180 How often to sync the schedule 3 minutes b
217. art of Celery can be extended or used on its own Custom pool implementations serializers compression schemes logging schedulers consumers producers autoscalers bro ker transports and much more It supports e Brokers e RabbitMO Redis e MongoDB Beanstalk e CouchDB SQLAlchemy Django ORM Amazon SQS e and more Concurrency e multiprocessing e Eventlet gevent e threads single threaded e Result Stores e AMQP Redis e memcached MongoDB e SQLAIchemy Django ORM e Apache Cassandra e Serialization e pickle json yaml msgpack e zlib bzip2 compression e Cryptographic message signing Features 2 2 Getting Started 7 Celery Documentation Release 3 0 25 e Monitoring A stream of monitoring events is emitted by workers and is used by built in and external tools to tell you what your cluster is doing in real time Read more e Workflows Simple and complex workflows can be composed using a set of powerful primitives we call the canvas including grouping chaining chunking and more Read more e Time amp Rate Limits You can control how many tasks can be executed per second minute hour or how long a task can be allowed to run and this can be set as a default for a specific worker or individually for each task type Read more e Scheduling You can specify the time to run a task in seconds or a datetime or or you can use periodic tasks for recurring
218. as the final route for the task Broadcast Celery can also support broadcast routing Here is an example exchange broadcast_tasks that delivers copies of tasks to all workers connected to it from kombu common import Broadcast CELERY_QUEUES ll Broadcast broadcast_tasks CELERY_ROUTES ll tasks reload_cache queue broadcast_tasks Now the tasks reload_tasks task will be sent to every worker consuming from this queue Broadcast amp Results Note that Celery result does not define what happens if two tasks have the same task_id If the same task is distributed to more than one worker then the state history may not be preserved It is a good idea to set the task ignore_result attribute in this case 2 3 9 Monitoring and Management Guide 104 Chapter 2 Contents Celery Documeniation Release 3 0 25 e Introduction e Workers celery Command Line Management Utility Commands Specifying destination nodes Flower Real time Celery web monitor Features Usage celery events Curses Monitor RabbitMQ Inspecting queues e Redis Inspecting queues e Munin e Events Snapshots Custom Camera Real time processing e Event Reference Task Events x task sent task received task started task succeeded task failed task revoked x task retried Worker Events worker online worker heartbeat x worker offlin
219. ask but it won t terminate an already executing task unless the terminate option is set If terminate is set the worker child process processing the task will be terminated The default signal sent is TERM but you can specify this using the signal argument Signal can be the uppercase name of any signal defined in the signal module in the Python Standard Library Terminating a task also revokes it Example gt gt gt celery control revoke d9078da5 9915 40a0 bfal 392c7bde42ed gt gt gt celery control revoke d9078da5 9915 40a0 bfal 392c7bde42ed terminate True gt gt gt celery control revoke d9078da5 9915 40a0 bfal 392c7bde42ed terminate True signal SIGKILL Persistent revokes Revoking tasks works by sending a broadcast message to all the workers the workers then keep a list of revoked tasks in memory If you want tasks to remain revoked after worker restart you need to specify a file for these to be stored in either by using the statedb argument to celery worker or the CELERYD_STATE_DB setting Note that remote control commands must be working for revokes to work Remote control commands are only sup ported by the RabbitMQ amqp Redis and MongDB transports at this point Time Limits New in version 2 0 pool support processes 2 3 User Guide 83 Celery Documentation Release 3 0 25 Soft or hard The time limit
220. ask decorator syntax e celeryd now sends events if enabled with the E argument 460 Chapter 2 Contents Celery Documeniation Release 3 0 25 Excellent for monitoring tools one is already in the making http github com celery celerymon Current events include worker heartbeat _ task received succeeded failed retried worker online worker offline You can now delete revoke tasks that has already been applied You can now set the hostname celeryd identifies as using the hostname argument Cache backend now respects the CELERY_TASK_RESULT_EXPIRES setting Message format has been standardized and now uses ISO 8601 format for dates instead of datetime celeryd now responds to the SIGHUP signal by restarting itself Periodic tasks are now scheduled on the clock Le timedelta hours 1 means every hour at 00 minutes not every hour from the server starts To revert to the previous behaviour you can set PeriodicTask relative True Now supports passing execute options to a TaskSets list of args e g gt gt gt ts TaskSet add 2 2 countdown 1 4 4 countdown 2 tee 18 8 countdown 3 gt gt gt ts run Got a 3x performance gain by setting the prefetch count to four times the concurrency from an average task round trip of 0 1s to 0 03s A new Setting has been added CELERYD_PREFETCH_MULTIPLIER which is set to 4 by defau
221. asks crawl_the_web task to have a soft time limit of one minute and a hard time limit of two minutes gt gt gt celery control time_limit tasks crawl_the_web Only tasks that starts executing after the time limit change will be affected Rate Limits Changing rate limits at runtime Example changing the rate limit for the myapp mytask task to accept 200 tasks a minute on all servers gt gt gt celery control rate_limit myapp mytask 200 m 84 Chapter 2 Contents Celery Documeniation Release 3 0 25 Example changing the rate limit on a single host by specifying the destination host name gt gt gt celery control rate_limit myapp mytask 200 m destination workerl example com Max tasks per child setting New in version 2 0 pool support processes With this option you can configure the maximum number of tasks a worker can execute before it s replaced by a new process This is useful if you have memory leaks you have no control over for example from closed source C extensions The option can be set using the workers maxtasksperchild argument or _ using the CELERYD_MAX_TASKS_PER_CHILD setting Autoscaling New in version 2 2 pool support processes gevent The autoscaler component is used to dynamically resize the pool based on load The autoscaler adds more pool processes when there is work to do and start
222. ast 1 but you can select another region by configuring the BROKER_TRANSPORT_OPTIONS setting BROKER_TRANSPORT_OPTIONS region eu west l1 See also An overview of Amazon Web Services regions can be found here http aws amazon com about aws globalinfrastructure Visibility Timeout The visibility timeout defines the number of seconds to wait for the worker to acknowledge the task before the message is redelivered to another worker Also see caveats below This option is set via the BROKER_TRANSPORT_OPTIONS setting BROKER_TRANSPORT_OPTIONS visibility_timeout 3600 1 hour The default visibility timeout is 30 seconds Polling Interval The polling interval decides the number of seconds to sleep between unsuccessful polls This value can be either an int or a float By default the value is 1 second which means that the worker will sleep for one second whenever there are no more messages to read You should note that more frequent polling is also more expensive so increasing the polling interval can save you money The polling interval can be set via the BROKER_TRANSPORT_OPTIONS setting BROKER_TRANSPORT_OPTIONS polling_interval 0 3 Very frequent polling intervals can cause busy loops which results in the worker using a lot of CPU time If you need sub millisecond precision you should consider using another transport like RabbitMQ lt broker amgqp gt or Redis lt broker r
223. aster examples celery_http_gateway 96 Chapter 2 Contents Celery Documeniation Release 3 0 25 2 3 8 Routing Tasks Note Alternate routing concepts like topic and fanout may not be available for all transports please consult the transport comparison table e Basics Automatic routing Changing the name of the default queue x How the queues are defined Manual routing e AMQP Primer Messages Producers consumers and brokers Exchanges queues and routing keys Exchange types x Direct exchanges x Topic exchanges Related API commands Hands on with the API e Routing Tasks Defining queues Specifying task destination Routers Broadcast Basics Automatic routing The simplest way to do routing is to use the CELERY_CREATE_MISSING_QUEUES setting on by default With this setting on a named queue that is not already defined in CELERY_QUEUES will be created automatically This makes it easy to perform simple routing tasks Say you have two servers x and y that handles regular tasks and one server z that only handles feed related tasks You can use this configuration CELERY_ROUTES feed tasks import_feed queue feeds With this route enabled import feed tasks will be routed to the feeds queue while all other tasks will be routed to the default queue named celery
224. atch_uid is specified e sender The registered sender to disconnect e weak The weakref state to disconnect e dispatch_uid the unique identifier of the receiver to disconnect send sender named Send signal from sender to all connected receivers If any receiver raises an error the error propagates back through send terminating the dispatch loop so it is quite possible to not have all receivers called if a raises an error Parameters e sender The sender of the signal Either a specific object or None e named Named arguments which will be passed to receivers Returns a list of tuple pairs receiver response send_robust sender named Send signal from sender to all connected receivers catching errors Parameters e sender The sender of the signal Can be any python object normally one registered with a connect if you actually want something to occur e named Named arguments which will be passed to receivers These argu ments must be a subset of the argument names defined in providing_args Returns a list of tuple pairs receiver response Raises DispatcherKeyError if any receiver raises an error specifically any subclass of Except ion the error instance is returned as the result for that receiver celery utils dispatch saferef Safe weakrefs originally from pyDispatcher Provides a way to safely weakref any function including bound methods which aren t ha
225. ather add the project directory to the Python path 44 Chapter 2 Contents Celery Documeniation Release 3 0 25 import os import sys sys path append os path dirname os path realpath __file_ INSTALLED_APPS myapp This makes more sense from the reusable app perspective anyway Context request contains information and state related to the executing task The request defines the following attributes id The unique id of the executing task taskset The unique id of the taskset this task is a member of if any chord The unique id of the chord this task belongs to if the task is part of the header args Positional arguments kwargs Keyword arguments retries How many times the current task has been retried An integer starting at 0 is_eager Set to True if the task is executed locally in the client and not by a worker eta The original ETA of the task if any This is in UTC time depending on the CELERY_ENABLE_UTC setting expires The original expiry time of the task if any This is in UTC time depending on the CELERY_ENABLE_UTC setting logfile The file the worker logs to See Logging loglevel The current log level used hostname Hostname of the worker instance executing the task delivery_info Additional message delivery information This is a mapping containing the exchange and routing key used to deliver this task Used by e g ret ry to resend the task to the same d
226. ation tools by explicitly specifying dynamically created attributes in the celery and celery task modules e Terminating a task now results in RevokedTaskError instead of aWorkerLostError e AsyncResult revoke now accepts terminate and signal arguments e The task revoked event now includes new fields terminated signum and expired e The argument to TaskRevokedError is now one of the reasons revoked expired or terminated e Old Task class does no longer use classmethods for push_request and pop_request Issue 912 e GroupResult now supports the children attribute Issue 916 e AsyncResult collect now respects the intermediate argument Issue 917 e Fixes example task in documentation Issue 902 e Eventlet fixed so that the environment is patched as soon as possible e eventlet Now warns if celery related modules that depends on threads are imported before eventlet is patched e Improved event and camera examples in the monitoring guide e Disables celery command setuptools entrypoints if the command can t be loaded e Fixed broken dump_request example in the tasks guide 2 12 21 3 0 5 release date 2012 08 01 04 00 P M BST e Now depends on kombu 2 3 1 billiard 2 7 3 11 e Fixed a bug with the B option cannot pickle thread lock objects Issue 894 Issue 892 django celery 154 e The restart_pool control command now requires the CELERYD_POOL_RESTARTS setting to be enabled T
227. ay is true then the recorded buffer will be applied State freeze_while fun With a function to apply freezes the stream before and replays the buffer after the function returns e EventReceiver capture Now supports a timeout keyword argument celeryd The mediator thread is now disabled if CELERY_RATE_LIMITS is enabled and tasks are directly sent to the pool without going through the ready queue Optimization Fixes e Pool Process timed out by TimeoutHandler must be joined by the Supervisor so don t remove it from the internal process list See issue 192 TaskPublisher delay_task now supports exchange argument so exchange can be overridden when sending tasks in bulk using the same publisher See issue 187 celeryd no longer marks tasks as revoked if CELERY_IGNORE_RESULT is enabled See issue 207 AMQP Result backend Fixed bug with result get if CELERY_TRACK_STARTED enabled result get would stop consuming after receiving the STARTED state Fixed bug where new processes created by the pool supervisor becomes stuck while reading from the task Queue See http bugs python org issue 10037 Fixed timing issue when declaring the remote control command reply queue This issue could result in replies being lost but have now been fixed Backward compatible LoggerAdapter implementation Now works for Python 2 4 Also added support for several new method
228. b completion conn None counter 1 default line dispatch cid argline Dispatch and execute the command Lookup order is builtins gt amqp display_command_help cmd short False do_exit args The exit command do_help args get_amqp_api_command cmd arglist With a command name and a list of arguments convert the arguments to Python values and find the corresponding method on the AMQP channel object Returns tuple of method processed_args Example gt gt gt get_amqp_api_command queue delete pobox yes no lt bound method Channel queue_delete of Channel object at Ox gt gt get_names identchars inc_counter lt method wrapper next of itertools count object at 0x7fb7631ddd40 gt needs_reconnect False note m Say something to the user Disabled if silent onecmd line Parse line and execute command parseline line Parse input line Returns tuple of three items command_name arglist original_line E g gt gt gt parseline queue delete A B C queue delete A B C queue delete A B C 298 Chapter 2 Contents Celery Documeniation Release 3 0 25 prompt prompt_fmt d gt respond retval What to do with the return value of a command say m class celery bin camqadm Spec args kwargs AMQP Command specification Used to convert arguments
229. base Celery task celery task task args kwargs Decorator to create a task class out of any callable Examples task def refresh_feed url return Feed objects get url url refresh With setting extra options and using retry task max_retries 10 def refresh_feed url try return Feed objects get url url refresh except socket error exc refresh_feed retry exc exc Calling the resulting task 2 13 API Reference 249 Celery Documentation Release 3 0 25 gt gt gt refresh_feed http example com rss lt Feed http example com rss gt gt gt refresh_feed delay http example com rss Async ye ac6ad5c lt AsyncResult d0f4 da0b 4669 ba03 d5ab5ac6ad5d gt celery task periodic_task args options Decorator to create a task class out of any callable Examples task def refresh_feed url return Feed objects get url url refresh With setting extra options and using retry from celery task import current task exchange feeds def refresh_feed url try return Feed objects get url url refresh except socket error exc current retry exc exc Calling the resulting task gt gt gt refresh_feed http example com rss Regular lt Feed http example com rss gt gt gt gt refresh_feed delay http example com rss AsyncResult 8998d0f4 da0b 4669 ba03 d5ab5ac clas
230. bbitMQ This will set the default HA policy for a queue and the value can either be a string usually a11 CELERY_QUEUE_HA_POLICY all Using all will replicate the queue to all current nodes Or you can give it a list of nodes to replicate to CELERY_QUEUE_HA_ POLICY rabbit hostl rabbit host2 Using a list will implicitly set x ha policy to nodes and x ha policy paranms to the given list of nodes See http www rabbitmq com ha html for more information CELERY_WORKER_DIRECT This option enables so that every worker has a dedicated queue so that tasks can be routed to specific workers The queue name for each worker is automatically generated based on the worker hostname and a dq suffix using the C dq exchange For example the queue name for the worker with hostname w1 example com becomes wl example com dq Then you can route the task to the task by specifying the hostname as the routung key and the C dq exchange CELERY_ROUTES tasks add exchange MCdo routing_key fw example comi This setting is mandatory if you want to use the move_to_worker features of celery contrib migrate CELERY_CREATE_MISSING_QUEUES If enabled default any queues specified that are not defined in CELERY_QUEUES will be automatically created See Automatic routing CELERY_DEFAULT_QUEUE The name o
231. before however for custom apps the task decorator now returns a special PromiseProxy object that is only evaluated on access All promises will be evaluated when app finalize is called or implicitly when the task registry is first used Smart app option The app option now auto detects e If the provided path is a module it tries to get an attribute named celery e If the provided path is a package it tries to import a submodule named celery and get the celery attribute from that module E g if you have a project named proj where the celery app is located in from proj celery import celery then the following will be equivalent celery worker app proj S celery worker app proj celery S celery worker app proj celery celery In Other News e New CELERYD_WORKER_LOST_WAIT to control the timeout in seconds before billiard WorkerLostError is raised when a worker can not be signalled Issue 595 2 10 What s new in Celery 3 0 Chiastic Slide 193 Celery Documeniation Release 3 0 25 Contributed by Brendon Crawford e Redis event monitor queues are now automatically deleted Issue 436 e App instance factory methods have been converted to be cached descriptors that creates a new subclass on access This means that e g celery Worker is an actual class and will work as expected when class Worker celery Worker e New signal task_success e Multiproces
232. btask to work with reduce link_error other_subtask Add a callback task to be applied if an error occurs while executing this task Returns other_subtask to work with reduce set Set arbitrary options same as options update This is a chaining method call i e it returns itself flatten_links Gives a recursive list of dependencies unchain if you will but with links intact Proxies ce ce lery current_app The currently set app for this thread lery current_task The task currently being executed only set in the worker or when eager apply is used 2 13 2 celery app Celery Application e Proxies e Functions e Data 2 13 API Reference 233 Celery Documentation Release 3 0 25 Proxies celery app default_app lt Celery default 0x7fb766b79910 gt Functions celery app app_or_ default app None Function returning the app provided or the default app if none The environment variable CELERY_TRACE_APP is used to trace app leaks When enabled an exception is raised if there is no active app celery app enable_trace celery app disable_trace Data celery app default_loader default The default loader is the default loader used by old applications This is deprecated and should no longer be used as it s set too early to be affected by loader argument 2 13 3 celery app task e celery app task l celery app tas
233. c 2 2 link reset_buffers si Only the execution options can be set when a subtask is immutable so it s not possible to call the subtask with partial args kwargs Note In this tutorial I sometimes use the prefix operator to subtasks You probably shouldn t use it in your production code but it s a handy shortcut when experimenting in the Python shell gt gt gt subtask gt gt gt is the same as gt gt gt subtask delay get Callbacks New in version 3 0 Callbacks can be added to any task using the link argument to apply_async add apply_async 2 2 link other_task subtask The callback will only be applied if the task exited successfully and it will be applied with the return value of the parent task as argument As I mentioned earlier any arguments you add to subtask will be prepended to the arguments specified by the subtask itself If you have the subtask gt gt gt add subtask args 10 subtask delay result becomes gt gt gt add apply_async args result 10 Now let s call our add task with a callback using partial arguments gt gt gt add apply_async 2 2 link add subtask 8 As expected this will first launch one task calculating 2 2 then another task calculating 4 8 The Primitives New in version 3 0 2 3 User Guide 69 Celery Documentation Release 3 0 25 Overview e group The group primitive is a subtask that takes
234. c expires now timedelta days 2 expires in 2 days set using datetime e HHHA Example The delay method is convenient as it looks like calling a regular function task delay argl arg2 kwargl x kwarg2 y Using apply_async instead you have to write task apply_async args argl arg2 kwargs kwargl x kwarg2 y Tip If the task is not registered in the current process you can use send_task to call the task by name instead So delay is clearly convenient but if you want to set additional execution options you have to use apply_async The rest of this document will go into the task execution options in detail All examples use a task called add returning the sum of two arguments celery task def add x y return x y There s another way You will learn more about this later while reading about the Canvas but subtask s are objects used to pass around the signature of a task invocation for example to send it over the network and they also support the Calling API task s argl arg2 kwargl x kwargs2 y apply_async Linking callbacks errbacks Celery supports linking tasks together so that one task follows another The callback task will be applied with the result of the parent task as a partial argument add apply_async 2 2 link add s 16 2 3 User Guide 61 Celery Documentation Release 3 0 25 Wha
235. can embed it into celeryd like this celeryd beat Eml d celerybeat in celeryd e The supervisor has been removed This means the S and supervised options to celeryd is no longer supported Please use something like http supervisord org instead e TaskSet join has been removed use TaskSetResult join instead e The task status DONE has been renamed to SUCCESS e AsyncResult is_done has been removed use AsyncResult successful instead e The worker no longer stores errors if Task ignore_result is set to revert to the previous behaviour set CELERY_STORE_ERRORS_EVEN_IF_IGNORED to True e The statistics functionality has been removed in favor of events so the S and statistics switches has been removed e The module celery task strategy has been removed e celery discovery has been removed and it s autodiscover function is now in celery loaders djangoapp Reason Internal API e The CELERY _LOADER environment variable now needs loader class name in addition to module name 2 15 History 459 Celery Documentation Release 3 0 25 E g where you previously had celery loaders default you now need cel ery loaders default Loader using the previous syntax will result in a Deprecation Warning e Detecting the loader is now lazy and so is not done when importing celery loaders To make this happen celery loaders settings has be
236. cated by the memcached libraries so we now automatically cast to int unit tests No longer emits logging and warnings in test output Now depends on carrot version 0 10 7 Added CELERY_REDIRECT_STDOUTS and CELERYD_REDIRECT_STDOUTS_LEVEL settings CELERY_REDIRECT_STDOUTS is used by celeryd and celerybeat All output to stdout and stderr will be redirected to the current logger if enabled CELERY_REDIRECT_STDOUTS_LEVEL decides the log level used and is WARNING by default Added CELERYBEAT_SCHEDULER setting This setting is used to define the default for the S option to celerybeat Example CELERYBEAT_SCHEDULER djcelery schedulers DatabaseScheduler Added Task expires Used to set default expiry time for tasks New remote control commands add_consumer and cancel_consumer add_consumer queue exchange exchange_type routing_key xoptions Tells the worker to declare and consume from the specified declaration cancel_consumer queue_name Tells the worker to stop consuming from queue by queue name Commands also added to celeryctl and inspect Example using celeryctl to start consuming from queue queue in exchange exchange of type direct using binding key key S celeryctl inspect add_consumer queu xchange direct key S celeryctl inspect cancel_cons
237. ccurring in process cleanup could mask task errors happening at process cleanup but log them instead This way they will not interfere with publishing the task result Issue 365 celeryd Fixed a bug where cel 2 2 5 release date 2011 03 28 06 00 Important Notes e Now depends on Kombu 1 0 7 Defining tasks did not work properly when using the Django she11_plus utility Issue 366 AsyncResult get did not accept the interval and propagate arguments eryd would not shutdown ifa socket error was raised P M CEST 2 15 History 411 Celery Documentation Release 3 0 25 News e Our documentation is now hosted by Read The Docs http docs celeryproject org and all links have been changed to point to the new URL Logging Now supports log rotation using external tools like logrotate d Issue 321 This is accomplished by using the Wat chedFileHandler which re opens the file if it is re named or deleted tut otherqueues now documents how to configure Redis Database result backends e gevent Now supports ETA tasks But gevent still needs CELERY_DISABLE_RATE_LIMITS True to work e TaskSet User Guide now contains TaskSet callback recipes e Eventlet New signals eventlet_pool_started eventlet_pool_preshutdown eventlet_pool_postshutdown eventlet_pool_apply See celery signals for more information e New BROKER_TRANSPORT_OPTIONS setting can be used to pass additi
238. ceback class celery backends database models TaskSet taskset_id result TaskSet result date_done id result taskset_id to_dict 2 14 Internals 375 Celery Documentation Release 3 0 25 celery backends database session celery backends database session SQLAIchemy sessions ce ce ce ce lery backends lery backends lery backends lery backends celery utils database session database session database session database session e celery backends database session j ResultSession dburi kwargs create_session dburi short_lived_sessions False kwargs get_engine dburi kwargs setup_results engine celery utils Utility functions celery utils MP_MAIN FILE None Billiard sets this when execv is enabled We use it to find out the name of the original __main__ module so that we can properly rewrite the name of the task to be that of App main ce ce ce ce ce lery utils cry Return stacktrace of all active threads From https gist github com 737056 e celery utils j lery utils WORKER_DIRECT_EXCHANGE lt unbound Exchange C dq direct gt Exchange for worker direct queues lery utils WORKER_DIRECT_QUEUE_FORMAT s dq Format for worker direct queue names lery utils deprecated description None deprecation None removal None alternative None lery utils fun_takes_kwargs fun kwlist With a
239. cheme to use Defaults to the CELERY_MESSAGE_COMPRESSION setting Can be gzip or bzip2 or any custom compression schemes that have been registered with the kombu compression registry Please see Compression for more information Task backend The result store backend to use for this task Defaults to the CELERY_RESULT_BACKEND setting Task acks_late If set to True messages for this task will be acknowledged after the task has been executed not just before which is the default behavior Note that this means the task may be executed twice if the worker crashes in the middle of execution which may be acceptable for some applications 48 Chapter 2 Contents Celery Documeniation Release 3 0 25 The global default can be overridden by the CELERY_ACKS_LATE setting Task track_started If True the task will report its status as started when the task is executed by a worker The default value is False as the normal behaviour is to not report that level of granularity Tasks are either pending finished or waiting to be retried Having a started status can be useful for when there are long running tasks and there is a need to report which task is currently running The host name and process id of the worker executing the task will be available in the state metadata e g result info pid The global default can be overridden by the CELERY_TRACK_STARTED setting
240. choice to separate it from the Celery codebase 174 Chapter 2 Contents Celery Documeniation Release 3 0 25 e billiard Billiard is a fork of the Python multiprocessing module containing many performance and stability improvements It is an eventual goal that these improvements will be merged back into Python one day It is also used for compatibility with older Python versions e python dateutil The dateutil module is used by Celery to parse ISO 8601 formatted time strings as well as its relativedelta class which is used in the implementation of crontab style periodic tasks django celery If you use django celery then you don t have to install celery separately as it will make sure that the required version is installed django celery does not have any other dependencies kombu Kombu depends on the following packages amqp The underlying pure Python amap client implementation AMQP being the default broker this is a natural dependency e anyjson anyjson is an utility library to select the best possible JSON implementation Note For compatibility reasons additional packages may be installed if you are running on older Python versions for example Python 2 6 depends on the import lib and ordereddict libraries Also to handle the dependencies for popular configuration choices Celery defines a number of bundle packages see Bundles Is Celery heavy weight Celery poses very little overhead both i
241. ct intermediate False kwargs Iterator like get will wait for the task to complete but will also follow AsyncResult and ResultSet returned by the task yielding for each result in the tree An example would be having the following tasks task def A how_many return group B s i for i in xrange how_many task def B i return pow2 delay i task def pow2 i return i xx 2 2 13 API Reference 251 Celery Documentation Release 3 0 25 Calling collect would return gt gt gt result A delay 10 gt gt gt list result collect lOp 1 4 9 16 25 36 49 64 81 AsyncResult failed Returns True if the task failed AsyncResult forget Forget about and possibly remove the result of this task AsyncResult get timeout None propagate True interval 0 5 Wait until task is ready and return its result Warning Waiting for tasks within a task may lead to deadlocks Please read Avoid launching synchronous subtasks Parameters e timeout How long to wait in seconds before the operation times out e propagate Re raise exception if the task failed e interval Time to wait in seconds before retrying to retrieve the result Note that this does not have any effect when using the amqp result store backend as it does not use polling Raises celery exceptions TimeoutError if timeout is not None and the result does not arrive within timeout second
242. ctime s levelname s processName s task_name s task_id s message s See the Python logging module for more information about log formats CELERY_REDIRECT_STDOUTS If enabled stdout and stderr will be redirected to the current logger Enabled by default Used by celeryd and celerybeat CELERY_REDIRECT_STDOUTS_LEVEL The log level output to stdout and stderr is logged as Can be one of DEBUG INFO WARNING ERROR or CRITICAL Default is WARNING Security CELERY_SECURITY_KEY New in version 2 5 The relative or absolute path to a file containing the private key used to sign messages when Message Signing is used CELERY_SECURITY_CERTIFICATE New in version 2 5 The relative or absolute path to an X 509 certificate file used to sign messages when Message Signing is used 2 4 Configuration and defaults 145 Celery Documentation Release 3 0 25 CELERY_SECURITY_CERT_STORE New in version 2 5 The directory containing X 509 certificates used for Message Signing Can be a glob with wildcards for example etc certs pem Custom Component Classes advanced CELERYD_BOOT_STEPS This setting enables you to add additional components to the worker process It should be a list of module names with celery abstract Component classes that augments functionality in the worker CELERYD_POOL Name of the pool class used by the worker You can use a custom pool class name or select one of the bu
243. cumeniation Release 3 0 25 I want to e get the return value of a task e use logging from my task e learn about best practices e create a custom task base class e add a callback to a group of tasks e split a task into several chunks e optimize the worker e see a list of built in task states create custom task states e set a custom task name e track when a task starts e retry a task when it fails e get the id of the current task e know what queue a task was delivered to e see a list of running workers e purge all messages e inspect what the workers are doing e see what tasks a worker has registerd e migrate tasks to a new broker e see a list of event message types e contribute to Celery e learn about available configuration settings e receive email when a task fails e get a list of people and companies using Celery e write my own remote control command e change worker queues at runtime Jump to Brokers e Applications e Tasks e Calling Workers e Daemonizing e Monitoring e Optimizing e Security e Routing e Configuration Django e Contributing e Signals e FAQ e API Reference Installation You can install Celery either via the Python Package Index PyPI or from source 2 2 Getting Started 9 Celery Documeniation Release 3 0 25 To install using pip pip install U Celery To install using easy_install easy_install U Celery Bundles
244. currency argv short_opts None long_opts None With short and long opt alternatives that specify the command line option to set the pool this makes sure that anything that needs to be patched is completed as early as possible e g eventlet gevent monkey patches 394 Chapter 2 Contents Celery Documeniation Release 3 0 25 celery platforms parse_gid gid Parse group id gid can be an integer gid or a string group name if a group name the gid is taken from the password file celery platforms parse_uid uid Parse user id uid can be an integer uid or a string user name if a user name the uid is taken from the password file celery platforms pyimplementation Returns string identifying the current Python implementation celery platforms set_mp_process_title progname info None hostname None Set the ps name using the multiprocessing process name Only works if setproctit1le is installed celery platforms set_process_title progname info None Set the ps name for the currently running process Only works if setproctit1le is installed celery platforms setgid gid Version of os setgid supporting group names celery platforms setgroups groups Set active groups from a list of group ids celery platforms setuid uid Version of os setuid supporting usernames celery platforms shellsplit s Compat version of shlex split that supports the posix option whic
245. cuted inspect scheduled List scheduled ETA tasks S celery inspect scheduled These are tasks reserved by the worker because they have the eta or countdown argument set inspect reserved List reserved tasks S celery inspect reserved This will list all tasks that have been prefetched by the worker and is currently waiting to be executed does not include tasks with an eta inspect revoked List history of revoked tasks S celery inspect revoked inspect registered List registered tasks S celery inspect registered inspect stats Show worker statistics S celery inspect stats control enable_events Enable events 106 Chapter 2 Contents Celery Documeniation Release 3 0 25 S celery control enable_events e control disable_events Disable events S celery control disable_events e migrate Migrate tasks from one broker to another EXPERIMENTAL celery migrate redis localhost amqp localhost This command will migrate all the tasks on one broker to another As this command is new and experimental you should be sure to have a backup of the data before proceeding Note All inspect commands supports a timeout argument This is the number of seconds to wait for responses You may have to increase this timeout if you re not getting a response due to latency Specifying destination nodes By default the inspect commands operates on all workers You can specify a single or a list of workers by us
246. d Set to True if the task expired Worker Signals celeryd_after_setup This signal is sent after the worker instance is set up but before it calls run This means that any queues from the Q option is enabled logging has been set up and so on It can be used to e g add custom queues that should always be consumed from disregarding the Q option Here s an example that sets up a direct queue for each worker these queues can then be used to route a task to any specific worker from celery signals import celeryd_after_setup celeryd_after_setup connect def setup_direct_queue sender instance xxkwargs queue_name s dq sender sender is the instance app amqp queues select_add queue_name Provides arguments e sender Hostname of the worker e instance This is the celery apps worker Worker instance to be initialized Note that only the app and hostname attributes have been set so far and the rest of __ init __ has not been executed e conf The configuration of the current app celeryd_init This is the first signal sent when celeryd starts up The sender is the host name of the worker so this signal can be used to setup worker specific configuration 124 Chapter 2 Contents Celery Documeniation Release 3 0 25 from celery signals import celeryd_init celeryd_init connect sender workerl2 example com def configure_worker12 conf None xkwargs conf CELERY_DEFAULT_RATE_LIMIT 10 m
247. d as a task in parallel possibly on different nodes The callback is then applied with the return value of each task in the header The task id returned by chord is the id of the callback so you can wait for it to complete and get the final return value but remember to never have a task wait for other tasks Error handling So what happens if one of the tasks raises an exception This was not documented for some time and before version 3 1 the exception value will be forwarded to the chord callback From 3 1 errors will propagate to the callback so the callback will not be executed instead the callback changes to failure state and the error is set to the ChordError exception gt gt gt c chord gt gt gt result c gt gt gt result get Traceback most recent call last File lt stdin gt line 1 in lt module gt File x celery result py line 120 in get interval interval File x celery backends amqp py line 150 in wait_for raise self exception_to_python meta result dd s 4 4 raising_task s add s 8 8 a 2 3 User Guide 77 Celery Documeniation Release 3 0 25 aay 4d eee Falsea celery exceptions ChordError Dependency 97de6f3f ea67 4517 a21c d867c61lfcb47 ValueError something so thing If you re running 3 0 14 or later you can enable the new behavior via the CELERY_CHORD_PROPAGATES setting CELERY_CHORD_PROPA
248. d by the BROKER_HEARTBEAT_CHECKRATE setting which by default is double the rate of the heartbeat value so for the default 10 seconds the heartbeat is checked every 5 seconds BROKER_HEARTBEAT_CHECKRATE transports supported pyamap At intervals the worker will monitor that the broker has not missed too many heartbeats The rate at which this is checked is calculated by dividing the BROKER_HEARTBEAT value with this value so if the heartbeat is 10 0 and the rate is the default 2 0 the check will be performed every 5 seconds twice the heartbeat sending rate BROKER_USE_SSL Use SSL to connect to the broker Off by default This may not be supported by all transports BROKER_POOL_LIMIT New in version 2 3 The maximum number of connections that can be open in the connection pool The pool is enabled by default since version 2 5 with a default limit of ten connections This number can be tweaked depending on the number of threads greenthreads eventlet gevent using a connection For example running eventlet with 1000 greenlets that use a connection to the broker contention can arise and you should consider increasing the limit If set to None or 0 the connection pool will be disabled and connections will be established and closed for every use Default since 2 5 is to use a pool of 10 connections 2 4 Configuration and defaults 137 Celery Documeniation Release 3 0 25 BROKER_CONNECTIO
249. d s 8 gt gt gt res get 16 This can also be written using pipes gt gt gt add s 2 2 add s 4 add s 8 get e Immutable subtasks Signatures can be partial so arguments can be added to the existing arguments but you may not always want that for example if you don t want the result of the previous task in a chain In that case you can mark the subtask as immutable so that the arguments cannot be changed gt gt gt add subtask 2 2 immutable True There s also an si shortcut for this 70 Chapter 2 Contents Celery Documeniation Release 3 0 25 gt gt gt add si 2 2 Now you can create a chain of independent tasks instead gt gt gt res add si 2 2 add si 4 4 add s 8 8 gt gt gt res get 16 gt gt gt res parent get gt gt gt res parent parent get e Simple group You can easily create a group of tasks to execute in parallel gt gt gt from celery import group gt gt gt res group add s i i for i in xrange 10 gt gt gt res get timeout 1 0 2 4 6 8 10 12 14 16 18 For primitives apply_async is special as it will create a temporary task to apply the tasks in for example by applying the group gt gt gt g group add s i i for i in xrange 10 gt gt gt g lt lt applying the act of sending the messages for the tasks in the group will happen in the current process but with
250. d to retry tasks notably for expected errors that is catchable with the try block The AMQP transaction is not used for these errors if the task raises an exception it is still acknowledged The acks_late setting would be used when you need the task to be executed again if the worker for some reason crashes mid execution It s important to note that the worker is not known to crash and if it does it is usually an unrecoverable error that requires human intervention bug in the worker or task code In an ideal world you could safely retry any task that has failed but this is rarely the case Imagine the following task celery task def process_upload filename tmpfile Increment a file count stored in a database increment_file_counter add_file_metadata_to_db filename tmpfile copy_file_to_destination filename tmpfile If this crashed in the middle of copying the file to its destination the world would contain incomplete state This is not a critical scenario of course but you can probably imagine something far more sinister So for ease of programming we have less reliability It s a good default users who require it and know what they are doing can still enable acks_late and in the future hopefully use manual acknowledgement In addition Task retry has features not available in AMQP transactions delay between retries max retries etc So use retry for Python errors and if your task is idempotent combine that
251. d will be prepended to the args in the signature gt gt gt partial add s 2 inc gt gt gt partial delay 4 2 4 gt gt gt partial apply_async 4 same omplete signature e Any keyword arguments added will be merged with the kwargs in the signature with the new keyword arguments taking precedence gt gt gt s add s 2 2 gt gt gt s delay debug True gt add 2 2 debug True gt gt gt s apply_async kwargs debug True same e Any options added will be merged with the options in the signature with the new options taking precedence gt gt gt s add subtask 2 2 countdown 10 gt gt gt s apply_async countdown 1 countdown is now 1 You can also clone subtasks to augment these gt gt gt s add s 2 proj tasks add 2 gt gt gt s clone args 4 kwargs debug True proj tasks add 2 4 debug True Immutability New in version 3 0 Partials are meant to be used with callbacks any tasks linked or chord callbacks will be applied with the result of the parent task Sometimes you want to specify a callback that does not take additional arguments and in that case you can set the subtask to be immutable gt gt gt add apply_async 2 2 link reset_buffers subtask immutable True The si shortcut can also be used to create immutable subtasks 68 Chapter 2 Contents Celery Documeniation Release 3 0 25 gt gt gt add apply_asyn
252. dded to each celeryd but you can also modify the options for ranges of or specific workers 3 workers Two with 3 processes and one with 10 processes celeryd multi start 3 c 3 c 1 10 leryd n celerydl myhost c 10 leryd n celeryd2 myhost c 3 leryd n celeryd3 myhost c 3 300 Chapter 2 Contents Celery Documeniation Release 3 0 25 can also specify options for named workers S celeryd multi start image video data c 3 c image 10 celeryd n image myhost c 10 celeryd n video myhost c 3 celeryd n data myhost c 3 ss and lists of c 1 3 can also be written as c 1 2 3 celeryd multi start 5 c 3 c 1 3 10 celeryd n celerydl myhost c 10 celeryd c fe e n celeryd2 myhost c 10 leryd n celeryd3 myhost c 10 leryd n celeryd4 myhost c 3 leryd n celeryd5 myhost c 3 lists also works with named workers celeryd multi start foo bar baz xuzzy c 3 c foo bar baz 10 celeryd n foo myhost c 10 celeryd n bar myhost c 10 celeryd n baz myhost c 10 celeryd n xuzzy myhost c 3 class celery bin celeryd_multi MultiTool env None fh None quiet False verbose False no_color False nosplash False DOWN FAILED OK colored error msg None execute_from_commandline argv cmd celeryd expand argv cmd None get argv cmd getpids p cmd callback None help argv cmd None info msg newline True kill argv cmd names argv
253. default_exchange Exchange default type direct media_exchange Exchange media type direct CELERY_QUEUES Queue default default_exchange routing_key default Queue videos media_exchange routing_key media video Queue images media_exchange routing_key media image Q Hi ERY_DEFAULT_QUEUE default 102 Chapter 2 Contents Celery Documeniation Release 3 0 25 CELERY_DEFAULT_EXCHANGE default CELERY_DEFAULT_ROUTING KEY default Here the CELERY_DEFAULT_QUEUE will be used to route tasks that doesn t have an explicit route The default exchange exchange type and routing key will be used as the default routing values for tasks and as the default values for entries in CELERY_QUEUES Specifying task destination The destination for a task is decided by the following in order 1 The Routers defined in CELERY_ROUTES 2 The routing arguments to Task apply_async 3 Routing related attributes defined on the Task itself It is considered best practice to not hard code these settings but rather leave that as configuration options by using Routers This is the most flexible approach but sensible defaults can still be set as task attributes Routers A router is a class that d
254. dic tasks from the Django Admin 2 3 7 HTTP Callback Tasks Webhooks e Basics Enabling the HTTP task e Django webhook example e Ruby on Rails webhook example e Calling webhook tasks Basics If you need to call into another language framework or similar you can do so by using HTTP callback tasks The HTTP callback tasks uses GET POST data to pass arguments and returns result as a JSON response The scheme to call a task is GET http example com mytask argl a arg2 b arg3 c or using POST POST http example com mytask Note POST data needs to be form encoded Whether to use GET or POST is up to you and your requirements The web page should then return a response in the following format if the execution was successful status success retval or if there was an error status failure reason Invalid moon alignment Enabling the HTTP task To enable the HTTP dispatch task you have to add celery task http to CELERY_IMPORTS or start the worker with I celery task http 2 3 User Guide 95 Celery Documeniation Release 3 0 25 Django webhook example With this information you could define a simple task in Django from django http import HttpResponse from anyjson import serialize def multiply request x int request GET x y int request GET y result x y r
255. dicated DATABASE_NUMBER for Celery you can also use database numbers to separate Celery applications from each other virtual hosts but this will not affect the monitoring events used by e g Flower as Redis pub sub commands are global rather than database based Munin This is a list of known Munin plug ins that can be useful when maintaining a Celery cluster 2 3 User Guide 111 Celery Documeniation Release 3 0 25 e rabbitmq munin Munin plug ins for RabbitMQ http github com ask rabbitmq munin e celery_tasks Monitors the number of times each task type has been executed requires celerymon http exchange munin monitoring org plugins celery_tasks 2 details e celery_task_states Monitors the number of tasks in each state requires celerymon http exchange munin monitoring org plugins celery_tasks details Events The worker has the ability to send a message whenever some event happens These events are then captured by tools like Flower and celery events to monitor the cluster Snapshots New in version 2 1 Even a single worker can produce a huge amount of events so storing the history of all events on disk may be very expensive A sequence of events describes the cluster state in that time period by taking periodic snapshots of this state you can keep all history but still only periodically write it to disk To take snapshots you need a Camera class with this you can define what should happen every tim
256. ding large messages may be expensive Database transactions Let s have a look at another example 2 3 User Guide 57 Celery Documeniation Release 3 0 25 from django db import transaction transaction commit_on_success def create_article request article Article objects create expand_abbreviations delay article pk This is a Django view creating an article object in the database then passing the primary key to a task It uses the commit_on_success decorator which will commit the transaction when the view returns or roll back if the view raises an exception There is a race condition if the task starts executing before the transaction has been committed The database object does not exist yet The solution is to always commit transactions before sending tasks depending on state from the current transaction transaction commit_manually def create_article request try article Article objects create except transaction rollback raise else transaction commit expand_abbreviations delay article pk Example Let s take a real wold example A blog where comments posted needs to be filtered for spam When the comment is created the spam filter runs in the background so the user doesn t have to wait for it to finish I have a Django blog application allowing comments on blog posts Ill describe parts of the models views and tasks for this application blog models py T
257. do workers delete tasks from the queue if they are unable to process them Can I call a task by name How can I get the task id of the current task Can I specify a custom task_id Can I use decorators with tasks Can I use natural task ids How can I run a task once another task has finished Can I cancel the execution of a task Why aren t my remote control commands received by all workers Can I send some tasks to only some servers Can I change the interval of a periodic task at runtime Does celery support task priorities Should I use retry or acks_late Can I schedule tasks to execute at a specific time How do I shut down celeryd safely How do I run celeryd in the background on platform e Django 28 Prequel The B beat option to celeryd doesn t work Asked Questions 173 Celery Documeniation Release 3 0 25 2 9 1 General What kinds of things should I use Celery for Answer Queue everything and delight everyone is a good article describing why you would use a queue in a web context These are some common use cases e Running something in the background For example to finish the web request as soon as possible then update the users page incrementally This gives the user the impression of good performance and snappiness even though the real work might actually take some time e Running something after the web req
258. dout stderr changed from INFO to ERROR e ImportErrors are now properly propagated when autodiscovering tasks e You can now use celery messaging establish_connection to establish a connection to the broker e When running as a separate service the periodic task scheduler does some smart moves to not poll too regularly If you need faster poll times you can lower the value of CELERYBEAT_MAX_LOOP_INTERVAL e You can now change periodic task intervals at runtime by making run_every a property or subclassing Period icTask is_due e The worker now supports control commands enabled through the use of a broadcast queue you can remotely revoke tasks or set the rate limit for a task type See celery task control e The services now sets informative process names as shown in ps listings if the setproctitle module is installed e NotRegistered now inherits from KeyError and TaskRegistry __getitem__ pop raises NotRegistered instead e You can set the loader via the CELERY_LOADER environment variable e You can now set CELERY_IGNORE_RESULT to ignore task results by default if enabled tasks doesn t save results or errors to the backend used e celeryd now correctly handles malformed messages by throwing away and acknowledging the message instead of crashing Bugs e Fixed a race condition that could happen while storing task results in the database Documentation e Re
259. e Introduction There are several tools available to monitor and inspect Celery clusters This document describes some of these as as well as features related to monitoring like events and broadcast com mands Workers celery Command Line Management Utility New in version 2 1 celery can also be used to inspect and manage worker nodes and to some degree tasks To list all the commands available do S celery help or to get help for a specific command do 2 3 User Guide 105 Celery Documentation Release 3 0 25 celery lt command gt help Commands shell Drop into a Python shell The locals will include the celery variable which is the current app Also all known tasks will be automati cally added to locals unless the without tasks flag is set Uses Ipython bpython or regular python in that order if installed You can force an implementation using force ipython I force bpython B or force python P status List active nodes in this cluster S celery status result Show the result of a task celery result t tasks add 4e196aa4 0141 4601 8138 7aa33db0f 577 Note that you can omit the name of the task as long as the task doesn t use a custom result backend purge Purge messages from all configured task queues celery purge inspect active List active tasks S celery inspect active These are all the tasks that are currently being exe
260. e env CELERYD_FSNOTIFY stat celery worker l info autoreload Pool Restart Command New in version 2 5 Requires the CELERYD_POOL_RESTARTS setting to be enabled The remote control command pool_restart sends restart requests to the workers child processes It is particularly useful for forcing the worker to import new modules or for reloading already imported modules This command does not interrupt executing tasks Example Running the following command will result in the foo and bar modules being imported by the worker processes gt gt gt celery control broadcast pool_restart arguments modules foo0 bar Use the reload argument to reload modules it has already imported gt gt gt celery control broadcast pool_restart arguments modules foo reload True If you don t specify any modules then all known tasks modules will be imported reloaded gt gt gt celery control broadcast pool_restart arguments reload True The modules argument is a list of modules to modify reload specifies whether to reload modules if they have previously been imported By default reload is disabled The pool_restart command uses the Python reload function to reload modules or you can provide your own custom reloader by passing the re loader argument Note Module reloading comes with caveats that are documented in reload Please r
261. e rtype Exception celery utils serialization find_pickleable_ exception exc loads lt built in function loads gt dumps lt built in func tion dumps gt With an exception instance iterate over its super classes by mro and find the first super exception that is pickleable It does not go below Exception i e it skips Exception BaseException and object If that happens you should use UnpickleableException instead Parameters exc An exception instance Returns the nearest exception if it s not Exception or below if it is it returns None irtype Exception 382 Chapter 2 Contents Celery Documeniation Release 3 0 25 celery utils serialization get_pickleable_etype cls loads lt built in function loads gt dumps lt built in function dumps gt celery utils serialization get_pickleable_ exception exc Make sure exception is pickleable celery utils serialization get_pickled_exception exc Get original exception from exception pickled using get_pickleable_exception celery utils serialization itermro cls stop celery utils serialization subclass_exception name parent module celery utils serialization unwanted_base_classes lt type exceptions StandardError gt lt type exceptions E List of base cla sses we probably don t want to reduce to celery utils threads celery utils threads Thre
262. e Type of exchange defaults to direct command to when empty broadcast to all workers e routing_key Optional routing key e options Additional options as supported by kombu entitiy Queue from_dict See broadcast for supported keyword arguments 2 13 API Reference 243 Celery Documentation Release 3 0 25 Control broadcast command arguments None destination None connection None re ply False timeout 1 limit None callback None channel None ex tra_kwargs Broadcast a control command to the celery workers Parameters e command Name of command to send e arguments Keyword arguments for the command e destination If set a list of the hosts to send the command to when empty broadcast to all workers connection Custom broker connection to use if not set a connection will be estab lished automatically e reply Wait for and return the reply e timeout Timeout in seconds to wait for the reply e limit Limit number of replies e callback Callback called immediately for each reply received Control cancel_consumer queue kwargs Tell all or specific workers to stop consuming from queue Supports the same keyword arguments as broadcast Control disable_events destination None kwargs Tell all or specific workers to enable events Control discard_all connection None Discard all waiting tasks This will ignore all tasks waiting fo
263. e celery backends amqp repair_uuid s celery backends mongodb e celery backends mongodb j 2 14 Internals 363 Celery Documentation Release 3 0 25 celery backends mongodb MongoDB result store backend class celery backends mongodb Bunch kw class celery backends mongodb MongoBackend args kwargs cleanup Delete expired metadata collection Get the metadata task collection database Get database from MongoDB connection and perform authentication if necessary mongodb_database celery mongodb_host localhost mongodb_max_pool_size 10 mongodb_options None mongodb_password None mongodb_port 27017 mongodb_taskmeta_collection celery_taskmeta mongodb_user None process_cleanup supports_autoexpire False celery backends redis e celery backends redis j celery backends redis Redis result store backend class celery backends redis RedisBackend host None port None db None password None expires None max_connections None url None kwargs Redis task result store client db 0 default Redis db number 0 delete key expire key value get key 364 Chapter 2 Contents Celery Documeniation Release 3 0 25 host localhost default Redis server hostname localhost implements_incr True incr key max_connections None Maximium number of connections in the pool mget keys password
264. e either by success of failure Returns True if all of the tasks has been executed remove result Removes result from the set it must be a member Raises KeyError if the result is not a member results None List of results in in the set revoke connection None terminate False signal None Send revoke signal to all workers for all tasks in the set Parameters 256 Chapter 2 Contents Celery Documeniation Release 3 0 25 e terminate Also terminate the process currently working on the task if any e signal Name of signal to send to process if terminate Default is TERM subtasks Deprecated alias to results successful Was all of the tasks successful Returns True if all of the tasks finished successfully i e did not raise an exception supports native_join update results Update set with the union of itself and an iterable with results waiting Are any of the tasks incomplete Returns True if one of the tasks are still waiting for execution class celery result TaskSetResult taskset_id results None kwargs Deprecated version of GroupResult itersubtasks Deprecated Use iter self results instead taskset_id total Deprecated Use len r celery result from_serializable r app None 2 13 14 celery task http e celery task http j celery task http Webhook task implementation class celery task http HttpDispatch url method task_kwargs kwarg
265. e stdout lt open file lt stdout gt mode w at 0x7fb76c556150 gt stderr lt open file lt stderr gt mode w at Ox7fb76c5561e0 gt show_reply True Start shell session with convenient access to celery symbols The following symbols will be added to the main globals ecelery the current application echord group chain chunks xmap xstarmap subtask Task eall registered tasks Example Session celery shell gt gt gt celery lt Celery default 0x1012d9fd0 gt gt gt gt add lt task tasks add gt gt gt gt add delay 2 2 lt AsyncResult 537b48c7 d6d3 427a a24a d1b4414035be gt invoke_bpython_shell1 invoke_default_shell invoke_fallback_shell1 invoke_ipython_shell1 296 Chapter 2 Contents Celery Documeniation Release 3 0 25 option_list lt Option at 0x7fb762af2a70 q quiet gt lt Option at 0x7fb762af2098 C no color gt lt Option at 0x7fb7 run force_ipython False force_bpython False force_python False without_tasks False event let False gevent False kwargs sortpri 0 class celery bin celery status app None no_color False stdout lt open file lt stdout gt mode w at 0x7fb76c556150 gt stderr lt open file lt stderr gt mode w at Ox7fb76c5561e0 gt show_reply True Show list of workers that are online option_list lt Option at 0x7fb762af2a70 q quiet gt lt Option at 0x7fb762af209
266. e Built in daemonization support of celeryd using celeryd multi is no longer experimental and is considered pro duction quality See Generic init scripts if you want to use the new generic init scripts e Added support for message compression using the C ELERY_MESSAG E_COMPR pression argument to apply_async This can also be set using routers ESSION setting or the com e celeryd Now logs stacktrace of all threads when receiving the S GUSR signal Does not work on cPython 2 4 Windows or Jython Inspired by https gist github com 737056 e Can now remotely terminate kill the worker process currently processing a task The revoke remote control command now supports a terminate argument Default signal is TERM but can be specified using the signal argument Signal can be the uppercase name of any signal defined in the signal module in the Python Standard Library Terminating a task also revokes it Example gt gt gt from celery task control import revoke gt gt gt revoke task_id terminate gt gt gt revoke task_id terminate 1 True True gt gt gt revoke task_id terminate l True signal KILL signal SIGKILL e TaskSetResult join_native Backend optimized version of join If available this version uses the backends ability to retrieve multiple results at once unlike join which fetches the results one by one So far only supported by the AMQP re
267. e about routing please see Routing Tasks Advanced Options These options are for advanced users who want to take use of AMQP s full routing capabilities Interested parties may read the routing guide e exchange Name of exchange or a kombu entity Exchange to send the message to e routing _key Routing key used to determine e priority A number between 0 and 9 where 0 is the highest priority Supported by redis beanstalk 2 3 4 Canvas Designing Workflows 66 Chapter 2 Contents Celery Documeniation Release 3 0 25 e Subtasks Partials Immutability Callbacks e The Primitives Chains Groups Chords Map amp Starmap Chunks Subtasks New in version 2 0 You just learned how to call a task using the tasks delay method in the calling guide and this is often all you need but sometimes you may want to pass the signature of a task invocation to another process or as an argument to another function for this Celery uses something called subtasks A subtask wraps the arguments keyword arguments and execution options of a single task invocation in a way such that it can be passed to functions or even serialized and sent across the wire e You can create a subtask for the add task using its name like this gt gt gt from celery import subtask gt gt gt subtask tasks add args 2 2 countdown 10 tasks add 2 2 This subtask has a signature of arity 2 two ar
268. e depending on binding to be deferred then you must not access any attributes on the returned object until the application is fully set up finalized send_task namel args kwargs ass J Send task by name Parameters e name Name of task to call e g tasks add e result_cls Specify custom result class Default is using AsyncResult Otherwise supports the same arguments as Task apply_async AsyncResult Create new result instance See AsyncResult GroupResult Create new taskset result instance See GroupResult worker_main argv None Run celeryd using argv Uses sys argv if argv is not specified Worker Worker application See Worker WorkController Embeddable worker See WorkController Beat Celerybeat scheduler application See Beat connection url default ssl transport_options J Establish a connection to the message broker Parameters url Either the URL or the hostname of the broker to use hostname URL Hostname IP address of the broker If an URL is used then the other argument below will be taken from the URL instead e userid Username to authenticate as e password Password to authenticate with e virtual_host Virtual host to use domain 230 Chapter 2 Contents Celery Documeniation Release 3 0 25 e port Port to connect to e ssl Defaults to the BROKER_USE_SSL setting e transport defaults
269. e kwargs Keyword arguments to apply e options Additional options to Task apply_async Note that if the first argument is a dict the other arguments will be ignored and the values in the dict will be used instead gt gt gt s subtask tasks add args 2 2 gt gt gt subtask s task tasks add args 2 2 kwargs options delay args kwargs Shortcut to apply_async apply _asyne args kwargs Apply this task asynchronously Parameters e args Partial args to be prepended to the existing args 232 Chapter 2 Contents Celery Documeniation Release 3 0 25 e kwargs Partial kwargs to be merged with the existing kwargs e options Partial options to be merged with the existing options See apply_async apply args kwargs j Same as apply_async but executed the task inline instead of sending a task message clone args kwargs Returns a copy of this subtask Parameters e args Partial args to be prepended to the existing args e kwargs Partial kwargs to be merged with the existing kwargs e options Partial options to be merged with the existing options replace args None kwargs None options None Replace the args kwargs or options set for this subtask These are only replaced if the selected is not None Link other_subtask Add a callback task to be applied if this task executes successfully Returns other_su
270. e mail server is listening on Default is 25 EMAIL_USE_SSL Use SSL when connecting to the SMTP server Disabled by default EMAIL_USE_TLS Use TLS when connecting to the SMTP server Disabled by default EMAIL_TIMEOUT Timeout in seconds for when we give up trying to connect to the SMTP server when sending emails The default is 2 seconds Example E Mail configuration This configuration enables the sending of error emails to george vandelay com and kramer vandelay com Enables error emails CELERY_SEND_TASK_ERROR_EMAILS True Name and email addresses of recipients DMINS George Costanza george vandelay com Cosmo Kramer kosmo vandelay com D Email address used as sender From field SERVER_EMAIL no reply vandelay com failserver configuration EMATL HOST mail vandelay com EMAIL PORT EMAIL_HOST_US EMAIL HOST_ 2 4 Configuration and defaults 143 Celery Documentation Release 3 0 25 Events CELERY_SEND_EVENTS Send events so the worker can be monitored by tools like celerymon CELERY_SEND_TASK_SENT_EVENT New in version 2 2 If enabled a task sent event will be sent for every task so tasks can be tracked before they are consumed by a worker Disabled by default CELERY_EVENT_SERIALIZER Message serialization format used when sending event messages Default is json See Ser
271. e of the proxy auto detection used in OS X This is now fixed by using a workaround See issue 143 Debian init scripts Commands should not run in a sub shell See issue 163 Debian init scripts Use the absolute path of celeryd to allow stat See issue 162 Documentation getting started broker installation Fixed typo set_permissions gt set_permissions Tasks User Guide Added section on database transactions See issue 169 Routing User Guide Fixed typo feed gt queue feeds See issue 169 H 1ERYD_CONCURRENCY and Documented the default values for the CE CELERYD_PREFETCH MULTIPLIER settings Tasks User Guide Fixed typos in the subtask example celery signals Documented worker_process_init Daemonization cookbook Need to export DIANGO_SETTINGS_MODULE in etc default celeryd Added some more FAQs from stack overflow Daemonization cookbook Fixed typo CELERYD_LOGFILE CELERYD_PIDFILE 2 15 History 435 Celery Documentation Release 3 0 25 2 0 to CELERYD_LOG_FILE CELERYD_PID_FILE Also added troubleshooting section for the init scripts 2 release date 2010 07 22 11 31 A M CEST e Routes When using the dict route syntax the exchange for a task could disappear making the task unroutable See issue 158 e Test suite now passing on Python 2 4 e No longer have to type PYTHONPATH to use celeryconfig in the curr
272. e removed Which means you need to change from celery decorators import task Into from celery import task e Module celery task may be removed not decided This means you should change from celery task import task into from celery import task and from celery task import Task into from celery import Task Note that the new Task class no longer uses classmethods for these methods e delay e apply_async e retry e apply e AsyncResult e subtask This also means that you can t call these methods directly on the class but have to instantiate the task first gt gt gt MyTask delay NO LONGER WORKS gt gt gt MyTask delay WORKS TaskSet TaskSet has been renamed to group and TaskSet will be removed in version 4 0 Old gt gt gt from celery task import TaskSet gt gt gt TaskSet add subtask i i for i in xrange 10 apply_async New gt gt gt from celery import group gt gt gt group add s i i for i in xrange 10 308 Chapter 2 Contents Celery Documeniation Release 3 0 25 Magic keyword arguments The magic keyword arguments accepted by tasks will be removed in 4 0 so you should start rewriting any tasks using the celery decorators module and depending on keyword arguments being passed to the task for example from celery decorators import task task def add x y task_id None print My task id is r task_id must be rewritten into
273. e result instance gt gt gt res children lt AsyncResult 8c350ac gt gt gt res children 0 get 64 The result instance also has a collect method that treats the result as a graph enabling you to iterate over the results gt gt gt list res collect lt AsyncResult 75720856 By default collect will raise an IncompleteSt ream exception if the graph is not fully formed one of the tasks has not completed yet but you can get an intermediate representation of the graph too gt gt gt for result value in res collect intermediate True You can link together as many tasks as you like and subtasks can be linked too gt gt gt s add s 2 2 gt gt gt s link mul s 4 gt gt gt s link log_result s You can also add error callbacks using the 1ink_error argument gt gt gt add apply_async 2 2 link_error log_error s gt gt gt add subtask 2 2 link_error log_error s Since exceptions can only be serialized when pickle is used the error callbacks take the id of the parent task as argument instead from proj celery import celery celery task def log_error task_id result celery AsyncResult task_id result get propagate False make sure result written with open os path join var errors task_id a as fh fh write n n s s 3s task_id result result result traceback To make it even easier to link tasks togethe
274. e same approach as the auto reloader found in e g the Django runserver command When auto reload is enabled the worker starts an additional thread that watches for changes in the file system New modules are imported and already imported modules are reloaded whenever a change is detected and if the processes pool is used the child processes will finish the work they are doing and exit so that they can be replaced by fresh processes effectively reloading the code File system notification backends are pluggable and Celery comes with three implementations e inotify Linux Used if the pyinotify library is installed If you are running on Linux this is the recommended implementation to install the pyinotify library you have to run the following command pip install pyinotify e kqueue OS X BSD e stat The fallback implementation simply polls the files using st at and is very expensive You can force an implementation by setting the CELERYD_FSNOTIFY environment variable env CELERYD_FSNOTIFY stat celeryd l info autoreload Contributed by Mher Movsisyan New CELERY_ANNOTATIONS setting This new setting enables the configuration to modify task classes and their attributes The setting can be a dict or a list of annotation objects that filter for tasks and return a map of attributes to change As an example this is an annotation to change the rate_1limit attribute for the tasks add task CELERY_ANNOTAT
275. e specified modules Cassandra backend Now expires results by using TTLs Functional test suite in funtests is now actually working properly and passing tests celeryev was trying to create the pidfile twice celery contrib batches Fixed problem where tasks failed silently Issue 393 Fixed an issue where logging objects would give lt Unrepresentable even though the objects were CELERY_TASK_ERROR_WHITE_LIST is now properly initialized in all loaders celeryd_detach now passes through command line configuration Remote control command add_consumer now does nothing if the queue is already being consumed from 2 15 4 Change history for Celery 2 2 2 15 History 409 Celery Documentation Release 3 0 25 2 2 8 Security Fixes 2 2 2 2 6 Important Notes Fixes 2 25 Important Notes News Fixes 2 2 4 Fixes 223 Fixes 2 22 Fixes 222 1 Fixes e 2 2 0 Important Notes News Fixes Experimental 2 2 8 release date 2011 11 25 16 00 P M GMT by Ask Solem Security Fixes e Security CELERYSA 0001 Daemons would set effective id s rather than real id s when the uid gid arguments to celeryd multi celeryd_detach celerybeat and celeryev were used This means privileges weren t properly dropped and that it would be possible to regain supervisor privileges later 2 2 7 release date 2011 06
276. e task_ready request Updates global state when a task is ready lery worker sta te task_reserved Updates global state when a task has been reserved lery worker sta te total_count defaultdict lt type int gt count of tasks executed by the worker sorted by type celery worker strategy e celery worker strategy j 2 14 Internals 335 Celery Documentation Release 3 0 25 celery worker strategy Task execution strategy optimization celery worker strategy default task app consumer celery worker autoreload e celery worker autoreload j celery worker autoreload This module implements automatic module reloading class celery worker autoreload Autoreloader controller modules None monitor_cls None options Tracks changes in modules and fires reload commands Monitor alias of StatMonitor body on_change files on_init on_poll_close hub on_poll_init hub stop class celery worker autoreload BaseMonitor files on_change None shutdown_event None interval 0 5 on_change modified start stop class celery worker autoreload InotifyMonitor modules on_change None kwargs File change monitor based on Linux kernel inotify subsystem on_change modified process_ event process_IN_ ATTRIB event process_IN_ MODIFY event start stop class celery worker autoreload KQueueMonitor args kwargs File c
277. e tests for a single test file only you can do so like this nosetests celery tests test_worker test_worker_job Creating pull requests When your feature bugfix is complete you may want to submit a pull requests so that it can be reviewed by the maintainers Creating pull requests is easy and also let you track the progress of your contribution Read the Pull Requests section in the Github Guide to learn how this is done 2 6 Contributing 157 Celery Documeniation Release 3 0 25 You can also attach pull requests to existing issues by following the steps outlined here http bit ly koJoso Calculating test coverage Code coverage in HTML nosetests with coverage3 cover3 html The coverage output will then be located at celery tests cover index html Code coverage in XML Cobertura style nosetests with coverage3 cover3 xml cover3 xml file coverage xml The coverage XML output will then be located at coverage xml Running the tests on all supported Python versions There is a tox configuration file in the top directory of the distribution To run the tests for all supported Python versions simply execute tox If you only want to test specific Python versions use the e option S tox e py25 py26 Building the documentation To build the documentation you need to install the dependencies listed in requirements docs txt pip E SVIRTUAL_ENV install U r requirements docs txt Af
278. e the state is captured You can write it to a database send it by email or something else entirely celery events is then used to take snapshots with the camera for example if you want to capture state every 2 seconds using the camera myapp Camera you run celery events with the following arguments S celery events c myapp Camera frequency 2 0 Custom Camera Cameras can be useful if you need to capture events and do something with those events at an interval For real time event processing you should use celery events Receiver directly like in Real time processing Here is an example camera dumping the snapshot to screen from pprint import pformat from celery events snapshot import Polaroid class DumpCam Polaroid def on_shutter self state if not state event_count No new events since last snapshot return print Workers s pformat state workers indent 4 print Tasks s pformat state tasks indent 4 print Total s events s tasks state event_count state task_count See the API reference for celery events state to read more about state objects Now you can use this cam with celery events by specifying it with the c option 112 Chapter 2 Contents Celery Documeniation Release 3 0 25 celery events c myapp DumpCam frequency 2 0 Or you can use it programmatically like this from celery import Celery from myapp import DumpCam def m
279. e to be moved it must return either 1 atuple of exchange routing_key or 2 a Queue instance or 3 any other true value which means the specified exchange and routing_key arguments will be used connection Custom connection to use e source Optional list of source queues to use instead of the default which is the queues in CELERY_QUEUES This list can also contain new Queue instances e exchange Default destination exchange e routing_key Default destination routing key e limit Limit number of messages to filter e callback Callback called after message moved with signature state body message e transform Optional function to transform the return value destination of the filter function Also supports the same keyword arguments as start_filter To demonstrate the move_task_by_id operation can be implemented like this def is_wanted_task body message if body id wanted_id return Queue foo exchange Exchange foo routing_key foo move is_wanted_task or with a transform def transform value if isinstance value basestring return Queue value Exchange value value return value move is_wanted_task transform transform The predicate may also return a tuple of exchange routing_key to specify the destination to where the task should be moved or a Queue instance Any other true value means that the task w
280. e to generate statistics with or even monitoring over longer time periods django celery now comes with a Celery monitor for the Django Admin interface To use this you need to run the django celery snapshot camera which stores snapshots to the database at config urable intervals To use the Django admin monitor you need to do the following 1 Create the new database tables S python manage py syncdb 2 Start the django celery snapshot camera S python manage py celerycam 3 Open up the django admin to monitor your cluster The admin interface shows tasks worker nodes and even lets you perform some actions like re voking and rate limiting tasks and shutting down worker nodes There s also a Debian init d script for celeryev available see Running the worker as a daemon for more information New command line arguments to celeryev c camera Snapshot camera class to use logfile f Log file loglevel 1 Log level maxrate r Shutter rate limit freq F Shutter frequency The camera argument is the name of a class used to take snapshots with It must support the interface defined by celery events snapshot Polaroid Shutter frequency controls how often the camera thread wakes up while the rate limit controls how often it will actually take a snapshot The rate limit can be an integer snapshots s or a rate limit string which has the same syntax as the task rate limi
281. e to the Code lt suffix 302 Chapter 2 Contents Celery Documeniation Release 3 0 25 e Philosophy The API gt RCP Precedence Rule e Conventions and Idioms Used Classes x Naming Default values x Exceptions x Composites e Applications vs single mode e Module Overview Philosophy The API gt RCP Precedence Rule e The API is more important than Readability e Readability is more important than Convention e Convention is more important than Performance unless the code is a proven hotspot More important than anything else is the end user API Conventions must step aside and any suffering is always alleviated if the end result is a better API Conventions and Idioms Used Classes Naming Follows PEP 8 e Class names must be CamelCase e but not if they are verbs verbs shall be lower_case test case for a class class TestMyClass Case BAD pass class test_MyClass Case GOOD pass test case for a function class TestMyFunction Case BAD pass class test_my_ function Case GOOD pass action class verb class UpdateTwitterStatus object BAD pass 2 14 Internals 303 Celery Documeniation Release 3 0 25 class update_twitter_status object pass Note Sometimes it makes sense to have a class mask as a function and there is precedence for this in the stdlib e g contextmanager Celery examples include s
282. e using Django Python standard library import xxx Python standard library from xxx import Third party packages Django packages Other modules from the current package Within these sections the imports should be sorted by module name Example import threading import time from collections import deque from Queue import Queue Empty from datastructures import TokenBucket from utils import timeutils from utils compat import all izip_longest chain_from_iterable 160 Chapter 2 Contents Celery Documeniation Release 3 0 25 e Wildcard imports must not be used from xxx import e For distributions where Python 2 5 is the oldest support version additional rules apply Absolute imports must be enabled at the top of every module from _ future_ import absolute_import If the module uses the with statement it must also enable that from _ future_ import with_statement Every future import must be on its own line as older Python 2 5 releases did not support import ing multiple features on the same future import line Good from __future__ import absolute_import from _ future_ import with_statement Bad from __future__ import absolute_import with_statement Note that this rule does not apply if the package does not include support for Python 2 5 e Note that we use new style relative imports when the distribution does not support Python versions below 2 5 from impo
283. e version number must be updated two places celery __init__ py e docs include introduction txt After you have changed these files you must render the README files There is a script to convert sphinx syntax to generic reStructured Text syntax and the paver task readme does this for you S paver readme Now commit the changes git commit a m Bumps version to X Y 2 and make a new version tag git tag vX Y Z git push tags Releasing Commands to make a new public stable release paver releaseok checks pep8 autodoc index runs tests and more paver removepyc Remove pyc files git clean xdn Check that there s no left over files in the repo python setup py sdist upload Upload package to PyPI If this is a new release series then you also need to do the following e Go to the Read The Docs management interface at http readthedocs org projects celery fromdocs celery e Enter Edit project 164 Chapter 2 Contents Celery Documeniation Release 3 0 25 Change default branch to the branch of this series e g 2 4 for series 2 4 e Also add the previous version under the versions tab Updating bundles First you need to make sure the bundle entrypoints have been installed but either running develop or install python setup py develop Then make sure that you have your PyPI credentials stored in pypirc and execute the command S python setup py upload_bundles
284. ead this documentation and make sure your modules are suitable for reloading See also e http pyunit sourceforge net notes reloading html e http www indelible org ink python reloading e http docs python org library functions html reload Inspecting workers celery control inspect lets you inspect running workers It uses remote control commands under the hood You can also use the celery command to inspect workers and it supports the same commands as the Celery control interface 88 Chapter 2 Contents Celery Documeniation Release 3 0 25 Inspect all nodes gt gt gt i celery control inspect Specify multiple nodes to inspect gt gt gt i celery control inspect workerl example com worker2 example com Specify a single node to inspect gt gt gt i celery control inspect workerl example com Dump of registered tasks You can get a list of tasks registered in the worker using the registered gt gt gt i registered workerl example com tasks add tasks sleeptask Dump of currently executing tasks You can get a list of active tasks using active gt gt gt i active workerl example com name tasks sleeptask id 32666e9b 809c 41fa 8e93 5ae0c80afbbf raraga 8 kwargs Dump of scheduled ETA tasks You can get a list of tasks waiting to be scheduled by u
285. ecides the routing options for a task All you need to define a new router is to create a class with a route_for_task method class MyRouter object def route_for_task self task args None kwargs None if task myapp tasks compress_video return exchange video exchange_type topic routing_key video compress return None If you return the queue key it will expand with the defined settings of that queue in CELERY_QUEUES queue video routing_key video compress becomes gt queue video exchange video exchange_type topic routing_key video compress You install router classes by adding them to the CELERY_ROUTES setting CELERY_ROUTES MyRouter Router classes can also be added by name CELERY_ROUTES myapp routers MyRouter For simple task name gt route mappings like the router example above you can simply drop a dict into CELERY_ROUTES to get the same behavior 2 3 User Guide 103 Celery Documentation Release 3 0 25 Q Hi ELERY_ROUTES myapp tasks compress_video queue video routing_key video compress th The routers will then be traversed in order it will stop at the first router returning a true value and use that
286. ecorators with tasks Answer Yes But please see note in the sidebar at Basics Can I use natural task ids Answer Yes but make sure it is unique as the behavior for two tasks existing with the same id is undefined The world will probably not explode but at the worst they can overwrite each others results How can I run a task once another task has finished Answer You can safely launch a task inside a task Also a common pattern is to add callbacks to tasks from celery utils log import get_task_logger logger get_task_logger __name__ celery task def add x y return x y celery task ignore_result True def log_result result logger info log_result got Sr result Invocation 2 9 Frequently Asked Questions 181 Celery Documentation Release 3 0 25 gt gt gt add s 2 2 log_result s delay See Canvas Designing Workflows for more information Can I cancel the execution of a task Answer Yes Use result revoke gt gt gt result add apply_async args 2 2 countdown 120 gt gt gt result revoke or if you only have the task id gt gt gt from celery import current_app as celery gt gt gt celery control revoke task_id Why aren t my remote control commands received by all workers Answer To receive broadcast remote control commands every worker node uses its host name to create a unique queue name to listen to so if you have more than one worker with
287. ection errors occurring in timer callbacks so that the connection can be reset The modules in CELERY_IMPORTS and CELERY_INCLUDE are now imported in the original order Issue 1161 The modules in CELERY_IMPORTS will be imported first then continued by CELERY_INCLUDE Thanks to Joey Wilhelm New bash completion for celery available in the git repository 212 Chapter 2 Contents Celery Documeniation Release 3 0 25 https github com celery celery tree 3 0 extra bash completion You can source this file or put it in bash_completion d to get auto completion for the celery command line utility The node name of a worker can now include unicode characters Issue 1186 The repr of a crontab object now displays correctly Issue 972 events State no longer modifies the original event dictionary No longer uses Logger warn deprecated in Python 3 Cache Backend Now works with chords again Issue 1094 Chord unlock now handles errors occurring while calling the callback Generic worker init d script Status check is now performed by querying the pid of the instance instead of sending messages Contributed by Milen Pavlov Improved init scripts for CentOS Updated to support celery 3 x conventions Now uses CentOS built in status and killproc Support for multi node multi pid worker services Standard color coded CentOS service init output A
288. ed earlier and you can verify that by looking at the workers console output Calling a task returns an AsyncResult instance which can be used to check the state of the task wait for the task to finish or get its return value or if the task failed the exception and traceback But this isn t enabled by default and you have to configure Celery to use a result backend which is detailed in the next section Keeping Results If you want to keep track of the tasks states Celery needs to store or send the states somewhere There are several built in result backends to choose from SQLAIchemy Django ORM Memcached Redis AMQP RabbitMQ and MongoDB or you can define your own For this example you will use the amgp result backend which sends states as messages The backend is specified via the backend argument to Celery or via the CELERY_RESULT_BACKEND setting if you choose to use a configuration module celery Celery tasks backend amqp broker amqp or if you want to use Redis as the result backend but still use RabbitMQ as the message broker a popular combination celery Celery tasks backend redis localhost broker amqp To read more about result backends please see Result Backends Now with the result backend configured let s call the task again This time you ll hold on to the AsyncResult instance returned when you call a task gt gt gt result
289. edis database BROKER_URL redis localhost 6379 0 Where the URL is in the format of redis password hostname port db_number all fields after the scheme are optional and will default to localhost on port 6379 using database 0 Visibility Timeout The visibility timeout defines the number of seconds to wait for the worker to acknowledge the task before the message is redelivered to another worker Be sure to see Caveats below This option is set via the BROKER_TRANSPORT_OPTIONS setting BROKER_TRANSPORT_OPTIONS visibility_timeout 3600 1 hour The default visibility timeout for Redis is 1 hour Results If you also want to store the state and return values of tasks in Redis you should configure these settings CELERY_RESULT_BACKEND redis localhost 6379 0 For a complete list of options supported by the Redis result backend see Redis backend settings Caveats e If a task is not acknowledged within the Visibility Timeout the task will be redelivered to another worker and executed This causes problems with ETA countdown retry tasks where the time to execute exceeds the visibil ity timeout in fact if that happens it will be executed again and again in a loop So you have to increase the visibility timeout to match the time of the longest ETA you are planning to use Note that Celery will redeliver messages at worker shutdown so having a long visibility timeout will onl
290. edis gt Queue Prefix By default Celery will not assign any prefix to the queue names If you have other services using SQS you can configure it do so using the BROKER_TRANSPORT_OPTIONS setting BROKER_TRANSPORT_OPTIONS queue_name_prefix celery Caveats e If a task is not acknowledged within the visibility_timeout the task will be redelivered to another worker and executed 16 Chapter 2 Contents Celery Documeniation Release 3 0 25 This causes problems with ETA countdown retry tasks where the time to execute exceeds the visibil ity timeout in fact if that happens it will be executed again and again in a loop So you have to increase the visibility timeout to match the time of the longest ETA you are planning to use Note that Celery will redeliver messages at worker shutdown so having a long visibility timeout will only delay the redelivery of lost tasks in the event of a power failure or forcefully terminated workers Periodic tasks will not be affected by the visibility timeout as it is a concept separate from ETA countdown The maximum visibility timeout supported by AWS as of this writing is 12 hours 43200 seconds BROKER_TRANSPORT_OPTIONS visibility_timeout 43200 e SQS does not yet support worker remote control commands e SQS does not yet support events and so cannot be used with celery events celerymon or the Django Admin monitor Results Multiple
291. eel that it is time too Python 2 6 should be widely available at this point and we urge you to upgrade but if that is not possible you still have the option to continue using the Celery 3 0 and important bug fixes introduced in Celery 3 1 will be back ported to Celery 3 0 upon request UTC timezone is now used This means that ETA countdown in messages are not compatible with Celery versions prior to 2 5 You can disable UTC and revert back to old local time by setting the CELERY_ENABLE_UTC setting Redis Ack emulation improvements Reducing the possibility of data loss Acks are now implemented by storing a copy of the message when the message is consumed The copy is not removed until the consumer acknowledges or rejects it This means that unacknowledged messages will be redelivered either when the connection is closed or when the visibility timeout is exceeded e Visibility timeout This is a timeout for acks so that if the consumer does not ack the message within this time limit the message is redelivered to another consumer The timeout is set to one hour by default but can be changed by configuring a transport option BROKER_TRANSPORT_OPTIONS visibility_timeout 18000 5 hours Note Messages that have not been acked will be redelivered if the visibility timeout is exceeded for Celery users this means that ETA countdown tasks that are scheduled to execute with a time that exceeds
292. elease 3 0 25 Celery is a simple flexible and reliable distributed system to process vast amounts of messages while providing operations with the tools required to maintain such a system It s a task queue with focus on real time processing while also supporting task scheduling Celery has a large and diverse community of users and contributors you should come join us on IRC or our mailing list Celery is Open Source and licensed under the BSD License Contents 1 Celery Documentation Release 3 0 25 2 Contents CHAPTER 1 Getting Started e If you are new to Celery you can get started by following the First Steps with Celery tutorial e You can also check out the FAQ Celery Documentation Release 3 0 25 4 Chapter 1 Getting Started CHAPTER 2 Contents 2 1 Copyright Celery User Manual by Ask Solem Copyright 2009 2013 Ask Solem All rights reserved This material may be copied or distributed only subject to the terms and conditions set forth in the Creative Commons Attribution Noncommercial Share Alike 3 0 United States License You must give the original author credit You may not use this work for commercial purposes If you alter transform or build upon this work you may distribute the resulting work only under the same or similar license to this one Note While the Celery documentation is offered under the Creative Commons attribution nonconmmercial share alike 3
293. elery Documeniation Release 3 0 25 Group Results The group task returns a special result too this result works just like normal task results except that it works on the group as a whole gt gt gt from celery import group gt gt gt from tasks import add gt gt gt job group add subtask 2 2 add subtask 4 4 add subtask 8 8 add subtask 16 16 add subtask 32 32 gt gt gt result job apply_async gt gt gt result ready have all subtasks completed True gt gt gt result successful were all subtasks successful True gt gt gt result join 4 8 16 32 64 The GroupResult takes a list of AsyncResult instances and operates on them as if it was a single task It supports the following operations successful Returns True if all of the subtasks finished successfully e g did not raise an exception e failed Returns True if any of the subtasks failed e waiting Returns True if any of the subtasks is not ready yet e ready Return True if all of the subtasks are ready e completed_count Returns the number of completed subtasks e revoke Revokes all of the subtasks e iterate Iterates over the return values of the subtasks as they finish one by one e join Gather the results for all of the subtasks and return a list with them ordered by the order of which they were called Chords New in version 2 3 76 Chapter 2 Contents
294. elery app routes MapRoute map Creates a router out of a dict route_for_task task args kwargs class celery app routes Router routes None queues None create_missing False app None expand destination route lookup_route task args None kwargs None route options task args kwargs celery app routes prepare routes Expands the CELERY_ROUTES setting celery security certificate e celery security certificate j celery security certificate X 509 certificates class celery security certificate CertStore Base class for certificate stores add_cert cert itercerts an iterator over the certificates class celery security certificate Certificate cert X 509 certificate get_id Serial number issuer pair uniquely identifies a certificate get_issuer Returns issuer CA as a string get_serial_number Returns the certificates serial number has_expired Check if the certificate has expired 368 Chapter 2 Contents Celery Documeniation Release 3 0 25 verify data signature digest Verifies the signature for string containing data class celery security certificate FSCertStore path File system certificate store celery security key e celery security key j celery security key Private key for the security serializer class celery security key PrivateKey key sign data digest sign string containing data celery security
295. elery platform module has been renamed to celery platforms to not collide with the built in plat form module You have to remove the old plat form py and maybe plat form pyc file from your previous Celery installation To do this use python to find the location of this module python gt gt gt import celery platform gt gt gt celery platform lt module celery platform from opt devel celery celery platform pyc gt Here the compiled module is in opt devel celery celery to remove the offending files do rm f opt devel celery celery platform py 2 15 History 427 Celery Documentation Release 3 0 25 News e Added support for expiration of AMQP results requires RabbitMQ 2 1 0 The new configuration option CELERY_AMOP_TASK_RESULT_EXPIRES sets the expiry time in seconds can be int or float CELERY_AMOP_TASK_RESULT_EXPIRES CELERY_AMOP_TASK_RESULT_EXPIRE ll 30 60 30 minutes 0 80 s n I e celeryev Event Snapshots If enabled celeryd sends messages about what the worker is doing These messages are called events The events are used by real time monitors to show what the cluster is doing but they are not very useful for monitoring over a longer period of time Snapshots lets you take pictures of the clusters state at regular intervals This can then be stored in a databas
296. elog 2 15 2 Change history for Celery 2 4 e 2 4 5 e 2 44 Security Fixes Fixes e 2 4 3 e 2 4 2 e 2 4 1 e 2 4 0 Important Notes News 2 4 5 release date 2011 12 02 05 00 PM GMT by Ask Solem e Periodic task interval schedules were accidentally rounded down resulting in some periodic tasks being executed early e Logging of humanized times in the celerybeat log is now more detailed e New Brokers section in the Getting Started part of the Documentation This replaces the old tut otherqueues tutorial and adds documentation for MongoDB Beanstalk and CouchDB 2 4 4 release date 2011 11 25 16 00 P M GMT by Ask Solem 2 15 History 399 Celery Documentation Release 3 0 25 Security Fixes e Security CELERYSA 0001 Daemons would set effective id s rather than real id s when the uid gid arguments to celeryd multi celeryd_detach celerybeat and celeryev were used This means privileges weren t properly dropped and that it would be possible to regain supervisor privileges later Fixes e Processes pool Fixed rare deadlock at shutdown Issue 523 Fix contributed by Ionel Maries Christian e Webhook tasks issued the wrong HTTP POST headers Issue 515 The Content Type header has been changed from application json application x www form urlencoded and adds a proper Content Length header Fix contributed by Mitar e Daemonization tutorial Adds a configura
297. en converted back to the local timezone when received by a worker You can change the local timezone using the CELERY_TIMEZONE setting Installing the pytz library is recom mended when using a custom timezone to keep timezone definition up to date but it will fallback to a system defini tion of the timezone if available UTC will enabled by default in version 3 0 Note django celery will use the local timezone as specified by the TIME_ZONE setting it will also honor the new USE_TZ setting introuced in Django 1 4 New security serializer using cryptographic signing A new Serializer has been added that signs and verifies the signature of messages The name of the new serializer is auth and needs additional configuration to work see Security See also 200 Chapter 2 Contents Celery Documeniation Release 3 0 25 Security Contributed by Mher Movsisyan Experimental support for automatic module reloading Starting celeryd with the autoreload option will enable the worker to watch for file system changes to all imported task modules imported and also any non task modules added to the CELERY_IMPORTS setting or the I include option This is an experimental feature intended for use in development only using auto reload in production is discouraged as the behavior of reloading a module in Python is undefined and may cause hard to diagnose bugs and crashes Celery uses th
298. en renamed to load_settings and is now a function returning the settings object celery loaders current_loader is now also a function returning the current loader So loader current_loader needs to be changed to loader current_loader Deprecations e The following configuration variables has been renamed and will be deprecated in v2 0 CELERYD_DAEMON_LOG_FORMAT gt CELERYD_LOG_FORMAT CELERYD_DAEMON_LOG_LEVEL gt CELERYD_LOG_LEVEL CELERY_AMQP_CONNECTION_TIMEOUT gt CELERY_BROKER_CONNECTION_TIMEOUT CELERY_AMQP_CONNECTION_RETRY gt CELERY_BROKER_CONNECTION_RETRY CELERY_AMQP_CONNECTION_MAX_RETRIES gt CELERY_BROKER_CONNECTION_MAX_RETRIES SEND_CELERY_TASK_ ERROR _EMAILS gt CELERY_SEND_TASK_ERROR_EMAILS e The public API names in celery conf has also changed to a consistent naming scheme e We now support consuming from an arbitrary number of queues To do this we had to rename the configuration syntax If you use any of the custom AMQP routing options queue exchange routing_key etc you should read the new FAQ entry Can I send some tasks to only some servers The previous syntax is deprecated and scheduled for removal in v2 0 e TaskSet run has been renamed to TaskSet apply_async TaskSet run has now been deprecated and is scheduled for removal in v2 0 News e Rate limiting support per task type or globally e New periodic task system e Automatic registration e New cool t
299. en takes any iterable and if the object is an generator it will cache the evaluated list on first access so that the generator can be consumed multiple times celery utils functional unidgq it Returns all unique elements in it preserving order celery utils term e celery utils term I celery utils term Terminals and colors class celery utils term colored s kwargs Terminal colored text Example gt gt gt c colored enabled True gt gt gt print str c red the quick c blue brown c bold fox c magenta c underline jumps over c yellow the lazy c green dog black s blink s blue s bold s bright s cyan s embed green s iblue s icyan s igreen s imagenta s ired s iwhite s iyellow s magenta s no_color node s op 2 14 Internals 379 Celery Documentation Release 3 0 25 red s reset s reverse s underline s white s yellow s celery utils term fg s celery utils timeutils e celery utils timeutils j celery utils timeutils This module contains various utilities related to dates and times exception celery utils timeutils AmbiguousTimeError class celery utils timeutils LocalTimezone Local time implementation taken from Python s docs Used only when pytz isn t available and most likely inaccurate If you re having trouble w
300. end_task now emits a warning when used in combination with CELERY_ALWAYS_EAGER Issue 581 Contributed by Mher Movsisyan apply_async now forwards the original keyword arguments to apply when CELERY_ALWAYS_EAGER is enabled celeryev now tries to re establish the connection if the connection to the broker is lost Issue 574 celeryev Fixed a crash occurring if a task has no associated worker information Fix contributed by Matt Williamson The current date and time is now consistently taken from the current loaders now method Now shows helpful error message when given a config module ending in py that can t be imported celeryctl The xpires and eta arguments to the apply command can now be an ISO 8601 formatted string celeryctl now exits with exit status EX_UNAVAILABLE 69 if no replies have been received 2 12 Change history 2 12 Change history 205 Celery Documentation Release 3 0 25 310 25 Security Fixes e 3 0 24 3 0 23 e 3 0 22 e 3 0 21 e 3 0 20 e 3 0 19 e 3 0 18 3 0 17 e 3 0 16 3 10 15 e 3 0 14 e 3 0 13 3 0 12 3 0 11 e 3 0 10 e 3 0 9 e 3 0 8 3 0 7 e 3 0 6 e 3 0 5 e 3 0 4 3 0 3 3 0 2 3 0 1 e 3 0 0 Chiastic Slide If you re looking for versions prior to 3 0 x you should go to History 2 12 1 3 0 25 release date 2014 07 10 05 00 P M UTC Security Fixes e Security CELERYSA 0002 Insecure default uma
301. ent directory This is accomplished by the default loader ensuring that the current directory is in sys path when loading the config module sys path is reset to its original state after loading Adding the current working directory to sys path without the user knowing may be a security issue as this means someone can drop a Python module in the users directory that executes arbitrary commands This was the original reason not to do this but if done only when loading the config module this means that the behavior will only apply to the modules imported in the config module which I think is a good compromise certainly better than just explicitly setting PYTHONPATH anyway Experimental Cassandra backend added celeryd SIGHUP handler accidentally propagated to worker pool processes In combination with 7a7c44e39344789f1 1b5346e9cc8340f5fe4846c this would make each child process start a new celeryd when the terminal window was closed celeryd Do not install SIGHUP handler if running from a terminal This fixes the problem where celeryd is launched in the background when closing the terminal celeryd Now joins threads at shutdown See issue 152 Test tear down Don t use atexit but nose s teardown functionality instead See issue 154 Debian init script for celeryd Stop now works correctly Task logger warn method added synonym for warning Can now define a white list of errors to send error emails for Exa
302. entedError on platforms where this is not supported Is sue 320 Coloring of log messages broke if the logged object was not a string Fixed several typos in the init script documentation A regression caused Task exchange and Task routing_key to no longer have any effect This is now fixed Routing Userguide Fixes typo routers in CELERY_ROUTES must be instances not classes celeryev did not create pidfile even though the pidfile argument was set Task logger format was no longer used Issue 317 The id and name of the task is now part of the log message again A safe version of repr is now used in strategic places to ensure objects with a broken __repr_ does not crash the worker or otherwise make errors hard to understand Issue 298 414 Chapter 2 Contents Celery Documeniation Release 3 0 25 e Remote control command act ive_queues did not account for queues added at runtime In addition the dictionary replied by this command now has a different structure the exchange key is now a dictionary containing the exchange declaration in full e The 0 option to celeryd removed unused queue declarations so routing of tasks could fail Queues are no longer removed but rather app amqp queues consume_from is used as the list of queues to consume from This ensures all queues are available for routing purposes e celeryctl Now supports the inspect active_queues command 2 2 2 re
303. eply worker local total tasks sleeptask 6 pool timeouts None None processes 60376 60377 max concurrency 2 max tasks per child None put guarded by semaphore True 438 Chapter 2 Contents Celery Documeniation Release 3 0 25 e New remote control command dump_active Gives a list of tasks currently being executed by the worker By default arguments are passed through repr in case there are arguments that is not JSON encodable If you know the arguments are JSON safe you can pass the argument safe True Example reply gt gt gt broadcast dump_active arguments safe False reply True worker local iti as ro l1 G 1 id 802e93e9 e470 47ed b913 06de8510aca2 e Added experimental support for persistent revokes Use the Sl statedb argument to celeryd to enable it celeryd statedb var run celeryd This will use the file var run celeryd db as the shelve module automatically adds the db suffix 2 0 0 release date 2010 07 02 02 30 PM CEST Foreword Celery 2 0 contains backward incompatible changes the most important being that the Django dependency has been removed so Celery no longer supports Django out of the box but instead as an add on package called django celery We re very sorry for breaking backwards compatibility but there s also many new and exciting features to
304. er Events should only be enabled if you have an active monitor consuming them or if you purge the event queue period ically e AMQP backend results When running with the AMQP result backend every task result will be sent as a message If you don t collect these results they will build up and RabbitMQ will eventually run out of memory Results expire after 1 day by default It may be a good idea to lower this value by configuring the CELERY_TASK_RESULT_EXPIRES setting If you don t use the results for a task make sure you set the ignore_result option Can I use Celery with Active MQ STOMP Answer No It used to be supported by Carrot but is not currently supported in Kombu What features are not supported when not using an AMQP broker This is an incomplete list of features not available when using the virtual transports e Remote control commands supported only by Redis e Monitoring with events may not work in all virtual transports The header and fanout exchange types fanout is supported by Redis 2 9 7 Tasks How can I reuse the same connection when calling tasks Answer See the BROKER_POOL_LIMIT setting The connection pool is enabled by default since version 2 5 Sudo in a subprocess returns None There is a sudo configuration option that makes it illegal for process without a tty to run sudo Defaults requiretty If you have this configuration in your etc sudoers file
305. er is the task class being executed Provides arguments e task_id Id of the task to be executed e task The task being executed e args the tasks positional arguments e kwargs The tasks keyword arguments task_postrun Dispatched after a task has been executed Sender is the task class executed Provides arguments e task_id Id of the task to be executed e task The task being executed e args The tasks positional arguments e kwargs The tasks keyword arguments e retval The return value of the task e state Name of the resulting state task_success Dispatched when a task succeeds Sender is the task class executed Provides arguments e result Return value of the task 2 3 User Guide 123 Celery Documeniation Release 3 0 25 task_failure Dispatched when a task fails Sender is the task class executed Provides arguments e task_id Id of the task e exception Exception instance raised e args Positional arguments the task was called with e kwargs Keyword arguments the task was called with e traceback Stack trace object e einfo The celery datastructures ExceptionInfo instance task_revoked Dispatched when a task is revoked terminated by the worker Sender is the task class revoked terminated Provides arguments e terminated Set to True if the task was terminated e signum Signal number used to terminate the task If this is None and terminated is True then TERM should be assumed e expire
306. eral kinds of events trigger signals you can connect to these signals to perform actions as they trigger Example connecting to the task_sent signal from celery signals import task_sent task_sent connect def task_sent_handler sender None task_id None task None args None kwargs None xkwds print Got signal task_sent for task id s task_id Some signals also have a sender which you can filter by For example the task_sent signal uses the task name as a sender so you can connect your handler to be called only when tasks with name tasks add has been sent by providing the sender argument to connect task_sent connect sender tasks add def task_sent_handler sender None task_id None task None args None kwargs None xxkwds print Got signal task_sent for task id s task_id 122 Chapter 2 Contents Celery Documeniation Release 3 0 25 Signals Task Signals task_sent Dispatched when a task has been sent to the broker Note that this is executed in the client process the one sending the task not in the worker Sender is the name of the task being sent Provides arguments task_id Id of the task to be executed task The task being executed args the tasks positional arguments kwargs The tasks keyword arguments eta The time to execute the task taskset Id of the taskset this task is part of if any task_prerun Dispatched before a task is executed Send
307. erkey id weakref receiver mappings connect args kwargs Connect receiver to sender for signal Parameters e receiver A function or an instance method which is to receive signals Re ceivers must be hashable objects if weak is True then receiver must be weak referencable more precisely saferef safe_ref must be able to create a reference to the receiver Receivers must be able to accept keyword arguments If receivers have a dispatch_uid attribute the receiver will not be added if another receiver already exists with that dispatch_uid e sender The sender to which the receiver should respond Must either be of type Signal or None to receive events from any sender e weak Whether to use weak references to the receiver By default the module will attempt to use weak references to the receiver objects If this parameter is false then strong references will be used e dispatch_uid An identifier used to uniquely identify a particular instance of a receiver This will usually be a string though it may be anything hashable disconnect receiver None sender None weak True dispatch_uid None Disconnect receiver from sender for signal If weak references are used disconnect need not be called The receiver will be removed from dispatch automatically Parameters 2 14 Internals 389 Celery Documentation Release 3 0 25 e receiver The registered receiver to disconnect May be none if disp
308. ers sum of A best practice is to use the module name as a namespace this way names won t collide if there s already a task with that name defined in another module gt gt gt celery task name tasks add gt gt gt def add x y return x y You can tell the name of the task by investigating its name attribute gt gt gt add name tasks add Which is exactly the name that would have been generated anyway if the module name is tasks py tasks py celery task def add x y return x y gt gt gt from tasks import add gt gt gt add name tasks add Automatic naming and relative imports Relative imports and automatic name generation does not go well together so if you re using relative imports you should set the name explicitly For example if the client imports the module myapp tasks as tasks and the worker imports the module as myapp tasks the generated names won t match and an Not Registered error will be raised by the worker This is also the case if using Django and using project myapp INSTALLED_APPS project myapp The worker will have the tasks registered as project myapp tasks while this is what happens in the client if the module is imported as myapp tasks gt gt gt from myapp tasks import add gt gt gt add name myapp tasks add For this reason you should never use project app but r
309. ery Documeniation Release 3 0 25 cleanup cleanup_signal lt Signal Signal gt clear_after False install on_cleanup on_shutter state shutter shutter_signal lt Signal Signal gt timer lt module celery utils timer2 from celery utils timer2 pyc gt celery events snapshot eveam camera freq 1 0 maxrate None loglevel 0 logfile None pid file None timer None app None celery events cursesmon s celery events cursesmon j celery events cursesmon Graphical monitor of Celery events using curses class celery events cursesmon CursesMonitor state keymap None app None alert callback title None alert_remote_control_reply reply background 7 display height display_task_row lineno task display width draw find_position foreground 0 format_row uuid task worker timestamp state greet celeryev 3 0 25 Chiastic Slide handle_keypress help j up k down i info t traceback r result c revoke c quit help _title Keys info_str Info init_screen 2 14 Internals 373 Celery Documentation Release 3 0 25 keyalias 258 J 259 K 343 I keymap limit move_selection direction 1 move_selection_down move_selection_up nap online_str Workers online readline x y resetscreen revoke_selection safe_add_str y x string args kwargs screen
310. ery Documentation Release 3 0 25 celery concurrency celery concurrency j celery concurrency Pool implementation abstract factory and alias definitions celery concurrency get_implementation cls celery concurrency solo e celery concurrency solo j celery concurrency solo Single threaded pool implementation class celery concurrency solo TaskPool args kwargs Solo task pool blocking inline fast celery concurrency processes celery concurrency processes j celery concurrency processes Pool implementation using multiprocessing We use the billiard fork of multiprocessing which contains numerous improvements class celery concurrency processes TaskPool limit None putlocks True fork ing_enable True callbacks_propagate options Multiprocessing Pool implementation class Pool processes None initializer None initargs maxtasksperchild None timeout None soft_timeout None lost_worker_timeout 10 0 max_restarts None max_restart_freq 1 on_process_up None on_process_down None on_timeout_set None on_timeout_cancel None threads True semaphore None putlocks False al low_restart False Class which supports an async version of applying functions to arguments class Process group None target None name None args kwargs daemon None kw Process objects represent activity that is run in a separate process The class is analagous to threading
311. ery exceptions CPendingDeprecationWarning exception celery exceptions ChordError A task part of the chord raised an exception exception celery exceptions Ignore A task can raise this to ignore doing state updates exception celery exceptions ImproperlyConfigured Celery is somehow improperly configured exception celery exceptions IncompleteStream Found the end of a stream of data but the data is not yet complete exception celery exceptions InvalidTaskError The task has invalid data or is not properly constructed 2 13 API Reference 265 Celery Documentation Release 3 0 25 exception celery exceptions MaxRetriesExceededError The tasks max restart limit has been exceeded exception celery exceptions NotConfigured Celery has not been configured as no config module has been found exception celery exceptions NotRegistered The task is not registered exception celery exceptions QueueNotFound Task routed to a queue not in CELERY_QUEUES exception celery exceptions RetryTaskError message None exc None when None kwargs The task is to be retried later exc None Exception if any that caused the retry to happen humanize message None Optional message describing context of retry when None Time of retry ETA either int or datetime exception celery exceptions SecurityError Security related exceptions Handle with care exception celery exceptions SystemTerminate Signals that t
312. ery installation more secure Areas of Concern Broker It is imperative that the broker is guarded from unwanted access especially if it is publically accesible By default workers trust that the data they get from the broker has not been tampered with See Message Signing for information on how to make the broker connection more trusthworthy The first line of defence should be to put a firewall in front of the broker allowing only white listed machines to access it Keep in mind that both firewall misconfiguration and temproraily disabling the firewall is common in the real world Solid security policy includes monitoring of firewall equipment to detect if they have been disabled be it accidentally or on purpose In other words one should not blindly trust the firewall either 116 Chapter 2 Contents Celery Documeniation Release 3 0 25 If your broker supports fine grained access control like RabbitMQ this is something you should look at enabling See for example http www rabbitmq com access control html Client In Celery client refers to anything that sends messages to the broker e g web servers that apply tasks Having the broker properly secured doesn t matter if arbitrary messages can be sent through a client Need more text here Worker The default permissions of tasks running inside a worker are the same ones as the privileges of the worker itself This applies to resources such as memory f
313. ery series 2 2 Celery requires a message broker to send and receive messages The RabbitMQ Redis and MongoDB broker trans ports are feature complete but there s also support for a myriad of other solutions including using SQLite for local development Celery can run on a single machine on multiple machines or even across data centers Get Started If this is the first time you re trying to use Celery or you are new to Celery 3 0 coming from previous versions then you should read our getting started tutorials e First Steps with Celery e Next Steps Celery is Chapter 2 Contents Celery Documeniation Release 3 0 25 e Simple Celery is easy to use and maintain and it doesn t need configuration files It has an active friendly community you can talk to for support including a mailing list and an IRC channel Here s one of the simplest applications you can make from celery import Celery celery Celery hello broker amqp guest localhost celery task def hello return hello world e Highly Available Workers and clients will automatically retry in the event of connection loss or failure and some brokers support HA in way of Master Master or Master Slave replication e Fast A single Celery process can process millions of tasks a minute with sub millisecond round trip latency using RabbitMQ py librabbitmgq and optimized settings e Flexible Almost every p
314. ery task control import broadcast gt gt gt broadcast dump_reserved reply True myworkerl lt TaskRequest gt e New remote control command dump_schedule Dumps the workers currently registered ETA schedule These are tasks with an eta or countdown argument waiting to be executed by the worker gt gt gt from celery task control import broadcast gt gt gt broadcast dump_schedule reply True wl w3 w2 0 2010 05 12 11 06 00 priO lt TaskRequest name opalfeeds tasks refresh_feed_slice id 95b45760 4e73 4ce8 8eac f100aa80273a w rgs lt Feeds freq_max 3600 freq min 60 start 2184 0 stop 3276 0 gt v cwargs page 2 gt w4 0 2010 05 12 11 00 00 priO lt TaskRequest name opalfeeds tasks refresh id c053480b 58fb 422 args lt Feeds freq_ma start 1092 0 stop 2184 0 gt kwargs page 1L gt 1 2010 05 12 11 12 00 priO lt TaskRequest name opalfeeds tasks refresh_fe _feed_slice 8d30a464edfe freq_min 60 id ab8bc59e 6cf8 44b8 88d0 f args lt Feeds freq_m f 3600 freq min start 327 kwargs page Fixes e Mediator thread no longer blocks for more than 1 second With rate limits enabled and when there was a lot of remaining time the mediator thread could block shutdown and potentially block other jobs from coming in e Remote rate li
315. erybeat or etc default celeryd 168 Chapter 2 Contents Celery Documeniation Release 3 0 25 Example configuration This is an example configuration for a Python project etc default celerybeat Where to chdir at start CELERYBEAT_CHDIR opt Myproject Extra arguments to celerybeat CELERYBEAT_OPTS schedule var run celerybeat schedule Example Django configuration This is an example configuration for those using django celery etc default celerybeat Where the Django project is CELERYBEAT_CHDIR opt Project Name of the projects settings module export DJANGO_SETTINGS_MODULE Ssettings Path to celerybeat CELERYBEAT opt Project manage py celerybeat Extra arguments to celerybeat CELERYBEAT_OPTS schedule var run celerybeat schedule Available options e CELERYBEAT_OPTS Additional arguments to celerybeat see celerybeat help for a list e CELERYBEAT_PID_FILE Full path to the PID file Default is var run celeryd pid e CELERYBEAT_LOG_FILE Full path to the celeryd log file Default is var log celeryd log e CELERYBEAT_LOG_LEVEL Log level to use for celeryd Default is INFO e CELERYBEAT Path to the celeryd program Default is celeryd You can point this to an virtualenv or even use manage py for django e CELERYBEAT_USER User to run celeryd as Default is current user e CELERYBEAT_GROUP Group to run celeryd as Defau
316. es sages on the broker migrating from Contributed by John Watson e Worker Prefetch count increments are now optimized and grouped together e Worker No longer calls consume on the remote control command queue twice Probably didn t cause any problems but was unecessary Internals e app broker_connection is now app connection Both names still work e Compat modules are now generated dynamically upon use These modules are celery messaging celery log celery decorators and celery registry e celery utils refactored into multiple modules celery utils text celery utils imports celery utils functional e Now using kombu utils encoding instead of celery utils encoding e Renamed module celery routes gt celery app routes e Renamed package celery db gt celery backends database e Renamed module celery abstract gt celery worker bootsteps e Command line docs are now parsed from the module docstrings e Test suite directory has been reorganized e setup py now reads docs from the requirements directory e Celery commands no longer wraps output Issue 700 196 Chapter 2 Contents Celery Documeniation Release 3 0 25 Contributed by Thomas Johansson 2 10 4 Experimental celery contrib methods Task decorator for methods This is an experimental module containing a task decorator and a task decorator filter that can be used to create tasks out of methods from celery contrib methods import
317. esents the concept of back of the envelope calculations by asking the question How much water flows out of the Mississippi River in a day The point of this exercise is to show that there is a limit to how much data a system can process in a timely manner Back of the envelope calculations can be used as a means to plan for this ahead of time In Celery If a task takes 10 minutes to complete and there are 10 new tasks coming in every minute the queue will never be empty This is why it s very important that you monitor queue lengths A way to do this is by using Munin You should set up alerts that will notify you as soon as any queue has reached an unacceptable size This way you can take appropriate action like adding new worker nodes or revoking unnecessary tasks General Settings librabbitmgq If you re using RabbitMQ AMQP as the broker then you can install the 1ibrabbitmgq module to use an optimized client written in C pip install librabbitmq The amqp transport will automatically use the librabbitmq module if it s installed or you can also specify the transport you want directly by using the pyamqp or librabbitmq prefixes Broker Connection Pools The broker connection pool is enabled by default since version 2 5 You can tweak the BROKER_POOL_LIMIT setting to minimize contention and the value should be based on the number of active threads greenthreads using broker connections 2 The ch
318. esponse status success retval result return HttpResponse serialize response mimetype application json Ruby on Rails webhook example or in Ruby on Rails def multiply x params x to_i y params y to_i status status gt success retval gt x y render json gt status end You can easily port this scheme to any language framework new examples and libraries are very welcome Calling webhook tasks To call a task you can use the URL class gt gt gt from celery task http import URL gt gt gt res URL http example com multiply get_async x 10 y 10 URL is a shortcut to the Ht tpDispatchTask You can subclass this to extend the functionality gt gt gt from celery task http import HttpDispatchTask gt gt gt res HttpDispatchTask delay url http example com multiply deg method GET x 10 y 10 gt gt gt res get 100 The output of celery worker or the log file if enabled should show the task being executed INFO MainProcess Task celery task http HttpDispatchTask f2cc8efc 2al4 40cd 85ad flc77c94beeb processed 100 Since calling tasks can be done via HTTP using the djcelery views apply view calling tasks from other languages is easy For an example service exposing tasks via HTTP you should have a look at examples celery_http_gateway in the Celery distribution http github com celery celery tree m
319. essage instance to publish e routing_key Routing key e mandatory Currently not supported e immediate Currently not supported type direct unbind_from source routing_key nowait False arguments None Delete previously created exchange binding from the server class AMOPBackend Producer channel exchange None routing_key None serializer None auto_declare None compression None on_return None Message Producer Parameters e channel Connection or channel e exchange Optional default exchange e routing_key Optional default routing key e serializer Default serializer Default is json e compression Default compression method Default is no compression e auto_declare Automatically declare the default exchange at instantiation De fault is True 2 14 Internals 361 Celery Documentation Release 3 0 25 e on_return Callback to call for undeliverable messages when the mandatory or immediate arguments to publish is used This callback needs the following signature exception exchange routing_key message Note that the producer needs to drain events to use this feature auto_declare True channel close compression None connection declare Declare the exchange This happens automatically at instantiation if aut o_declare is enabled exchange None maybe_declare entity retry False retry_policy Declare
320. estina tion queue Availability of keys in this dict depends on the message broker used called_directly This flag is set to true if the task was not executed by the worker callbacks A list of subtasks to be called if this task returns successfully errback A list of subtasks to be called if this task fails utc Set to true the caller has utc enabled CELERY_ENABLE_UTC An example task accessing information in the context is celery task def add x y print Executing task id Gime args sr kwargs aie add request id add request args add request kwargs return x y current_task can also be used 2 3 User Guide 45 Celery Documentation Release 3 0 25 from celery import current_task celery task def add x y request current_task request print Executing task id r args r kwargs Sr b request id request args request kwargs return x y Logging The worker will automatically set up logging for you or you can configure logging manually A special logger is available named celery task you can inherit from this logger to automatically get the task name and unique id as part of the logs The best practice is to create a common logger for all of your tasks at the top of your module from celery utils log import get_task_logger logger get_task_logger __name__ celery task def add x y logger info Adding s s x y return x y
321. et_logger which simply gets the logger not setting the level and adds a NullHandler e Loggers are no longer passed around instead every module using logging defines a module global logger that is used throughout e All loggers inherit from a common logger called celery e Before task get_logger would setup a new logger for every task and even set the loglevel This is no longer the case Instead all task loggers now inherit from a common celery task logger that is set up when programs call setup_logging_subsystem Instead of using LoggerAdapter to augment the formatter with the task_id and task_name field the task base logger now use a special formatter adding these values at runtime from the currently executing task e In fact task get_logger is no longer recommended it is better to add a module level logger to your tasks module For example like this from celery utils log import get_task_logger logger get_task_logger __name__ celery task def add x y logger debug Adding r Sr x y return x y The resulting logger will then inherit from the celery task logger so that the current task name and id is included in logging output e Redirected output from stdout stderr is now logged to a celery redirected logger e In addition a few warnings warn have been replaced with logger warn e Now avoids the no handlers for logger multiprocessing warning Task registry no lon
322. eta Scheduled time as a datet ime datetime object e priority Unused e enter_after msecs entry priority 0 time lt built in function time gt e handle_error exc_info e info e on_error None Le queue underlying datastructure le schedule le stop apply _after args kwargs rgs kwargs apply interval args kwargs ensure_started enter entry eta priority None enter_after args kwargs exit_after msecs priority 10 on_tick None 386 Chapter 2 Contents Celery Documeniation Release 3 0 25 Timer running False Timer stop celery utils timer2 to_timestamp d default_timezone tzfile usr share zoneinfo UTC celery utils imports e celery utils import j celery utils import Utilities related to importing modules and symbols by name exception celery utils imports NotAPackage celery utils imports cwd_in_path args kwds celery utils imports find_module module path None imp None Version of imp find_module supporting dots celery utils imports import_from_cwd module imp None package None Import module but make sure it finds modules located in the current directory Modules located in the current directory has precedence over modules located in sys path celery utils imports instantiate name args kwargs Instantiate class by name See symbol_by_name celery utils imports module_file module
323. eue using settings CELERY_AMQP_EXCHANGE set tings CELERY AMQP_ROUTING_KEY and settings CELERY_AMQP_CONSUMER_QUEUE 0 1 6 release date 2009 04 28 02 13 P M CET Introducing TaskSet A set of subtasks is executed and you can find out how many or if all them are done excellent for progress bars and such Now catches all exceptions when running Task __call__ so the daemon doesn t die This doesn t happen for pure functions yet only Task classes autodiscover now works with zipped eggs celeryd Now adds current working directory to sys path for convenience The run_every attribute of PeriodicTask classes can now be a datetime timedelta object celeryd You can now set the DJANGO_PROJECT_DIR variable for celeryd and it will add that to sys path for easy launching Can now check if a task has been executed or not via HTTP You can do this by including the celery urls py into your project gt gt gt url r celery include celery urls then visiting the following url 2 15 History 473 Celery Documentation Release 3 0 25 http mysite celery S task_id done this will return a JSON dictionary like e g gt gt gt task id Stask_id executed true e delay_task now returns string id not uuid UUID instance e Now has PeriodicTasks to have cron like functionality e Project changed name from crunchy to celery The details of the name change request is in docs name_change_req
324. even if the task is otherwise configured to ignore results 2 13 API Reference 239 Celery Documentation Release 3 0 25 Task subtask args None starargs starkwargs Returns subt ask object for this task wrapping arguments and execution options for a single task invo cation Task time_limit None Hard time limit Defaults to the CELERYD_TASK_TIME_LIMIT setting ask track_started False If enabled the task will report its status as started when the task is executed by a worker Disabled by default as the normal behaviour is to not report that level of granularity Tasks are either pending finished or waiting to be retried Having a started status can be useful for when there are long running tasks and there is a need to report which task is currently running The application default can be overridden using the CELERY_TRACK_STARTED setting Task update_state task_id None state None meta None Update task state Parameters e task_id Id of the task to update defaults to the id of the current task e state New state str e meta State metadata dict class celery app task TaskType Meta class for tasks Automatically registers the task in the task registry except if the abstract attribute is set If no name attribute is provided then no name is automatically set to the name of the module it was defined in and the class name 2 13 4 celery app am
325. events based on a simple interval or crontab expressions supporting minute hour day of week day of month and month of year Read more e Autoreloading In development workers can be configured to automatically reload source code as it changes including inotify 7 support on Linux Read more e Autoscaling Dynamically resizing the worker pool depending on load or custom metrics specified by the user used to limit memory usage in shared hosting cloud environments or to enforce a given quality of service Read more e Resource Leak Protection The maxtasksperchild option is used for user tasks leaking resources like memory or file descriptors that are simply out of your control Read more e User Components Each worker component can be customized and additional components can be defined by the user The worker is built up using boot steps a dependency graph enabling fine grained control of the worker s internals Framework Integration Celery is easy to integrate with web frameworks some of which even have integration packages Django django celery Pyramid pyramid_celery Pylons celery pylons Flask not needed web2py web2py celery Tornado tornado celery The integration packages are not strictly necessary but they can make development easier and sometimes they add important hooks like closing database connections at fork 2 Quickjump 8 Chapter 2 Contents Celery Do
326. every event consumed the state is updated so the state represents the state of the cluster at the time of the last event Snapshots celery events snapshot can be used to take pictures of this state at regular intervals to e g store that in a database class celery events state Element Base class for worker state elements class celery events state State callback None workers None tasks None taskheap None max_workers_in_memory 5000 max_tasks_in_memory 10000 Records clusters state alive_workers Returns a list of seemingly alive workers clear ready True clear_tasks ready True event event event_count 0 freeze while fun args kwargs get_or_create_task uuid Get or create task by uuid 280 Chapter 2 Contents Celery Documeniation Release 3 0 25 get_or_create_worker hostname kwargs Get or create worker by hostname itertasks limit None task_count 0 task_event type fields Process task event task_types Returns a list of all seen task types tasks_by timestamp imit None Get tasks by timestamp Returns a list of uuid task tuples tasks_by_ type name limit None Get all tasks by type Returns a list of uuid task tuples tasks_by_ worker hostname limit None Get all tasks by worker Returns a list of uuid task tuples worker_event type fields Process worker event class celery events state Task fields Task State inf
327. f the default queue used by apply_async if the message has no route or no custom queue has been specified This queue must be listed in CELERY_QUEUES If CELERY_QUEUES is not specified then it is automatically created containing one queue entry where this name is used as the name of that queue 2 4 Configuration and defaults 135 Celery Documeniation Release 3 0 25 The default is celery See also Changing the name of the default queue CELERY_DEFAULT_EXCHANGE Name of the default exchange to use when no custom exchange is specified for a key in the CELERY_QUEUES setting The default is celery CELERY_DEFAULT_EXCHANGE_TYPE Default exchange type used when no custom exchange type is specified for a key in the CELERY_QUEUES setting The default is direct CELERY_DEFAULT_ROUTING_KEY The default routing key used when no custom routing key is specified for a key in the CELERY_QUEUES setting The default is celery CELERY_DEFAULT_DELIVERY_MODE Can be transient or persistent The default is to send persistent messages Broker Seitings CELERY_ACCEPT_CONTENT A whitelist of content types serializers to allow If a message is received that is not in this list then the message will be discarded with an error By default any content type is enabled including pickle and yaml so make sure untrusted parties do not have access
328. ference now split into two sections API reference and internal module reference 0 8 4 release date 2010 02 05 01 52 P M CEST e Now emits a warning if the detach argument is used detach should not be used anymore as it has several not easily fixed bugs related to it Instead use something like start stop daemon Supervisord or launchd os x e Make sure logger class is process aware even if running Python gt 2 6 e Error emails are not sent anymore when the task is retried 0 8 3 release date 2009 12 22 09 43 A M CEST e Fixed a possible race condition that could happen when storing querying task results using the database backend 462 Chapter 2 Contents Celery Documeniation Release 3 0 25 e Now has console script entry points in the setup py file so tools like Buildout will correctly install the programs celeryd and celeryinit 0 8 2 release date 2009 11 20 03 40 P M CEST e QOS Prefetch count was not applied properly as it was set for every message received which apparently behaves like receive one more instead of only set when our wanted value changed 0 8 1 release date 2009 11 16 05 21 P M CEST Very important note This release with carrot 0 8 0 enables AMQP QoS quality of service which means the workers will only receive as many messages as it can handle at a time As with any release you should test this version upgrade on your development servers before rolling it out to product
329. ffice hours 8am 5pm Execute on the second day of every month Execute on every even numbered day Execute on the first and third weeks of the month Execute on 11th of May every year Execute on the first month of every quarter See celery schedules crontab for more documentation Starting the Scheduler To start the celery beat service S celery beat You can also start embed beat inside the worker by enabling workers B option this is convenient if you only intend to use one worker node celery worker B Beat needs to store the last run times of the tasks in a local database file named celerybeat schedule by default so it needs access to write in the current directory or alternatively you can specify a custom location for this file celery beat s home celery var run celerybeat schedule Note To daemonize beat see Running the worker as a daemon 94 Chapter 2 Contents Celery Documeniation Release 3 0 25 Using custom scheduler classes Custom scheduler classes can be specified on the command line the S argument The default scheduler is celery beat PersistentScheduler which is simply keeping track of the last run times in a local database file a shelve django celery also ships with a scheduler that stores the schedule in the Django database celery beat S djcelery schedulers DatabaseScheduler Using django celery s scheduler you can add modify and remove perio
330. file name depending on Python version Can also be set via the schedule argument to celerybeat CELERYBEAT_MAX_LOOP_INTERVAL The maximum number of seconds celerybeat can sleep between checking the schedule The default for this value is scheduler specific For the default celerybeat scheduler the value is 300 5 minutes but for e g the django celery database scheduler it is 5 seconds because the schedule may be changed externally and so it must take changes to the schedule into account Also when running celerybeat embedded B on Jython as a thread the max interval is overridden and set to 1 so that it s possible to shut down in a timely manner Monitor Server celerymon CELERYMON_LOG_FORMAT The format to use for log messages Default is asctime s levelname s processName s message s See the Python logging module for more information about log formats 2 5 Django Release 3 0 Date July 10 2014 2 5 Django 147 Celery Documeniation Release 3 0 25 2 5 1 First steps with Django Configuring your Django project to use Celery You need four simple steps to use celery with your Django project 1 Install the django celery library S pip install django celery 2 Add the following lines to sett ings py import djcelery djcelery setup_loader 3 Add djcelery to INSTALLED_APPS 4 Create the celery database tables If you are using south for schema migrations you ll want to S py
331. for everything else from kombu import Exchange Queue CELERY_QUEUES Queue default Exchange default routing_key default Queue videos Exchange media routing_key media video Queue images Exchange media routing_key media image ELERY_DEFAULT_QUEUE default ERY_DEFAULT_EXCHANGE_TYPE direct ELERY DEFAULT _ROUTING_KEY default ll OO Qo H Exchange types The exchange type defines how the messages are routed through the exchange The exchange types defined in the stan dard are direct topic fanout and headers Also non standard exchange types are available as plug ins to RabbitMQ like the last value cache plug in by Michael Bridgen Direct exchanges Direct exchanges match by exact routing keys so a queue bound by the routing key video only receives messages with that routing key Topic exchanges Topic exchanges matches routing keys using dot separated words and the wildcard characters matches a single word and matches zero or more words With routing keys like usa news usa weather norway news and norway weather bindings could be news all news usa all items in the USA or usa weather all USA weather items Related API commands exchange declare exchange_name type passive durable auto delete internal Declares an exchange by name
332. formed of your ideas and progress It many not be possible to get consensus from upstream or even from your colleagues about the correct implementation for an idea so don t feel obliged to have that agreement before you begin but at least keep the outside world informed of your work and publish your work in a way that allows outsiders to test discuss and contribute to your efforts When you disagree consult others Disagreements both political and technical happen all the time and the Celery community is no exception It is important that we resolve disagreements and differing views constructively and with the help of the community and community process If you really want to go a different way then we encourage you to make a derivative distribution or alternate set of packages that still build on the work we ve done to utilize as common of a core as possible When you are unsure ask for help Nobody knows everything and nobody is expected to be perfect Asking questions avoids many problems down the road and so questions are encouraged Those who are asked questions should be responsive and helpful However when asking a question care must be taken to do so in an appropriate forum 2 6 Contributing 153 Celery Documeniation Release 3 0 25 Step down considerately Developers on every project come and go and Celery is no different When you leave or disengage from the project in whole or in part we ask that you do so
333. g state in the database can be convenient for many especially for web applications with a database already in place but it also comes with limitations e Polling the database for new states is expensive and so you should increase the polling intervals of operations such as result get e Some databases use a default transaction isolation level that is not suitable for polling tables for changes In MySQL the default transaction isolation level is REPEATABLE READ which means the transaction will not see changes by other transactions until the transaction is committed It is recommended that you change to the READ COMMITTED isolation level Built in States PENDING Task is waiting for execution or unknown Any task id that is not known is implied to be in the pending state STARTED Task has been started Not reported by default to enable please see celery Task track_started metadata pid and hostname of the worker process executing the task SUCCESS Task has been successfully executed metadata result contains the return value of the task propagates Yes ready Yes FAILURE Task execution resulted in failure metadata result contains the exception occurred and traceback contains the backtrace of the stack at the point when the exception was raised propagates Yes RETRY Task is being retried metadata result contains the exception that caused the retry and traceback contains the backtrace of the stack at the point when the e
334. generic init d celeryd Documentation e Added User guide section Monitoring e Added user guide section Periodic Tasks Moved from getting started periodic tasks and updated e tutorials external moved to new section community e References has been added to all sections in the documentation This makes it easier to link between documents 2 15 History 433 Celery Documentation Release 3 0 25 2 15 6 Change history for Celery 2 0 2 0 3 Fixes Documentation e 2 0 2 2 0 1 e 2 0 0 Foreword Upgrading for Django users Upgrading for others x Database result backend x Cache result backend Backward incompatible changes News 2 0 3 release date 2010 08 27 12 00 P M CEST Fixes celeryd Properly handle connection errors happening while closing consumers No longer depends on the mailer package celeryd Events are now buffered if the connection is down then sent when the connection is re established This package had a name space collision with django mailer so its functionality was replaced default database is now 0 inspect registered_tasks was requesting an invalid command because of a typo See issue 170 Redis result backend Documentation typos Redis doesn t have database names but database numbers The e CELERY_ROUTES Values defined in the route should now have precedence over values defined in CELERY_QUEUES when mer
335. ger global Every Celery instance now has its own task registry You can make apps share registries by specifying it gt gt gt appl Celery gt gt gt app2 Celery tasks appl tasks Note that tasks are shared between registries by default so that tasks will be added to every subsequently created task registry As an alternative tasks can be private to specific task registries by setting the shared argument to the task decorator celery task shared False def add x y return x y 192 Chapter 2 Contents Celery Documeniation Release 3 0 25 Abstract tasks are now lazily bound The Task class is no longer bound to an app by default it will first be bound and configured when a concrete subclass is created This means that you can safely import and make task base classes without also initializing the app environment from celery task import Task class DebugTask Task abstract True def _ call_ self xargs xxkwargs print CALLING Sr self return self run x args xxkwargs gt gt gt DebugTask lt unbound DebugTask gt gt gt gt celeryl task base DebugTask def add x y a8 return x y gt gt gt add __class__ lt class add of lt Celery default 0x101510d10 gt gt Lazy task decorators The task decorator is now lazy when used with custom apps That is if accept_magic_kwargs is enabled herby called compat mode the task decorator executes inline like
336. get Calculate the reference key for this reference Currently this is a two tuple of the id s of the target object and the target function respectively class celery utils dispatch saferef BoundNonDescriptorMethodWeakref target on_delete None A specialized BoundMethodWeakref for platforms where instance methods are not descriptors It assumes that the function name and the target attribute name are the same instead of assuming that the function is a descriptor This approach is equally fast but not 100 reliable because functions can be stored on an attribute named differenty than the function s name such as in gt gt gt class A object pass gt gt gt def foo self ae return foo gt gt gt A bar foo But this shouldn t be a common use case So on platforms where methods aren t descriptors such as Jython this implementation has the advantage of working in the most cases celery utils dispatch saferef get_bound_method_weakref target on_delete Instantiates the appropiate BoundMet hodWeakRef depending on the details of the underlying class method implementation celery utils dispatch saferef safe_ref target on_delete None Return a safe weak reference to a callable target Parameters e target the object to be weakly referenced if it s a bound method reference will create a BoundMet hodWeakref otherwise creates a simple weakref ref e on_delete if provided will have a hard reference sto
337. ging the two With the follow settings CELERY_QUEUES cpubound exchange cpubound routing_key cpubound CELERY_ROUTES tasks add queue cpubound routing_key tasks add serializer json The final routing options for tasks add will become exchange cpubound UeOulumncgmrcey Measksmadall serializer json 434 Celery Documeniation Release 3 0 25 This was not the case before the values in CELERY_QUEUES would take precedence Worker crashed if the value of CELERY_TASK_ERROR_WHITELIST was not an iterable apply Make sure kwargs task_id is always set AsyncResult traceback Now returns None instead of raising KeyError if traceback is missing inspect Replies did not work correctly if no destination was specified Can now store result metadata for custom states celeryd A warning is now emitted if the sending of task error emails fails celeryev Curses monitor no longer crashes if the terminal window is resized See issue 160 celeryd On OS X it is not possible to run os exec in a process that is threaded This breaks the SIGHUP restart handler and is now disabled on OS X emitting a warning instead See issue 152 celery execute trace Properly handle raise str which is still allowed in Python 2 4 See issue 175 Using urllib2 in a periodic task on OS X crashed becaus
338. go model objects They shouldn t be passed on as arguments to tasks It s almost always better to re fetch the object from the database when the task is running instead as using old data may lead to race conditions Imagine the following scenario where you have an article and a task that automatically expands some abbreviations in it class Article models Model title models CharField body models TextField celery task def expand abbreviations article article body replace MyCorp My Corporation article save First an author creates an article and saves it then the author clicks on a button that initiates the abbreviation task gt gt gt article Article objects get id 102 gt gt gt expand_abbreviations delay model_object Now the queue is very busy so the task won t be run for another 2 minutes In the meantime another author makes changes to the article so when the task is finally run the body of the article is reverted to the old version because the task had the old body in its argument Fixing the race condition is easy just use the article id instead and re fetch the article in the task body celery task def expand_abbreviations article_id article Article objects get id article_id article body replace MyCorp My Corporation article save gt gt gt expand_abbreviations article_id There might even be performance benefits to this approach as sen
339. gs e celery worker state j 334 Chapter 2 Contents Celery Documeniation Release 3 0 25 celery worker state Internal worker state global This includes the currently active and reserved tasks statistics and revoked tasks class celery worker state Persistent filename This is the persistent data stored by the worker when st at edb is enabled ce ce ce ce ce ce ce ce ce ce It currently only stores revoked task id s close db merge d open protocol 2 save storage lt module shelve from usr lib python2 7 shelve pyc gt sync d lery worker sta te REVOKES MAX 10000 maximum number of revokes to keep in memory lery worker sta how many seconds lery worker sta te REVOKE_EXPIRES 3600 a revoke will be active before being expired when the max limit has been exceeded te SOFTWARE_INFO sw_sys Linux sw_ident py celery sw_ver 3 0 25 Worker software platform information lery worker sta te active_requests set set of currently active Request s lery worker sta te reserved_requests set set of all reserved Request s lery worker sta the list of currently lery worker sta te revoked LimitedSet revoked tasks Persistent if statedb set te task_accepted request Updates global state when a task has been accepted lery worker sta t
340. gs This is equivalent to calling write for each string lery utils log ensure_process_aware_logger Make sure process name is recorded when loggers are used lery utils log get_logger name lery utils log get_multiprocessing_logger lery utils log get_task_logger name lery utils log mlevel level lery utils log reset_multiprocessing_logger lery utils log set_in_sighandler value celery utils text e celery utils text j celery utils text Text formatting utilities celery utils text abbr S max ellipsis 388 Chapter 2 Contents Celery Documeniation Release 3 0 25 celery utils text abbrtask S max celery utils text dedent s n 4 sep n celery utils text dedent_initial s n 4 celery utils text ensure_2lines s sep n celery utils text ill_paragraphs s width sep n celery utils text indent t indent 0 sep n Indent text celery utils text Join l sep n celery utils text pluralize n text suffix s celery utils text pretty value width 80 nl_width 80 sep n kw celery utils text truncate text maxlen 128 suffix Truncates text to a maximum number of characters celery utils dispatch celery utils dispatch signal Signal class class celery utils dispatch signal Signal providing_args None Base class for all signals receivers Internal attribute holds a dictionary of receriv
341. gs None task_id None producer None connec tion None router None link None link_error None publisher None add_to_parent True options Apply tasks asynchronously by sending a message Parameters e args The positional arguments to pass on to the task a List or tuple e kwargs The keyword arguments to pass on to the task a dict e countdown Number of seconds into the future that the task should execute De faults to immediate execution do not confuse with the immediate flag as they are unrelated e eta A datetime object describing the absolute time and date of when the task should be executed May not be specified if countdown is also supplied Do not confuse this with the immediate flag as they are unrelated e expires Either a int describing the number of seconds or a datetime object that describes the absolute time and date of when the task should expire The task will not be executed after the expiration time e connection Re use existing broker connection instead of establishing a new one e retry If enabled sending of the task message will be retried in the event of connec tion loss or failure Default is taken from the CELERY_TASK_ PUBLISH RETRY setting Note you need to handle the producer connection manually for this to work e retry_policy Override the retry policy used See the CELERY_TASK_PUBLISH_RETRY setting e routing_key Custom routing
342. guments 2 2 and sets the countdown execution option to 10 or you can create one using the task s subt ask method gt gt gt add subtask 2 2 countdown 10 add 2 2 There is also a shortcut using star arguments gt gt gt add s 2 2 tasks add 2 2 Keyword arguments are also supported gt gt gt add s 2 2 debug True tasks add 2 2 debug True la From any subtask instance you can inspect the different fields gt gt gt s add subtask 2 2 debug True countdown 10 gt gt gt s args 2 2 gt gt gt s kwargs debug True gt gt gt s options countdown 10 It supports the Calling API which means it takes the same arguments as the apply _async method 2 3 User Guide 67 Celery Documentation Release 3 0 25 gt gt gt add apply_async args kwargs xoptions gt gt gt add subtask args kwargs options apply_async gt gt gt add apply_async 2 2 countdown 1 gt gt gt add subtask 2 2 countdown 1 apply_async e You can t define options with s but a chaining set call takes care of that gt gt gt add s 2 2 set countdown 1 proj te add 2 2 Partials A subtask can be applied too gt gt gt add s 2 2 delay gt gt gt add s 2 2 apply_async countdown 1 Specifying additional args kwargs or options to apply_async delay creates partials e Any arguments adde
343. gured to expire if left unused it was not possible to enable this by default because this was only available in recent RabbitMQ versions 2 1 1 With this change enabling a result backend will be a conscious choice which will hopefully lead the user to read the documentation and be aware of any common pitfalls with the particular backend The default backend is now a dummy backend celery backends base DisabledBackend Saving state is simply an noop operation and AsyncResult wait result state etc will raise a Not ImplementedError telling the user to configure the result backend For help choosing a backend please see Result Backends If you depend on the previous default which was the AMQP backend then you have to set this explicitly before upgrading CELERY_RESULT_BACKEND amqp Note For django celery users the default backend is still dat abase and results are not disabled by default e The Debian init scripts have been deprecated in favor of the generic init d init scripts In addition generic init scripts for celerybeat and celeryev has been added News e Automatic connection pool support The pool is used by everything that requires a broker connection For example calling tasks sending broadcast commands retrieving results with the AMQP result backend and so on The pool is disabled by default but you can enable it by configuring the BROKER_POOL_LIMIT setting BROKER_PO
344. h was first added in Python 2 6 Posix behavior will be disabled if running under Windows celery platforms strargv argv celery _ state e celery _state j celery _state This is an internal module containing thread state like the current_app and current_task This module shouldn t be used directly celery _state current_app lt Celery _main__ 0x7fb76929 c510 gt Proxy to current app celery _state current_task None Proxy to current task celery _state default_app lt Celery default 0x7fb766b79910 gt Global default app used when no current app celery _state get_current_app 2 14 Internals 395 Celery Documentation Release 3 0 25 celery _state get_current_task Currently executing task celery _state get_current_worker_task Currently executing task that was applied by the worker This is used to differentiate between the actual task executed by the worker and any task that was called within a task using task __call___ or task apply celery _state set_default_app app 2 15 History This section contains historical change histories for the latest version please visit Change history Release 3 0 Date July 10 2014 2 15 1 Change history for Celery 2 5 e NNN nin in wn N News Fixes e 2 5 1 Fixes e 2 5 0 2 5 5 release date 2012 06 06 16 00 PM BST by Ask Solem This is a dummy release performed for the following goals e Protect
345. handle_error exc_info hedule info hedule on_error None hedule queue Snapshot of underlying datastructure hedule schedule hedule stop class celery utils timer2 Timer schedule None on_error None on_tick None max_interval None kwargs class Entry fun args None kwargs None args cancel cancelled fun kwargs tref class Timer Schedule max_interval None on_error None kwargs ETA scheduler class Entry fun args None kwargs None args cancel cancelled fun kwargs 2 14 Internals 385 Celery Documentation Release 3 0 25 Timer Timer Timer Timer Timer Timer Timer Timer Timer Timer Timer Timer Timer Timer Timer Schedul tref Timer Schedul imer Schedul imer Schedul imer Schedul imer Schedul imer Schedul imer Schedul e apply_ after msecs fun args kwargs priority 0 e apply_ at eta fun args kwargs priority 0 e apply entry entry e apply interval msecs fun args kwargs priority 0 e cancel tref e clear le empty Is the schedule empty le enter entry eta None priority 0 Enter function into the scheduler Parameters imer Schedul imer Schedul imer Schedul imer Schedul imer Schedul Snapshot of Timer Schedul imer Schedul apply _at a cancel tref clear empty next queue run e entry Item to enter e
346. hange monitor based on BSD kernel event notifications add_events poller 336 Chapter 2 Contents Celery Documeniation Release 3 0 25 close poller handle event events on_poll_close hub on_poll_init hub start stop celery worker autoreload Monitor alias of StatMonitor class celery worker autoreload StatMonitor files on_change None shutdown_event None interval 0 5 File change monitor based on the stat system call start class celery worker autoreload WorkerComponent w autoreload None kwargs ce ce create w create_ev w create_threaded w name autoreloader namespace worker requires pool lery worker autoreload default_implementation lery worker autoreload f ile_hash filename algorithm md5 celery worker autoscale e celery worker autoscale j celery worker autoscale This module implements the internal thread responsible for growing and shrinking the pool according to the current autoscale settings The autoscale thread is only enabled if autoscale has been enabled on the command line class celery worker autoscale Autoscaler pool max_concurrency min_concurrency 0 keepalive 30 mutex None body force_scale_down n force_scale_up n info 2 14 Internals 337 Celery Documentation Release 3 0 25 maybe_scale processes qty scale_down n scale_up n update max None min None
347. hanged using the environment variable envvar CELERY_RDB_PORT By default the debugger will only be available from the local host to enable access from the outside you have to set th nvironment variable envvar CELERY_RDB_HOST When celeryd encounters your breakpoint it will log the following information INFO MainProcess Got task from broker tasks add d7261c71 4962 47e5 b342 2448bedd20e8 WARNING PoolWorker 1 Remote Debugger 6900 Please telnet 127 0 0 1 6900 Type exit in session to continue 418 Chapter 2 Contents Celery Documeniation Release 3 0 25 2011 01 18 14 25 44 119 WARNING PoolWorker 1 Remote Debugger 6900 Waiting for client If you telnet the port specified you will be presented with a pdb shell code block bash telnet localhost 6900 Connected to localhost Escape character is gt opt devel demoapp tasks py 128 add gt return result Pdb Enter help to get a list of available commands It may be a good idea to read the Python Debugger Manual _ if you have never used pdb before e Events are now transient and is using a topic exchange instead of direct The CELERYD_EVENT_EXCHANGE CELERYD_EVENT_ROUTING_KEY CEL ERYD_EVENT_EXCHANGE_TYPE settings are no longer in use This means events will not be stored until there is a consumer and the events will be gone as soon as t
348. he __ init __ constructor will only be called once per process and that the task class is semantically closer to an Actor If you have a task from celery import Task class NaiveAuthenticateServer Task def init self self users george password def run self username password try return self users username password except KeyError return False And you route every request to the same process then it will keep state between requests This can also be useful to cache resources e g a base Task class that caches a database connection from celery import Task class DatabaseTask Task abstract True 52 Chapter 2 Contents Celery Documeniation Release 3 0 25 _db None property def db self if self _db is None self _db Database connect return self _db that can be added to tasks like this celery task base DatabaseTask def process_rows for row in process_rows db table all The db attribute of the process_rows task will then always stay the same in each process Abstract classes Abstract classes are not registered but are used as the base class for new task types from celery import Task class DebugTask Task abstract True def after_return self xargs xkwargs o print Task returned tr self request celery task base DebugTask def add x y return x y Handlers after_return self status retval
349. he __main__ module Required for standalone scripts If set this will be used instead of __main__ when automatically generating task names conf Current configuration current_task The instance of the task that is being executed or None amqp AMQP related functionality amqp backend Current backend instance loader Current loader instance control Remote control control events Consuming and sending events events log Logging Log 228 Chapter 2 Contents Celery Documeniation Release 3 0 25 tasks Task registry Accessing this attribute will also finalize the app pool Broker connection pool pool This attribute is not related to the workers concurrency pool Task Base task class for this app close Cleans up after application like closing any pool connections Only necessary for dynamically created apps for which you can use the with statement with Celery set_as_current False as app with app connection as conn pass bugreport Returns a string with information useful for the Celery core developers when reporting a bug config_from_object obj silent False Reads configuration from object where object is either an object or the name of a module to import Parameters silent If true then import errors will be ignored gt gt gt celery config_from_object myapp celeryconfig gt gt gt from myapp import celeryconfig gt gt gt celery config_from_object cele
350. he bug By default GitHub will email you to let you know when new comments have been made on your bug In the event you ve turned this feature off you should check back on occasion to ensure you don t miss any questions a developer trying to fix the bug might ask Issue Trackers Bugs for a package in the Celery ecosystem should be reported to the relevant issue tracker e Celery http github com celery celery issues e Django Celery http github com celery django celery issues e Celery Pylons http bitbucket org ianschenck celery pylons issues e Kombu http github com celery kombu issues If you are unsure of the origin of the bug you can ask the Mailing list or just use the Celery issue tracker 2 6 3 Contributors guide to the codebase There s a seperate section for internal details including details about the codebase and a style guide Read Contributors Guide to the Code for more 154 Chapter 2 Contents Celery Documeniation Release 3 0 25 2 6 4 Versions Version numbers consists of a major version minor version and a release number Since version 2 1 0 we use the versioning semantics described by semver http semver org Stable releases are published at PyPI while development releases are only available in the GitHub git repository as tags All version tags starts with v so version 0 8 0 is the tag v0 8 0 2 6 5 Branches Current active version branches e master http github com celery celery
351. he cancel_consumer control command To force all workers in the cluster to cancel consuming from a queue you can use the celery control program S celery control cancel_consumer foo The dest ination argument can be used to specify a worker or a list of workers to act on the command 86 Chapter 2 Contents Celery Documeniation Release 3 0 25 celery control cancel_consumer foo d workerl local You can also cancel consumers programmatically using the celery control cancel_consumer method gt gt gt myapp control cancel_consumer foo reply True u workerl local u ok u no longer consuming from u foo Queues List of active queues You can get a list of queues that a worker consumes from by using the act ive_queues control command S celery inspect active_queues esa Like all other remote control commands this also supports the dest ination argument used to specify which workers should reply to the request celery inspect active_queues d workerl local Lanes This can also be done programmatically by using the celery control inspect active_queues method gt gt gt myapp inspect active_queues PESA gt gt gt myapp inspect workerl local active_queues PETN Autoreloading New in version 2 5 pool support processes eventlet gevent threads solo Starting celery worker with the autoreload option will enable the worker to watch for
352. he comment model looks like this from django db import models from django utils translation import ugettext_lazy as _ class Comment models Model name models CharField _ name max_length 64 email_address models EmailField _ email address homepage models URLField _ home page blank True verify_exists False comment models TextField _ comment pub_date models DateTimeField _ Published date editable False auto_add_now True is_spam models BooleanField _ spam default False ditable False class Meta verbose_name _ comment verbose_name_plural _ comments 58 Chapter 2 Contents Celery Documeniation Release 3 0 25 In the view where the comment is posted I first write the comment to the database then I launch the spam filter task in the background blog views py from django import forms from django http import HttpResponseRedirect from django template context import RequestContext from django shortcuts import get_object_or_404 render_to_respons from blog import tasks from blog models import Comment class CommentForm forms ModelForm class Meta model Comment def add_comment request slug template_name comments create html post get_object_or_404 Entry slug slug remote_addr request META get REMOTE_ADDR if request method post form CommentFo
353. he consumer stops Also it means there can be multiple monitors running at the same time The routing key of an event is the type of event e g worker started worker heartbeat task succeeded etc This means a consumer can filter on specific types to only be alerted of the events it cares about Each consumer will create a unique queue meaning it is in effect a broadcast exchange This opens up a lot of possibilities for example the workers could listen for worker events to know what workers are in the neighborhood and even restart workers when they go down or use this information to optimize tasks autoscaling Note The event exchange has been renamed from celeryevent to celeryev so it does not collide with older versions If you would like to remove the old exchange you can do so by executing the following command camgqadm exchange delete celeryevent e celeryd now starts without configuration and configuration can be specified directly on the command line Configuration options must appear after the last argument separated by two dashes celeryd l info I tasks broker host localhost broker vhost app e Configuration is now an alias to the original configuration so changes to the original will reflect Celery at runtime e celery conf has been deprecated and modifying celery conf ALWAYS_EAGER will no longer have any effect The default configuration is now available in the celery app defaults
354. he hard time limit comes New command line arguments to celeryd added time limit and soft time limit What s left This won t work on platforms not supporting signals and specifically the SIGUSR1 signal yet So an alternative the ability to disable the feature all together on nonconforming platforms must be implemented Also when the hard time limit is exceeded the task result should be a TimeLimitExceeded exception e Test suite is now passing without a running broker using the carrot in memory backend e Log output is now available in colors Log level Color DEBUG Blue WARNING Yellow CRITICAL Magenta ERROR Red This is only enabled when the log output is a tty You can explicitly enable disable this feature using the CELERYD_LOG_COLOR setting e Added support for task router classes like the django multi db routers New setting CELERY_ROUTES This is a single or a list of routers to traverse when sending tasks Dictionaries in this list converts toa celery routes MapRoute instance Examples 2 15 History 445 Celery Documentation Release 3 0 25 gt gt gt CELERY_ROUTES cele default myta cpu bound n d media routing_key media video encode gt gt gt CEI ERY_ROUTES myapp tasks Router celery ping d Where myapp tasks Router could be class Router object
355. he worker should terminate exception celery exceptions TaskRevokedError The task has been revoked so no result available exception celery exceptions TimeoutError The operation timed out 2 13 21 celery loaders e celery loaders j celery loaders Loaders define how configuration is read what happens when workers start when tasks are executed and so on celery loaders current_loader args kwargs celery loaders get_loader_cls loader Get loader class by name alias celery loaders load_settings args kwargs 266 Chapter 2 Contents Celery Documeniation Release 3 0 25 2 13 22 celery loaders app e celery loaders app j celery loaders app The default loader used with custom app instances class celery loaders app AppLoader app None kwargs 2 13 23 celery loaders default e celery loaders default l celery loaders default The default loader used when no custom app has been initialized celery loaders default C_WNOCONF False Warns if configuration file is missing if C_WNOCONF is set class celery loaders default Loader app None kwargs The loader used by the default app read_configuration Read configuration from celeryconfig py and configure celery and Django so it can be used by regular Python setup_settings settingsdict 2 13 24 celery loaders base e celery loaders base j celery loaders base Loader base class c
356. his change was necessary as the multiprocessing event that the restart command depends on is responsible for creating many semaphores file descriptors resulting in problems in some environ ments e chain apply now passes args to the first task Issue 889 2 12 Change history 223 Celery Documentation Release 3 0 25 e Documented previously secret options to the Django Celery monitor in the monitoring userguide Issue 396 e Old changelog are now organized in separate documents for each series see History 2 12 22 3 0 4 release date 2012 07 26 07 00 PM BST e Now depends on Kombu 2 3 e New experimental standalone Celery monitor Flower See Flower Real time Celery web monitor to read more about it Contributed by Mher Movsisyan e Now supports AMQP heartbeats if using the new pyamap transport The py amap transport requires the amap library to be installed pip install amqp Then you need to set the transport URL prefix to pyamgqp The default heartbeat value is 10 seconds but this can be changed using the BROKER_HEARTBEAT setting BROKER_HEARTBEAT 5 0 If the broker heartbeat is set to 10 seconds the heartbeats will be monitored every 5 seconds double the hertbeat rate See the Kombu 2 3 changelog for more information e Now supports RabbitMQ Consumer Cancel Notifications using the pyamqp transport This is essential when running RabbitMQ in a cluster
357. his is used by StartStopComponents to keep the original service object requires List of component names this component depends on Note that the dependencies must be in the same namespace class celery worker bootsteps ComponentType Metaclass for components class celery worker bootsteps Namespace name None app None A namespace containing components Every component must belong to a namespace When component classes are created they are added to the mapping of unclaimed components The components will be claimed when the namespace they belong to is created Parameters e name Set the name of this namespace e app Set the Celery app for this namespace apply parent kwargs Apply the components in this namespace to an object This will apply the __init__ and include methods of each components with the object as argument For StartStopComponents the services created will also be added the the objects components attribute bind_component name parent kwargs Bind component to parent object and this namespace import_module module load_modules Will load the component modules this namespace depends on modules Subclasses can override this to return a list of modules to import before components are claimed name None class celery worker bootsteps StartStopComponent parent kwargs include parent start stop terminable False terminate 2 14 Internals 339 Cel
358. hostname Hostname of the worker e timestamp Event timestamp e freq Heartbeat frequency in seconds float e sw_ident Name of worker software e g py celery e sw_ver Software version e g 2 2 0 e sw_sys Operating System e g Linux Windows Darwin worker heartbeat signature worker heartbeat hostname timestamp freq sw_ident sw_ver sw_sys active processed Sent every minute if the worker has not sent a heartbeat in 2 minutes it is considered to be offline hostname Hostname of the worker e timestamp Event timestamp 2 3 User Guide 115 Celery Documentation Release 3 0 25 e freq Heartbeat frequency in seconds float sw_ident Name of worker software e g py celery sw_ver Software version e g 2 2 0 sw_sys Operating System e g Linux Windows Darwin active Number of currently executing tasks e processed Total number of tasks processed by this worker worker offline signature worker offline hostname timestamp freq sw_ident sw_ver sw_sys The worker has disconnected from the broker 2 3 10 Security e Introduction e Areas of Concern Broker Client Worker e Serializers e Message Signing e Intrusion Detection Logs Tripwire Introduction While Celery is written with security in mind it should be treated as an unsafe component Depending on your Security Policy there are various steps you can take to make your Cel
359. hs to dot format gt gt gt with open graph dot w as fh res parent parent graph to_dot fh and create images dot Tpng graph dot o graph png 74 Chapter 2 Contents Celery Documeniation Release 3 0 25 8 72c3995 6fa0 46ca 98c2 5al9155afclO 285fa253 fcf8 42ef 8b95 0078897e8 3e6 463afec2 5ed4 4036 b22d ba067ec64f52 Groups New in version 3 0 A group can be used to execute several tasks in parallel The group function takes a list of subtasks gt gt gt from celery import group gt gt gt from proj tasks import add gt gt gt group add s 2 2 add s 4 4 proj tasks add 2 2 proj tasks add 4 4 If you call the group the tasks will be applied one after one in the current process and a TaskSetResult instance is returned which can be used to keep track of the results or tell how many tasks are ready and so on gt gt gt g group add s 2 2 add s 4 4 gt gt gt res g gt gt gt res get 4 8 However if you call apply_async on the group it will send a special grouping task so that the action of calling the tasks happens in a worker instead of the current process gt gt gt res g apply_async gt gt gt res get 4 8 Group also supports iterators gt gt gt group add s i i for i in xrange 100 A group is a subtask instance so it can be used in combination with other subtasks 2 3 User Guide 75 C
360. ializers Broadcast Commands CELERY_BROADCAST_QUEUE Name prefix for the queue used when listening for broadcast messages The workers host name will be appended to the prefix to create the final queue name Default is celeryctl CELERY_BROADCAST_EXCHANGE Name of the exchange used for broadcast messages Default is celeryctl CELERY_BROADCAST_EXCHANGE_TYPE Exchange type used for broadcast messages Default is fanout Logging CELERYD_HIJACK_ROOT_LOGGER New in version 2 2 By default any previously configured logging options will be reset because the Celery programs hijacks the root logger If you want to customize your own logging then you can disable this behavior Note Logging can also be customized by connecting to the celery signals setup_logging signal 144 Chapter 2 Contents Celery Documeniation Release 3 0 25 CELERYD_LOG_COLOR Enables disables colors in logging output by the Celery apps By default colors are enabled if 1 the app is logging to a real terminal and not a file 2 the app is not running on Windows CELERYD_LOG_FORMAT The format to use for log messages Default is asctime s levelname s processName s message s See the Python logging module for more information about log formats CELERYD_TASK_LOG_FORMAT The format to use for log messages logged in tasks Can be overridden using the loglevel option to celeryd Default is as
361. ib methods task_method task args kwargs 2 13 31 celery events e celery events j celery events Events is a stream of messages sent for certain actions occurring in the worker and clients if CELERY_SEND_TASK_SENT_EVENT is enabled used for monitoring purposes celery events Event type _fields None fields Create an event An event is a dictionary the only required field is type class celery events EventDispatcher connection None hostname None enabled True chan nel None buffer_while_offline True app None serial izer None Send events as messages Parameters e connection Connection to the broker 278 Chapter 2 Contents Celery Documeniation Release 3 0 25 e hostname Hostname to identify ourselves as by default uses the hostname returned by socket gethostname e enabled Set to False to not actually publish any events making send a noop operation e channel Can be used instead of connection to specify an exact channel to use when sending events e buffer_while_offline If enabled events will be buffered while the connection is down flush must be called as soon as the connection is re established You need to close this after use DISABLED_TRANSPORTS set sql app None close Close the event dispatcher copy_buffer other disable enable flush publish type fields producer retry False
362. ible since otherwise the thread which handles the result will get blocked BasePool close BasePool did_start_ok BasePool info BasePool init_callbacks kwargs BasePool is_green False set to true if pool uses greenlets BasePool maintain_pool args kwargs BasePool maybe_handle_result args BasePool num processes BasePool on_apply args kwargs BasePool on_close BasePool on_hard_timeout job BasePool on_soft_timeout job BasePool on_start BasePool on_stop BasePool on_terminate BasePool readers BasePool requires_mediator False set to true if pool requires the use of a mediator thread e g if applying new items can block the current thread BasePool restart BasePool rlimit_safe True set to true if pool supports rate limits this is here for gevent which currently does not implement the necessary timers BasePool signal_safe True set to true if the pool can be shutdown from within a signal handler BasePool start BasePool stop BasePool terminate BasePool terminate_job pid BasePool timers 348 Chapter 2 Contents Celery Documeniation Release 3 0 25 BasePool uses_semaphore False only used by multiprocessing pool BasePool writers celery concurrency base apply_ target target args kwargs callback None ac cept_callback None pid None _ celery concurrency threads minefield e celery concurrency threads j celery concurrenc
363. ibuted by Alexander A Sosnovskiy 2 12 15 3 0 11 release date 2012 09 26 04 00 P M UTC security low generic init d scripts changed permissions of var log amp var run In the daemonization tutorial the recommended directories were as follows CELERYD_LOG_FILE var log celery n log CELERYD_PID_FILE var run celery n pid But in the scripts themselves the default files were var log celery n log and var run celery n pid so if the user did not change the location by configuration the directories var log and var run would be created and worse have their permissions and owners changed This change means that Default pid file is var run celery n pid Default log file is var log celery n log The directories are only created and have their permissions changed if no custom locations are Set Users can force paths to be created by calling the create paths subcommand sudo etc init d celeryd create paths Upgrading Celery will not update init scripts To update the init scripts you have to re download the files from source control and update them manually You can find the init scripts for version 3 0 x at http github com celery celery tree 3 0 extra generic init d Now depends on billiard 2 7 3 17 Fixes request stack protection when app is initialized more than once Issue 1003 ETA tasks now properly works when system timezone is not the same as the configured timezone Issue 1004
364. igure the root logger instead of only configuring our custom logger In addition we don t hijack the multiprocessing logger anymore but instead use a custom logger name for different applications Application Logger Name celeryd celery celerybeat celery beat celeryev celery ev This means that the oglevel and logfile arguments will affect all registered loggers even those from 3rd party libraries Unless you configure the loggers manually as shown below that is Users can choose to configure logging by subscribing to the signal celery signals setup_logging signal from logging config import fileConfig from celery import signals signals setup_logging connect 2 15 History 429 Celery Documeniation Release 3 0 25 def setup_logging xkwargs fileConfig logging conf If there are no receivers for this signal the logging subsystem will be configured using the loglevel logfile argument this will be used for all defined loggers Remember that celeryd also redirects stdout and stderr to the celery logger if manually configure logging you also need to redirect the stdouts manually from logging config import fileConfig from celery import log def setup_logging kwargs import logging fileConfig logging conf stdouts logging getLogger mystdoutslogger log redirect_stdouts_to_logger stdouts loglevel logging WARNING celeryd Added command line o
365. ile systems and devices An exception to this rule is when using the multiprocessing based task pool which is currently the default In this case the task will have access to any memory copied as a result of the fork call does not apply under MS Windows and access to memory contents written by parent tasks in the same worker child process Limiting access to memory contents can be done by launching every task in a subprocess fork execve Limiting file system and device access can be accomplished by using chroot jail sandboxing virtual machines or other mechanisms as enabled by the platform or additional software Note also that any task executed in the worker will have the same network access as the machine on which it s running If the worker is located on an internal network it s recommended to add firewall rules for outbound traffic Serializers The default pickle serializer is convenient because it supports arbitrary Python objects whereas other serializers only work with a restricted set of types But for the same reasons the pickle serializer is inherently insecure and should be avoided whenever clients are untrusted or unauthenticated You can disable untrusted content by specifying a whitelist of accepted content types in the CELERY_ACCEPT_CONTENT setting New in version 3 0 18 Note This setting was first supported in version 3 0 18 If you re running an earlier version it will
366. ill be moved to the default exchange routing_key celery contrib migrate move_by_ idmap map kwargs Moves tasks by matching fromatask_id queue mapping where queue is a queue to move the task to Example gt gt gt reroute_idmap 5bee6e82 f4ac 468e bd3d 13e8600250bc Queue ada8652d aef3 466b abd2 becdaflb82b3 Queue 3a2b140d 7db1 41lba ac90 c36a0ef4ablf Queue queues hipri es 2 13 API Reference 275 Celery Documeniation Release 3 0 25 celery contrib migrate move_by taskmap map kwargs Moves tasks by matching from atask_name queue mapping where queue is the queue to move the task to Example gt gt gt reroute_idmap tasks add Queue tasks mul Queue celery contrib migrate move_task_by_id fask_id dest kwargs Find a task by id and move it to another queue ce ce ce ce ce Parameters task_id Id of task to move dest Destination queue Also supports the same keyword arguments as move lery lery lery lery lery contrib contrib contrib contrib contrib migrate prepare_queues queues migrate republish producer message exchange None routing_key None re move_props application_headers content_type con tent_encoding headers migrate start_filter app conn filter limit None timeout 1 0 ack_mess
367. ilt in aliases processes eventlet gevent Default is processes CELERYD_POOL_RESTARTS If enabled the worker pool can be restarted using the pool_restart remote control command Disabled by default CELERYD_AUTOSCALER New in version 2 2 Name of the autoscaler class to use Default is celery worker autoscale Autoscaler CELERYD_AUTORELOADER Name of the autoreloader class used by the worker to reload Python modules and files that have changed Default is Ccelery worker autoreload Autoreloader CELERYD_CONSUMER Name of the consumer class used by the worker Default is celery worker consumer Consumer CELERYD_MEDIATOR Name of the mediator class used by the worker Default is celery worker controllers Mediator 146 Chapter 2 Contents Celery Documeniation Release 3 0 25 CELERYD_TIMER Name of the ETA scheduler class used by the worker Default is celery utils timer2 Timer or one over rided by the pool implementation Periodic Task Server celerybeat CELERYBEAT_SCHEDULE The periodic task schedule used by celerybeat See Entries CELERYBEAT_SCHEDULER The default scheduler class Default is celery beat PersistentScheduler Can also be set via the S argument to celerybeat CELERYBEAT_SCHEDULE_FILENAME Name of the file used by PersistentScheduler to store the last run times of periodic tasks Can be a relative or absolute path but be aware that the suffix db may be appended to the
368. in a way that minimizes disruption to the project This means you should tell people you are leaving and take the proper steps to ensure that others can pick up where you leave off 2 6 2 Reporting a Bug Bugs can always be described to the Mailing list but the best way to report an issue and to ensure a timely response is to use the issue tracker 1 Create a GitHub account You need to create a GitHub account to be able to create new issues and participate in the discussion 2 Determine if your bug is really a bug You should not file a bug if you are requesting support For that you can use the Mailing list or IRC 3 Make sure your bug hasn t already been reported Search through the appropriate Issue tracker If a bug like yours was found check if you have new information that could be reported to help the developers fix the bug 4 Collect information about the bug To have the best chance of having a bug fixed we need to be able to easily reproduce the conditions that caused it Most of the time this information will be from a Python traceback message though some bugs might be in design spelling or other errors on the website docs code If the error is from a Python traceback include it in the bug report We also need to know what platform you re running Windows OSX Linux etc the version of your Python inter preter and the version of Celery and related packages that you were running when the bug occurred 5 Submit t
369. in base daemon_options default_pidfile None default_logfile None 2 13 36 celery bin celeryd The celery worker command previously known as celeryd See also See Preload Options lt c P concurrency Number of child processes processing the queue The default is the number of CPUs available on your system pool Pool implementation processes default eventlet gevent solo or threads f logfile Path to log file If no logfile is specified stderr is used 1 loglevel Logging level choose between DEBUG INFO WARNING ERROR CRITICAL or FATAL n hostname Set custom hostname e g foo example com B beat Also run the celerybeat periodic task scheduler Please note that there must only be one instance of this service Q queues List of queues to enable for this worker separated by comma By default all configured queues are enabled Example Q video image I include Comma separated list of additional modules to import Example I foo tasks bar tasks 288 Chapter 2 Contents Celery Documeniation Release 3 0 25 s schedule Path to the schedule database if running with the B option Defaults to celerybeat schedule The extension db may be appended to the filename scheduler Scheduler class to use Default is celery beat PersistentScheduler S statedb Path to the state database The extension db may be appended to the filename Default defaul
370. including RabbitMQ You can enable this using the BROKER_USE_SSL setting It is also possible to add additional encryption and security to messages if you have a need for this then you should contact the Mailing list Is it safe to run celeryd as root Answer No We re not currently aware of any security issues but it would be incredibly naive to assume that they don t exist so running the Celery services celeryd celerybeat celeryev etc as an unprivileged user is recommended 2 9 6 Brokers Why is RabbitMQ crashing Answer RabbitMQ will crash if it runs out of memory This will be fixed in a future release of RabbitMQ please refer to the RabbitMQ FAQ http www rabbitmq com faq html node runs out of memory Note This is no longer the case RabbitMQ versions 2 0 and above includes a new persister that is tolerant to out of memory errors RabbitMQ 2 1 or higher is recommended for Celery If you re still running an older version of RabbitMQ and experience crashes then please upgrade Misconfiguration of Celery can eventually lead to a crash on older version of RabbitMQ Even if it doesn t crash this can still consume a lot of resources so it is very important that you are aware of the common pitfalls e Events 2 9 Frequently Asked Questions 179 Celery Documentation Release 3 0 25 Running celeryd with the E event s option will send messages for events happening inside of the work
371. ing Inherits the umask of the parent process by default workdir Optional directory to change to after detaching class celery bin base Command app None get_app None Base class for command line applications Parameters e app The current app e get_app Callable returning the current app if no app provided Parser alias of O ptionParser args Arg list used in help check_args args create_parser prog_name command None description Text to print in help before option list die msg status 1 286 Chapter 2 Contents Celery Documeniation Release 3 0 25 doc None early version argv enable_config_from_cmdline False Enable if the application should support config from the cmdline epilog None Text to print at end of help execute_from_commandline argv None Execute application from command line Parameters argv The list of command line arguments Defaults to sys argv expanduser value find_app app get_cls_by_ name name get_options Get supported command line options handle_argv prog_name argv Parses command line arguments from argv and dispatches to run Parameters e prog_name The program name argv 0 e argv Command arguments Exits with an error message if supports_args is disabled and argv contains positional arguments leaf True Set to true if this command doesn t have subcommands maybe_patch_concurrency argv None
372. ing error log message now includes traceback information Worker The startup banner now includes system platform celery inspect status control now gives an error if used with an SQL based broker transport 2 12 9 3 0 17 release date 2013 03 22 04 00 00 P M UTC Now depends on kombu 2 5 8 Now depends on billiard 2 7 3 23 RabbitMQ Redis thread less and lock free rate limit implementation This means that rate limits pose minimal overhead when used with RabbitMQ Redis or future trans ports using the eventloop and that the rate limit implementation is now thread less and lock free The thread based transports will still use the old implementation for now but the plan is to use the timer also for other broker transports in Celery 3 1 Rate limits now works with eventlet gevent if using RabbitMQ Redis as the broker A regression caused task ret ry to ignore additional keyword arguments Extra keyword arguments are now used as execution options again Fix contributed by Simon Engledew 2 12 Change history 211 Celery Documeniation Release 3 0 25 Windows Fixed problem with the worker trying to pickle the Django settings module at worker startup generic init d No longer double quotes SCELERYD_CHDIR Issue 1235 generic init d Removes bash specific syntax Fix contributed by Par Wieslander Cassandra Result Backend Now handles the AllServersUnavailable error Issue 1010 Fix contributed by Jared Bie
373. ing the destination argument S celery inspect d wl w2 reserved Flower Real time Celery web monitor Flower is a real time web based monitor and administration tool for Celery It is under active development but is already an essential tool Being the recommended monitor for Celery it obsoletes the Django Admin monitor celerymon and the ncurses based monitor Flower is pronounced like flow but you can also use the botanical version if you prefer Features e Real time monitoring using Celery Events Task progress and history Ability to show task details arguments start time runtime and more Graphs and statistics e Remote Control View worker status and statistics Shutdown and restart worker instances Control worker pool size and autoscale settings View and modify the queues a worker instance consumes from View currently running tasks View scheduled tasks ETA countdown View reserved and revoked tasks Apply time and rate limits Configuration viewer Revoke or terminate tasks 2 3 User Guide 107 Celery Documentation Release 3 0 25 e HTTP API Screenshots Celery Flower amp CE localhost 5555 workers xa Celery Flower Workers Tasks Monitor Docs About Workers a Shut Down Name Status Concurrency Completed Tasks Running Tasks Queues O celery1 pi local Crs 4 13902 0 images data video O celery2 pi local Online 4 13900 0 images
374. init on_close None List of callbacks to be called when the loop is exiting applied with the hub instance as sole argument on_init None List of callbacks to be called when the loop is initialized applied with the hub instance as sole argument on_task None List of callbacks to be called when a task is received Takes no arguments remove fd scheduler start Called by StartStopComponent at worker startup stop Called by StartStopComponent at worker shutdown update_readers readers update_writers writers celery worker control e celery worker control j celery worker control Remote control commands class celery worker control Panel dict None kwargs data time_limit lt function time_limit at 0x7fb764db6848 gt revoke lt function revoke at 0x7fb7650ba488 gt dump_ classmethod register method name None Internals 333 Celery Documentation Release 3 0 25 ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce lery wor lery wor lery wor lery wor lery worker lery worker lery worker lery worker Ker lery worker lery worker lery worker lery worker lery worker lery worker lery worker Ker Ker Ker lery worker control Returns the queues lery worker control control control GOGNCEOL control control contr
375. install Homebrew into 101 but you can choose whichever destination even in your home directory if you want as one of the strengths of Homebrew is that it s relocatable Homebrew is actually a git repository so to install Homebrew you first need to install git Download and install from the disk image at http code google com p git osx installer downloads list can 3 When git is installed you can finally clone the repository storing it at the 101 location git clone git github com mxcl homebrew lol 2 2 Getting Started 11 Celery Documentation Release 3 0 25 Brew comes with a simple utility called brew used to install remove and query packages To use it you first have to add it to PATH by adding the following line to the end of your profile export PATH lol bin lol sbin SPATH Save your profile and reload it source profile Finally we can install rabbitmq using brew S brew install rabbitmq Configuring the system host name If you re using a DHCP server that is giving you a random host name you need to permanently configure the host name This is because RabbitMQ uses the host name to communicate with nodes Use the scutil command to permanently set your host name S sudo scutil set HostName myhost local Then add that host name to etc hosts so it s possible to resolve it back into an IP address T2 a0 Ore L localhost myhost myhost local If you start the rabbitmg server your
376. ion Important changes e If you re using Python lt 2 6 and you use the multiprocessing backport then multiprocessing version 2 6 2 1 is required All AMQP _ settings has been renamed to BROKER_ and in addition AMQP_SERVER has been renamed to BROKER_HOST so before where you had AMQP_SERVER localhost AMQP_PORT 5678 AMOP_USER myuser AMOP_PASSWORD mypassword AMOP_VHOST celery You need to change that to BROKER_HOST localhost BROKER_PORT 5678 BROKER_USER myuser BROKER_PASSWORD mypassword BROKER_VHOST celery Custom carrot backends now need to include the backend class name so before where you had CARROT_BACKEND mycustom backend module you need to change it to CARROT_BACKEND mycustom backend module Backend where Backend is the class name This is probably Backend as that was the previously implied name 2 15 History 463 Celery Documentation Release 3 0 25 e New version requirement for carrot 0 8 0 Changes Incorporated the multiprocessing backport patch that fixes the processName error Ignore the result of PeriodicTask s by default Added a Redis result store backend Allow etc default celeryd to define additional options for the celeryd init script MongoDB periodic tasks issue when using different time than UTC fixed Windows specific Negate test for available os fork thanks miracle2k No
377. ion wl example com or using the celery control command S celery control d wl example com autoscale 10 5 pool_grow pool_shrink Tells workers to add or remove pool processes These commands are available programmatically as celery control pool_grow celery control pool_shrink gt gt gt celery control pool_grow 2 destination wl example com gt gt gt celery contorl pool_shrink 2 destination wl example com or using the celery control command celery control d wl example com pool_grow 2 celery control d wl example com pool_shrink 2 e celery control now supports rate_limit amp time_limit commands See celery control help for details Crontab now supports Day of Month and Month of Year arguments See the updated list of examples at Crontab schedules Immutable subtasks subtask s can now be immutable which means that the arguments will not be modified when calling callbacks gt gt gt chain add s 2 2 clear_static_electricity si means it will not receive the argument of the parent task and si is a shortcut to gt gt gt clear_static_electricity subtask immutable True 2 10 What s new in Celery 3 0 Chiastic Slide 191 Celery Documeniation Release 3 0 25 Logging Improvements Logging support now conforms better with best practices e Classes used by the worker no longer uses app get_default_logger but uses celery utils log g
378. ion is now available by turning on the DEBUG log level loglevel DEBUG e Functions methods with a timeout argument now works correctly 466 Chapter 2 Contents Celery Documeniation Release 3 0 25 0 4 1 0 4 0 New celery strategy even_time_distribution With an iterator yielding task args kwargs tuples evenly dis tribute the processing of its tasks throughout the time window available Log message Unknown task ignored now has log level ERROR Log message Got task from broker is now emitted for all tasks even if the task has an ETA estimated time of arrival Also the message now includes the ETA for the task if any Acknowledgement now happens in the pool callback Can t do ack in the job target as it s not pickleable can t share AMQP connection etc Added note about delay hanging in README Tests now passing in Django 1 1 Fixed discovery to make sure app is in INSTALLED_APPS Previously overridden pool behavior process reap wait until pool worker available etc is now handled by multiprocessing Pool itself Convert statistics data to Unicode for use as kwargs Thanks Lucy release date 2009 07 02 01 42 PM CET Fixed a bug with parsing the message options mandatory routing_key priority immediate release date 2009 07 01 07 29 P M CET Adds eager execution celery execute apply Task apply executes the function blocking until the task is done for API compatibility it retur
379. ion re raise task errors New signal celery signals worker_process_init Sent inside the pool worker process at init 446 Chapter 2 Contents Celery Documeniation Release 3 0 25 e celeryd Q option Ability to specify list of queues to use disabling other configured queues For example if CELERY_QUEUES defines four queues image video data and default the follow ing command would make celeryd only consume from the image and video queues S celeryd Q image video e celeryd New return value for the revoke control command Now returns Mokw Stasi sad trevoked instead of True e celeryd Can now enable disable events using remote control Example usage gt gt gt from celery task control import broadcast gt gt gt broadcast enable_events gt gt gt broadcast disable_events e Removed top level tests directory Test config now in celery tests config This means running the unit tests doesn t require any special setup celery tests __init__ now con figures the CELERY_CONFIG_MODULE and CELERY_LOADER environment variables so when nosetests imports that the unit test environment is all set up Before you run the tests you need to install the test requirements pip install r requirements test txt Running all tests nosetests Specifying the tests to run nosetests celery tests test_task Produci
380. ionalError Issue 634 e Tasks that called ret ry was not acknowledged if acks late was enabled Fix contributed by David Markey e The message priority argument was not properly propagated to Kombu Issue 708 Fix contributed by Eran Rundstein 2 11 What s new in Celery 2 5 Celery aims to be a flexible and reliable best of breed solution to process vast amounts of messages in a distributed fashion while providing operations with the tools to maintain such a system Celery has a large and diverse community of users and contributors you should come join us on IRC or our mailing list To read more about Celery you should visit our website While this version is backward compatible with previous versions it is important that you read the following section If you use Celery in combination with Django you must also read the django celery changelog lt djcelery version 2 5 0 gt and upgrade to django celery 2 5 This version is officially supported on CPython 2 5 2 6 2 7 3 2 and 3 3 as well as PyPy and Jython e Important Notes Broker connection pool now enabled by default Rabbit Result Backend Exchange is no longer auto delete Solution for hanging workers but must be manually enabled e Optimizations e Deprecations Removals Deprecations e News Timezone support New security serializer using cryptographic signing Experimental support for automatic module reloading New CELERY_ANNOTATIONS
381. ions available in the Redis connection pool used for sending and retrieving results MongoDB backend settings Note The MongoDB backend requires the pymongo library http github com mongodb mongo python driver tree master CELERY_MONGODB_BACKEND_ SETTINGS This is a dict supporting the following keys e host Host name of the MongoDB server Defaults to localhost e port The port the MongoDB server is listening to Defaults to 27017 e user User name to authenticate to the MongoDB server as optional e password Password to authenticate to the MongoDB server optional e database The database name to connect to Defaults to celery e taskmeta_collection The collection name to store task meta data Defaults to celery_taskmeta 132 Chapter 2 Contents Celery Documeniation Release 3 0 25 e max_pool_size Passed as max_pool_size to PyMongo s Connection or MongoClient constructor It is the max imum number of TCP connections to keep open to MongoDB at a given time If there are more open connections than max_pool_size sockets will be closed when they are released Defaults to 10 e options Additional keyword arguments to pass to the mongodb connection constructor See the pymongo docs to see a list of arguments supported Example configuration CELERY_RESULT_BACKEND mongodb CELERY_MONGODB_BACKEND_SETTINGS Witesiem RO Gc pele OOK port 30000 database mydb task
382. is executed on_task_init task_id task This method is called before a task is executed on_worker_init This method is called when the worker celery worker starts on_worker_process_init This method is called when a child process starts on_worker_shutdown This method is called when the worker celery worker shuts down override_backends read_configuration shutdown_worker worker initialized False 268 Chapter 2 Contents Celery Documeniation Release 3 0 25 e celery states States Sets x READY_STATES UNREADY_STATES EXCEPTION_STATES PROPAGATE_STATES x ALL_STATES Misc 2 13 25 celery states Built in task states States See States Sets READY_STATES Set of states meaning the task result is ready has been executed UNREADY_STATES Set of states meaning the task result is not ready has not been executed EXCEPTION_STATES Set of states meaning the task returned an exception PROPAGATE_STATES Set of exception states that should propagate exceptions to the user ALL_STATES Set of all possible states Misc celery states PRECEDENCE SUCCESS FAILURE None REVOKED STARTED RECEIVED RETRY PE State precedence None represents the precedence of an unknown state Lower index means higher precedence 2 13 API Reference 269 Celery Documentation Release 3 0 25 celery states PRECEDENCE_
383. is set in two values soft and hard The soft time limit allows the task to catch an exception to clean up before it is killed the hard timeout is not catchable and force terminates the task A single task can potentially run forever if you have lots of tasks waiting for some event that will never happen you will block the worker from processing new tasks indefinitely The best way to defend against this scenario happening is enabling time limits The time limit time limit is the maximum number of seconds a task may run before the process executing it is terminated and replaced by a new process You can also enable a soft time limit soft time limit this raises an exception the task can catch to clean up before the hard time limit kills it from myapp import celery from celery exceptions import SoftTimeLimitExceeded celery task def mytask try do_work except SoftTimeLimitExceeded clean_up_in_a_hurry Time limits can also be set using the CELERYD_TASK_TIME_LIMIT CELERYD_TASK_SOFT_TIME_LIMIT settings Note Time limits do not currently work on Windows and other platforms that do not support the STGUSR1 signal Changing time limits at runtime New in version 2 3 broker support amqp redis mongodb There is a remote control command that enables you to change both soft and hard time limits for a task named time_limit Example changing the time limit for the t
384. is_spam akismet comment_check user_ip remote_addr comment_content comment comment comment_author comment name comment_author_email comment email_address if is_spam comment is_spam True comment save return is_spam 2 3 3 Calling Tasks e Basics e Linking callbacks errbacks e ETA and countdown e Expiration e Message Sending Retry e Serializers e Compression e Connections e Routing options Basics This document describes Celery s uniform Calling API used by task instances and the canvas The API defines a standard set of execution options as well as three methods e apply_async args kwargs Sends a task message e delay xargs xkwargs Shortcut to send a task message but does not support execution options e calling __call__ Applying an object supporting the calling API e g add 2 2 means that the task will be exe cuted in the current process and not by a worker a message will not be sent 60 Chapter 2 Contents Celery Documeniation Release 3 0 25 Quick Cheat Sheet delay arg kwarg value always a shortcut to apply_async apply_async arg kKwarg value apply_async countdown 10 executes 10 seconds from now apply_async eta now timedelta seconds 10 executes 10 seconds from now specifed using eta e T apply_async countdown 60 expires 120 executes in one minute from now but ex pires after 2 minutes e T apply_asyn
385. it github com username celery git When the repository is cloned enter the directory to set up easy access to upstream changes 156 Chapter 2 Contents Celery Documeniation Release 3 0 25 S cd celery S git remote add upstream git github com celery celery git S git fetch upstream If you need to pull in new changes from upstream you should always use the rebase option to git pull git pull rebase upstream master With this option you don t clutter the history with merging commit notes See Rebasing merge commits in git If you want to learn more about rebasing see the Rebase section in the Github guides If you need to work on a different branch than master you can fetch and checkout a remote branch like this git checkout track b 3 0 devel origin 3 0 devel For a list of branches see Branches Running the unit test suite To run the Celery test suite you need to install a few dependencies A complete list of the dependencies needed are located in requirements test txt Installing the test requirements pip E SVIRTUAL_ENV install U r requirements test txt When installation of dependencies is complete you can execute the test suite by calling nosetests S nosetests Some useful options to nosetests are t S Stop running the tests at the first test that fails Don t capture output e nologcapture Don t capture log output Run with verbose output If you want to run th
386. it than the above See http yaml org for more information 64 Chapter 2 Contents Celery Documeniation Release 3 0 25 msgpack msgpack is a binary serialization format that is closer to JSON in features It is very young however and support should be considered experimental at this point See http msgpack org for more information The encoding used is available as a message header so the worker knows how to deserialize any task If you use a custom serializer this serializer must be available for the worker The following order is used to decide which serializer to use when sending a task 1 The serializer execution option 2 The Task serializer attribute 3 The CELERY_TASK_SERIALIZER setting Example setting a custom serializer for a single task invocation gt gt gt add apply_async 10 10 serializer json Compression Celery can compress the messages using either gzip or bzip2 You can also create your own compression schemes and register them in the kombu compression registry The following order is used to decide which compression scheme to use when sending a task 1 The compression execution option 2 The Task compression attribute 3 The CELERY_MESSAGE_COMPRESSION attribute Example specifying the compression used when calling a task gt gt gt add apply_async 2 2 compression zlib Connections Automatic Pool Su
387. it will never stop retrying Task name None Name of the task classmethod Task on_bound app This method can be defined to do additional actions when the task class is bound to an app Task on_failure exc task_id args kwargs einfo Error handler 2 13 API Reference 237 Celery Documentation Release 3 0 25 This is run by the worker when the task fails Parameters e exc The exception raised by the task e task_id Unique id of the failed task e args Original arguments for the task that failed e kwargs Original keyword arguments for the task that failed e einfo Except ionInfo instance containing the traceback The return value of this handler is ignored Task on_retry exc task_id args kwargs einfo Retry handler This is run by the worker when the task is to be retried Parameters e exc The exception sent to retry e task_id Unique id of the retried task e args Original arguments for the retried task e kwargs Original keyword arguments for the retried task e einfo ExceptionInfo instance containing the traceback The return value of this handler is ignored Task on_success retval task_id args kwargs Success handler Run by the worker if the task executes successfully Parameters e retval The return value of the task e task_id Unique id of the executed task e args Original arguments for the executed task e kwargs Origi
388. it_for args kwargs class celery backends base KeyValueStoreBackend args kwargs chord_keyprefix chord unlock delete key expire key value get key get_key_for_chord group_id Get the cache key for the chord waiting on group with given id get_key_for_group group_id Get the cache key for a group by id get_key_for_task fask_id Get the cache key for a task by id get_many fask_ids timeout None interval 0 5 group_keyprefix celery taskset meta implements_incr False incr key mget keys on_chord_apply group_id body result None kwargs on_chord_part_return task propagate None set key value task_keyprefix celery task meta celery backends base unpickle_backend cls args kwargs Returns an unpickled backend celery backends database e celery backends database I celery backends database SQLAIchemy result store backend class celery backends database DatabaseBackend dburi None expires None en gine_options None kwargs The database result backend ResultSession cleanup Delete expired metadata 2 14 Internals 355 Celery Documentation Release 3 0 25 subpolling_interval 0 5 celery backends database retry fun celery backends cache e celery backends cache j celery backends cache Memcache and in memory cache result backend class celery backends cache CacheBackend expires None backend N
389. ith this class don t waste your time just install pytz dst dt tzname dt utcoffset dt celery utils timeutils delta_resolution dt delta Round a datetime to the resolution of a timedelta If the timedelta is in days the datetime will be rounded to the nearest days if the timedelta is in hours the datetime will be rounded to the nearest hour and so on until seconds which will just return the original datetime celery utils timeutils humanize_seconds secs prefix sep Show seconds in human form e g 60 is 1 minute 7200 is 2 hours Parameters prefix Can be used to add a preposition to the output e g in will give second but add nothing to now c in 1 celery utils timeutils is_naive dt Returns True if the datetime is naive does not have timezone information celery utils timeutils localize dt tz Convert aware datetime to another timezone celery utils timeutils make_aware dt tz Sets the timezone for a datetime object celery utils timeutils maybe_iso8601 dt Either datetime str gt datetime or None gt None celery utils timeutils maybe_make_aware dt tz None 380 Chapter 2 Contents Celery Documeniation Release 3 0 25 celery utils timeutils maybe_timedelta delta Coerces integer to timedelta if delta is an integer celery utils timeutils rate rate Parses rate strings such as 100 m 2 h or 0 5 s and con
390. k Task Implementation Task request context and the base task class class celery app task Task Task base class When called tasks apply the run method This method must be defined by all tasks that is unless the call_ _ method is overridden AsyncResult task_id kwargs Get AsyncResult instance for this kind of task Parameters task_id Task id to get result for class ErrorMail task kwargs Defines how and when task error e mails should be sent Parameters task The task instance that raised the error subject and body are format strings which are passed a context containing the following keys name Name of the task eid UUID of the task 234 Chapter 2 Contents Celery Documeniation Release 3 0 25 exc String representation of the exception eargs Positional arguments ekwargs Keyword arguments etraceback String representation of the traceback ehostname Worker hostname should_send context exc Returns true or false depending on if a task error mail should be sent for this type of error exception Task MaxRetriesExceededError The tasks max restart limit has been exceeded Task abstract Task Strategy celery worker strategy default Execution strategy used or the qualified name of one None If True the task is an abstract base class Task accept_magic_kwargs False If disabled the worker will not forward magic keyword arguments
391. k takes a feed URL as a single argument and imports that feed into a Django model called Feed We ensure that it s not possible for two or more workers to import the same feed at the same time by setting a cache key consisting of the MD5 checksum of the feed URL The cache key expires after some time in case something unexpected happens you never know right from celery import task from celery utils log import get_task_logger from django core cache import cache from django utils hashcompat import md5_constructor as md5 from djangofeeds models import Feed logger get_task_logger __name__ LOCK_EXPIRE 60 5 Lock expires in 5 minutes task bind True def import_feed self feed_url The cache key consists of the task name and the MD5 digest of the feed URL feed_url_digest md5 feed_url hexdigest o lock_id s lock s self name feed_url_hexdigest cache add fails if if the key already exists acquire_lock lambda cache add lock_id true LOCK_EXPIRE memcache delete is very slow but we have to use it to take advantage of using add for atomic locking release_lock lambda cache delete lock_id logger debug Importing feed s feed_url if acquire_lock try feed Feed objects import_feed feed_url finally release_lock return feed url logger debug Feed s is already being imported by another worker feed_url 2 9
392. kedizon 0 6 0 release date 2009 08 07 06 54 A M CET Important changes e Fixed a bug where tasks raising unpickleable exceptions crashed pool workers So if you ve had pool workers mysteriously disappearing or problems with celeryd stopping working this has been fixed in this version e Fixed a race condition with periodic tasks The task pool is now supervised so if a pool worker crashes goes away or stops responding it is automati cally replaced with a new one e Task name is now automatically generated out of class module name e g djangotwitter tasks UpdateStatusesTask Very convenient No idea why we didn t do this be fore Some documentation is updated to not manually specify a task name News e Tested with Django 1 1 e New Tutorial Creating a click counter using carrot and celery e Database entries for periodic tasks are now created at celeryd startup instead of for each check which has been a forgotten TODO XXxX in the code for a long time e New settings variable CELERY_TASK_RESULT_EXPIRES Time in seconds or a datetime timedelta ob ject for when after stored task results are deleted For the moment this only works for the database backend e celeryd now emits a debug log message for which periodic tasks has been launched e The periodic task table is now locked for reading while getting periodic task status MySQL only so far seeking patches for other engines A lot more debugging informat
393. ks import MyPeriodicTask gt gt gt MyPeriodicTask delay Watch celeryd s log file to see if it s able to find the task or if some other error is happening Why won t my periodic task run Answer See Why won t my Task run How do I purge all waiting tasks Answer You can use the celery purge command to purge all configured task queues S celery purge or programatically gt gt gt from celery import current_app as celery gt gt gt celery control purge 1753 If you only want to purge messages from a specific queue you have to use the AMQP API or the celery amgp utility celery amqp queue purge lt queue name gt The number 1753 is the number of messages deleted You can also start ce leryd with the purge argument to purge messages when the worker starts I ve purged messages but there are still messages left in the queue Answer Tasks are acknowledged removed from the queue as soon as they are actually executed After the worker has received a task it will take some time until it is actually executed especially if there are a lot of tasks already waiting for execution Messages that are not acknowledged are held on to by the worker until it closes the con nection to the broker AMQP server When that connection is closed e g because the worker was stopped the tasks will be re sent by the broker to the next available worker or the same worker when it has been restarted so to properly
394. kwargs retries 0 eran H2007 ME nme 3 Ole Or oie Rn Serialization Several types of serialization formats are supported using the content_type message header The MIME types supported by default are shown in the following table Scheme MIME Type json application json yaml application x yaml pickle application x python serialize msgpack application x msgpack 2 14 5 The Big Instance Refactor The app branch is a work in progress to remove the use of a global configuration in Celery Celery can now be instantiated which means several instances of Celery may exist in the same process space Also large parts can be customized without resorting to monkey patching 314 Chapter 2 Contents Celery Documeniation Release 3 0 25 Examples Creating a Celery instance gt gt gt from celery import Celery celery Celery celery config_from_object celeryconfig celery config_from_envvar CELERY_CONFIG_MODULE gt gt gt gt gt gt gt gt gt Creating tasks celery task def add x y return x y Creating custom Task subclasses Task celery create_task_cls class DebugTask Task abstract True def on_failure self import pdb pdb set_trace xargs xkwargs celery task base DebugTask def add x y return x y Starting a worker worker celery Worker loglevel INFO Getting access to the configuration
395. l Result Now properly forwards apps to GroupResults when deserializing Issue 1249 Fix contributed by Charles Axel Dein GroupResult revoke now supports the terminate and signal keyword arguments Worker Multiprocessing pool workers now import task modules configuration before setting up the logging system so that logging signals can be connected before they re dispatched chord The AsyncResul1t instance returned now has its parent attribute set to the header GroupResult This is consistent with how chain works 2 12 10 3 0 16 release date 2013 03 07 04 00 00 P M UTC Happy International Women s Day We have a long way to go so this is a chance for you to get involved in one of the organizations working for making our communities more diverse PyLadies http pyladies com Girls Who Code http www girlswhocode com Women Who Code http www meetup com Women Who Code SF Now depends on kombu version 2 5 7 Now depends on billiard version 2 7 3 22 AMQP heartbeats are now disabled by default Some users experiences issues with heartbeats enabled and it s not strictly necessary to use them If you re experiencing problems detecting connection failures you can re enable heartbeats by configuring the BROKER_HEARTBEAT setting Worker Now propagates connection errors occurring in multiprocessing callbacks so that the connection can be reset Issue 1226 Worker Now propagates conn
396. l a SIGTERM SIGINT handler that saves the celerybeat schedule Beat logfile None Beat loglevel None Beat redirect_stdouts None Beat redirect_stdouts_level None Beat run Beat schedule None Beat scheduler_cls None Beat set_process_title Beat setup_logging colorize None Beat start_scheduler Beat startup_info beat 2 13 35 celery bin base e Preload Options e Daemon Options 2 13 API Reference 285 Celery Documentation Release 3 0 25 Preload Options These options are supported by all commands and usually parsed before command specific arguments A app app instance to use e g module attr_name b broker url to broker default is amqp guest localhost loader name of custom loader class to use config Name of the configuration module Daemon Options These options are supported by commands that can detach into the background daemon They will be present in any command that also has a detach option f logfile Path to log file If no logfile is specified stderr is used pidfile Optional file used to store the process pid The program will not start if this file already exists and the pid is still alive uid User id or user name of the user to run as after detaching gid Group id or group name of the main group to change to after detaching umask Effective umask in octal of the process after detach
397. lass celery loaders base BaseLoader app None kwargs The base class for loaders Loaders handles Reading celery client worker configurations What happens when a task starts See on_task_init What happens when the worker starts See on_worker_init 2 13 API Reference 267 Celery Documentation Release 3 0 25 What happens when the worker shuts down See on_worker_shutdown eWhat modules are imported to find tasks builtin_modules frozenset cmdline _config_parser args namespace celery _re_type lt _sre SRE_Pattern object at Ox7fb768d5cbe8 gt extra_types json lt function loads at Ox7fb768fcO848 gt override_types dict json list json tuple json conf Loader configuration config_from_envvar variable_name silent False config _from_object obj silent False configured False error_envvar_not_set The environment variable r is not set nand as such the configuration could not be loade find module module import_default_modules import_from_cwd module imp None package None import_module module package None import_task_module module init_worker init_worker_process mail mail_admins subject body fail_silently False sender None to None host None port None user None password None timeout None use_ssl False use_tls False now utc True on_process_cleanup This method is called after a task
398. le Command l l i The command must then support the interface of celery bin base Command e contrib migrate New utilities to move tasks from one queue to another move_tasks move_task_by_id e The task sent event now contains exchange and routing_key fields e Fixes bug with installing on Python 3 Fix contributed by Jed Smith 2 12 26 3 0 0 Chiastic Slide release date 2012 07 07 01 30 P M BST by Ask Solem See What s new in Celery 3 0 Chiastic Slide 2 13 API Reference Release 3 0 Date July 10 2014 2 13 API Reference 227 Celery Documentation Release 3 0 25 2 13 1 celery e Application e Grouping Tasks e Proxies Application class celery Celery main __main__ broker amgqp Nocalhost Parameters e main Name of the main module if running as __main__ e broker URL of the default broker used e loader The loader class or the name of the loader class to use Default is celery loaders app AppLoader backend The result store backend class or the name of the backend class to use Default is the value of the CELERY_RESULT_BACKEND setting e amqp AMQP object or class name e events Events object or class name e log Log object or class name e control Control object or class name e set_as_current Make this the global current app e tasks A task registry or the name of a registry class main Name of t
399. le disable events start Start the consumer Automatically survives intermittent connection failure and will retry establishing the connection and restart consuming messages stop Stop consuming Does not close the broker connection so be sure to call close_connection when you are finished with it stop_consumers close_connection True join True Stop consuming tasks and broadcast commands also stops the heartbeat thread and event dispatcher Parameters close_connection Set to False to skip closing the broker connection stop_pidbox_node task_consumer None The consumer used to consume task messages timer None A timer used for high priority internal tasks such as sending heartbeats update_strategies celery worker consumer INVALID_TASK_ERROR Received invalid task message s nThe message has been ignorec Error message for when an invalid task message is received celery worker consumer PREFETCH_COUNT_MAX 65535 Prefetch count can t exceed short class celery worker consumer QoS consumer initial_value Thread safe increment decrement of a channels prefetch_count Parameters e consumer A kombu messaging Consumer instance e initial_value Initial prefetch count value decrement_eventually n Decrement the value but do not update the channels QoS The MainThread will be responsible for calling update when necessary increment_eventually n Increment the val
400. lease date 2011 02 03 04 00 P M CET Fixes Celerybeat could not read the schedule properly so entries in CELERYBEAT_SCHEDULE would not be sched uled Task error log message now includes exc_info again The eta argument can now be used with task retry Previously it was overwritten by the countdown argument celeryd multi celeryd_detach Now logs errors occuring when executing the celeryd command daemonizing tutorial Fixed typo time limit 300 gt time limit 300 Colors in logging broke non string objects in log messages setup_task_logger no longer makes assumptions about magic task kwargs 2 2 1 release date 2011 02 02 04 00 P M CET Fixes e Eventlet pool was leaking memory Issue 308 e Deprecated function celery execute delay_task was accidentally removed now available again BasePool on_terminate stub did not exist e celeryd detach Adds readable error messages if user group name does not exist e Smarter handling of unicode decod errors when logging errors 2 2 0 release date 2011 02 01 10 00 AM CET 2 15 History 415 Celery Documeniation Release 3 0 25 Important Notes e Carrot has been replaced with Kombu Kombu is the next generation messaging framework for Python fixing several flaws present in Carrot that was hard to fix without breaking backwards compatibility Also it adds First class support for virtual transports Redis Django ORM SQLAIchem
401. ler Examples 292 Chapter 2 Contents Celery Documeniation Release 3 0 25 celery beat 1 info celery beat s var run celerybeat schedul detach celery beat S djcelery schedulers DatabaseScheduler Command celery bin celerybeat BeatCommand sortpri 20 class celery bin celery call app None no_color False stdout lt open file lt stdout gt mode w at Ox7fb76c556150 gt stderr lt open file lt stderr gt mode w at Ox7fb76c5561e0 gt show_reply True Call a task by name Examples celery call tasks add args 2 2 celery call tasks add args 2 2 countdown 10 args lt task_name gt option_list lt Option at 0x7fb762af2a70 q quiet gt lt Option at 0x7fb762af2098 C no color gt lt Option at 0x7fb7 run name _ kw sortpri 0 celery bin celery command fun name None sortpri 0 class celery bin celery control app None no_color False stdout lt open file lt stdout gt mode w at Ox7fb76c556150 gt stderr lt open file lt stderr gt mode w at 0x7fb76c5561e0 gt show_reply True Workers remote control Availability RabbitMQ amqp Redis and MongoDB transports Examples celery control enable_events timeout 5 celery control d workerl example com enable_events celery control d wl e com w2 e com enable_events celery control d wl e com add_consumer queue_name ce
402. lery Documeniation Release 3 0 25 import requests from urlparse import urlparse from celery contrib batches import Batches wot_api_target https api mywot com 0 4 public_link_json app task base Batches flush_every 100 flush_interval 10 def wot_api requests sig lambda url url reponses wot_api_real sig request args x xrequest kwargs for request in requests use mark_as_done to manually return response data for response request in zip reponses requests app backend mark_as_done request id response def wot_api_real urls domains urlparse url netloc for url in urls response requests get wot_api_target params hosts join set domains return response json domain for domain in domains Using the API is done as follows gt gt gt wot_api delay http example com Note If you don t have an app instance then use the current app proxy instead from celery import current_app app backend mark_as_done request id response API class celery contrib batches Batches Strategy task app consumer apply buffer requests args kwargs flush requests flush_every 10 Maximum number of message in buffer flush_interval 30 Timeout in seconds before buffer is flushed anyway run requests class celery contrib batches SimpleRequest id name args kwargs delivery_info hostname Pickleable request 2 13 A
403. lery contrib rdb Now works when sockets are in non blocking mode Fix contributed by Theo Spears The inspect reserved remote control command included active started tasks with the reserved tasks Issue 1030 The task_failure signal received a modified traceback object meant for pickling purposes this has been fixed so that it now receives the real traceback instead The task decorator silently ignored positional arguments it now raises the expected TypeError instead Issue 1125 The worker will now properly handle messages with invalid eta expires fields Issue 1232 The pool_restart remote control command now reports an error if the CELERYD_POOL_RESTARTS setting is not set celery conf add_defaults can now be used with non dict objects Fixed compatibility problems in the Proxy class Issue 1087 The class attributes _ module__ __name__and___doc___ are now meaningful string objects Thanks to Marius Gedminas MongoDB Backend The MONGODB_BACKEND_SETTINGS setting now accepts a opt ion key that lets you forward arbitrary kwargs to the underlying pymongo Connection object Issue 1015 Beat The daily backend cleanup task is no longer enabled for result backends that support automatic result expiration Issue 1031 Canvas list operations now takes application instance from the first task in the list instead of depending on the current_app Issue 1249 Worker Message decod
404. lery control d wl e com cancel_consumer queue_name celery control d wl e com add_consumer queu xchange direct rkey add_consumer method queue exchange None exchange_type direct routing_key None kwargs lt queue gt exchange type routing_key autoscale method max None min None kwargs max min call method args options cancel_consumer method queue kwargs lt queue gt choices time_limit 1 0 tell worker s to modify the time limit for a task type cancel_consumer 1 0 tell wor name control pool_grow method n 1 kwargs N 1 2 13 API Reference 293 Celery Documentation Release 3 0 25 cel pool_shrink method n 1 kwargs N 1 rate_limit method task_name rate_limit kwargs lt task_name gt lt rate_limit gt e g 5 s 5 m 5 h gt sortpri 0 time_limit method task_name soft hard None kwargs lt task_name gt lt soft_secs gt hard_secs ery bin celery determine_exit_status ret cel ery bin celery ensure_broadcast_supported app class celery bin celery events args kwargs Event stream utilities Commands celery events app proj start graphical monitor requires curses celery events d app proj dump events to screen celery events b amgp celery events C lt camera gt options run snapshot camera Examples celery events celery events d
405. lery task sets TaskSet app TaskSet app TaskSetResult x celery result TaskSetResult app TaskSetResult e app AsyncResult celery result BaseAsyncResult celery result AsyncResult e celery bin celeryd WorkerCommand celery apps worker Worker x celery worker WorkerController celery worker consumer Consumer celery worker job TaskRequest celery events EventDispatcher celery worker control ControlDispatch celery woker control registry Panel celery pidbox BroadcastPublisher celery pidbox BroadcastConsumer celery worker controllers Mediator celery beat EmbeddedService celery bin celeryev run_celeryev celery events snapshot evcam x celery events snapshot Polaroid celery events EventReceiver celery events cursesmon evtop 318 Chapter 2 Contents Celery Documeniation Release 3 0 25 celery events EventReceiver celery events cursesmon CursesMonitor celery events dumper celery events EventReceiver celery bin celeryctl celeryctl celery bin celeryctl Command e celery bin caqmadm AMQPAdmin celery bin celerybeat BeatCommand celery apps beat Beat x celery beat Service celery beat Scheduler 2 14 6 Internal Module Reference Release 3 0 Date July 10 2014 celery worker e celery worker j celery worker WorkController can be used to instantiate in process workers The worker consists of several components all managed by boot steps mod celery worker bootstep
406. lerybeat The celery beat command See also See Preload Options and Daemon Options detach Detach and run in the background as a daemon s schedule Path to the schedule database Defaults to celerybeat schedule The extension db may be appended to the filename Default is default s S scheduler Scheduler class to use Default is celery beat PersistentScheduler max interval Max seconds to sleep between schedule iterations f logfile Path to log file If no logfile is specified stderr is used 1 loglevel Logging level choose between DEBUG INFO WARNING ERROR CRITICAL or FATAL class celery bin celerybeat BeatCommand app None get_app None doc n nThe program celery beat command n n program celery beat n n seealso n n See ref preload option enable_config_from_cmdline True get_options run detach False logfile None pidfile None uid None gid None umask None work ing_directory None kwargs supports_args False celery bin celerybeat main 2 13 38 celery bin celeryev The celery events command See also See Preload Options and Daemon Options d dump Dump events to stdout c camera Take snapshots of events using this camera detach Camera Detach and run in the background as a daemon F freq frequency Camera Shutter frequency Default is every 1 0 seconds 290 Chapter 2 Contents Celery Documeniation
407. leted EventDispatcher No longer creates AMQP channel if events are disabled Added required RPM package names under bdist_rpm section to support building RPMs from the sources using setup py Running unit tests NOSE_VERBOSE environment var now enables verbose output from Nose celery execute apply Pass log file log level arguments as task kwargs See issue 110 celery execute apply Should return exception not Except ionInfo on error See issue 111 Added new entries to the FAQs 450 Chapter 2 Contents Celery Documeniation Release 3 0 25 Should I use retry or acks_late Can I call a task by name 1 0 4 release date 2010 05 31 09 54 A M CEST e Changelog merged with 1 0 5 as the release was never announced 1 0 3 release date 2010 05 15 03 00 P M CEST Important notes e Messages are now acknowledged just before the task function is executed This is the behavior we ve wanted all along but couldn t have because of limitations in the mul tiprocessing module The previous behavior was not good and the situation worsened with the release of 1 0 1 so this change will definitely improve reliability performance and operations in general For more information please see http bit ly 29hom6T e Database result backend result now explicitly sets null True as django picklefield version 0 1 5 changed the default behavior right under our noses See http bit ly
408. librabbitmgq Very fast Python AMQP client written in C git https github com celery librabbitmq PyPI http pypi python org pypi librabbitmq celerymon Celery monitor web service git https github com celery celerymon PyPI http pypi python org pypi celerymon django celery Django lt gt Celery Integration git https github com celery django celery PyPI http pypi python org pypi django celery docs http docs celeryproject org en latest django cl Actor framework git https github com celery cl PyPI http pypi python org pypi cl cyme Distributed Celery Instance manager git https github com celery cyme PyPI http pypi python org pypi cyme docs http cyme readthedocs org Deprecated e Flask Celery git https github com ask Flask Celery PyPI http pypi python org pypi Flask Celery e carrot git https github com ask carrot PyPI http pypi python org pypi carrot e ghettoq 2 6 Contributing 163 Celery Documeniation Release 3 0 25 git https github com ask ghettoq PyPI http pypi python org pypi ghettoq e kombu sqlalchemy git https github com ask kombu sqlalchemy PyPI http pypi python org pypi kombu sqlalchemy e django kombu git https github com ask django kombu PyPI http pypi python org pypi django kombu e pylibrabbitmq Old name for Librabbitma git None PyPI http pypi python org pypi pylibrabbitmq 2 6 11 Release Procedure Updating the version number Th
409. lity requirements you are encouraged to use RabbitMQ or another AMQP broker Redis database also use polling so they are likely to consume more resources However if you for some reason are not able to use AMQP feel free to use these alternatives They will probably work fine for most use cases and note that the above points are not specific to Celery If using Redis database as a queue worked fine for you before it probably will now You can always upgrade later if you need to Is Celery multilingual Answer Yes celeryd is an implementation of Celery in Python If the language has an AMQP client there shouldn t be much work to create a worker in your language A Celery worker is just a program connecting to the broker to process messages Also there s another way to be language independent and that is to use REST tasks instead of your tasks being functions they re URLs With this information you can even create simple web servers that enable preloading of code See User Guide Remote Tasks 2 9 3 Troubleshooting MySQL is throwing deadlock errors what can do Answer MySQL has default isolation level set to REPEATABLE READ if you don t really need that set it to READ COMMITTED You can do that by adding the following to your my cnf mysqld transaction isolation READ COMMITTED For more information about InnoDB s transaction model see MySQL The InnoDB Transaction Model and Locking in the MySQL user
410. ll not be triggered in this case BaseBackend supports_native_join False If true the backend must implement get_many BaseBackend wait_for task_id timeout None propagate True interval 0 5 Wait for task and return its result If the task raises an exception this exception will be re raised by wait_for If timeout is not None this raises the celery exceptions TimeoutError exception if the oper ation takes longer than timeout seconds class celery backends base BaseDictBackend args kwargs delete_group group_id forget task_id get_children task_id Get the list of subtasks sent by a task get_group_meta group_id cache True get_result task_id Get the result of a task get_status task_id Get the status of a task get_task_meta task_id cache True get_traceback task_id Get the traceback for a failed task is_cached task_id reload_group_result group_id reload_task_result task_id restore_group group_id cache True Get the result for a group save_group group_id result Store the result of an executed group store_result fask_id result status traceback None kwargs Store task result and status class celery backends base DisabledBackend args kwargs get_result args kwargs get_status args kwargs get_traceback args kwargs 354 Chapter 2 Contents Celery Documeniation Release 3 0 25 store_result args kwargs wa
411. lock instance used for events 2 Create the task registry 3 Set itself as the current app but not if the set__as_current argument was disabled 4 Call the Celery on_init callback does nothing by default The task decorator does not actually create the tasks at the point when it s called instead it will defer the creation of the task to happen either when the task is used or after the application has been finalized This example shows how the task is not created until you use the task or access an attribute in this case repr gt gt gt celery task gt gt gt def add x y return x y gt gt gt type add class celery local PromiseProxy gt gt gt gt add __evaluated__ gt gt gt add __evaluated__ True Finalization of the app happens either explicitly by calling Celery finalize or implicitly by accessing the tasks attribute Finalizing the object will 1 Copy tasks that must be shared between apps Tasks are shared by default but if the shared argument to the task decorator is disabled then the task will be private to the app it s bound to 2 Evaluate all pending task decorators 3 Make sure all tasks are bound to the current app Tasks are bound to apps so that it can read default values from the configuration 2 3 User Guide 39 Celery Documentation Release 3 0 25 The default app Celery did not always work this way it used t
412. logging This to ensure we don t get additional decoding errors when trying to log the failure app config_from_object app config_from_envvar now works for all loaders Now emits a user friendly error message if the result backend name is unknown Issue 349 celery contrib batches Now sets loglevel and logfile in the task request so task get_logger works with batch tasks Issue 357 celeryd An exception was raised if using the amqp transport and the prefetch count value exceeded 65535 Issue 359 The prefetch count is incremented for every received task with an ETA countdown defined The prefetch count is a short so can only support a maximum value of 65535 If the value exceeds the maximum value we now disable the prefetch count it is re enabled as soon as the value is below the limit again cursesmon Fixed unbound local error Issue 303 eventlet gevent is now imported on demand so autodoc can import the modules without having eventlet gevent installed celeryd Ack callback now properly handles Att ributeError Task after_return is now always called after the result has been written Cassandra Result Backend Should now work with the latest pycassa version multiprocessing Pool No longer cares if the putlock semaphore is released too many times this can happen if one or more worker processes are killed SQLAlIchemy Result Backend Now returns accidentally removed dat e_done again Issue 325 Task request contex
413. ls debug Utilities for debugging memory usage celery utils debug sample_mem Sample RSS memory usage Statistics can then be output by calling memdump celery utils debug memdump samples 10 Dump memory statistics Will print a sample of all RSS memory samples added by calling samp1le_mem and in addition print used RSS memory after gc collect 2 13 API Reference 263 Celery Documentation Release 3 0 25 celery utils debug sample x n k 0 Given a list x a sample of length n of that list is returned E g if n is 10 and x has 100 items a list of every 10th item is returned k can be used as offset celery utils debug mem_rss Returns RSS memory usage as a humanized string celery utils debug ps Returns the global psutil Process instance or None if psutil is not installed 2 13 19 celery utils mail e celery utils mail I celery utils mail How task error emails are formatted and sent class celery utils mail ErrorMail task kwargs Defines how and when task error e mails should be sent Parameters task The task instance that raised the error subject and body are format strings which are passed a context containing the following keys name Name of the task UUID of the task eexc String representation of the exception eargs Positional arguments ekwargs Keyword arguments traceback String representation of the traceback ehostname Worker hostname E
414. lse propagate False IGNORE_STATES frozenset IGNORED RETRY Builts a function that tracing the tasks execution catches all exceptions and saves the state and result of the task execution to the result backend If the call was successful it saves the result to the task result backend and sets the task status to SUCCESS If the call raises RetryTaskError it extracts the original exception uses that as the result and sets the task status to RETRY If the call results in an exception it saves the exception as the task result and sets the task status to FAILURE Returns a function that takes the following arguments param uuid The unique id of the task param args List of positional args to pass on to the function param kwargs Keyword arguments mapping to pass on to the function keyword request Request dict celery task trace eager_trace_task task uuid args kwargs request None opts celery task trace mro_lookup cls attr stop monkey_patched Returns the first node by MRO order that defines an attribute Parameters e stop A list of types that if reached will stop the search e monkey_patched Use one of the stop classes if the attr s module origin is not in this list this to detect monkey patched attributes Returns None if the attribute was not found celery task trace report_internal_error task exc celery task trace reset_worker_optimizations celery
415. lt Improved support for webhook tasks celery task rest is now deprecated replaced with the new and shiny celery task http With more reflective names sensible interface and it s possible to override the methods used to perform HTTP requests The results of task sets are now cached by storing it in the result backend Changes Now depends on carrot gt 0 8 1 New dependencies billiard python dateutil django picklefield No longer depends on python daemon The uuid distribution is added as a dependency when running Python 2 4 Now remembers the previously detected loader by keeping it in the CELERY_LOADER environment variable This may help on windows where fork emulation is used ETA no longer sends datetime objects but uses ISO 8601 date format in a string for better compatibility with other platforms No longer sends error mails for retried tasks Task can now override the backend used to store results Refactored the ExecuteWrapper apply and CELERY_ALWAYS_EAGER now also executes the task callbacks and signals Now using a proper scheduler for the tasks with an ETA 2 15 History 461 Celery Documentation Release 3 0 25 This means waiting eta tasks are sorted by time so we don t have to poll the whole list all the time e Now also imports modules listed in CELERY_IMPORTS when running with django as documented e Log level for st
416. lt celery utils threads _LocalStack object at 0x7fb76403be50 gt run url None method GET kwargs url None exception celery task http InvalidResponseError The remote server gave an invalid response class celery task http MutableURL url Object wrapping a Uniform Resource Locator Supports editing the query parameter list You can convert the object back to a string the query will be properly urlencoded Examples gt gt gt url URL http www google com 6580 foo bar x 3 amp y 4 fo0 gt gt gt url query gt gt gt str url ee ae ee www daongle com 6580 foo harr v a46x aHt Nttp WWW yoogle 1 SOE bar y 1 x 3Fi gt gt gt url query x 10 gt gt gt url query update George Costanza gt gt gt str url Fh py yoogle com 6580 foo bar y 4 amp x 10 amp George Costanza foo 258 Chapter 2 Contents Celery Documeniation Release 3 0 25 exception celery task http RemoteExecuteError The remote task gave a custom error class celery task http URL url dispatcher None HTTP Callback URL Supports requesting an URL asynchronously Parameters e url URL to request e dispatcher Class used to dispatch the request By default this is HttpDispatchTask dispatcher alias of HttpDispatchTask get_async kwargs post_async kwargs exception celery task http UnknownStatusError The remote server gave an unknown status celery task http
417. lt is current user Troubleshooting If you can t get the init scripts to work you should try running them in verbose mode sh x etc init d celeryd start This can reveal hints as to why the service won t start Also you will see the commands generated so you can try to run the celeryd command manually to read the resulting error output For example my sh x output does this start stop daemon start chdir opt App release app quiet oknodo background make pidfil pidfile var run celeryd pid exec opt App release app manage py celeryd time limit 300 f var log celeryd log l1 INFO 2 8 Tutorials 169 Celery Documeniation Release 3 0 25 Run the celeryd command after exec without the to show the actual resulting output opt App release app manage py celeryd time limit 300 f var log celeryd log 1 INFO supervisord e extra supervisord launchd OS X e extra mac Windows See this excellent external tutorial http www calazan com windows tip run applications in the background using task scheduler CentOS In CentOS we can take advantage of built in service helpers such as the pid based status checker function in etc init d functions See the sample script in http github com celery celery tree 3 0 extra centos 2 8 2 Debugging Tasks Remotely using pdb Basics celery contrib rdb is an extended version of pdb that enables remote debuggi
418. m number of members before we start evicting expired members e expires Time in seconds before a membership expires add value Add a new member 2 14 Internals 371 Celery Documentation Release 3 0 25 as_dict chronologically clear Remove all members expires first Get the oldest member maxlen pop_value value Remove membership by finding value purge limit None update other heappush lt built in function heappush gt LRUCache class celery datastructures LRUCache limit None LRU Cache implementation using a doubly linked list to track access Parameters limit The maximum number of keys to keep in the cache When a new key is inserted and the limit has been exceeded the Least Recently Used key will be discarded from the cache incr key delta items iteritems itervalues keys update args kwargs values celery events snapshot e celery events snapshot j celery events snapshot Consuming the events as a stream is not always suitable so this module implements a system to take snapshots of the state of a cluster at regular intervals There is a full implementation of this writing the snapshots to a database in djcelery snapshots in the django celery distribution class celery events snapshot Polaroid state freq 1 0 maxrate None cleanup_freq 3600 0 timer None app None cancel capture 372 Chapter 2 Contents Cel
419. mbination with Django you must also read the django celery changelog and upgrade to django celery 3 0 This version is officially supported on CPython 2 5 2 6 2 7 3 2 and 3 3 as well as PyPy and Jython 2 10 1 Highlights Overview e A new and improved API that is both simpler and more powerful Everyone must read the new First Steps with Celery tutorial and the new Next Steps tutorial Oh and why not reread the user guide while you re at it There are no current plans to deprecate the old API so you don t have to be in a hurry to port your applications The worker is now thread less giving great performance improvements The new Canvas makes it easy to define complex workflows Ever wanted to chain tasks together This is possible but not just that now you can even chain together groups and chords or even combine multiple chains Read more in the Canvas user guide All of Celery s command line programs are now available from a single celery umbrella command This is the last version to support Python 2 5 Starting with Celery 3 1 Python 2 6 or later is required Support for the new librabbitmg C client Celery will automatically use the 1ibrabbitmgq module if installed which is a very fast and memory optimized replacement for the py amqp module Redis support is more reliable with improved ack emulation Celery now always uses UTC Over 600 commits 30k additions 36k deletions In comparison 1 0 2 0 had 18k additio
420. ment passed to the task decorator will actually be set as an attribute of the resulting task class and this is a list of the built in attributes General Task name The name the task is registered as You can set this name manually or a name will be automatically generated using the module and class name See Names Task request If the task is being executed this will contain information about the current request Thread local storage is used See Context Task abstract Abstract classes are not registered but are used as the base class for new task types 2 3 User Guide 47 Celery Documentation Release 3 0 25 Task max_retries The maximum number of attempted retries before giving up If the number of retries exceeds this value a MaxRet riesExceeded exception will be raised NOTE You have to call ret ry manually as it will not automatically retry on exception Task default_retry delay Default time in seconds before a retry of the task should be executed Can be either int or float Default is a 3 minute delay Task rate_limit Set the rate limit for this task type which limits the number of tasks that can be run in a given time frame Tasks will still complete when a rate limit is in effect but it may take some time before it s allowed to start If this is None no rate limit is in effect If it is an integer or float it is interpreted as tasks per second The rate limits can be specified in seconds
421. meta_collection my_taskmeta_collection Cassandra backend settings Note The Cassandra backend requires the pycassa library http pypi python org pypi pycassa To install the pycassa package use pip or easy_install S pip install pycassa This backend requires the following configuration directives to be set CASSANDRA_SERVERS List of host port Cassandra servers e g localhost 9160 CASSANDRA_KEYSPACE The keyspace in which to store the results e g Casks_keyspace CASSANDRA_COLUMN_FAMILY The column family in which to store the results eg tasks CASSANDRA_READ_CONSISTENCY The read consistency used Values can be ONE QUORUM or ALL CASSANDRA_WRITE_CONSISTENCY The write consistency used Values can be ONE QUORUM or ALL 2 4 Configuration and defaults 133 Celery Documeniation Release 3 0 25 CASSANDRA_DETAILED_MODE Enable or disable detailed mode Default is False This mode allows to use the power of Cassandra wide columns to store all states for a task as a wide column instead of only the last one To use this mode you need to configure your ColumnFamily to use the TimeUUID type as a comparator create column family task_results with comparator TimeUUIDType CASSANDRA_OPTIONS Options to be passed to the pycassa connection pool optional Example configuration CASSANDRA_SERVERS localhost 9160 CASSANDRA_KEYSPACE
422. mits was not properly applied Issue 98 e Now handles exceptions with Unicode messages correctly in TaskRequest on_failure e Database backend TaskMeta result default value should be None not empty string 454 Chapter 2 Contents Celery Documeniation Release 3 0 25 1 0 2 release date 2010 03 31 12 50 P M CET e Deprecated CELERY_BACKEND please use CELERY_RESULT_BACKEND instead e We now use a custom logger in tasks This logger supports task magic keyword arguments in formats The default format for tasks CELERYD_TASK_LOG_FORMAT now includes the id and the name of tasks so the origin of task log messages can easily be traced Example output 2010 03 25 13 11 20 317 INFO PoolWorker 1 tasks add a6e 1 c5ad 60d9 42a0 8b24 9e39363125a4 Hello from add To revert to the previous behavior you can set CELERYD_TASK_LOG_FORMAT S asctime s levelname s processName s message s wee strip e Unit tests Don t disable the django test database tear down instead fixed the underlying issue which was caused by modifications to the DATABASE_NAME setting Issue 82 e Django Loader New config CELERY_DB_REUSE_MAX max number of tasks to reuse the same database connection The default is to use a new connection for every task We would very much like to reuse the connection but a safe number of reuses is not known and we don
423. mple CELERY_TASK_ERROR_WHITELIST myapp MalformedInputError See issue 153 celeryd Now handles overflow exceptions in time mktime while parsing the ETA field LoggerWrapper Try to detect loggers logging back to stderr stdout making an infinite loop Added celery task control inspect Inspects a running worker Examples 436 Chapter 2 Contents Celery Documeniation Release 3 0 25 Inspect a single worker gt gt gt 1 inspect myworker example com Inspect several workers gt gt gt i inspect myworker example com myworker2 example com Inspect all workers consuming on this vhost gt gt gt i inspect Methods Get currently executing tasks gt gt gt i active Get currently reserved tasks gt gt gt i reserved Get the current eta schedul gt gt gt i scheduled Worker statistics and info gt gt gt i stats List of currently revoked tasks gt gt gt i revoked List of registered tasks gt gt gt i registered_tasks e Remote control commands dump_active dump_reserved dump_schedule now replies with detailed task requests Containing the original arguments and fields of the task requested In addition the remote control command set_loglevel has been added this only changes the log level for the main process e Worker control command execution now catches errors and returns their string representa
424. mple usage gt gt gt minutes crontab_parser 60 parse 15 0 15 30 45 gt gt gt hours crontab_parser 24 parse 4 0 4 8 12 16 20 gt gt gt day_of_week crontab_parser 7 parse x O 1 2 3 45 5p 6l It can also parse day_of_month and month_of_year expressions if initialized with an minimum of Example usage gt gt gt days_of_month crontab_parser 31 1 parse 3 lg 4 F 10 23 16 19 22 25 28 31 gt gt gt months_of_year crontab_parser 12 1 parse 2 ie 3p By Te Sy 11 gt gt gt months_of_year crontab_parser 12 1 parse 2 12 2 2 4 6 8 10 12 The maximum possible expanded value returned is found by the formula max_ min_ 1 exception ParseException Raised by crontab_parser when the input can t be parsed crontab_parser parse spec celery schedules maybe_schedule s relative False class celery schedules schedule run_every None relative False nowfun None app human_seconds is due last_run_at Returns tuple of two items is_due next_time_to_run where next time to run is in seconds e g True 20 means the task should be run now and the next time to run is in 20 seconds False 12 means the task should be run in 12 seconds You can override this to decide the interval at runtime but keep in mind the value of CELERYBEAT MAX _LOOP_INTERVAL which decides the maximum number of seconds celerybea
425. mport task class X object task def add self x y return x y or with any task decorator from celery contrib methods import task_method class X object celery task filter task_method def add self x y return x y Note The task must use the new Task base class celery Task and the old base class using classmethods celery task Task celery task base Task This means that you have to use the task decorator from a Celery app instance and not the old API from celery import task BAD from celery task import task ALSO GOOD celery Celery celery task filter task_method def foo self pass ALSO GOOD from celery import current_app current_app task filter task_method def foo self pass 2 13 API Reference 277 Celery Documentation Release 3 0 25 Caveats e Automatic naming won t be able to know what the class name is The name will still be module_name task_name so two methods with the same name in the same module will collide so that only one task can run class A object task def add self x y return x y class B object task def add self x y return x y would have to be written as class A object task name A add def add self x y return x y class B object task name B add def add self x y return x y celery contrib methods task args kwargs class celery contr
426. mum number of seconds float or integer to wait between retries Default is 0 2 For example the default policy correlates to 2 3 User Guide 63 Celery Documentation Release 3 0 25 add apply_async 2 2 retry True retry_policy Maxeanbetisnes 3 Mintkervalmstanre 0 interval_step 0 2 imneervalmmax 0 2 the maximum time spent retrying will be 0 4 seconds It is set relatively short by default because a connection failure could lead to a retry pile effect if the broker connection is down e g many web server processes waiting to retry blocking other incoming requests Serializers Security The pickle module allows for execution of arbitrary functions please see the security guide Celery also comes with a special serializer that uses cryptography to sign your messages Data transferred between clients and workers needs to be serialized so every message in Celery has a content_type header that describes the serialization method used to encode it The default serializer is pickle but you can change this using the CELERY_TASK_SERIALIZER setting or for each individual task or even per message There s built in support for pickle JSON YAML and msgpack and you can also add your own custom serializers by registering them into the Kombu serializer registry see ref kombu guide serialization Each option has its advantages and disadvantages json JS
427. n is lost from celery import current_app Global pool pool current_app amgqp PublisherPool limit 10 def my_view request with pool acquire as publisher add apply_async 2 2 publisher publisher retry True 2 15 5 Change history for Celery 2 1 2 15 History 423 Celery Documentation Release 3 0 25 e 2 1 4 Fixes Documentation e 2 1 3 e 2 1 2 Fixes 2 1 1 Fixes News e 2 1 0 Important Notes News Fixes Experimental Documentation 2 1 4 release date 2010 12 03 12 00 P M CEST Fixes e Execution options to apply_async now takes precedence over options returned by active routers This was a regression introduced recently Issue 244 e celeryev curses monitor Long arguments are now truncated so curses doesn t crash with out of bounds errors Issue 235 e celeryd Channel errors occurring while handling control commands no longer crash the worker but are instead logged with severity error e SQLAIchemy database backend Fixed a race condition occurring when the client wrote the pending state Just like the Django database backend it does no longer save the pending state Issue 261 Issue 262 e Error email body now uses repr exception instead of str exception as the latter could result in Unicode decode errors Issue 245 e Error email timeout value is now configurable by using the EMATL TIM EOUT setting
428. n memory footprint and performance But please note that the default configuration is not optimized for time nor space see the Optimizing guide for more information Is Celery dependent on pickle Answer No Celery can support any serialization scheme and has built in support for JSON YAML Pickle and msgpack Also as every task is associated with a content type you can even send one task using pickle and another using JSON The default serialization format is pickle simply because it is convenient it supports sending complex Python objects as task arguments If you need to communicate with other languages you should change to a serialization format that is suitable for that You can set a global default serializer the default serializer for a particular Task or even what serializer to use when sending a single task instance 2 9 Frequently Asked Questions 175 Celery Documentation Release 3 0 25 Is Celery for Django only Answer No Celery does not depend on Django anymore To use Celery with Django you have to use the django celery package Do I have to use AMQP RabbitMQ Answer No You can also use Redis Beanstalk CouchDB MongoDB or an SQL database see Brokers These virtual transports may have limited broadcast and event functionality For example remote control commands only works with AMQP and Redis Redis or a database won t perform as well as an AMQP broker If you have strict reliabi
429. n rab bitmq redis or use forced execv for some other reason Pool now sets a current_process index attribute that can be used to create as many log files as there are processes in the pool e Canvas chord group chain no longer modifies the state when called Previously calling a chord group chain would modify the ids of subtasks so that gt gt gt c chord add s 2 2 add s 4 4 xsum s gt gt gt c gt gt gt c lt call again at the second time the ids for the tasks would be the same as in the previous invocation This is now fixed so that calling a subtask won t mutate any options e Canvas Chaining a chord to another task now works Issue 965 e Worker Fixed a bug where the request stack could be corrupted if relative imports are used Problem usually manifested itself as an exception while trying to send a failed task result NoneType does not have id attribute Fix contributed by Sam Cooke e Tasks can now raise Ignore to skip updating states or events after return Example from celery exceptions import Ignore task def custom_revokes if redis sismember tasks revoked custom_revokes request id raise Ignore 2 12 Change history 219 Celery Documentation Release 3 0 25 The worker now makes sure the request task stacks are not modified by the initial Task __call_ This would previously be a problem if a custom task class defined __call__ and also called
430. n which execution should occur must be represented by entries in all three of the day and month attributes For example if day_of_week is 0 and day_of_month is every seventh day only months that begin on Sunday and are also in the month_of_year attribute will have execution events Or day_of_week is 1 and day_of_month is 1 7 15 21 means every first and third monday of every month present in month_of_year is due last_run_at Returns tuple of two items is_due next_time_to_run where next time to run is in seconds See celery schedules schedule is_due for more information now remaining_delta last_run_at tz None Returns when the periodic task should run next as a timedelta remaining_estimate last_run_at Returns when the periodic task should run next as a timedelta class celery schedules crontab_parser max_ 60 min_ 0 Parser for crontab expressions Any expression of the form groups see BNF grammar below is accepted and expanded to a set of numbers These numbers represent the units of time that the crontab needs to run on digit sen QU 4 toe dow tee mainaa number digit dow 260 Chapter 2 Contents Celery Documeniation Release 3 0 25 steps number range number number numspec x range expr numspec steps groups expr expr The parser is a general purpose one useful for parsing hours minutes and day_of_week expressions Exa
431. nal keyword arguments for the executed task The return value of this handler is ignored Task rate_limit None Rate limit for this task type Examples None no rate limit 700 s hundred tasks a second 100 m hundred tasks a minute 100 h hundred tasks an hour Task request Get current request object Task retry args None kwargs None exc None throw True eta None countdown None max_retries None options Retry the task Parameters e args Positional arguments to retry with e kwargs Keyword arguments to retry with 238 Chapter 2 Contents Celery Documeniation Release 3 0 25 as as as as as as as as e exc Custom exception to report when the max restart limit has been exceeded de fault MaxRetriesExceededError If this argument is set and retry is called while an exception was raised sys exc_info is set it will attempt to reraise the current exception If no exception was raised it will raise the exc argument provided e countdown Time in seconds to delay the retry for e eta Explicit time and date to run the retry at must be a dat et ime instance e max_retries If set overrides the default retry limit e options Any extra options to pass on to meth apply_async e throw If this is False do not raise the Ret ryTaskError exception that tells the worker to mark the task as being retried Note that thi
432. ndled by the core weakref module class celery utils dispatch saferef BoundMethodWeakref target on_delete None Safe and reusable weak references to instance methods BoundMethodWeakref objects provide a mechanism for referencing a bound method without requiring that the method object itself which is normally a transient object is kept alive Instead the BoundMethodWeakref object keeps weak references to both the object and the function which together define the instance method key the identity key for the reference calculated by the class s calculate_key method applied to the target instance method deletion_methods sequence of callable objects taking single argument a reference to this object which will be called when either the target object or target function is garbage collected i e when this object becomes invalid These are specified as the on_delete parameters of safe_ref calls weak_self weak reference to the target object weak_func weak reference to the target function 390 Chapter 2 Contents Celery Documeniation Release 3 0 25 _all_instances class attribute pointing to all live BoundMethodWeakref objects indexed by the class s calcu late_key target method applied to the target objects This weak value dictionary is used to short circuit creation so that multiple references to the same object function pair produce the same BoundMethod Weakref instance classmethod calculate_key tar
433. nfigure a result backend The example project above already does that see the backend argument to Celery Let s look at some examples Groups A group calls a list of tasks in parallel and it returns a special result instance that lets you inspect the results as a group and retrieve the return values in order gt gt gt from celery import group gt gt gt from proj tasks import add gt gt gt group add s i i for i in xrange 10 get 6 12 14 16 18 0 2 4 6 8 10 e Partial group gt gt gt g group add s i for i in xrange 10 gt gt gt g 10 get ELGG ilp 12 43 14y 157 lo 17 187 19 Chains Tasks can be linked together so that after one task returns the other is called gt gt gt from celery import chain gt gt gt from proj tasks import add mul 2 2 Getting Started 31 Celery Documeniation Release 3 0 25 gt gt gt chain add s 4 4 mul s 8 get or a partial chain 2 4 8 gt gt gt g chain add s 4 mul s 8 gt gt gt g 4 get 64 Chains can also be written like this gt gt gt add s 4 4 mul s 8 get Chords A chord is a group with a callback gt gt gt from celery import chord gt gt gt from proj tasks import add xsum gt gt gt chord add s i i for i in xrange 10 xsum s get 90 A group chained to another task will be automatically converted to a chord gt gt gt grou
434. nfo 2 3 User Guide 55 Celery Documeniation Release 3 0 25 celery task def fetch_page url return myhttplib get url celery task def parse_page url page return myparser parse_document page celery task def store_page_info url info return PageInfo objects create url info Good def update_page_info url fetch_page gt parse_page gt store_page chain fetch_page s parse_page s store_page_info s url chain celery task def fetch_page url return myhttplib get url celery task def parse_page page return myparser parse_document page celery task ignore_result True def store_page_info info url PageInfo objects create url url info info Here I instead created a chain of tasks by linking together different subt ask s You can read about chains and other powerful constructs at Canvas Designing Workflows Performance and Sirategies Granularity The task granularity is the amount of computation needed by each subtask In general it is better to split the problem up into many small tasks than have a few long running tasks With smaller tasks you can process more tasks in parallel and the tasks won t run long enough to block the worker from processing other waiting tasks However executing a task does have overhead A message needs to be sent data may not be local etc So if the tasks are too fine grained the additional overhead may not be
435. ng revoke destination all reply False timeout 1 limit 0 Worker simply returns True gt gt gt from celery task control import revoke gt gt gt revoke 419e46eb cf6a 4271 86a8 442b7124132c reply True workerl True worker2 True e You can now add your own remote control commands Remote control commands are functions registered in the command registry Registering a com mand is done using celery worker control Panel register from celery task control import Panel Panel register def reset_broker_connection panel xkwargs panel consumer reset_connection return ok connection re established With this module imported in the worker you can launch the command using cel ery task control broadcast gt gt gt from celery task control import broadcast gt gt gt broadcast reset_broker_connection reply True workerl ok connection re established worker2 ok connection re established 2 15 History 453 Celery Documeniation Release 3 0 25 TIP You can choose the worker s to receive the command by using the destination argument gt gt gt broadcast reset_broker_connection destination workerl1 workerl ok connection re established e New remote control command dump_reserved Dumps tasks reserved by the worker waiting to be executed gt gt gt from cel
436. ng which resulted in the Errno 10 No child processes problem when detaching Fixed a possible DjangoUnicodeDecodeError being raised when saving pickled data to Django s mem cached cache backend Better Windows compatibility New version of the pickled field taken from http www djangosnippets org snippets 5S 13 New signals introduced task_sent task_prerun and task_postrun see celery signals for more infor mation TaskSetResult join caused TypeError when timeout None Thanks Jerzy Kozera Closes 31 views apply should return HittpResponse instance Thanks to Jerzy Kozera Closes 32 PeriodicTask Save conversion of run_every from int to timedelta to the class attribute instead of on the in stance 2 15 History 465 Celery Documentation Release 3 0 25 e Exceptions has been moved to celery exceptions but are still available in the previous module Try to rollback transaction and retry saving result if an error happens while setting task status with the database backend e jail refactored into celery execute ExecuteWrapper e views apply now correctly sets mime type to application json e views task_status now returns exception if state is RETRY e views task_status now returns traceback if state is FAILURE or RETRY e Documented default task arguments e Add a sensible __repr__ to ExceptionInfo for easier debugging e Fix documentation typo import map gt import dmap Thanks to mi
437. ng HTML coverage S nosetests with coverage3 The coverage output is then located in celery tests cover index html e celeryd New option version Dump version info and exit e celeryd mul1ti Tool for shell scripts to start multiple workers Some examples vel DEBUG celeryd multi start 10 1 INFO Q 1 3 images video Q 4 5 data Q default L 4 5 DEBUG 2 15 History 447 Celery Documentation Release 3 0 25 He qaQaQaaqaqn c get commands to start 10 workers with celeryd multi start 3 c 3 leryd n celerydl myhost c 3 leryd n celeryd2 myhost c 3 leryd n celeryd3 myhost c 3 start 3 named workers celeryd multi start image video data c 3 leryd n image myhost c 3 leryd n video myhost c 3 celeryd n data myhost c 3 ae ok QQ mM 4 qgqaaqanw c specify custom hostname celeryd multi start 2 n worker example com c 3 leryd n celerydl worker example com c 3 leryd n celeryd2 worker example com c 3 Additionl options are added to each celeryd but you can also modify the options for ranges of or single workers 3 workers Two with 3 processes and one with 10 processes celeryd multi start 3 c 3 c 1 10 leryd n celerydl myhost c 10 leryd n celeryd2 myhost c 3 leryd n celeryd3 myhost c 3 can also specify options for named workers celeryd multi start image video data c 3 c image 10
438. ng of processes that does not have terminal access Example usage from celery import task from celery contrib import rdb task def add x y result x y rdb set_trace lt s return result O ce o breakpoint set_trace sets a breakpoint at the current location and creates a socket you can telnet into to remotely debug your task The debugger may be started by multiple processes at the same time so rather than using a fixed port the debugger will search for an available port starting from the base port 6900 by default The base port can be changed using the environment variable CELERY_RDB_PORT By default the debugger will only be available from the local host to enable access from the outside you have to set the environment variable CELERY_RDB_HOST 170 Chapter 2 Contents Celery Documeniation Release 3 0 25 When the worker encounters your breakpoint it will log the following information INFO MainProcess Got task from broker tasks add d7261c71 4962 47e5 b342 24 4 8bedd20e8 WARNING PoolWorker 1 Remote Debugger 6900 Please telnet 127 0 0 1 6900 Type exit in session to continue 2011 01 18 14 25 44 119 WARNING PoolWorker 1 Remote Debugger 6900 Waiting for client If you telnet the port specified you will be presented with a pdb shell S telnet localhost 6900 Connected to localhost Escape character is gt opt devel demoa
439. ng that often affects newcomers The docs should probably use a list in examples as using a tuple for this doesn t even make sense Nonetheless there are many tutorials out there using a tuple and this change should be a help to new users Suggested by jsaxon cars Fixed a memory leak when using the thread pool Issue 486 Contributed by Kornelijus Survila The statedb was not saved at exit This has now been fixed and it should again remember previously revoked tasks when a statedb is enabled Adds EMAIL _USE_TLS to enable secure SMTP connections Issue 418 Contributed by Stefan Kjartansson Now handles missing fields in task messages as documented in the message format documentation Missing required field throws InvalidTaskError Missing args kwargs is assumed empty Contributed by Chris Chamberlin Fixed race condition in celery events state celerymon celeryev where task info would be removed while iterat ing over it Issue 501 The Cache Cassandra MongoDB Redis and Tyrant backends now respects the CELERY_RESULT_SERIALIZER Setting Issue 435 This means that only the database django sqlalchemy backends currently does not support using custom serializers Contributed by Steeve Morin Logging calls no longer manually formats messages but delegates that to the logging system so tools like Sentry can easier work with the messages Issue 445
440. ng the task decorator from models import User celery task def create_user username password User objects create username username password password There are also many options that can be set for the task these can be specified as arguments to the decorator celery task serializer json def create_user username password User objects create username username password password How do I import the task decorator The task decorator is available on your Celery instance if you don t know what that is then please read First Steps with Celery If you re using Django or are still using the old module based celery API then you can import the task decorator like this from celery import task task def add x y return x y Multiple decorators When using multiple decorators in combination with the task decorator you must make sure that the task deco rator is applied last which in Python oddly means that it must be the first in the list celery task decorator2 decoratorl def add x y return x y 2 3 User Guide 43 Celery Documeniation Release 3 0 25 Names Every task must have a unique name and a new name will be generated out of the function name if a custom name is not provided For example gt gt gt celery task name sum of two numbers gt gt gt def add x y return x y gt gt gt add name f wo numb
441. nregistered tasks You can specify subtasks even if you just have the name gt gt gt s subtask task_name args kwargs gt gt gt s delay The celery shell command now always adds the current directory to the module path The worker will now properly handle the pytz AmbiguousTimeError exception raised when an ETA countdown is prepared while being in DST transition Issue 1061 force_execv Now makes sure that task symbols in the original task modules will always use the correct app instance Issue 1072 AMQP Backend Now republishes result messages that have been polled using result ready and friends result get will not do this in this version Crontab schedule values can now wrap around This means that values like 11 1 translatesto 11 12 1 Contributed by Loren Abrams multi stopwait command now shows the pid of processes Contributed by Loren Abrams Handling of ETA countdown fixed when the CELERY_ENABLE_UTC setting is disabled Issue 1065 A number of uneeded properties were included in messages caused by accidentally passing Queue as_dict as message properties Rate limit values can now be float This also extends the string format so that values like 0 5 s works Contributed by Christoph Krybus Fixed a typo in the broadcast routing documentation Issue 1026 Rewrote confusing section about idempotence in the task user guide Fixed typo in the daemonization tutorial Issue 1055
442. ns 8k deletions 2 10 2 Important Notes Broadcast exchanges renamed The workers remote control command exchanges has been renamed a new pidbox name this is because the auto_delete flag on the exchanges has been removed and that makes it incompatible with earlier versions You can manually delete the old exchanges if you want using the celery amqp command previously called camgadm celery amqp exchange delete celeryd pidbox S celery amqp exchange delete reply celeryd pidbox Eventloop The worker is now running without threads when used with RabbitMQ AMQP or Redis as a broker resulting in e Much better overall performance e Fixes several edge case race conditions e Sub millisecond timer precision 2 10 What s new in Celery 3 0 Chiastic Slide 185 Celery Documeniation Release 3 0 25 e Faster shutdown times The transports supported are py amqp librabbitmgq redis and amqplib Hopefully this can be extended to include additional broker transports in the future For increased reliability the CELERY_FORCE_EXECV setting is enabled by default if the eventloop is not used New celery umbrella command All Celery s command line programs are now available from a single celery umbrella command You can see a list of subcommands and options by running S celery help Commands include e celery worker previously celeryd e celery beat previously celerybeat
443. ns an celery result EagerResult instance You can configure celery to always run tasks locally by setting the CELERY_ALWAYS_EAGER setting to True Now depends on anyjson 99 coverage using python coverage 3 0 0 3 20 release date 2009 06 25 08 42 PM CET New arguments to apply_async the advanced version of delay_task countdown and eta gt gt gt Run 10 seconds into the future gt gt gt res apply_async MyTask countdown 10 gt gt gt Run 1 day from noi gt gt gt res apply_async MyTask eta datetime now timedelta days 1 Now unlinks stale PID files Lots of more tests Now compatible with carrot gt 0 5 0 2 15 History 467 Celery Documentation Release 3 0 25 e IMPORTANT The subtask_ids attribute on the TaskSetResult instance has been removed To get this informa tion instead use gt gt gt subtask_ids subtask id for subtask in ts_res subtasks e Taskset run now respects extra message options from the task class e Task Add attribute ignore_result Don t store the status and return value This means you can t use the cel ery result AsyncResult to check if the task is done or get its return value Only use if you need the performance and is able live without these features Any exceptions raised will store the return value status as usual e Task Add attribute disable_error_emails to disable sending error emails for that task e Should now w
444. o fields None extra Information about this task suitable for on screen display merge state timestamp fields Merge with out of order event merge_rules RECEIVED name args kwargs retries eta expires How to merge out of order events Disorder is detected by logical ordering e g task received must have happened before a task failed event A merge rule consists of a state and a list of fields to keep from that state REC args means the name and args fields are always taken from the RECEIVED state and any values for these fields received before or after is simply ignored on_failed timestamp None fields Callback for the task failed event on_received timestamp None fields Callback for the task received event on_retried timestamp None fields Callback for the task ret ried event on_revoked timestamp None fields Callback for the task revoked event on_sent timestamp None fields Callback for the task sent event on_started timestamp None fields Callback for the task started event EIV ED name 2 13 API Reference 281 Celery Documentation Release 3 0 25 on_succeeded fimestamp None fields Callback for the task succeeded event on_unknown_event type timestamp None fields ready update state timestamp fields Update state from new event
445. o be that there was only a module based API and for backwards compatibility the old API is still there Celery always creates a special app that is the default app and this is used if no custom application has been instantiated The celery task module is there to accommodate the old API and should not be used if you use a custom app You should always use the methods on the app instance not the module based API For example the old Task base class enables many compatibility features where some may be incompatible with newer features such as task methods from celery task import Task OLD Task base class from celery import Task NEW base class The new base class is recommended even if you use the old module based API Breaking the chain While it s possible to depend on the current app being set the best practice is to always pass the app instance around to anything that needs it I call this the app chain since it creates a chain of instances depending on the app being passed The following example is considered bad practice from celery import current_app class Scheduler object def run self app current_app Instead it should take the app as an argument class Scheduler object def init self app self app app Internally Celery uses the celery app app_or_default function so that everything also works in the module based compatibility API from celery app import app_or_default
446. o necessary to call the celery security setup_security function Note that this will also disable all insucure serializers so that the worker won t accept messages with untrusted content types This is an example configuration using the auth serializer with the private key and certificate files located in etc ssl CELERY_SECURITY_KEY etc ssl private worker key CELERY_SECURITY_CERTIFICATE etc ssl certs worker pem CELERY_SECURITY_CERT_STORE etc ssl certs x pem from celery security import setup_security setup_security Note While relative paths are not disallowed using absolute paths is recommended for these files Also note that the auth serializer won t encrypt the contents of a message so if needed this will have to be enabled separately Intrusion Detection The most important part when defending your systems against intruders is being able to detect if the system has been compromised Logs Logs are usually the first place to look for evidence of security breaches but they are useless if they can be tampered with A good solution is to set up centralized logging with a dedicated logging server Acess to it should be restricted In addition to having all of the logs in a single place if configured correctly it can make it harder for intruders to tamper with your logs This should be fairly easy to
447. o now Now that you have read this document you should continue to the User Guide There s also an API reference if you are so inclined 2 2 5 Resources e Getting Help Mailing list IRC e Bug tracker e Wiki e Contributing e License Getting Help Mailing list For discussions about the usage development and future of celery please join the celery users mailing list 34 Chapter 2 Contents Celery Documeniation Release 3 0 25 IRC Come chat with us on IRC The celery channel is located at the Freenode network Bug tracker If you have any suggestions bug reports or annoyances please report them to our issue tracker at http github com celery celery issues Wiki http wiki github com celery celery Contributing Development of celery happens at Github http github com celery celery You are highly encouraged to participate in the development of celery If you don t like Github for some reason you re welcome to send regular patches Be sure to also read the Contributing to Celery section in the documentation License This software is licensed under the New BSD License See the LICENSE file in the top distribution directory for the full license text 2 3 User Guide Release 3 0 Date July 10 2014 2 3 1 Application e Main Name e Configuration e Laziness e Breaking the chain e Abstract Tasks The Celery library must be instantiated before use
448. ob TaskRequest object Tasks with an ETA are entered into the eta_schedule messages that can be immediately processed are moved directly to the ready_queue ScheduleConiroller The schedule controller is running the eta_schedule If the scheduled tasks eta has passed it is moved to the ready_queue otherwise the thread sleeps until the eta is met remember that the schedule is sorted by time Mediator The mediator simply moves tasks in the ready_queue over to the task pool for execution using celery worker job TaskRequest execute_using_pool TaskPool This is a slightly modified multiprocessing Pool It mostly works the same way except it makes sure all of the workers are running at all times If a worker is missing it replaces it with a new one 2 14 4 Task Messages e Message format e Extensions e Example message e Serialization 312 Chapter 2 Contents Celery Documeniation Release 3 0 25 Message format e task string Name of the task required e id string Unique id of the task UUID required e args list List of arguments Will be an empty list if not provided e kwargs dictionary Dictionary of keyword arguments Will be an empty dictionary if not provided e retries int Current number of times this task has been retried Defaults to 0 if not specified eta string ISO 8601 Estimated time of arrival This is the date and time in ISO 8601 format If not provided the message is not
449. of the full power of AMQP routing see the Routing Guide Remote Control If you re using RabbitMQ AMQP Redis or MongoDB as the broker then you can control and inspect the worker at runtime For example you can see what tasks the worker is currently working on celery A proj inspect active This is implemented by using broadcast messaging so all remote control commands are received by every worker in the cluster You can also specify one or more workers to act on the request using the dest ination option which is acomma separated list of worker host names celery A proj inspect active destination workerl example com If a destination is not provided then every worker will act and reply to the request The celery inspect command contains commands that does not change anything in the worker it only replies infor mation and statistics about what is going on inside the worker For a list of inspect commands you can execute celery A proj inspect help Then there is the celery control command which contains commands that actually changes things in the worker at runtime celery A proj control help For example you can force workers to enable event messages used for monitoring tasks and workers celery A proj control enable_events When events are enabled you can then start the event dumper to see what the workers are doing celery A proj events dump or you can start the curses interface
450. ogram continues This function will automatically install an atexit handler to release the lock at exit you can skip this by calling _create_pidlock instead Returns Pidfile Example pidlock create_pidlock var run app pid celery platforms detached logfile None pidfile None uid None gid None umask 0 workdir None fake False opts Detach the current process in the background daemonize Parameters e logfile Optional log file The ability to write to this file will be verified before the process is detached e pidfile Optional pidfile The pidfile will not be created as this is the responsibility of the child But the process will exit if the pid lock exists and the pid written is still running e uid Optional user id or user name to change effective privileges to e gid Optional group id or group name to change effective privileges to e umask Optional umask that will be effective in the child process 2 14 Internals 393 Celery Documentation Release 3 0 25 e workdir Optional new working directory e fake Don t actually detach intented for debugging purposes e opts Ignored Example from celery platforms import detached create_pidlock with detached logfile var log app log pidfile var run app pid uid nobody child process with b he pidfile is not locked pidlock create_pidlock var run app pid
451. oing Where to go from here If you want to learn more you should continue to the Next Steps tutorial and after that you can study the User Guide 2 2 4 Next Steps The First Steps with Celery guide is intentionally minimal In this guide I will demonstrate what Celery offers in more detail including how to add Celery support for your application and library This document does not document all of Celery s features and best practices so it s recommended that you also read the User Guide 24 Chapter 2 Contents Celery Documeniation Release 3 0 25 e Using Celery in your Application e Calling Tasks e Canvas Designing Workflows e Routing e Remote Control e Timezone e Optimization e What to do now Using Celery in your Application Our Project Project layout proj __init__ py celery py tasks py proj celery py from _ future__ import absolute_import from celery import Celery celery Celery proj celery broker amqp backend amqp include proj tasks Optional configuration see the application user guide celery conf update CELERY_TASK_RESULT_EXPIRES 3600 if name main__ celery start In this module you created our Ce le ry instance sometimes referred to as the app To use Celery within your project you simply import this instance e The broker argument specifies the URL of the broker to use See Choo
452. ol control control control control control control control control control lery worker control active_queues panel associated with each worker add_consumer panel queue exchange None exchange_type None routing_key None options autoscale panel max None min None cancel_consumer panel queue None _ disable_events panel dump_active panel safe False kwargs dump_conf panel kwargs dump_reserved panel safe False kwargs dump_revoked panel kwargs dump_schedule panel safe False kwargs dump_tasks panel taskinfoitems None kwargs enable events panel heartbeat panel ping panel kwargs pool_grow panel n 1 kwargs pool_restart panel modules None reload False reloader None kwargs pool_shrink panel n 1 kwargs rate_limit panel task_name rate_limit kwargs Set new rate limit for a task type See celery tas Parameters e task_name Type of task e rate_limit New rate limit lery worker control lery worker control Revoke task by task id lery worker control lery worker control lery worker control celery worker state k base Task rate_limit report panel revoke panel task_id terminate False signal None kwargs shutdown panel msg Got shutdown from remote kwargs Stats panel kwargs time_limit panel task_name None hard None soft None kwar
453. on or has exceeded the retry limit The result attribute then contains the exception raised by the task SUCCESS The task executed successfully The result attribute then contains the tasks return value AsyncResult status The tasks current state Possible values includes PENDING The task is waiting for execution STARTED The task has been started RETRY The task is to be retried possibly because of failure FAILURE The task raised an exception or has exceeded the retry limit The result attribute then contains the exception raised by the task SUCCESS The task executed successfully The result attribute then contains the tasks return value AsyncResult successful Returns True if the task executed successfully AsyncResult supports_native_join AsyncResult task_id AsyncResult traceback Get the traceback of a failed task 2 13 API Reference 253 Celery Documentation Release 3 0 25 AsyncResult wait timeout None propagate True interval 0 5 Wait until task is ready and return its result Warning Waiting for tasks within a task may lead to deadlocks Please read Avoid launching synchronous subtasks Parameters e timeout How long to wait in seconds before the operation times out e propagate Re raise exception if the task failed e interval Time to wait in seconds before retrying to retrieve the result Note that this does not have any effect when using the amqp result
454. on is dealt with by the Abort ableTask implementation Usage example In the consumer from celery contrib abortable import AbortableTask from celery utils log import get_task_logger logger get_logger __name__ class MyLongRunningTask AbortableTask 270 Chapter 2 Contents Celery Documeniation Release 3 0 25 def run self x xkwargs results for x in xrange 100 Check after every altern vely check when some timer is due is_aborted xkwargs t the aborted status and terminate gracefully logger warning Task aborted return y do_something_expensive x results append y logger info Task finished return results In the producer from myproject tasks import MyLongRunningTask def myview request async_result MyLongRunningTask delay async_result is of type AbortableAsyncResul Aft After 10 fte 10 seconds abort the task time sleep 10 async_result abort After the async_result abort call the task execution is not aborted immediately In fact it is not guaranteed to abort at all Keep checking the async_result status or call async_result wait to have it block until the task is finished Note In order to abort tasks there needs to be communication between the producer and the consumer This is currently implemented through the database backend Therefore this class will only work with the database backends class celery c
455. on_decode_error accept None add_queue queue Add a queue to the list of queues to consume from This will not start consuming from the queue for that you will have to call consume after add_queue_from_dict queue options This method is deprecated Instead please use consumer add_queue Queue from_dict d auto_declare True callbacks None cancel End all active queue consumers This does not affect already delivered messages but it does mean the server will not send any more messages for this consumer cancel_by queue queue Cancel consumer by queue name channel None close End all active queue consumers This does not affect already delivered messages but it does mean the server will not send any more messages for this consumer connection 2 14 Internals 357 Celery Documentation Release 3 0 25 consume no_ack None Start consuming messages Can be called multiple times but note that while it will consume from new queues added since the last call it will not cancel consuming from removed queues use cance1l_by_queue Parameters no_ack See no_ack consuming_from queue Returns True if the consumer is currently consuming from queue declare Declare queues exchanges and bindings This is done automatically at instantiation if auto_declare is set flow active Enable disable flow from peer This is a simple flow control mechanism that a peer
456. onal arguments to a particular broker transport e celeryd worker_pid is now part of the request info as returned by broadcast commands e TaskSet apply Taskset apply_async now accepts an optional taskset_id argument e The taskset_id if any is now available in the Task request context e SQLAIchemy result backend taskset_id and taskset_id columns now have a unique constraint Tables need to recreated for this to take affect e Task Userguide Added section about choosing a result backend e Removed unused attribute AsyncResult uuid Fixes e multiprocessing Pool Fixes race condition when marking job with WorkerLostError Issue 268 The process may have published a result before it was terminated but we have no reliable way to detect that this is the case So we have to wait for 10 seconds before marking the result with WorkerLostError This gives the result handler a chance to retrieve the result e multiprocessing Pool Shutdown could hang if rate limits disabled There was a race condition when the MainThread was waiting for the pool semaphore to be re leased The ResultHandler now terminates after 5 seconds if there are unacked jobs but no worker processes left to start them it needs to timeout because there could still be an ack result that we haven t consumed from the result queue It is unlikely we will receive any after 5 seconds with no worker processes e celerybeat Now creates pidfile even if the de
457. one options kwargs client delete key get key implements_incr True incr key mget keys on_chord_apply group_id body result None kwargs servers None set key value supports_autoexpire True supports _native_join True class celery backends cache DummyClient args kwargs ce ce delete key args kwargs get key args kwargs get_multi keys incr key delta set key value args kwargs lery backends cache get_best_memcache args kwargs lery backends cache import_best_memcache celery backends amqp e celery backends amqp j 356 Chapter 2 Contents Celery Documeniation Release 3 0 25 celery backends amqp The AMQP result backend This backend publishes results as messages class celery backends amgp AMQPBackend connection None exchange None ex change_type None persistent None serializer None auto_delete True kwargs Publishes results by sending messages exception BacklogLimitExceeded Too much state history to fast forward class AMOPBackend Consumer channel queues None no_ack None auto_declare None call backs None on_decode_error None on_message None ac cept None Message consumer Parameters e channel see channel e queues see queues e no_ack see no_ack e auto_declare see auto_declare e callbacks see callbacks e on_message See on_message e on_decode_error see
458. onfiguration Configuration is easy set the transport and configure the location of your MongoDB database BROKER_URL mongodb localhost 27017 database_name Where the URL is in the format of mongodb userid password hostname port database_name The host name will default to Localhost and the port to 27017 and so they are optional userid and password are also optional but needed if your MongoDB server requires authentication Results If you also want to store the state and return values of tasks in MongoDB you should see MongoDB backend settings Using Amazon SQS Installation For the Amazon SQS support you have to install the boto library S pip install U boto Configuration You have to specify SQS in the broker URL BROKER_URL sqs ABCDEFGHIJKLMNOPORST ZYXK7NiynG1TogH8Nj P 9n1lE73sq3 where the URL format is sqs aws_access_key_id aws_secret_access_key you must remember to include the at the end The login credentials can also be set using the environment variables AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY in that case the broker url may only be sqs 2 2 Getting Started 15 Celery Documentation Release 3 0 25 Note If you specify AWS credentials in the broker URL then please keep in mind that the secret access key may contain unsafe characters that needs to be URL encoded Options Region The default region is us e
459. ontrib abortable AbortableAsyncResult id backend None task_name None app None parent None Represents a abortable result Specifically this gives the AsyncResult a abort method which sets the state of the underlying Task to ABORTED abort Set the state of the task to ABORTED Abortable tasks monitor their state at regular intervals and terminate execution if so Be aware that invoking this method does not guarantee when the task will be aborted or even if the task will be aborted at all is_aborted Returns True if the task is being aborted class celery contrib abortable AbortableTask A celery task that serves as a base class for all Task s that support aborting during execution 2 13 API Reference 271 Celery Documentation Release 3 0 25 All subclasses of Abort ableTask must call the is_aborted method periodically and act accordingly when the call evaluates to True classmethod AsyncResult task_id Returns the accompanying AbortableAsyncResult instance backend lt celery backends cache CacheBackend object at 0x7fb767118c10 gt delivery mode 2 exchange_type direct is_aborted kwargs Checks against the backend whether this Abort ableAsyncResult is ABORTED Always returns False in case the task_id parameter refers to a regular non abortable Task Be aware that invoking this method will cause a hit in the backend for example a database query so find a good b
460. ore informa tion The previous syntax is still supported but will be deprecated in version 1 4 e TaskSet failed result was incorrect See issue 132 e Now creates different loggers per task class See issue 129 e Missing queue definitions are now created automatically You can disable this using the CELERY_CREATE_MISSING_QUEUES setting The missing queues are created with the following options 444 Chapter 2 Contents Celery Documeniation Release 3 0 25 CELERY_QUEUES name exchange name exchange_type direct routing_key name This feature is added for easily setting up routing using the Q option to celeryd celeryd Q video image See the new routing section of the User Guide for more information Routing Tasks e New Task option Task queue If set message options will be taken from the corresponding entry in CELERY_QUEUES exchange exchange_type and routing_key will be ignored e Added support for task soft and hard time limits New settings added CELERYD_TASK_TIME_LIMIT Hard time limit The worker processing the task will be killed and replaced with a new one when this is exceeded CELERYD_TASK_SOFT_TIME_LIMI Soft time limit The Soft TimeLimitExceeded exception will be raised when this is exceeded The task can catch this to e g clean up before t
461. ork on Windows although running in the background won t work so using the detach argument results in an exception being raised e Added support for statistics for profiling and monitoring To start sending statistics start celeryd with the Statistics option Then after a while you can dump the results by running python manage py celerystats See celery monitoring for more information e The celery daemon can now be supervised i e it is automatically restarted if it crashes To use this start celeryd with the supervised option or alternatively S e views apply View calling a task Example http e com celery apply task_name argl arg2 kwargl a amp amp kwarg2 b Warning Use with caution Do not expose this URL to the public without first ensuring that your code is safe e Refactored celery task It s now split into three modules celery task Contains apply_async delay_task discard_all and task shortcuts plus imports objects from celery task base and celery task builtins celery task base Contains task base classes Task PeriodicTask TaskSet AsynchronousMapTask ExecuteRe mote Task celery task builtins Built in tasks PingTask DeleteExpiredTaskMetaTask 0 3 7 release date 2008 06 16 11 41 P M CET e IMPORTANT Now uses AMQP s basic consume instead of basic get This means we re no longer polling the broker for new messages e IMPORTANT Default concurrency limit i
462. own deadlock condition with pthread locking primitives when fork is com bined with threads You should enable this setting if you are experiencing hangs deadlocks especially in combination with time limits or having a max tasks per child limit This option will be enabled by default in a later version This is not a problem on Windows as it does not have fork CELERYD_WORKER_LOST_WAIT In some cases a worker may be killed without proper cleanup and the worker may have published a result before terminating This value specifies how long we wait for any missing results before raising a WorkerLostError exception Default is 10 0 CELERYD_MAX_TASKS_PER_CHILD Maximum number of tasks a pool worker process can execute before it s replaced with a new one Default is no limit CELERYD_TASK_TIME_LIMIT Task hard time limit in seconds The worker processing the task will be killed and replaced with a new one when this is exceeded CELERYD_TASK_SOFT_TIME_LIMIT Task soft time limit in seconds The SoftTimeLimitExceeded exception will be raised when this is exceeded The task can catch this to e g clean up before the hard time limit comes Example 2 4 Configuration and defaults 141 Celery Documentation Release 3 0 25 from celery exceptions import SoftTimeLimitExceeded celery task def mytask try return do_work except SoftTimeLimitExceeded cleanup_in_a_hurry CELERY_STORE_ERRORS_EVEN_I
463. p add s i i for i in xrange 10 xsum s get 90 Since these primitives are all of the subtask type they can be combined almost however you want e g gt gt gt upload_document s file group apply_filter s for filter in filters Be sure to read more about workflows in the Canvas user guide Routing Celery supports all of the routing facilities provided by AMQP but it also supports simple routing where messages are sent to named queues The CELERY_ROUTES setting enables you to route tasks by name and keep everything centralized in one location celery conf update CELERY_ROUTES prok tasksradaii Squewed Maar br You can also specify the queue at runtime with the queue argument to apply_async gt gt gt from proj tasks import add gt gt gt add apply_async 2 2 queue hipri You can then make a worker consume from this queue by specifying the Q option celery A proj worker Q hipri You may specify multiple queues by using a comma separated list for example you can make the worker consume from both the default queue and the hipri queue where the default queue is named celery for historical reasons 32 Chapter 2 Contents Celery Documeniation Release 3 0 25 celery A proj worker Q hipri celery The order of the queues doesn t matter as the worker will give equal weight to the queues To learn more about routing including taking use
464. passwords and secret tokens You should still check the output before pasting anything on the internet Connection URLs now ignore multiple tokens Worker statedb Now uses pickle protocol 2 Py2 5 Fixed Python 3 compatibility issues Worker A warning is now given if a worker is started with the same node name as an existing worker Worker Fixed a deadlock that could occur while revoking tasks Issue 1297 Worker The HUP handler now closes all open file descriptors before restarting to ensure file descriptors does not leak Issue 1270 Worker Optimized storing loading the revoked tasks list Issue 1289 After this change the st atedb file will take up more disk space but loading from and storing the revoked tasks will be considerably faster what before took 5 minutes will now take less than a second Celery will now suggest alternatives if there s a typo in the broker transport name e g ampq gt amqp Worker The auto reloader would cause a crash if a monitored file was unlinked Fix contributed by Agris Ameriks Fixed AsyncResult pickling error Fix contributed by Thomas Minor Fixed handling of Unicode in logging output when using log colors Issue 427 ConfigurationView is now a MutableMapping Contributed by Aaron Harnly Fixed memory leak in LRU cache implementation 210 Chapter 2 Contents Celery Documeniation Release 3 0 25 Fix contributed by Romuald Brunet ce
465. plications config uration For example config FOO 10 celery add_defaults config is the same as celery conf update config except that data will not be copied and that it will not be pickled when the worker spawns child processes In addition the method accepts a callable def initialize_config insert heavy stuff that can t be done at import time here celery add_defaults initialize_config which means the same as the above except that it will not happen until the celery configuration is actually used As an example Celery can lazily use the configuration of a Flask app flask_app Flask celery Celery celery add_defaults lambda flask_app config e Revoked tasks were not marked as revoked in the result backend Issue 871 Fix contributed by Hynek Schlawack e Eventloop now properly handles the case when the epoll poller object has been closed Issue 882 e Fixed syntax error in funtests test_leak py Fix contributed by Catalin Iacob e group chunks Now accepts empty task list Issue 873 e New method names Celery default_connection connection_or_acquire Celery default_producer producer_or_acquire The old names still work for backward compatibility 2 12 23 3 0 3 release date 2012 07 20 09 17 P M BST by Ask Solem e amaplib passes the channel object as part of the delivery_info and it s not pickleable so we now remove it 2 12 Change history 225
466. pp tasks py 128 add gt return result Pdb Enter help to get a list of available commands It may be a good idea to read the Python Debugger Manual if you have never used pdb before To demonstrate we will read the value of the result variable change it and continue execution of the task Pdb result 4 Pdb result hello from rdb Pdb continue Connection closed by foreign host The result of our vandalism can be seen in the worker logs 2011 01 18 14 35 36 599 INFO MainProcess Task tasks add d7261c71 4962 47e5 b342 2448bedd20e8 succeeded in 61 481s hello from rdb Tips Enabling the breakpoint signal If the environment variable CELERY_RDBS1IG is set the worker will open up an rdb instance whenever the SIGUSR2 signal is sent This is the case for both main and worker processes For example starting the worker with CELERY_RDBSIG 1 celery worker 1l info You can start an rdb session for any of the worker processes by executing kill USR2 lt pid gt 2 8 3 Task Cookbook e Ensuring a task is only executed one at a time j 2 8 Tutorials 171 Celery Documeniation Release 3 0 25 Ensuring a task is only executed one at a time You can accomplish this by using a lock In this example we ll be using the cache framework to set a lock that is accessible for all workers It s part of an imaginary RSS feed importer called djangofeeds The tas
467. pport Since version 2 3 there is support for automatic connection pools so you don t have to manually handle connec tions and publishers to reuse connections The connection pool is enabled by default since version 2 5 See the BROKER_POOL_LIMIT setting for more information You can handle the connection manually by creating a publisher results with add app pool acquire block True as connection with add get_publisher connection as publisher try for args in numbers res add apply_async 2 2 publisher publisher results append res print res get for res in results Though this particular example is much better expressed as a group 2 3 User Guide 65 Celery Documentation Release 3 0 25 gt gt gt from celery import group 8 8 16 16 gt gt gt numbers 2 2 4 4 n for i in numbers apply_async gt gt gt res group add subtask gt gt gt res get 4 8 16 32 Routing options Celery can route tasks to different queues Simple routing name lt gt name is accomplished using the queue option add apply_async queue priority high You can then assign workers to the priority high queue by using the workers Q argument celery worker l info Q celery priority high See also Hard coding queue names in code is not recommended the best practice is to use configuration routers CELERY_ROUTES To find out mor
468. products in the Amazon Web Services family could be a good candidate to store or publish results with but there is no such result backend included at this point Warning Do not use the amqp backend with SQS It will create one queue for every task and the queues will not be collected This could cost you money that would be better spent contributing an AWS result store backend back to Celery Using CouchDB Installation For the CouchDB support you have to install additional dependencies You can install both Celery and these dependencies in one go using either the celery with couchdb or the django celery with couchdb bundles pip install U celery with couchdb Configuration Configuration is easy set the transport and configure the location of your CouchDB database BROKER_URL couchdb localhost 5984 database_name Where the URL is in the format of couchdb userid password hostname port database_name The host name will default to Localhost and the port to 5984 and so they are optional userid and password are also optional but needed if your CouchDB server requires authentication Results Storing task state and results in CouchDB is currently not supported Limitations The CouchDB message transport does not currently support e Remote control commands celeryctl broadcast 2 2 Getting Started 17 Celery Documentation Release 3 0 25 Using Beanstalk Installation For the Beanstalk support
469. pter 2 Contents Celery Documeniation Release 3 0 25 News Celery now supports task retries See Retrying for more information We now have an AMOP result store backend It uses messages to publish task return value and status And it s incredibly fast See issue 6 for more info AMQP QoS prefetch count implemented This to not receive more messages than we can handle Now redirects stdout stderr to the celeryd log file when detached Now uses inspect getargspec to only pass default arguments the task supports Add Task on_success on_retry on_failure handlers See celery task base Task on_success celery task base Task on_retry celery task base Task on_failure celery utils gen_unique_id Workaround for http bugs python org issue4607 You can now customize what happens at worker start at process init etc by creating your own loaders see celery loaders default celery loaders djangoapp celery loaders Support for multiple AMQP exchanges and queues This feature misses documentation and tests so anyone interested is encouraged to improve this situation celeryd now survives a restart of the AMQP server Automatically re establish AMQP broker connection if it s lost New settings AMQP_CONNECTION_RETRY Set to True to enable connection retries AMQP_CONNECTION_MAX_RETRIES Maximum number of restarts before we give up Default 100 Fix an incompatibility between python daemon and multiprocessi
470. ption I include A comma separated list of task modules to be imported Example celeryd I appl tasks app2 tasks celeryd now emits a warning if running as the root user euid is 0 celery messaging establish_connection Ability to override defaults used using keyword ar gument defaults celeryd Now uses multiprocessing freeze_support so that it should work with py2exe PyInstaller cx_Freeze etc celeryd Now includes more metadata for the STARTED state PID and host name of the worker that started the task See issue 181 subtask Merge additional keyword arguments to subtask into task keyword arguments e g gt gt gt s subtask 1 2 foo bar baz 1 gt gt gt s args 1 2 gt gt gt s kwarg o0o par haz s I See issue 182 celeryd Now emits a warning if there is already a worker node using the same name running on the same virtual host AMQP result backend Sending of results are now retried if the connection is down T AMQP result backend result get Wait for next state if state is not in READY_STATES TaskSetResult now supports subscription 430 Chapter 2 Contents Celery Documeniation Release 3 0 25 gt gt gt res TaskSet tasks apply_async gt gt gt res 0 get Added Task send_error_emails Task error_whitelist so these can be configured per task instead of just by the global setting Added Task
471. ptional and defaults to the particular transports default value Note Note that the path component virtual_host always starts with a forward slash This is necessary to distinguish between the virtual host empty and which are both acceptable virtual host names 2 15 History 401 Celery Documentation Release 3 0 25 A virtual host of becomes amap guest guest localhost 5672 and a virtual host of empty becomes amqp guest guest localhost 5672 So the leading slash in the path component is always required In addition the BROKER_URL setting has been added as an alias to BROKER_HOST Any broker setting specified in both the URL and in the configuration will be ignored if a setting is not provided in the URL then the value from the configuration will be used as default Also programs now support the b broker option to specify a broker URL on the command line celeryd b redis localhost celeryctl b amqp guest guest localhost e The environment variable CEL broker used ERY_BROK ER_URL can also be used to easily override the default e The deprecated celery loaders setup_loader function has been removed e The CE LERY_TASK ERROR_WHIT The error mail sending logic is now available as Task 1 reference in celery utils mail ELIST setting has been replaced by a more flexible appro
472. qp Sending and receiving messages using Kombu e AMQP e Queues TaskPublisher AMQP class celery app amqp AM P app Connection Broker connection class used Default is kombu connection Connection Consumer Base Consumer class used Default is kombu compat Consumer queues All currently defined task queues A Queues instance 240 Chapter 2 Contents Celery Documeniation Release 3 0 25 Queues queues create_missing None ha_policy None Create new Queues instance using queue defaults from the current configuration Router queues None create_missing None Returns the current task router TaskConsumer Return consumer configured to consume from the queues we are configured for app amgp queues consume_from TaskProducer Returns publisher used to send tasks You should use app send_task instead flush_routes default_queue default_exchange publisher_pool router routes Queues class celery app amqp Queues queues None default_exchange None create_missing True ha_policy None Queue name declaration mapping Parameters e queues Initial list tuple or dict of queues e create_missing By default any unknown queues will be added automatically but if disabled the occurrence of unknown queues in wanted will raise KeyError e ha_policy Default HA policy for queues with none set add queue kwargs Add new queue Parameters e queue Name of
473. r Task methods now works with the CELERY_ALWAYS_EAGER setting Issue 1478 Broadcast queues were accidentally declared when publishing tasks Issue 1540 New C_FAKEFORK environment variable can be used to debug the init scripts Setting this will skip the daemonization step so that errors printed to stderr after standard outs are closed can be seen C_FAKEFORK etc init d celeryd start This works with the celery multi command in general get_pickleable_etype did not always return a value Issue 1556 Fixed bug where app GroupResult restore would fall back to the default app Fixed rare bug where built in tasks would use the current_app maybe_fileno now handles ValueError 2 12 3 3 0 23 release date 2013 09 02 01 00 PM BST Now depends on Kombu 2 5 14 send_task did not honor link and link_error arguments This had the side effect of chains not calling unregistered tasks silently discarding them Fix contributed by Taylor Nelson celery state Optimized precedence lookup Contributed by Matt Robenolt Posix Daemonization did not redirect sys stdin to dev null Fix contributed by Alexander Smirnov 2 12 Change history 207 Celery Documentation Release 3 0 25 2 1 2 1 2 1 e Canvas group bug caused fallback to default app when appl y_async used Issue 1516 e Canvas generator arguments was not always pickleable 2 4 3 0 22 release date 2013 08 16 16
474. r None The consumer used to consume broadcast commands cancel_task_queue queue close close_connection Closes the current broker connection and all open channels connection None The broker connection consume_messages sleep lt built in function sleep gt min lt built in function min gt Empty lt class Queue Empty gt Consume messages forever or until an exception is raised 2 14 Internals 323 Celery Documentation Release 3 0 25 event_dispatcher None A celery events EventDispatcher for sending events handle_invalid_task body message exc handle_unknown_message body message handle_unknown_task body message exc heart None The thread that sends event heartbeats at regular intervals The heartbeats are used by monitors to detect that a worker went offline disappeared hostname None The current hostname Defaults to the system hostname info Returns information about this consumer instance as a dict This is also the consumer related info returned by celeryctl stats init_callback None Optional callback to be called when the connection is established Will only be called once even if the connection is lost and re established initial_prefetch_count 0 Initial QoS prefetch count for the task channel maybe_conn_error fun Applies function but ignores any connection or channel errors raised maybe_shutdown on_control body message Process remo
475. r execution and they will be deleted from the messaging server Returns the number of tasks discarded Control enable_events destination None kwargs Tell all or specific workers to enable events Control inspect Control ping destination None timeout 1 kwargs Ping all or specific workers Returns answer from alive workers See broadcast for supported keyword arguments Control pool_grow n destination None kwargs Tell all or specific workers to grow the pool by n Supports the same arguments as broadcast Control pool_shrink n destination None kwargs Tell all or specific workers to shrink the pool by n Supports the same arguments as broadcast Control purge connection None Discard all waiting tasks This will ignore all tasks waiting for execution and they will be deleted from the messaging server Returns the number of tasks discarded 244 Chapter 2 Contents Celery Documeniation Release 3 0 25 Control rate_limit task_name rate_limit destination None kwargs Tell all or specific workers to set a new rate limit for task by type Parameters e task_name Name of task to change rate limit for e rate_limit The rate limit as tasks per second or a rate limit string 100 m etc see celery task base Task rate_limit for more information See broadcast for supported keyword arguments Control revoke task_id destination None terminate F
476. r sending messages It can also be used for non AMQP brokers but different implementation may not implement all commands You can write commands directly in the arguments to celery amqp or just start with no arguments to start it in shell mode celery amqp gt connecting to amqp guest localhost 5672 gt connected 1 gt Here 1 gt is the prompt The number 1 is the number of commands you have executed so far Type help for a list of commands available It also supports auto completion so you can start typing a command and then hit the tab key to show a list of possible matches Let s create a queue you can send messages to celery amgp 1 gt exchange declare testexchange direct ok 2 gt queue declare testqueue ok queue testqueue messages 0 consumers 0 3 gt queue bind testqueue testexchange testkey ok This created the direct exchange testexchange and a queue named testqueue The queue is bound to the exchange using the routing key testkey 2 3 User Guide 101 Celery Documentation Release 3 0 25 From now on all messages sent to the exchange testexchange with routing key test key will be moved to this queue You can send a message by using the basic publish command 4 gt basic publish This is a message testexchange testkey ok Now that the message is sent you can retrieve it again You can use the basic get command here which polls for new messages on the queue which is al
477. r there is a special subtask called chain that lets you chain tasks together 2 3 User Guide 73 Celery Documentation Release 3 0 25 gt gt gt from celery import chain gt gt gt from proj tasks import add mul 4 4 8 10 gt gt gt res chain add s 4 4 mul s 8 mul s 10 proj tasks add 4 4 proj tasks mul 8 proj tasks mul 10 Calling the chain will call the tasks in the current process and return the result of the last task in the chain gt gt gt res chain add s 4 4 mul s 8 mul s 10 gt gt gt res get 640 And calling apply_async will create a dedicated task so that the act of calling the chain happens in a worker gt gt gt res chain add s 4 4 mul s 8 mul s 10 apply_async gt gt gt res get 640 It also sets parent attributes so that you can work your way up the chain to get intermediate results gt gt gt res parent get 64 gt gt gt res parent parent get Q fo gt gt gt res parent parent lt AsyncResult eeaad925 6778 4ad1 88c8 b2a63d017933 gt Chains can also be made using the pipe operator gt gt gt add s 2 2 mul s 8 mul s 10 apply_async Graphs In addition you can work with the result graph as a DependencyGraph gt gt gt res chain add s 4 4 mul s 8 mul s 10 gt gt gt res parent parent graph 285fa253 fcf8 42ef 8k 5 007889 You can even convert these grap
478. ration file to get you started It should contain all you need to run a basic Celery set up Broker settings BROKER_URL amqp guest guest localhost 5672 List of modules to import when celery starts CELERY_IMPORTS myapp tasks Using the database to store task state and results CELERY_RESULT_BACKEND database CELERY_RESULT_DBURI sqlite mydatabase db CELERY_ANNOTATIONS tasks add rate_limit 10 s 2 4 Configuration and defaults 127 Celery Documentation Release 3 0 25 2 4 2 Configuration Directives Time and date settings CELERY_ENABLE_UTC New in version 2 5 If enabled dates and times in messages will be converted to use the UTC timezone Note that workers running Celery versions below 2 5 will assume a local timezone for all messages so only enable if all workers have been upgraded Enabled by default since version 3 0 CELERY_TIMEZONE Configure Celery to use a custom time zone The timezone value can be any time zone supported by the pyt z library pytz must be installed for the selected zone to be used If not set then the systems default local time zone is used Warning Celery requires the pyt z library to be installed when using custom time zones other than UTC You can install it using pip or easy_install S pip install pytz Pytz is a library that defines the timzones of the world it changes quite frequently so it
479. ration module As an example you can configure the default serializer used for serializing task payloads by changing the CELERY_TASK_SERIALIZER setting celery conf CELERY_TASK_SERIALIZER json If you are configuring many settings at once you can use update celery conf update CELERY_TASK_SERIALIZER json CELERY_RESULT_SERIALIZER json CELERY_TIMEZONE Europe Oslo CELERY_ENABLE_UTC True For larger projects using a dedicated configuration module is useful in fact you are discouraged from hard coding periodic task intervals and task routing options as it is much better to keep this in a centralized location and especially for libraries it makes it possible for users to control how they want your tasks to behave you can also imagine your SysAdmin making simple changes to the configuration in the event of system trouble You can tell your Celery instance to use a configuration module by calling the config_from_object method celery config_from_object celeryconfig This module is often called celeryconfig but you can use any module name A module named celeryconfig py must then be available to load from the current directory or on the Python path it could look like this celeryconfig py 2 2 Getting Started 23 Celery Documentation Release 3 0 25 BROKER_
480. recision A value of 0 8 means that when the ETA of a task is met it will take at most 0 8 seconds for the task to be moved to the ready queue Pool Supervisor did not release the semaphore This would lead to a deadlock if all workers terminated prematurely Added Python version trove classifiers 2 4 2 5 2 6 and 2 7 Tests now passing on Python 2 7 Task __reduce__ Tasks created using the task decorator can now be pickled setup py nose added to tests_require Pickle should now work with SQLAIchemy 0 5 x New homepage design by Jan Henrik Helmers http celeryproject org New Sphinx theme by Armin Ronacher http docs celeryproject org Fixed pending xref errors shown in the HTML rendering of the documentation Apparently this was caused by new changes in Sphinx 1 0b2 Router classes in CELERY_ROUTES are now imported lazily Importing a router class in a module that also loads the Celery environment would cause a circular dependency This is solved by importing it when needed after the environment is set up CELERY_ROUTES was broken if set to a single dict This example in the docs should now work again CELERY_ROUTES feed tasks import_feed feeds CREATE_MISSING_QUEUES was not honored by apply_async New remote control command stats Dumps information about the worker like pool process ids and total number of tasks executed by type Example r
481. red to the callable to be called after the safe reference goes out of scope with the reference object either a weakref ref ora BoundMethodWeakref as argument celery platforms e celery platforms j celery platforms Utilities dealing with platform specifics signals daemonization users groups and so on class celery platforms DaemonContext pidfile None workdir None umask None fake False after_chdir None kwargs close args 2 14 Internals 391 Celery Documentation Release 3 0 25 open redirect_to_null fd exception celery platforms LockFailed Raised if a pidlock can t be acquired celery platforms PIDFile alias of Pidfile class celery platforms Pidfile path Pidfile This is the type returned by create_pidlock TIP Use the create_pidlock function instead which is more convenient and also removes stale pidfiles when the process holding the lock is no longer running acquire Acquire lock is_locked Returns true if the pid lock exists path None Path to the pid lock file read_pid Reads and returns the current pid release args Release lock remove Removes the lock remove_if_ stale Removes the lock if the process is not running does not respond to signals write _pid class celery platforms Signals Convenience interface to signals If the requested signal is not supported on the current platform the operation will be ignored
482. redirect_stdouts False redirect_level WARNING col orize None setup_handlers logger logfile format colorize formatter lt class cel ery utils log ColorFormatter gt kwargs setup_logger name celery args kwargs Deprecated No longer used setup_logging_subsystem loglevel None logfile None format None colorize None kwargs 2 13 API Reference 247 Celery Documentation Release 3 0 25 setup_task_loggers loglevel None logfile None format None gate False kwargs Setup the task logger If logfile is not specified then sys stderr is used Returns logger object supports_color colorize None logfile None class celery app log TaskFormatter fmt None use_color True format record 2 13 10 celery app utils colorize None propa celery app utils App utilities Compat settings bugreport tool pickling apps class celery app utils AppPickler Default application pickler unpickler build_kwargs args e celery app utils j build_standard_kwargs main changes loader backend amqp events log control ac cept_magic_kwargs config_source None construct cls kwargs prepare app kwargs celery app utils BUGREPORT_INFO nsoftware gt celery celery_v s kombu kombu_v s py py_v s n billiard Format used to generate bugreport information class celery app utils Settings changes defaults Celery settings object BROKER_B
483. rency Execution pool implementations processes eventlet gevent threads e celery db 306 Chapter 2 Contents Celery Documeniation Release 3 0 25 Database models for the SQLAIchemy database result backend should be moved into celery backends database e celery events Sending and consuming monitoring events also includes curses monitor event dumper and utilities to work with in memory cluster state e celery execute trace How tasks are executed and traced by the worker and in eager mode e celery security Security related functionality currently a serializer using cryptographic digests e celery task single mode interface to creating tasks and controlling workers e celery tests The unittest suite e celery utils Utility functions used by the celery code base Much of it is there to be compatible across Python versions e celery contrib Additional public code that doesn t fit into any other namespace 2 14 2 Celery Deprecation Timeline e Removals for version 4 0 Old Task API Compat Task Modules TaskSet x Magic keyword arguments Task attributes celery result celery loader Modules to Remove Settings BROKER Settings REDIS Result Backend Settings x Logging Settings Other Settings e Removals for version 2 0 Removals for version 4 0 Old Task API Compat Task Modules 2 14 Internals 307 Celery Documeniation Release 3 0 25 e Module celery decorators will b
484. reserving history only and theoretically someone could provide patches for these if they depend on a series that is no longer officially supported An archived version is named X Y archived Our currently archived branches are e 2 1 archived e 2 0 archived e 1 0 archived Feature branches Major new features are worked on in dedicated branches There is no strict naming requirement for these branches Feature branches are removed once they have been merged into a release branch 2 6 6 Tags Tags are used exclusively for tagging releases A release tag is named with the format vX Y 2Z e g v2 3 1 Experimental releases contain an additional identifier vX Y Z id e g v3 0 0 rc1 Experimental tags may be removed after the official release 2 6 7 Working on Features amp Patches Note Contributing to Celery should be as simple as possible so none of these steps should be considered mandatory You can even send in patches by email if that is your preferred work method We won t like you any less any contribution you make is always appreciated However following these steps may make maintainers life easier and may mean that your changes will be accepted sooner Forking and setting up the repository First you need to fork the Celery repository a good introduction to this is in the Github Guide Fork a Repo After you have cloned the repository you should checkout your copy to a directory on your machine S git clone g
485. result task_id meta state The backend interface is private and the terminology outdated so better to move this to Task so it can be used timer2 Set selfrunning False in stop so it won t try to join again on subsequent calls to stop Log colors are now disabled by default on Windows celery platform renamed to celery plat forms so it doesn t collide with the built in plat form module Exceptions occurring in Mediator Pool callbacks are now caught and logged instead of taking down the worker Redis result backend Now supports result expiration using the Redis EXPIRE command unit tests Don t leave threads running at tear down celeryd Task results shown in logs are now truncated to 46 chars Task __name__ is now an alias to self __class__ __name__ This way tasks introspects more like regular functions Task retry Now raises TypeError if kwargs argument is empty See issue 164 2 15 History 431 Celery Documentation Release 3 0 25 timedelta_seconds Use timedelta total_seconds if running on Python 2 7 TokenBucket Generic Token Bucket algorithm celery events state Recording of cluster state can now be paused and resumed including support for buffering State freeze buffer True Pauses recording of the stream If buffer is true events received while being frozen will be buffered and may be replayed later State thaw replay True Resumes recording of the stream If repl
486. right for maintainence tasks for services you d want to use basic consume instead Pop a message off the queue 5 gt basic get testqueue body This is a message delivery_info delivery_tag 1 exchange u testexchange message_count 0 redelivered False routing_key u testkey properties AMOP uses acknowledgment to signify that a message has been received and processed successfully If the message has not been acknowledged and consumer channel is closed the message will be delivered to another consumer Note the delivery tag listed in the structure above Within a connection channel every received message has a unique delivery tag This tag is used to acknowledge the message Also note that delivery tags are not unique across connec tions so in another client the delivery tag 7 might point to a different message than in this channel You can acknowledge the message you received using basic ack 6 gt basic ack 1 ok To clean up after our test session you should delete the entities you created 7 gt queue delete testqueu ok 0 messages deleted 8 gt exchange delete testexchang ok Routing Tasks Defining queues In Celery available queues are defined by the CELERY_QUEUES setting Here s an example queue configuration with three queues One for video one for images and one default queue for everything else
487. rkers child processes are functioning There was a greater chance of this bug occurring with maxtasksperchild ora time limit enabled This is a workaround for http bugs python org issue6721 msg140215 Be aware that while this fixes the logging library lock there could still be other locks initialized in the parent process introduced by custom code Fix contributed by Harm Verhagen e AMQP Result backend Now expires results by default The default expiration value is now taken from the CELERY_TASK_RESULT_EXPIRES setting The old CELERY_AMOP_TASK_RESULT_EXPIRES setting has been deprecated and will be re moved in version 4 0 Note that this means that the result backend requires RabbitMQ 1 1 0 or higher and that you have to disable expiration if you are running with an older version You can do so by disabling the CELERY_TASK_RESULT_EXPIRES setting CELERY_TASK_RESULT_EXPIRES None e Eventlet Fixed problem with shutdown Issue 457 e Broker transports can be now be specified using URLs The broker can now be specified as an URL instead This URL must have the format transport user password hostname port virtual_host for example the default broker is written as amqp guest guest localhost 5672 The scheme is required so that the host is identified as an URL and not just a host name User password port and virtual_host are o
488. rm request POST request FILES if form is_valid comment form save Check spam asynchronously tasks spam_filter delay comment_id comment id remote_addr remote_addr return HttpResponseRedirect post get_absolute_url else form CommentForm context RequestContext request form form return render_to_response template_name context_instance context To filter spam in comments I use Akismet the service used to filter spam in comments posted to the free weblog platform Wordpress Akismet is free for personal use but for commercial use you need to pay You have to sign up to their service to get an API key To make API calls to Akismet I use the akismet py library written by Michael Foord blog tasks py import celery from akismet import Akismet from django core exceptions import ImproperlyConfigured from django contrib sites models import Site from blog models import Comment 2 3 User Guide 59 Celery Documentation Release 3 0 25 celery task def spam_filter comment_id remote_addr None logger spam_filter get_logger logger info Running spam filter for comment s comment_id comment Comment objects get pk comment_id current_domain Site objects get_current domain akismet Akismet settings AKISMET_KEY http s domain if not akismet verify_key raise ImproperlyConfigured Invalid AKISMET_KEY
489. route the tasks according to the run time see Routing Tasks Reserve one task at a time When using early acknowledgement default a prefetch multiplier of 1 means the worker will reserve at most one extra task for every active worker process When users ask if it s possible to disable prefetching of tasks often what they really want is to have a worker only reserve as many tasks as there are child processes But this is not possible without enabling late acknowledgements acknowledgements A task that has been started will be retried if the worker crashes mid execution so the task must be idempotent see also notes at Should I use retry or acks_late You can enable this behavior by using the following configuration options CELERY_ACKS_ LATE True CELERYD_PREFETCH MULTIPLIER ll e Rate Limits The system responsible for enforcing rate limits introduces some overhead so if you re not using rate limits it may be a good idea to disable them completely This will disable one thread and it won t spend as many CPU cycles when the queue is inactive Set the CELERY_DISABLE_RATE_LIMITS setting to disable the rate limit subsystem CELERY _DISABLE_RATE LIMITS True 3 RabbitMQ and other brokers deliver messages round robin so this doesn t apply to an active system If there is no prefetch limit and you restart the cluster there will
490. rrors but this file was not immediately released Issue 923 Fixes Jython compatibility billiard forking_enable was called by all pools not just the processes pool which would result in a useless warning if the billiard C extensions were not installed 2 12 20 3 0 6 release date 2012 08 17 11 00 PM BST e Now depends on kombu 2 4 0 e Now depends on billiard 2 7 3 12 e Redis Celery now tries to restore messages whenever there are no messages in the queue 222 Chapter 2 Contents Celery Documeniation Release 3 0 25 e Crontab schedules now properly respects CELERY_TIMEZONE setting It s important to note that crontab schedules uses UTC time by default unless this setting is set Issue 904 and django celery 150 e billiard enable_forking is now only set by the processes pool e The transport is now properly shown by celery report Issue 913 e The app argument now works if the last part is a module name Issue 921 e Fixed problem with unpickleable exceptions billiard 12 e Adds task_name attribute to EagerResult which is always None Issue 907 e Old Task class in celery task no longer accepts magic kwargs by default Issue 918 A regression long ago disabled magic kwargs for these and since no one has complained about it we don t have any incentive to fix it now e The inspect reserved control command did not work properly e Should now play better with static analyz
491. rses monitor displaying task and worker history You can inspect the result and traceback of tasks and it also supports some management commands like rate limiting and shutting down workers This monitor was started as a proof of concept and you probably want to use Flower instead Starting celery events You should see a screen like celery events is also used to start snapshot cameras see Snapshots S celery events camera lt camera class gt frequency 1 0 and it includes a tool to dump events to stdout S celery events dump For a complete list of options use help S celery events help RabbitMQ To manage a Celery cluster it is important to know how RabbitMQ can be monitored RabbitMQ ships with the rabbitmqctl 1 command with this you can list queues exchanges bindings queue lengths the memory usage of each queue as well as manage users virtual hosts and their permissions 2 3 User Guide 109 Celery Documentation Release 3 0 25 110 Chapter 2 Contents Celery Documeniation Release 3 0 25 Note The default virtual host is used in these examples if you use a custom virtual host you have to add the p argument to the command e g rabbitmqctl list_queues p my_vhost Inspecting queues Finding the number of tasks in a queue rabbitmqctl list_queues name messages messages_ready messages_unacknowledged Here messages_ready is the number of messages ready
492. rt submodule 2 6 9 Contacts This is a list of people that can be contacted for questions regarding the official git repositories PyPI packages Read the Docs pages If the issue is not an emergency then it is better to report an issue Committers Ask Solem github https github com ask twitter http twitter com asksol Mher Movsisyan github https github com mher Steeve Morin github https github com steeve twitter http twitter com steeve 2 6 Contributing 161 Celery Documeniation Release 3 0 25 Website The Celery Project website is run and maintained by Mauro Rocco github https github com fireantology twitter https twitter com fireantology with design by Jan Henrik Helmers web http www helmersworks com twitter http twitter com helmers 2 6 10 Packages celery git https github com celery celery CI http travis ci org celery celery PyPI http pypi python org pypi celery docs http docs celeryproject org kombu Messaging framework git https github com celery kombu CI http travis ci org celery kombu PyPI http pypi python org pypi kombu docs http kombu readthedocs org billiard Fork of multiprocessing containing improvements that will eventually be merged into the Python stdlib git https github com celery billiard PyPI http pypi python org pypi billiard 162 Chapter 2 Contents Celery Documeniation Release 3 0 25
493. rts of your app a custom Django test runner does the trick Celery provides a simple test runner but it s easy enough to roll your own if you have other things that need to be done http docs djangoproject com en dev topics testing defining a test runner For this example we ll use the djcelery contrib test_runner to test the add task from the Tasks examples in the Celery documentation To enable the test runner set the following settings 150 Chapter 2 Contents Celery Documeniation Release 3 0 25 H EST_RUNNER djcelery contrib test_runner CeleryTestSuiteRunner Then we can put the tests in a tests py somewhere from django test import TestCase from myapp tasks import add class AddTestCase TestCase def testNoError self Test that the add task runs with no errors and returns the correct result result add delay 8 8 self assertEquals result get 16 self assertTrue result successful This test assumes that you put your example add task in maypp tasks so adjust the import for wherever you put the class 2 6 Contributing 2 6 Contributing 151 Celery Documeniation Release 3 0 25 e Community Code of Conduct Be considerate Be respectful Be collaborative When you disagree consult others When you are unsure ask for help Step down considerately e Reporting a Bug Issue Trackers e Contributors
494. rved in memory However this is not dangerous as the broker will resend them to another worker when the channel is closed WARNING stop does not close the connection This is because some pre acked messages may be in processing and they need to be finished before the channel is closed For celeryd this means the pool must finish the tasks it has acked early then close the connection class celery worker consumer BlockingConsumer ready_queue init_callback lt function noop at Ox7fb768d6c848 gt send_events False hostname None _ initial_prefetch_count 2 pool None app None timer None controller None hub None amgheart beat None kwargs consume_messages class celery worker consumer Component parent kwargs Consumer w create w last True name consumer namespace worker class celery worker consumer Consumer ready_queue init_callback lt function noop at 0x7fb768d6c848 gt send_events False hostname None initial_prefetch_count 2 pool None app None timer None controller None hub None amqheart beat None kwargs Listen for messages received from the broker and move them to the ready queue for task processing Parameters e ready_queue See ready_queue timer See timer add_task_queue queue exchange None exchange_type None routing_key None options apply _eta_task task Method called by the timer to apply a task with an ETA countdown broadcast_consume
495. ry objects Leave blank if using built in serialization as our library properly sets content_encoding properties Message properties headers Message headers PERSISTENT_DELIVERY_MODE 2 TRANS IENT_DELIVERY_MODE 1 360 Chapter 2 Contents Celery Documeniation Release 3 0 25 attrs name None type None arguments None durable lt type bool gt passive lt type bool gt auto_delete False bind_to exchange routing_key arguments None nowait False kwargs Binds the exchange to another exchange Parameters nowait If set the server will not respond and the call will not block waiting for a response Default is False can_cache_ declaration declare nowait False passive None Declare the exchange Creates the exchange on the broker Parameters nowait If set the server will not respond and a response will not be waited for Default is False delete if_unused False nowait False Delete the exchange declaration on server Parameters e if unused Delete only if the exchange has no bindings Default is False e nowait If set the server will not respond and a response will not be waited for Default is False delivery_mode 2 durable True name passive False publish message routing_key None mandatory False immediate False exchange None Publish message Parameters e message M
496. ry worker Q default hostname x example com user y S celery worker Q default hostname y example com If you want you can even have your feed processing worker handle regular tasks as well maybe in times when there s a lot of work to do user z celery worker Q feed_tasks default hostname z example com If you have another queue but on another exchange you want to add just specify a custom exchange and exchange type from kombu import Exchange Queue CELERY_QUEUES Queue feed_tasks routing_key feed Queue regular_tasks routing_key task Queue image_tasks exchange Exchange mediatasks type direct routing_key image compress If you re confused about these terms you should read up on AMQP See also In addition to the AVQP Primer below there s Rabbits and Warrens an excellent blog post describing queues and exchanges There s also AMQP in 10 minutes Flexible Routing Model and Standard Exchange Types For users of RabbitMQ the RabbitMQ FAQ could be useful as a source of information AMQP Primer Messages A message consists of headers and a body Celery uses headers to store the content type of the message and its content encoding The content type is usually the serialization format used to serialize the message The body contains the name of the task to execute the task id UUID the arguments to apply it wi
497. ryconfig config_from_envvar variable_name silent False Read configuration from environment variable The value of the environment variable must be the name of a module to import gt gt gt os environ CELERY_CONFIG_MODULE myapp celeryconfig gt gt gt celery config_from_envvar CELERY_CONFIG_MODULE add_defaults d Add default configuration from dict d If the argument is a callable function then it will be regarded as a promise and it won t be loaded until the configuration is actually needed This method can be compared to gt gt gt celery conf update d with a difference that 1 no copy will be made and 2 the dict will not be transferred when the worker spawns child processes so it s important that the same configuration happens at import time when pickle restores the object on the other side start argv None Run celery using argv Uses sys argv if argv is not specified task fun Decorator to create a task class out of any callable Examples 2 13 API Reference 229 Celery Documentation Release 3 0 25 celery task def refresh_feed url return with setting extra options celery task exchange feeds def refresh_feed url return App Binding For custom apps the task decorator returns proxy objects so that the act of creating the task is not per formed until the task is used or the task registry is accessed If you ar
498. ryd All log messages now includes exc_info 2 1 1 release date 2010 10 14 02 00 P M CEST Fixes e Now working on Windows again Removed dependency on the pwd grp modules snapshots Fixed race condition leading to loss of events celeryd Reject tasks with an eta that cannot be converted to a time stamp See issue 209 concurrency processes pool The semaphore was released twice for each task both at ACK and result ready This has been fixed and it is now released only once per task e docs configuration Fixed typo CELERYD_TASK_SOFT_TIME_LIMIT gt CELERYD_TASK_SOFT_TIME_LIMIT See issue 214 control command dump_scheduled was using old info attribute celeryd multi Fixed set changed size during iteration bug occurring in the restart command 2 15 History 425 Celery Documentation Release 3 0 25 e celeryd Accidentally tried to use additional command line arguments News This would lead to an error like got multiple values for keyword argument concurrency Additional command line arguments are now ignored and does not produce this error However we do reserve the right to use positional arguments in the future so please do not depend on this behavior celerybeat Now respects routers and task execution options again celerybeat Now reuses the publisher instead of the connection Cache result backend Using float as the expires argument to cache set is depre
499. s twitter update TokenBucketQueue fill_rate 300 feed refresh Queue video compress TokenBucketQueue fill_rate 2 The get operation will iterate over these until one of the buckets is able to return an item The underlying datastructure is a dict so the order is ignored here Parameters task_registry The task registry used to get the task type class for a given task name 2 14 Internals 329 Celery Documentation Release 3 0 25 add_bucket_for_type fask_name Add a bucket for a task type Will read the tasks rate limit and create a TokenBucket Queue if it has one If the task doesn t have a rate limit Fast Queue will be used instead clear Delete the data in all of the buckets empty Returns True if all of the buckets are empty get block True timeout None Retrive the task from the first available bucket Available as in there is an item in the queue and you can consume tokens from it get_bucket_for_type task_name Get the bucket for a particular task type get_nowait init_with_registry Initialize with buckets for all the task types in the registry items Flattens the data in all of the buckets into a single list put request Put a Request into the appropiate bucket put_nowait request Put a Request into the appropiate bucket qsize Get the total size of all the queues refresh Refresh rate limits for all task types in the registry
500. s class celery worker Beat w beat False kwargs Component used to embed a celerybeat process This will only be enabled if the beat argument is set create w name beat namespace worker class celery worker EvLoop w kwargs create w include_if w name ey namespace worker 2 14 Internals 319 Celery Documentation Release 3 0 25 class celery worker Namespace name None app None This is the boot step namespace of the WorkController It loads modules from CELERYD_BOOT_STEPS and its own set of built in boot step modules builtin_boot_steps celery worker autoscale celery worker autoreload celery worker consumer celery work modules name worker class celery worker Pool w autoscale None autoreload False no_execv False kwargs The pool component Describes how to initialize the worker pool and starts and stops the pool during worker startup shutdown Adds attributes eautoscale pool emax_concurrency min_concurrency create w semaphore None max_restarts None name pool namespace worker on_poll_init pool w hub requires queues beat class celery worker Queues parent kwargs This component initializes the internal queues used by the worker create w name queues namespace worker requires ev celery worker RUN 1 Worker states
501. s If the remote call raised an exception then that exception will be re raised AsyncResult get_leaf AsyncResult graph AsyncResult id None The task s UUID AsyncResult info When the task has been executed this contains the return value If the task raised an exception this will be the exception instance AsyncResult iterdeps intermediate False AsyncResult parent None Parent result if part of a chain AsyncResult ready Returns True if the task has been executed If the task is still running pending or is waiting for retry then False is returned AsyncResult result When the task has been executed this contains the return value If the task raised an exception this will be the exception instance AsyncResult revoke connection None terminate False signal None Send revoke signal to all workers Any worker receiving the task or having reserved the task must ignore it Parameters 252 Chapter 2 Contents Celery Documeniation Release 3 0 25 e terminate Also terminate the process currently working on the task if any e signal Name of signal to send to process if terminate Default is TERM AsyncResult serializable AsyncResult state The tasks current state Possible values includes PENDING The task is waiting for execution STARTED The task has been started RETRY The task is to be retried possibly because of failure FAILURE The task raised an excepti
502. s celeryconfig py CELERY_ENABLE_UTC True CELERY_TIMEZONE Europe London Example 2 Using a configuration module from celery import Celery celery Celery import celeryconfig celery config_from_object celeryconfig Example 3 Using a configuration class object from celery import Celery celery Celery class Config CELERY_ENABLE_UTC True CELERY_TIMEZONE Europe London celery config_from_object Config config_from_envvar The Celery config_from_envvar takes the configuration module name from an environment variable For example to load configuration from a module specified in the environment variable named CELERY_CONFIG_MODULE GI import os from celery import Celery Set default configuration module name os environ setdefault CELERY_CONFIG_MODULE celeryconfig celery Celery celery config_from_envvar CELERY_CONFIG_MODUL Kal 38 Chapter 2 Contents Celery Documeniation Release 3 0 25 You can then specify the configuration module to use via the environment CELERY_CONFIG_MODULE celeryconfig prod celery worker 1 info Laziness The application instance is lazy meaning that it will not be evaluated until something is actually needed Creating a Celery instance will only do the following 1 Create a logical c
503. s Make task HTTP request and collect the task result Parameters e url The URL to request e method HTTP method used Currently supported methods are GET and POST e task_kwargs Task keyword arguments e logger Logger used for user system feedback dispatch Dispatch callback and return result http_headers 2 13 API Reference 257 Celery Documentation Release 3 0 25 make_request url method params Makes an HTTP request and returns the response timeout 5 user_agent celery 3 0 25 class celery task http HttpDispatchTask Task dispatching to an URL Parameters e url The URL location of the HTTP callback task e method Method to use when dispatching the callback Usually GET or POST e kwargs Keyword arguments to pass on to the HTTP callback url If this is set this is used as the default URL for requests Default is to require the user of the task to supply the url as an argument as this attribute is intended for subclasses method If this is set this is the default method used for requests Default is to require the user of the task to supply the method as an argument as this attribute is intended for subclasses accept_magic_kwargs False backend lt celery backends cache CacheBackend object at 0x7fb767118c10 gt delivery_mode 2 exchange_type direct method None name celery task http HttpDispatchTask rate_limit None request_stack
504. s fatal makeRecord _log log isEnabledFor addHan dler removeHandler 432 Chapter 2 Contents Celery Documeniation Release 3 0 25 Experimental e celeryd multi Added daemonization support celeryd multi can now be used to start stop and restart worker nodes celeryd multi start jerry elaine george kramer This also creates PID files and log files celeryd jerry pid celeryd jerry log To specify a location for these files use the pidfile and logfile arguments with the n format celeryd multi start jerry elaine george kramer logfile var log celeryd n log pidfile var run celeryd n pid Stopping celeryd multi stop jerry elaine george kramer Restarting The nodes will be restarted one by one as the old ones are shutdown celeryd multi restart jerry elaine george kramer Killing the nodes WARNING Will discard currently executing tasks celeryd multi kill jerry elaine george kramer See celeryd multi help for help e celeryd multi start command renamed to show celeryd multi start will now actually start and detach worker nodes To just generate the commands you have to use celeryd multi show e celeryd Added pidfile argument The worker will write its pid when it starts The worker will not be started if this file exists and the pid contained is still alive e Added generic init d script using celeryd multi http github com celery celery tree master extra
505. s celery task Task Deprecated Task base class Modern applications should use celery Task instead See also celery task base BaseTask 2 13 12 celery task base Deprecated e celery task base j celery task base The task implementation has been moved to celery app task This contains the backward compatible Task class used in the old API and shouldn t be used in new applications celery task base BaseTask alias of Task 250 Chapter 2 Contents Celery Documeniation Release 3 0 25 class celery task base PeriodicTask A periodic task is a task that adds itself to the CELERYBEAT_SCHEDULE setting class celery task base TaskType Meta class for tasks Automatically registers the task in the task registry except if the abstract attribute is set If no name attribute is provided then no name is automatically set to the name of the module it was defined in and the class name 2 13 13 celery result e celery result j celery result Task results state and groups of results class celery result AsyncResult id backend None task_name None app None parent None Query task state Parameters e id see id backend see backend exception TimeoutError Error raised for timeouts AsyncResult app None AsyncResult backend None The task result backend to use AsyncResult build_graph intermediate False AsyncResult children AsyncResult colle
506. s means the task will be marked as failed if the task raises an exception or successful if it returns Raises celery exceptions RetryTaskError To tell the worker that the task has been re sent for retry This always happens unless the throw keyword argument has been explicitly set to False and is considered normal operation Example gt gt gt task gt gt gt def tweet auth message twitter Twitter oauth auth try twitter post_status_update message except twitter FailWhale exc Retry in 5 minutes raise tweet retry countdown 60 x 5 exc exc Although the task will never return above as retry raises an exception to notify the worker we use return in front of the retry to convey that the rest of the block will not be executed k run args kwargs The body of the task executed by workers k s args kwargs S xa k gt subtask a k k send_error_emails False If enabled an email will be sent to ADMINS whenever a task of this type fails k serializer pickle The name of a serializer that are registered with kombu serialization registry Default is pickle k si args kwargs Si xa k gt subtask a k immutable True k soft_time_limit None Soft time limit Defaults to the CELERYD_TASK_SOFT_TIME_LIMIT setting k starmap it Creates a xstarmap task from it k store_errors_even_if_ignored False When enabled errors will be stored
507. s now set to the number of CPUs available on the system e IMPORTANT tasks register Renamed task_name argument to name so gt gt gt tasks register func task_name mytask has to be replaced with 468 Chapter 2 Contents Celery Documeniation Release 3 0 25 0 3 3 0 3 2 0 3 1 gt gt gt tasks register func name mytask The daemon now correctly runs if the pidlock is stale Now compatible with carrot 0 4 5 Default AMQP connection timeout is now 4 seconds AsyncResult read was always returning True Only use README as long_description if the file exists so easy_install doesn t break celery view JSON responses now properly set its mime type apply_async now has a connection keyword argument so you can re use the same AMQP connection if you want to execute more than one task Handle failures in task_status view such that it won t throw 500s Fixed typo AMQP_SERVER in documentation to AMQP_HOST Worker exception emails sent to administrators now works properly No longer depends on django so installing celery won t affect the preferred Django version installed Now works with PostgreSQL psycopg2 again by registering the PickledObject field celeryd Added detach option as an alias to daemon and it s the term used in the documentation from now on Make sure the pool and periodic task worker thread is terminated properly at exit So Ctrl C works again Now depends on python daemon Remo
508. s removing processes when the workload is low It s enabled by the autoscale option which needs two numbers the maximum and minimum number of pool processes autoscale AUTOSCALE Enable autoscaling by providing max_concurrency min_concurrency Example autoscale 10 3 always keep 3 processes but grow to 10 if necessary You can also define your own rules for the autoscaler by subclassing Autoscaler Some ideas for met rics include load average or the amount of memory available You can specify a custom autoscaler with the CELERYD_AUTOSCALER setting Queues A worker instance can consume from any number of queues By default it will consume from all queues defined in the CELERY_QUEUES setting which if not specified defaults to the queue named celery You can specify what queues to consume from at startup by giving a comma separated list of queues to the Q option celery worker l info Q foo bar baz 2 3 User Guide 85 Celery Documentation Release 3 0 25 If the queue name is defined in CELERY_QUEUES it will use that configuration but if it s not de fined in the list of queues Celery will automatically generate a new queue for you depending on the CELERY_CREATE_MISSING_QUEUES option You can also tell the worker to start and stop consuming from a queue at runtime using the remote control commands add_consumer
509. scheduled but will be executed asap e expires string ISO 8601 New in version 2 0 2 Expiration date This is the date and time in ISO 8601 format If not provided the message will never expire The message will be expired when the message is received and the expiration date has been exceeded Extensions Extensions are additional keys in the message body that the worker may or may not support If the worker finds an extension key it doesn t support it should optimally reject the message so another worker gets a chance to process it e taskset string The taskset this task is part of if any e chord subtask 2 14 Internals 313 Celery Documentation Release 3 0 25 New in version 2 3 Signifies that this task is one of the header parts of a chord The value of this key is the body of the cord that should be executed when all of the tasks in the header has returned e utc bool New in version 2 5 If true time uses the UTC timezone if not the current local timezone should be used e callbacks lt list gt subtask New in version 3 0 A list of subtasks to apply if the task exited successfully e errbacks lt list gt subtask New in version 3 0 A list of subtasks to apply if an error occurs while executing the task Example message This is an example invocation of the celery task PingTask task in JSON format id 4cc7438e afd4 4f8f a2f3 f 46567e7ca77 Cask celery task PingTask args
510. se date 2013 01 07 04 00 00 P M UTC Now depends on Kombu 2 5 py amap has replaced amaplib as the default transport gaining support for AMQP 0 9 and the RabbitMQ extensions including Consumer Cancel Notifications and heartbeats support for multiple connection URLs for failover Read more in the Kombu 2 5 changelog Now depends on billiard 2 7 3 19 Fixed a deadlock issue that could occur when the producer pool inherited the connection pool instance of the parent process The loader option now works again Issue 1066 celery umbrella command All subcommands now supports the workdir option Issue 1063 Groups included in chains now give GroupResults Issue 1057 Previously it would incorrectly add a regular result instead of a group result but now this works 4 4 4 8 16 8 gt gt gt res add s 2 2 group add s 4 add s 8 add s 16 gt gt gt res lt GroupResult aQdacf905 c704 499e b03a 8d445e6398f7 4346501c cb99 4ad8 8577 12256c7a22bl1 b12ead10 a622 4d44 86e9 3193a778f345 26c7a420 11f3 4b33 8fac 66cd3b62abfd gt Chains can now chain other chains and use partial arguments Issue 1057 Example 2 12 Change history 215 Celery Documentation Release 3 0 25 gt gt gt cl add s 2 add s 4 gt gt gt c2 add s 8 add s 16 gt gt gt c3 cl c2 8 2 4 8 4 16 gt gt gt assert c3 8 get 38 Subtasks can now be used with u
511. seBacke Mark a BaseBacke BaseBacke BaseBacke Prepare BaseBacke BaseBacke Prepare BaseBacke nd mark_as_ revoked task_id reason nd mark_as_started task_id meta task as started nd on_chord_apply group_id body result None countdown 1 kwargs nd on_chord_part_return task propagate True nd prepare_exception exc exception for serialization nd prepare_expires value type None nd prepare_value result value for storage nd process_cleanup Cleanup actions to do at the end of a task worker process BaseBacke Reload BaseBacke Reload BaseBacke Get the BaseBacke nd reload_group_result task_id group result even if it has been previously fetched nd reload_task_result task_id task result even if it has been previously fetched nd restore_group group_id cache True result of a group nd save_group group_id result Store the result and status of a task BaseBacke nd store_result task_id result status traceback None Store the result and status of a task 2 14 Internals 353 Celery Documentation Release 3 0 25 BaseBackend subpolling_interval None Time to sleep between polling each individual item in ResultSet iterate as opposed to the interval argu ment which is for each pass BaseBackend supports_autoexpire False If true the backend must automatically expire results The daily backend_cleanup periodic task wi
512. ses ak events OFF enable E to monitor this worker kk kk Queues kkKKKKK celery xchange celery direct binding celery KKK SSS 2012 06 08 16 23 51 078 WARNING MainProcess celery halcyon local has started The broker is the URL you specifed in the broker argument in our celery module you can also specify a different broker on the command line by using the b option Concurrency is the number of multiprocessing worker process used to process your tasks concurrently when all of these are busy doing work new tasks will have to wait for one of the tasks to finish before it can be processed The default concurrency number is the number of CPU s on that machine including cores you can specify a custom number using c option There is no recommended value as the optimal number depends on a number of factors but if your tasks are mostly I O bound then you can try to increase it experimentation has shown that adding more than twice the number of CPU s is rarely effective and likely to degrade performance instead 26 Chapter 2 Contents Celery Documeniation Release 3 0 25 Including the default multiprocessing pool Celery also supports using Eventlet Gevent and threads see Concur rency Events is an option that when enabled causes Celery to send monitoring messages events for actions occurring in the worker These can be used by monitor programs like celery events and Flower
513. sing a Broker for more information e The backend argument specifies the result backend to use It s used to keep track of task state and results While results are disabled by default I use the amqp backend here because I demonstrate how retrieving results work later you may want to use a different backend for your application They all have different strengths and weaknesses If you don t need results it s better to disable them Results can also be disabled for individual tasks by setting the task ignore_result True option See Keeping Results for more information 2 2 Getting Started 25 Celery Documeniation Release 3 0 25 e The include argument is a list of modules to import when the worker starts You need to add our tasks module here so that the worker is able to find our tasks proj tasks py from __future__ import absolute_import from proj celery import celery celery task def add x y return x y celery task def mul x y return x x y celery task def xsum numbers return sum numbers Starting the worker The celery program can be used to start the worker S celery worker app proj l info When the worker starts you should see a banner and some messages celery halcyon local v3 0 Chiastic Slide KKK K x xxx x Configuration KKK broker amgp guest localhost 5672 ee app __main__ 0x1012d8590 ak concurrency 8 proces
514. sing logs are now only emitted if the MP_LOG environment variable is set e The Celery instance can now be created with a broker URL celery Celery broker redis e Result backends can now be set using an URL Currently only supported by redis Example use CELERY_RESULT_BACKEND redis localhost 1 e Heartbeat frequency now every 5s and frequency sent with event The heartbeat frequency is now available in the worker event messages so that clients can decide when to consider workers offline based on this value e Module celery actors has been removed and will be part of cl instead e Introduces new celery command which is an entrypoint for all other commands The main for this command can be run by calling celery start e Annotations now supports decorators if the key startswith E g def debug_args fun wraps fun def _inner xargs xkwargs print ARGS r args return _inner CELERY_ANNOTATIONS tasks add call__ debug_args Also tasks are now always bound by class so that annotated methods end up being bound e Bugreport now available as a command and broadcast command Get it from a Python repl gt gt gt import celery gt gt gt print celery bugreport Using the celery command line program 194 Chapter 2 Contents Celery Documeniation Release 3 0 25 S celery report Get it
515. sing scheduled gt gt gt i scheduled workerl example com eta 2010 06 07 09 07 52 priority 0 request name tasks sleept rid 1a7980ea 8b19 rargs i VLIJ ask 413e 91d2 0b74 3844c4d kwargs eta 2010 06 07 09 07 53 priority 0 request name tasks sleeptask id 49661b9a aa22 4120 94b7 9ee8031d219d args 2 kwargs Note These are tasks with an eta countdown argument not periodic tasks 2 3 User Guide 89 Celery Documentation Release 3 0 25 Dump of reserved tasks Reserved tasks are tasks that has been received but is still waiting to be executed You can get a list of these using reserved gt gt gt 1 reserved workerl example com Additional Commands Remote shutdown This command will gracefully shut down the worker remotely gt gt gt celery control broadcast shutdown shutdown all workers gt gt gt celery control broadcast shutdown destination workerl example com Ping This command requests a ping from alive workers The workers reply with the string pong and that s just about it It will use the default one second timeout for replies unless you specify a custom timeout gt gt gt celery control ping timeout 0 5 workerl example com pong
516. sively Redis Priority support The message s priority field is now respected by the Redis transport by having multiple lists for each named queue The queues are then consumed by in order of priority The priority field is a number in the range of 0 9 where 0 is the default and highest priority The priority range is collapsed into four steps by default since it is unlikely that nine steps will yield more benefit than using four steps The number of steps can be configured by setting the priority_steps transport option which must be a list of numbers in sorted order gt gt gt BROKER_TRANSPORT_OPTIONS Tormloritvastepsa 0 2 4 6 8 9 Priorities implemented in this way is not as reliable as priorities on the server side which is why the feature is nicknamed quasi priorities Using routing is still the suggested way of ensuring quality of service as client implemented priorities fall short in a number of ways e g if the worker is busy with long running tasks has prefetched many messages or the queues are congested Still it is possible that using priorities in combination with routing can be more beneficial than using routing or priorities alone Experimentation and monitoring should be used to prove this Contributed by Germ n M Bravo Redis Now cycles queues so that consuming is fair This ensures that a very busy queue won t block messages from other queues and ensures that all queues have an eq
517. sk The built in utility used to daemonize the Celery worker service sets an insecure umask by default umask 0 This means that any files or directories created by the worker will end up having world writable permissions Special thanks to Red Hat for originally discovering and reporting the issue This version will no longer set a default umask by default so if unset the umask of the parent process will be used 2 12 2 3 0 24 release date 2013 10 11 04 40 P M BST 206 Chapter 2 Contents Celery Documeniation Release 3 0 25 Now depends on Kombu 2 5 15 Now depends on billiard version 2 7 3 34 AMQP Result backend No longer caches queue declarations The queues created by the AMQP result backend are always unique so caching the declarations caused a slow memory leak Worker Fixed crash when hostname contained Unicode characters Contributed by Daodao The worker would no longer start if the P solo pool was selected Issue 1548 Redis Cache result backends would not complete chords if any of the tasks were retried Issue 1401 Task decorator is no longer lazy if app is finalized AsyncResult Fixed bug with copy AsyncResult when no current_app available ResultSet Now properly propagates app when passed string id s Loader now ignores CELERY_CONF 1G_MODULE if value is empty string Fixed race condition in Proxy object where it tried to delete an attribute twice resulting in Att ributeErro
518. sk messages are converted to requests within the worker The request information is also available as the task s context the task request attribute 474 Chapter 2 Contents CHAPTER 3 Indices and tables e genindex e modindex e search 475 Celery Documentation Release 3 0 25 476 Chapter 3 Indices and tables Bibliography AOC1 Breshears Clay Section 2 2 1 The Art of Concurrency O Reilly Media Inc May 15 2009 ISBN 13 978 0 596 52153 0 477 Celery Documentation Release 3 0 25 478 Bibliography Python Module Index ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce ce cel cel cel cel cel ce ce ce ce ce backends backends Dins lery 228 lery lery lery lery lery lery lery lery lery lery lery lery lery lery lery lery lery lery lery lery lery lery lery lery lery lery lery lery ery _state 395 app 233 app abstract 367 app amqp 240 app annotations 367 app builtins 246 app control 242 app defaults 242 app log 247 app registry 246 app routes 368 app task 234 app utils 248 apps beat 284 apps worker 282 backends 352 amqp 356 base 352 cache 356 cassandra 365 database 355 database models 375 database session 376 mongodb 363 redis 364 backends backends backends backends
519. sk request children Contains the result instances of the subtasks the currently executing task has applied x AsyncResult children Returns the tasks dependencies as a list of AsyncResult ResultSet in stances x AsyncResult iterdeps Recursively iterates over the tasks dependencies yielding parent node tuples Raises IncompleteStream if any of the dependencies has not returned yet x AsyncResult graph A DependencyGraph of the tasks dependencies This can also be used to convert to dot format with open graph dot as fh result graph to_dot fh which can than be used to produce an image dot Tpng graph dot o graph png e A new special subtask called chain is also included gt gt gt from celery import chain 2 2 gt gt gt res chain add subtask 2 2 mul s Ee De dix apply_async gt gt gt res get 16 gt gt gt res parent get 32 gt gt gt res parent parent get 4 e Adds AsyncResult get_leaf Waits and returns the result of the leaf subtask That is the last node found when traversing the graph but this means that the graph can be dimensional only in effect a list 188 Chapter 2 Contents Celery Documeniation Release 3 0 25 e Adds subtask link subtask subtask link_error subtask Shortcut tos options setdefault link append subtask e Adds subtask flatten_links Returns a flattened list of all dependencies recur
520. so to choose one you need to consider the drawbacks of each individual backend For many tasks keeping the return value isn t even very useful so it s a sensible default to have Also note that result backends are not used for monitoring tasks and workers for that Celery uses dedicated event messages see Monitoring and Management Guide If you have a result backend configured you can retrieve the return value of a task 28 Chapter 2 Contents Celery Documeniation Release 3 0 25 gt gt gt res add delay 2 2 gt gt gt res get timeout 1 4 You can find the task s id by looking at the id attribute gt gt gt res id d6 b3aea2 fb9b 4ebc 8da4 848818db9114 You can also inspect the exception and traceback if the task raised an exception in fact result get will propa gate any errors by default gt gt gt res add delay 2 gt gt gt res get timeout 1 Traceback most recent call last File lt stdin gt line 1 in lt module gt File opt devel celery celery result py line 113 in get interval interval File opt devel celery celery backends amqp py line 138 in wait_for raise self exception_to_python meta result TypeError add takes exactly 2 arguments 1 given If you don t wish for the errors to propagate then you can disable that by passing the propagate argument gt gt gt res get propagate False 5 G TypeError add ly 2 argumen
521. ssue 615 The limit is set to the current recursion limit divided by 8 which is 125 by default To get or set the current recursion limit use sys getrecursionlimit and sys setrecursionlimit More information is now preserved in the pickleable traceback This has been added so that Sentry can show more details Contributed by Sean O Connor CentOS init script has been updated and should be more flexible Contributed by Andrew McFague MongoDB result backend now supports forget Contributed by Andrew McFague e task retry now re raises the original exception keeping the original stack trace Suggested by ojii The uid argument to daemons now uses initgroups to set groups to all the groups the user is a member of Contributed by Lukasz Oles celeryctl Added she11 command The shell will have the current_app celery and all tasks automatically added to locals celeryctl Added migrate command The migrate command moves all tasks from one broker to another Note that this is experimental and you should have a backup of the data before proceeding Examples 2 11 What s new in Celery 2 5 203 Celery Documentation Release 3 0 25 celeryctl migrate redis localhost amqp localhost celeryctl migrate amgp localhost vl amgp localhost v2 python manage py celeryctl migrate django redis e Routers can now override the exchange and rout ing_key used to create missing queues Is
522. st bindings command Lists the current or all available bindings depending on the broker transport used Heartbeat is now sent every 30 seconds previously every 2 minutes ResultSet join_native and iter_native is now supported by the Redis and Cache result backends This is an optimized version of join using the underlying backends ability to fetch multiple results at once Can now use SSL when sending error e mails by enabling the EMATL_USE_SSL setting events default_dispatcher Context manager to easily obtain an event dispatcher instance using the connection pool Import errors in the configuration module will not be silenced anymore ResultSet iterate Now supports the timeout propagate and interval arguments with_default_connection gt with default_connection TaskPool apply_async Keyword arguments callbacks and errbacks has been renamed to callback and errback and take a single scalar value instead of a list No longer propagates errors occurring during process cleanup Issue 365 Added TaskSetResult delete which will delete a previously saved taskset result Celerybeat now syncs every 3 minutes instead of only at shutdown Issue 382 Monitors now properly handles unknown events so user defined events are displayed Terminating a task on Windows now also terminates all of the tasks child processes Issue 384 celeryd I include option now always searches the current directory to import th
523. started Timer start Timer stop celery concurrency eventlet apply_target target args kwargs callback None ac cept_callback None getpid None 344 Chapter 2 Contents Celery Documeniation Release 3 0 25 celery concurrency geventt experimental i celery concurrency gevent j celery concurrency gevent gevent pool implementation class celery concurrency gevent Schedule args kwargs clear queue class celery concurrency gevent TaskPool args kwargs class Timer schedule None on_error None on_tick None max_interval None kwargs class Schedule args kwargs clear queue TaskPool Timer ensure_started TaskPool Timer start TaskPool Timer stop askPool grow n askPool is_green True askPool num_processes askPool on_apply target args None kwargs None callback None accept_callback None timeout None timeout_callback None _ askPool on_start askPool on_stop askPool rlimit_safe False askPool shrink n askPool signal_safe False class celery concurrency gevent Timer schedule None on_error None on_tick None max_interval None kwargs class Schedule args kwargs clear queue 2 14 Internals 345 Celery Documentation Release 3 0 25 Timer ensure_started Timer start Timer stop celery concurrency gevent apply_ timeout target args
524. store backend as it does not use polling Raises celery exceptions TimeoutError if timeout is not None and the result does not arrive within timeout seconds If the remote call raised an exception then that exception will be re raised celery result BaseAsyncResult alias of AsyncResult class celery result EagerResult id ret_value state traceback None Result that we know has already been executed forget get timeout None propagate True kwargs ready result The tasks return value revoke args kwargs state The tasks state status The tasks state supports _native_join task_name None traceback The traceback if the task failed wait timeout None propagate True kwargs class celery result GroupResult id None results None kwargs Like ResultSet but with an associated id This type is returned by group and the deprecated TaskSet meth celery task TaskSet apply_async method It enables inspection of the tasks state and return values as a single entity Parameters e id The id of the group e results List of result instances children 254 Chapter 2 Contents Celery Documeniation Release 3 0 25 delete backend None Remove this result if it was previously saved id None The UUID of the group classmethod restore id backend None Restore previously saved group result results None List iterator of results in the group save backend None Sa
525. store_errors_even_if_ignored so it can be changed per Task not just by the global setting The crontab scheduler no longer wakes up every second but implements remaining_estimate Optimization celeryd Store FAILURE result if the WorkerLostError exception occurs worker process disappeared celeryd Store FAILURE result if one of the TimeLimitExceeded exceptions occurs Refactored the periodic task responsible for cleaning up results The backend cleanup task is now only added to the schedule if CELERY_TASK_RESULT_EXPIRES is set If the schedule already contains a periodic task named celery backend_cleanup it won t change it so the behavior of the backend cleanup task can be easily changed The task is now run every day at 4 00 AM rather than every day since the first time it was run using crontab schedule instead of run_every Renamed celery task builtins DeleteExpiredTaskMetaTask gt celery task builtins backend_cleanup The task itself has been renamed from celery delete_expired_task_meta to cel ery backend_cleanup See issue 134 Implemented AsyncResult forget for sqla cache redis tyrant backends Forget and remove task result See issue 184 TaskSetResult join Added propagate True argument When set to False exceptions occurring in subtasks will not be re raised Added Task update_state task_id state meta as a shortcut to task backend store_
526. sue 577 By default this will always use the name of the queue but you can now have a router return exchange and routing_key keys to set them This is useful when using routing classes which decides a destination at runtime Contributed by Akira Matsuzaki e Redis result backend Adds support for a max_connections parameter It is now possible to configure the maximum number of simultaneous connections in the Redis connection pool used for results The default max connections setting can be configured using the CELERY_REDIS_MAX CONNECTIONS setting or it can be changed individually by RedisBackend max_connections int Contributed by Steeve Morin e Redis result backend Adds the ability to wait for results without polling Contributed by Steeve Morin e MongoDB result backend Now supports save and restore taskset Contributed by Julien Poissonnier e There s a new Security guide in the documentation e The init scripts has been updated and many bugs fixed Contributed by Chris Streeter e User tilde is now expanded in command line arguments e Can now configure CELERYCTL envvar in etc default celeryd While not necessary for operation celeryctl is used for the celeryd status command and the path to celeryctl must be configured for that to work The daemonization cookbook contains examples Contributed by Jude Nagurney e The MongoDB result backend can now use Replica Sets Contributed by Ivan Metzl
527. sult backend Support for memcached and Redis may be added later e Improved implementations of TaskSetResultjoin and AsyncResult wait An interval keyword argument have been added to both so the polling interval can be specified default interval is 0 5 seconds A propagate keyword argument have been added to result wait errors will be re turned instead of raised if this is set to False 2 15 History 421 Celery Documentation Release 3 0 25 Warning You should decrease the polling interval when using the database result backend as frequent polling can result in high database load e The PID of the child worker process accepting a task is now sent as a field with the task started event e The following fields have been added to all events in the worker class sw_ident Name of worker software e g celeryd sw_ver Software version e g 2 2 0 sw_sys Operating System e g Linux Windows Darwin e For better accuracy the start time reported by the multiprocessing worker process is used when calculating task duration Previously the time reported by the accept callback was used e celerybeat New built in daemonization support using the detach option e celeryev New built in daemonization support using the detach option e TaskSet apply_async Now supports custom publishers by using the publisher argument e Added CELERY_SEND_TASK_SENT_EVENT setting
528. sult backends iterate timeout None propagate True interval 0 5 Iterate over the return values of the tasks as they finish one by one Raises The exception if any of the tasks raised an exception join timeout None propagate True interval 0 5 Gathers the results of all tasks as a list in order Note This can be an expensive operation for result store backends that must resort to polling e g database You should consider using join_native if your backend supports it Warning Waiting for tasks within a task may lead to deadlocks Please see Avoid launching syn chronous subtasks Parameters e timeout The number of seconds to wait for results before the operation times out e propagate If any of the tasks raises an exception the exception will be re raised e interval Time to wait in seconds before retrying to retrieve a result from the set Note that this does not have any effect when using the amqp result store backend as it does not use polling Raises celery exceptions TimeoutError if timeout is not None and the operation takes longer than timeout seconds join_native timeout None propagate True interval 0 5 Backend optimized version of join New in version 2 2 Note that this does not support collecting the results for different task types using different backends This is currently only supported by the amqp Redis and cache result backends ready Did all of the tasks complet
529. super Because of problems the fast local optimization has been disabled and can only be enabled by setting the USE_FAST_LOCALS attribute Worker Now sets a default socket timeout of 5 seconds at shutdown so that broken socket reads do not hinder proper shutdown Issue 975 More fixes related to late eventlet gevent patching Documentation for settings out of sync with reality CELERY_TASK_PUBLISH_RETRY Documented as disabled by default but it was enabled by default since 2 5 as stated by the 2 5 changelog CELERY_TASK_PUBLISH_RETRY_POLICY The default max_retries had been set to 100 but documented as being 3 and the interval_max was set to 1 but documented as 0 2 The default setting are now set to 3 and 0 2 as it was originally documented Fix contributed by Matt Long Worker Log messages when connection established and lost have been improved The repr of a crontab schedule value of 0 should be Issue 972 Revoked tasks are now removed from reserved active state in the worker Issue 969 Fix contributed by Alexey Zatelepin gevent Now supports hard time limits using gevent Timeout Documentation Links to init scripts now point to the 3 0 branch instead of the development branch master Documentation Fixed typo in signals user guide Issue 986 instance app queues gt instance app amaqp queues Eventlet gevent The worker did not properly set the custom app
530. t can sleep between re checking the periodic task intervals So if you dynamically change the next run at value and the max interval is set to 5 minutes it will take 5 minutes for the change to take effect so you may consider lowering the value of CELERYBEAT_MAX_LOOP_INTERVAL if responsiveness is of importance to you Scheduler max interval variance 2 13 API Reference 261 Celery Documentation Release 3 0 25 The default max loop interval may vary for different schedulers For the default scheduler the value is 5 minutes but for e g the django celery database scheduler the value is 5 seconds maybe_make_aware dt now relative False remaining_estimate last_run_at seconds to_local dt tz utc_enabled 2 13 16 celery signals e celery signals j celery signals This module defines the signals Observer pattern sent by both workers and clients Functions can be connected to these signals and connected functions are called whenever a signal is called See Signals for more information 2 13 17 celery security e celery security j celery security Module implementing the signing message serializer celery security disable_untrusted_serializers whitelist None celery security setup_security allowed_serializers None key None cert None store None digest shal serializer json Setup the message signing serializer Disables
531. t gt release_local loc gt gt gt hasattr loc Eeoa With this function one can release Local objects as well as StackLocal objects However it is not possible to release data held by proxies that way one always has to retain a reference to the underlying local object in order to be able to release it New in version 0 6 1 celery utils timer2 e timer2 i timer2 Scheduler for Python functions class celery utils timer2 Entry fun args None kwargs None args cancel cancelled fun kwargs tref class celery utils timer2 Schedule max_interval None on_error None kwargs ETA scheduler class Entry fun args None kwargs None args cancel cancelled fun kwargs tref Schedule apply_ after msecs fun args kwargs priority 0 384 Chapter 2 Contents Celery Documeniation Release 3 0 25 sc sc sc sc sc Sc SG Sc sc Sc Sc SG sc SG hedule apply_at eta fun args kwargs priority 0 hedule apply entry entry hedule apply_ interval msecs fun args kwargs priority 0 hedule cancel tref hedule clear hedule empty Is the schedule empty hedule enter entry eta None priority 0 Enter function into the scheduler Parameters e entry Item to enter e eta Scheduled time as a datet ime datetime object e priority Unused hedule enter_after msecs entry priority 0 time lt built in function time gt hedule
532. t processes eventlet gevent blocking threads solo see note broker support amqp redis mongodb Workers have the ability to be remote controlled using a high priority broadcast message queue The commands can be directed to all or a specific list of workers Commands can also have replies The client can then wait for and collect those replies Since there s no central authority to know how many workers are available in the cluster there is also no way to estimate how many workers may send a reply so the client has a configurable timeout the deadline in seconds for replies to arrive in This timeout defaults to one second If the worker doesn t reply within the deadline it doesn t necessarily mean the worker didn t reply or worse is dead but may simply be caused by network latency or the worker being slow at processing commands so adjust the timeout accordingly In addition to timeouts the client can specify the maximum number of replies to wait for If a destination is specified this limit is set to the number of destination hosts Note The solo and threads pool supports remote control commands but any task executing will block any waiting control command so it is of limited use if the worker is very busy In that case you must increase the timeout waiting for replies in the client The broadcast function This is the client function used to send commands to the workers Some remote control commands also have
533. t Backend Settings Setting name Replace with BROKER_HOS BROKER_URL BROKER_POR BROKER_UR ER_USER BROKER_UR BROKER_PASSWORD BROKER_UR BROKER_VHOST BROKER_UR BROKER_INSIST no alternative Setting name Replace with CELERY_REDIS_HOST CELERY_RESULT_BACKEND CELERY_REDIS_PORT CELERY_RESULT_BACKEND CELERY_REDIS_DB CELERY_RESULT_BACKEND CELERY_REDIS_PASSWORD CELERY_RESULT_BACKEND REDIS_HOST CELERY_RESULT_BACKEND REDIS_PORT CELERY_RESULT_BACKEND REDIS_DB CELERY_RESULT_BACKEND REDIS_PASSWORD CELERY_RESULT_BACKEND 310 Chapter 2 Contents Celery Documeniation Release 3 0 25 Setting name Replace with CELERYD_LOG_LEVEL loglevel CELERYD_LOG_FILE logfile Logging Settings CELERYBEAT_LOG_LEVEL loglevel CELERYBEAT_LOG_FILE loglevel CELERYMON_LOG_LEVEL loglevel CELERYMON_LOG_FILE loglevel Setting name Replace with Other Settings CELERY_TASK_ERROR_WITELIST Annotate Task ErrorMail CELERY_AMOQP_TASK_RESULT_EXPIRES CELERY_TASK_RESULT_EXPIRES Removals for version 2 0 The following settings will be removed Setting n
534. t ach option is not set 412 Chapter 2 Contents Celery Documeniation Release 3 0 25 eventlet gevent The broadcast command consumer is now running in a separate greenthread This ensures broadcast commands will take priority even if there are many active tasks Internal module celery worker controllers renamed to celery worker mediator celeryd Threads now terminates the program by calling os _exit as it is the only way to ensure exit in the case of syntax errors or other unrecoverable errors Fixed typo in maybe_t imedelta Issue 352 celeryd Broadcast commands now logs with loglevel debug instead of warning AMQP Result Backend Now resets cached channel if the connection is lost Polling results with the AMQP result backend was not working properly Rate limits No longer sleeps if there are no tasks but rather waits for the task received condition Performance improvement ConfigurationView iter dict should return keys not items Issue 362 celerybeat PersistentScheduler now automatically removes a corrupted schedule file Issue 346 Programs that doesn t support positional command line arguments now provides a user friendly error message Programs no longer tries to load the configuration file when showing version Issue 347 Autoscaler The all processes busy log message is now severity debug instead of error celeryd If the message body can t be decoded it is now passed through safe_str when
535. t backend settings RabbitMQ Result Backend The RabbitMQ result backend amqp is special as it does not actually store the states but rather sends them as messages This is an important difference as it means that a result can only be retrieved once If you have two processes waiting for the same result one of the processes will never receive the result Even with that limitation it is an excellent choice if you need to receive state changes in real time Using messaging means the client does not have to poll for new states There are several other pitfalls you should be aware of when using the RabbitMQ result backend 2 3 User Guide 49 Celery Documentation Release 3 0 25 e Every new task creates a new queue on the server with thousands of tasks the broker may be overloaded with queues and this will affect performance in negative ways If you re using RabbitMQ then each queue will be a separate Erlang process so if you re planning to keep many results simultaneously you may have to increase the Erlang process limit and the maximum number of file descriptors your OS allows e Old results will be cleaned automatically based on the CELERY_TASK_RESULT_EXPIRES setting By de fault this is set to expire after 1 day if you have a very busy cluster you should lower this value For a list of options supported by the RabbitMQ result backend please see AVOP backend settings Database Result Backend Keepin
536. t is s The add s call used here is called a subtask I talk more about subtasks in the canvas guide where you can also learn about chain which is a simpler way to chain tasks together In practice the link execution option is considered an internal primitive and you will probably not use it directly but rather use chains instead Here the result of the first task 4 will be sent to a new task that adds 16 to the previous result forming the expression 2 2 16 20 You can also cause a callback to be applied if task raises an exception errback but this behaves differently from a regular callback in that it will be passed the id of the parent task not the result This is because it may not always be possible to serialize the exception raised and so this way the error callback requires a result backend to be enabled and the task must retrieve the result of the task instead This is an example error callback celery task def error_handler uuid result AsyncResult uuid exc result get propagate False print Task r raised exception Sr n r amp exc result traceback it can be added to the task using the 1ink_error execution option add apply_async 2 2 link_error error_handler s In addition both the link and 1ink_error options can be expressed as a list add apply_async 2 2 link add s 16 other_task s The callbacks errbacks will then be called in order and all callbacks will be c
537. t s E events Send events that can be captured by monitors like celeryev celerymon and others purge Purges all waiting tasks before the daemon is started WARNING This is unrecoverable and the tasks will be deleted from the messaging server time limit Enables a hard time limit in seconds int float for tasks soft time limit Enables a soft time limit in seconds int float for tasks maxtasksperchild Maximum number of tasks a pool worker can execute before it s terminated and replaced by a new worker pidfile Optional file used to store the workers pid The worker will not start if this file already exists and the pid is still alive autoscale Enable autoscaling by providing max_concurrency min_concurrency Example autoscale 10 3 always keep 3 processes but grow to 10 if necessary autoreload Enable autoreloading no execv Don t do execv after multiprocessing child fork class celery bin celeryd WorkerCommand app None get_app None doc n nThe program celery worker command previously known as celeryd n n program celery worker n n enable_config_from_cmdline True execute_from_commandline argv None get_options namespace celeryd run args kwargs supports_args False with_pool_option argv celery bin celeryd main 2 13 API Reference 289 Celery Documentation Release 3 0 25 2 13 37 celery bin ce
538. t strings 200 m 10 s I h etc 428 Chapter 2 Contents Celery Documeniation Release 3 0 25 For the Django camera case this rate limit can be used to control how often the snapshots are written to the database and the frequency used to control how often the thread wakes up to check if there s anything new The rate limit is off by default which means it will take a snapshot for every frequency seconds e broadcast Added callback argument this can be used to process replies immediately as they arrive e celeryctl New command line utility to manage and inspect worker nodes apply tasks and inspect the results of tasks See also The celery Command Line Management Utility section in the User Guide Some examples celeryctl apply tasks add a 2 2 countdown 10 celeryctl inspect active celeryctl inspect registered_tasks celeryctl inspect scheduled celeryctl inspect help celeryctl apply help mM Mm WH e Added the ability to set an expiry date and time for tasks Example gt gt gt Task expires after one minute from now gt gt gt task apply_async args kwargs expires 60 gt gt gt Also supports datetime gt gt gt task apply_async args kwargs xpires datetime now timedelta days 1 When a worker receives a task that has been expired it will be marked as revoked TaskRevokedError e Changed the way logging is configured We now conf
539. t will be used Defaults to the number of available CPUs CELERYD_PREFETCH_MULTIPLIER How many messages to prefetch at a time multiplied by the number of concurrent processes The default is 4 four messages for each process The default setting is usually a good choice however if you have very long running tasks waiting in the queue and you have to start the workers note that the first worker to start will receive four times the number of messages initially Thus the tasks may not be fairly distributed to the workers Note Tasks with ETA countdown are not affected by prefetch limits Task result backend settings CELERY_RESULT_BACKEND Deprecated aliases CELERY_BACKEND The backend used to store task results tombstones Disabled by default Can be one of the following e database Use a relational database supported by SQLAIchemy See Database backend settings e cache Use memcached to store the results See Cache backend settings e mongodb Use MongoDB to store the results See MongoDB backend settings e redis Use Redis to store the results See Redis backend settings e amgp Send results back as AMQP messages See AMQP backend settings e cassandra Use Cassandra to store the results See Cassandra backend settings e ironcache Use IronCache to store the results See JronCache backend settings CELERY_RESULT_SERIALIZER Result serialization format Default is pickle See Serializers for information about s
540. task_id args kwargs einfo Handler called after the task returns Parameters e status Current task state e retval Task return value exception e task_id Unique id of the task e args Original arguments for the task that failed e kwargs Original keyword arguments for the task that failed e einfo ExceptionInfo instance containing the traceback if any The return value of this handler is ignored on_failure self exc task_id args kwargs einfo This is run by the worker when the task fails Parameters 2 3 User Guide 53 Celery Documentation Release 3 0 25 e exc The exception raised by the task e task_id Unique id of the failed task e args Original arguments for the task that failed e kwargs Original keyword arguments for the task that failed e einfo Exceptiontnfo instance containing the traceback The return value of this handler is ignored on_retry self exc task_id args kwargs einfo This is run by the worker when the task is to be retried Parameters e exc The exception sent to retry e task_id Unique id of the retried task e args Original arguments for the retried task e kwargs Original keyword arguments for the retried task e einfo ExceptionInfo instance containing the traceback The return value of this handler is ignored on_success self retval task_id args kwargs Run by the worker if the task execu
541. task_method class Counter object def init self self value 1 celery task name Counter increment filter task_method def increment self n 1 self value 1 return self value See celery contrib methods for more information 2 10 5 Unscheduled Removals Usually we don t make backward incompatible removals but these removals should have no major effect e The following settings have been renamed CELERYD_ETA_ SCHEDULER gt CELERYD_TIMER CELERYD_ETA_SCHEDULER_PRECISION gt CELERYD_TIMER_PRECISION 2 10 6 Deprecations See the Celery Deprecation Timeline e The celery backends pyredis compat module has been removed Use celery backends redis instead e The following undocumented API s has been moved control inspect add_consumer gt celery control add_consumer control inspect cancel_consumer gt celery control cancel_consumer control inspect enable_events gt celery control enable_events control inspect disable_events gt celery control disable_events This way inspect is only used for commands that do not modify anything while idempotent control commands that make changes are on the control objects 2 10 What s new in Celery 3 0 Chiastic Slide 197 Celery Documentation Release 3 0 25 2 10 7 Fixes e Retry sqlalchemy backend operations on DatabaseError Operat
542. te control command message on_decode_error message exc Callback called if an error occurs while decoding a message received Simply logs the error and acknowledges the message so it doesn t enter a loop Parameters e message The message with errors e exc The original exception instance on_poll_init hub on_task task task_reserved lt built in method add of set object at Ox7fb763d30de8 gt to_system_tz lt bound method _Zone to_system of lt celery utils timeutils _Zone object at Ox7fb766cac950 gt gt Handle received task If the task has an eta we enter it into the ETA schedule otherwise we move it the ready queue for imme diate processing pidbox_node None The process mailbox kombu pidbox node pool None The current worker pool instance ready_queue None The queue that holds tasks ready for immediate processing receive_message body message Handles incoming messages 324 Chapter 2 Contents Celery Documeniation Release 3 0 25 Parameters e body The message body e message The kombu message object reset_connection Re establish the broker connection and set up consumers heartbeat and the event dispatcher reset_pidbox_node Sets up the process mailbox restart_count l restart_heartbeat Restart the heartbeat thread This thread sends heartbeat events at intervals so monitors can tell if the worker is off line missing send_events False Enab
543. te from now gt gt gt add apply_async 10 10 expires 60 gt gt gt Also supports datetime gt gt gt from datetime import datetime timedelta gt gt gt add apply_async 10 10 kwargs xpires datetime now timedelta days 1 When a worker receives an expired task it will mark the task as REVOKED TaskRevokedError Message Sending Retry Celery will automatically retry sending messages in the event of connection failure and retry behavior can be config ured like how often to retry or a maximum number of retries or disabled all together To disable retry you can set the ret ry execution option to False add apply_async 2 2 retry False Related Settings CELERY_TASK_PUBLISH_RETRY e CKELERY_TASK_PUBLISH_RETRY_POLICY H Retry Policy A retry policy is a mapping that controls how retries behave and can contain the following keys e max_retries Maximum number of retries before giving up in this case the exception that caused the retry to fail will be raised A value of 0 or None means it will retry forever The default is to retry 3 times interval_start Defines the number of seconds float or integer to wait between retries Default is 0 which means the first retry will be instantaneous e interval_step On each consecutive retry this number will be added to the retry delay float or integer Default is 0 2 e interval_max Maxi
544. ter these dependencies are installed you should be able to build the docs by running S cd docs S rm rf build S make html Make sure there are no errors or warnings in the build output After building succeeds the documentation is available at build html Verifying your contribution To use these tools you need to install a few dependencies These dependencies can be found in requirements pkgutils txt Installing the dependencies pip E SVIRTUAL_ENV install U r requirements pkgutils txt 158 Chapter 2 Contents Celery Documeniation Release 3 0 25 pyflakes amp PEP8 To ensure that your changes conform to PEP8 and to run pyflakes execute paver flakes To not return a negative exit code when this command fails use the E option this can be convenient while developing paver flake8 E API reference To make sure that all modules have a corresponding section in the API reference please execute S paver autodoc S paver verifyindex If files are missing you can add them by copying an existing reference file If the module is internal it should be part of the internal reference located in docs internals reference If the module is public it should be located in docs reference For example if reference is missing for the module celery worker awesome and this module is considered part of the public API use the following steps S cd docs reference S cp celery schedules rst celery worker
545. tes successfully Parameters e retval The return value of the task e task_id Unique id of the executed task e args Original arguments for the executed task e kwargs Original keyword arguments for the executed task The return value of this handler is ignored on_retry How it works Here comes the technical details this part isn t something you need to know but you may be interested All defined tasks are listed in a registry The registry contains a list of task names and their task classes You can investigate this registry yourself gt gt gt from celery import current_app gt gt gt current_app tasks rd_unlock celery chor d_unlock gt ckend_cleanup gt 54 Chapter 2 Contents Celery Documeniation Release 3 0 25 This is the list of tasks built in to celery Note that tasks will only be registered when the module they are defined in is imported The default loader imports any modules listed in the CELERY_IMPORTS setting The entity responsible for registering your task in the registry is the metaclass TaskType If you want to register your task manually you can mark the task as abstract class MyTask Task abstract True This way the task won t be registered but any task inheriting from it will be When tasks are sent no actual function code is sent with it just the name of the task to execute When the worker then receives the message it
546. test suite Contributed by Milen Pavlov ResultSet join now always works with empty result set Issue 1219 A group consisting of a single task is now supported Issue 1219 Now supports the pycallgraph program Issue 1051 Fixed Jython compatibility problems Django tutorial Now mentions that the example app must be added to INSTALLED_APPS Issue 1192 2 12 11 3 0 15 release date 2013 02 11 04 30 00 P M UTC e Now depends on billiard 2 7 3 21 which fixed a syntax error crash e Fixed bug with CELERY_SEND_TASK_SENT_EVENT 2 12 12 3 0 14 release date 2013 02 08 05 00 00 P M UTC e Now depends on Kombu 2 5 6 e Now depends on billiard 2 7 3 20 e execv is now disabled by default 2 12 Change history 213 Celery Documentation Release 3 0 25 It was causing too many problems for users you can still enable it using the CELERYD_FORCE_EXECV setting execv was only enabled when transports other than amqp redis was used and it s there to prevent deadlocks caused by mutexes not being released before the process forks Sadly it also changes the environment introducing many corner case bugs that is hard to fix without adding horrible hacks Deadlock issues are reported far less often than the bugs that execv are causing so we now disable it by default Work is in motion to create non blocking versions of these transports so that execv is not necessary
547. th and some additional metadata like the number of retries or an ETA This is an example task message represented as a Python dictionary task myapp tasks add id 54086c5e 6193 4575 8308 dbab76798756 args 4 4 kwargs Producers consumers and brokers The client sending messages is typically called a publisher or a producer while the entity receiving messages is called a consumer The broker is the message server routing messages from producers to consumers You are likely to see these terms used a lot in AMQP related material 2 3 User Guide 99 Celery Documeniation Release 3 0 25 Exchanges queues and routing keys 1 Messages are sent to exchanges 2 An exchange routes messages to one or more queues Several exchange types exists providing different ways to do routing or implementing different messaging scenarios 3 The message waits in the queue until someone consumes it 4 The message is deleted from the queue when it has been acknowledged The steps required to send and receive messages are 1 Create an exchange 2 Create a queue 3 Bind the queue to the exchange Celery automatically creates the entities necessary for the queues in CELERY_QUEUES to work except if the queue s auto_declare setting is set to False Here s an example queue configuration with three queues One for video one for images and one default queue
548. the exchange if it hasn t already been declared during this session on_return None publish body routing_key None delivery_mode None mandatory False immediate False priority 0 content_type None content_encoding None serializer None head ers None compression None exchange None retry False retry_policy None de clare properties Publish message to the specified exchange Parameters body Message body routing_key Message routing key delivery_mode See delivery_mode mandatory Currently not supported immediate Currently not supported priority Message priority A number between 0 and 9 content_type Content type Default is auto detect content_encoding Content encoding Default is auto detect serializer Serializer to use Default is auto detect compression Compression method to use Default is none headers Mapping of arbitrary headers to pass along with the message body exchange Override the exchange Note that this exchange must have been declared declare Optional list of required entities that must have been de clared before publishing the message The entities will be declared using maybe_declare retry Retry publishing or declaring entities if the connection is lost retry_policy Retry configuration this is the keywords supported by ensure J 362 Chapter 2 Contents Celery Documeniation Release 3 0 2
549. the queue e exchange Name of the exchange e routing_key Binding key e exchange_type Type of exchange e options Additional declaration options add_compat name options consume_from format indent 0 indent_first True Format routing table into string for log dumps new_missing name 2 13 API Reference 241 Celery Documentation Release 3 0 25 select_add queue kwargs Add new task queue that will be consumed from even when a subset has been selected using the Q option select_remove queue select_subset wanted Sets consume_from by selecting a subset of the currently defined queues Parameters wanted List of wanted queue names TaskPublisher class celery app amqp TaskPublisher channel None exchange None args kwargs Deprecated version of TaskProducer 2 13 5 celery app defaults e celery app defaults j celery app defaults Configuration introspection and defaults class celery app defaults Option default None args kwargs alt None deprecate_by None remove_by None to_python value typemap bool lt function strtobool at 0x7fb768d6f488 gt string lt type str gt tuple lt type tuple gt int lt type ir celery app defaults find args kwargs celery app defaults find_deprecated_settings source celery app defaults flatten d ns 2 13 6 celery app control e celer
550. the same host name the control commands will be received in round robin between them To work around this you can explicitly set the host name for every worker using the hostname argument to celeryd celeryd hostname hostname 1 celeryd hostname hostname 2 etc etc Can I send some tasks to only some servers Answer Yes You can route tasks to an arbitrary server using AMQP and a worker can bind to as many queues as it wants See Routing Tasks for more information Can I change the interval of a periodic task at runtime Answer Yes You can use the Django database scheduler or you can override PeriodicTask is_due or turn Periodic Task run_every into a property class MyPeriodic PeriodicTask def run self H T property def run_every self return get_interval_from_database 182 Chapter 2 Contents Celery Documeniation Release 3 0 25 Does celery support task priorities Answer No In theory yes as AMQP supports priorities However RabbitMQ doesn t implement them yet The usual way to prioritize work in Celery is to route high priority tasks to different servers In the real world this may actually work better than per message priorities You can use this in combination with rate limiting to achieve a highly responsive system Should I use retry or acks_late Answer Depends It s not necessarily one or the other you may want to use both Task retry is use
551. the tasks user guide Calling tasks is described in detail in the Calling Guide Canvas Designing Workflows You just learned how to call a task using the tasks delay method and this is often all you need but sometimes you may want to pass the signature of a task invocation to another process or as an argument to another function for this Celery uses something called subtasks A subtask wraps the arguments and execution options of a single task invocation in a way such that it can be passed to functions or even serialized and sent across the wire You can create a subtask for the add task using the arguments 2 2 and a countdown of 10 seconds like this gt gt gt add subtask 2 2 countdown 10 tasks add 2 2 There is also a shortcut using star arguments gt gt gt add s 2 2 tasks add 2 2 And there s that calling API again Subtask instances also supports the calling API which means that they have the delay and apply_async methods But there is a difference in that the subtask may already have an argument signature specified The add task takes two arguments so a subtask specifying two arguments would make a complete signature gt gt gt sl add s 2 2 gt gt gt res sl delay gt gt gt res get 4 But you can also make incomplete signatures to create what we call partials incomplete partial add 2 gt gt gt s2 add s 2 s2 is now a partial subtask that needs another arg
552. the visibility timeout will be executed twice or more If you plan on using long ETA countdowns you should tweak the visibility timeout accordingly Setting a long timeout means that it will take a long time for messages to be redelivered in the event of a power failure but if so happens you could temporarily set the visibility timeout lower to flush out messages when you start up the systems again 2 10 3 News Chaining Tasks Tasks can now have callbacks and errbacks and dependencies are recorded e The task message format have been updated with two new extension keys Both keys can be empty undefined or a list of subtasks callbacks 2 10 What s new in Celery 3 0 Chiastic Slide 187 Celery Documentation Release 3 0 25 Applied if the task exits successfully with the result of the task as an argument errbacks Applied if an error occurred while executing the task with the uuid of the task as an argument Since it may not be possible to serialize the exception instance it passes the uuid of the task instead The uuid can then be used to retrieve the exception and traceback of the task from the result backend link and link_error keyword arguments has been added to apply_async These add callbacks and errbacks to the task and you can read more about them at Linking callbacks errbacks We now track what subtasks a task sends and some result backends supports retrieving this information x ta
553. ther people and you in turn will depend on the work of others Any decision you take will affect users and colleagues and we expect you to take those consequences into account when making decisions Even if it s not obvious at the time our contributions to Ubuntu will impact the work of others For example changes to code infrastructure policy documentation and translations during a release may negatively impact others work Be respectful The Celery community and its members treat one another with respect Everyone can make a valuable contribution to Celery We may not always agree but disagreement is no excuse for poor behavior and poor manners We might all experience some frustration now and then but we cannot allow that frustration to turn into a personal attack It s important to remember that a community where people feel uncomfortable or threatened is not a productive one We expect members of the Celery community to be respectful when dealing with other contributors as well as with people outside the Celery project and with users of Celery Be collaborative Collaboration is central to Celery and to the larger free software community We should always be open to collab oration Your work should be done transparently and patches from Celery should be given back to the community when they are made not just when the distribution releases If you wish to work on new code for existing upstream projects at least keep those projects in
554. this instance is called an application or app for short The application is thread safe so that multiple Celery applications with different configuration components and tasks can co exist in the same process space Let s create one now 2 3 User Guide 35 Celery Documentation Release 3 0 25 gt gt gt from celery import Celery gt gt gt celery Celery gt gt gt celery lt Celery main__ 0x100469fd0 gt The last line shows the textual representation of the application which includes the name of the celery class Celery the name of the current main module __main__ and the memory address of the object 0x100469fd0 Main Name Only one of these is important and that is the main module name let s look at why that is When you send a task message in Celery that message will not contain any source code but only the name of the task you want to execute This works similarly to how host names works on the internet every worker maintains a mapping of task names to their actual functions called the task registry Whenever you define a task that task will also be added to the local registry gt gt gt celery task def add x y return x y gt gt gt add lt task _ main__ add gt gt gt add name __main__ add gt gt gt celery tasks __main__ add lt task main add and there you see that __main__ again whenever Celery is not able to detect what module the function
555. thon manage py migrate djcelery For those who are not using south a normal syncdb will work S python manage py syncdb By default Celery uses RabbitMQ as the broker but there are several alternatives to choose from see Choosing a Broker All settings mentioned in the Celery documentation should be added to your Django project s sett ings py module For example you can configure the BROKER_URL setting to specify what broker to use BROKER_URL amqp guest guest localhost 5672 That s it Special note for mod_wsgi users If you re using mod_wsgi to deploy your Django application you need to include the following in your wsgi module import djcelery djcelery setup_loader Defining and calling tasks Tasks are defined by wrapping functions in the task decorator It is a common practice to put these in their own module named tasks py and the worker will automatically go through the apps in INSTALLED_APPS to import these modules For a simple demonstration create a new Django app called celerytest To create this app you need to be in the directory of your Django project where manage py is located and execute S python manage py startapp celerytest Next you have to add the new app to INSTALLED_APPS so that your Django project recognizes it This setting is a tuple list so just append celerytest as anew element at the end 148 Chapter 2 Contents Celery Documeniation Release 3 0 25 INSTA
556. tion e Installing the RabbitMQ Server Setting up RabbitMQ Installing RabbitMQ on OS X x Configuring the system host name Starting Stopping the RabbitMQ server Installation amp Configuration RabbitMQ is the default broker so it does not require any additional dependencies or initial configuration other than the URL location of the broker instance you want to use gt gt gt BROKER_URL amqp guest guest localhost 5672 For a description of broker URLs and a full list of the various broker configuration options available to Celery see Broker Settings Installing the RabbitMQ Server See Installing RabbitMQ over at RabbitMQ s website For Mac OS X see In stalling RabbitMQ on OS X Note If you re getting nodedown errors after installing and using rabbitmqctl then this blog post can help you identify the source of the problem http somic org 2009 02 19 on rabbitmqcetl and badrpcnodedown Setting up RabbitMQ To use celery we need to create a RabbitMQ user a virtual host and allow that user access to that virtual host rabbitmqctl add_user myuser mypassword rabbitmqctl add_vhost myvhost rabbitmqctl set_permissions p myvhost myuser x lx See the RabbitMQ Admin Guide for more information about access control Installing RabbitMQ on OSX The easiest way to install RabbitMQ on Snow Leopard is using Homebrew the new and shiny package management system for OS X In this example we ll
557. tion example using Django and virtualenv together Issue 505 Contributed by Juan Ignacio Catalano e generic init scripts now automatically creates log and pid file directories Issue 545 Contributed by Chris Streeter 2 4 3 release date 2011 11 22 18 00 P M GMT by Ask Solem e Fixes module import typo in celeryctl Issue 538 Fix contributed by Chris Streeter 2 4 2 release date 2011 11 14 12 00 P M GMT by Ask Solem e Program module no longer uses relative imports so that itis possible todo python m celery bin name 2 4 1 release date 2011 11 07 06 00 P M GMT by Ask Solem e celeryctl inspect commands was missing output e processes pool Decrease polling interval for less idle CPU usage e processes pool MaybeEncodingError was not wrapped in ExceptionInfo Issue 524 e celeryd would silence errors occuring after task consumer started 400 Chapter 2 Contents Celery Documeniation Release 3 0 25 e logging Fixed a bug where unicode in stdout redirected log messages couldn t be written Issue 522 2 4 0 release date 2011 11 04 04 00 P M GMT by Ask Solem Important Notes e Now supports Python 3 e Fixed deadlock in worker process handling Issue 496 A deadlock could occur after spawning new child processes because the logging library s mutex was not properly reset after fork The symptoms of this bug affecting would be that the worker simply stops processing tasks as none of the wo
558. tion in the reply e Functional test suite added celery tests functional case contains utilities to start and stop an embedded celeryd process for use in functional testing 2 0 1 release date 2010 07 09 03 02 P M CEST e multiprocessing pool Now handles encoding errors so that pickling errors doesn t crash the worker processes e The remote control command replies was not working with RabbitMQ 1 8 0 s stricter equivalence checks If you ve already hit this problem you may have to delete the declaration camqadm exchange delete celerycrgq or python manage py camgqadm exchange delete celerycrg 2 15 History 437 Celery Documentation Release 3 0 25 A bug sneaked in the ETA scheduler that made it only able to execute one task per second The scheduler sleeps between iterations so it doesn t consume too much CPU It keeps a list of the scheduled items sorted by time at each iteration it sleeps for the remaining time of the item with the nearest deadline If there are no eta tasks it will sleep for a minimum amount of time one second by default A bug sneaked in here making it sleep for one second for every task that was scheduled This has been fixed so now it should move tasks like hot knife through butter In addition a new setting has been added to control the minimum sleep interval CELERYD_ETA_SCHEDULER_PRECISION A good value for this would be a float between 0 and 1 depending on the needed p
559. tions_at_beginning argv index 0 with_pool_option argv class celery bin celery Command app None no_color False stdout lt open file lt stdout gt mode w at Ox7fb76c556150 gt stderr lt open file lt stderr gt mode w at Ox7fb76c5561e0 gt show_reply True args description 2 13 API Reference 291 Celery Documentation Release 3 0 25 error s help option_list lt Option at 0x7fb762af2a70 q quiet gt lt Option at 0x7fb762af2098 C no color gt out s fh None prettify n prettify dict_ok_error n prettify list n prog_name celery run_from_argv prog_name argv say_chat direction title body say_remote_command_rep y replies show_body True show_help command show_reply True usage command class celery bin celery Delegate args kwargs create_parser prog_name command get_options run args kwargs exception celery bin celery Error reason status 1 class celery bin celery amap args kwargs AMQP Administration Shell Also works for non amqp transports Examples celery amqp start shell mode celery amqp help show list of commands celery amqp exchange delete nam celery amqp queue delete queu celery amqp queue delete queue yes yes Command celery bin camqadm AMQPAdminCommand sortpri 30 class celery bin celery beat args kwargs Start the celerybeat periodic task schedu
560. to Python values and display various help and tooltips Parameters e args see args e returns see returns coerce index value Coerce value for argument at index E g if args is is_active bool gt gt gt coerce 0 False False format_arg name type default_value None format_response response Format the return value of this command in a human friendly way format_signature str_args_to_python argilist Process list of string arguments to values according to spec e g gt gt gt spec Spec queue str if_unused bool gt gt gt spec str_args_to_python pobox true pobox True celery bin camgqadm camgqadm args options celery bin camqadm dump_message message celery bin camqadm format_declare_queue ret celery bin camqadm main celery bin camgqadm say m fh lt open file lt stderr gt mode w at 0x7fb76c5561e0 gt 2 13 41 celery bin celeryd_multi e Examples j 2 13 API Reference 299 Celery Documeniation Release 3 0 25 Examples Single worker with explicit name and events enabled celeryd multi start Leslie E Pidfiles and logfiles are stored in the current directory by default Use pidfile and logfile argument to change this The abbreviation n will be expanded to the current node name S celeryd multi start Lesli E pidfile var
561. to the djcelery backends instead of the built in backends and configuration will be read from the Django settings Upgrading for others Database result backend The database result backend is now using SQLAIchemy instead of the Django ORM see Supported Databases for a table of supported databases The DATABASE_ settings has been replaced by a single setting CELERY_RESULT_DBURI The value here should be an SQLAIchemy Connection String some examples include CELERY_RESULT_DBURI sqlite celerydb sqlite mysql CELERY_RESULT_DBURI mysql scott tiger localhost foo P postgresql CELERY_RESULT_DBURI postgresql scott tiger localhost mydatabase oracle CELERY_RESULT_DBURI oracle scott tiger 127 0 0 1 1521 sidname See SQLAIchemy Connection Strings for more information about connection strings To specify additional SQLAIchemy database engine options you can use the CELERY_RESULT_ENGINE_OPTIONS setting 440 Chapter 2 Contents Celery Documeniation Release 3 0 25 verbose logging rom SQLAlchemy enables f ENGINE_OPTIONS echo CELERY_RESULT T e ecno True Cache result backend The cache result backend is no longer using the Django cache framework but it supports mostly the same configuration syntax CELERY_CACHE_BACKEND memcached A xample com 1
562. ts None force_execv None logfile None loglevel 40 max_tasks_per_child None mediator_cls None pool_cls None pool_putlocks None pool_restarts None prefetch_multiplier None process_task req Process task by sending it to the pool of workers process_task_sem req reload modules None reload False reloader None schedule_filename None scheduler_cls None send_events None should_use_eventloop signal_consumer_close start Starts the workers main loop state state_db None stop in_sighandler False Graceful shutdown of the worker server task_soft_time_limit None task_time_limit None terminate in_sighandler False Not so graceful shutdown of the worker server 2 13 API Reference 283 Celery Documentation Release 3 0 25 ce ce ce ce ce ce ce timer_cls None timer_precision None worker _lost_wait None Worker Worker Worker Worker Worker app None extra_info inherit_confopts lt class celery worker WorkController gt init_queues install_platform_tweaks worker Install platform specific tweaks and workarounds Worker loglevel None Worker on_consumer_ready consumer Worker osx_proxy_detection_workaround See http github com celery celery issues issue 161 Worker purge_messages Worker Worker Worker Worker Worker Worker Worker redirect_stdouts
563. ts 1 given In this case it will return the exception instance raised instead and so to check whether the task succeeded or failed you will have to use the corresponding methods on the result instance gt gt gt res failed True gt gt gt res successful False So how does it know if the task has failed or not It can find out by looking at the tasks state gt gt gt res state FAILURE A task can only be in a single state but it can progress through several states The stages of a typical task can be PENDING gt STARTED gt SUCCESS The started state is a special state that is only recorded if the CELERY_TRACK_STARTED setting is enabled or if the task track_started True option is set for the task The pending state is actually not a recorded state but rather the default state for any task id that is unknown which you can see from this example gt gt gt from proj celery import celery gt gt gt res celery AsyncResult this id does not exist gt gt gt res state PENDING If the task is retried the stages can become even more complex e g for a task that is retried two times the stages would be 2 2 Getting Started 29 Celery Documentation Release 3 0 25 PENDING gt STARTED gt RETRY gt STARTED gt RETRY gt STARTED gt SUCCESS To read more about task states you should see the States section in
564. tter_status apply a b In Other News e Now depends on Kombu 2 1 0 e Efficient Chord support for the memcached backend Issue 533 This means memcached joins Redis in the ability to do non polling chords Contributed by Dan McGee e Adds Chord support for the Rabbit result backend amqp The Rabbit result backend can now use the fallback chord solution e Sending QUIT to celeryd will now cause it cold terminate 202 Chapter 2 Contents Celery Documeniation Release 3 0 25 That is it will not finish executing the tasks it is currently working on Contributed by Alec Clowes New detailed mode for the Cassandra backend Allows to have a detailed mode for the Cassandra backend Basically the idea is to keep all states using Cassandra wide columns New states are then appended to the row as new columns the last state being the last column See the CASSANDRA_DETAILED_MODE setting Contributed by Steeve Morin The crontab parser now matches Vixie Cron behavior when parsing ranges with steps e g 1 59 2 Contributed by Daniel Hepper celerybeat can now be configured on the command line like celeryd Additional configuration must be added at the end of the argument list followed by for example celerybeat 1 info celerybeat max_loop_interval 10 0 Now limits the number of frames in a traceback so that celeryd does not crash on maximum recursion limit exceeded exceptions I
565. ture limit None timeout None wakeup Tru Note The wakeup argument to capture sends a signal to all workers to force them to send a heartbeat This way you can immediately see workers when the monitor starts You can listen to specific events by specifying the handlers 2 3 User Guide 113 Celery Documentation Release 3 0 25 from celery import Celery def my_monitor app state app events State def announce_failed_tasks event state event event task_id event uuid print TASK FAILED s s s event name task_id state task_id info def announce_dead_workers event state event event hostname event hostname if not state workers hostname alive print Worker s missed heartbeats hostname with app connection as connection recv app events Receiver connection handlers task failed announce_failed_tasks worker heartbeat announce_dead_workers recv capture limit None timeout None wakeup True if name main__ celery Celery broker amgp guest localhost my_monitor celery Event Reference This list contains the events sent by the worker and their arguments Task Events task sent signature task sent uuid name args kwargs retries eta expires queue exchange routing_key Sent when a task message is published and the CELERY_SEND_TASK_SENT_
566. ual chance of being consumed from This used to be the case before but the behavior was accidentally changed while switching to using blocking pop group chord chain are now subtasks e group is no longer an alias to TaskSet but new alltogether since it was very difficult to migrate the TaskSet class to become a subtask e A new shortcut has been added to tasks gt gt gt task s argl arg2 kw 1 as a shortcut to gt gt gt task subtask argl arg2 kw 1 e Tasks can be chained by using the operator gt gt gt add s 2 2 pow s 2 apply_async e Subtasks can be evaluated using the operator 2 10 What s new in Celery 3 0 Chiastic Slide 189 Celery Documeniation Release 3 0 25 gt gt gt add s 2 2 4 gt gt gt add s 2 2 pow s 2 is the same as gt gt gt chain add s 2 2 pow s 2 apply_async get A new subtask_type key has been added to the subtask dicts 39 66 This can be the string chord group 3 ee 39 66 chain chunks xmap or xstarmap maybe_subtask now uses subtask_type to reconstruct the object to be used when using non pickle serializers The logic for these operations have been moved to dedicated tasks celery chord celery chain and celery group subtask no longer inherits from AttributeDict It s now a pure dict subclass with properties for attribute access to the relevant keys The repr
567. ubtask chord inspect promise and more e Factory functions and methods must be CamelCase excluding verbs class Celery object def consumer_factory self BAD def Consumer self GOOD Default values Class attributes serve as default values for the instance as this means that they can be set by either instantiation or inheritance Example class Producer object active True serializer json def __init self serializer None self serializer serializer or self serializer must check for None when value can be false y self active active if active is not None else self active A subclass can change the default value TaskProducer Producer serializer pickle and the value can be set at instantiation gt gt gt producer TaskProducer serializer msgpack Exceptions Custom exceptions raised by an objects methods and properties should be available as an attribute and documented in the method property that throw This way a user doesn t have to find out where to import the exception from but rather use help obj and access the exception class from the instance directly Example class Empty Exception pass class Queue object 304 Chapter 2 Contents Celery Documeniation Release 3 0 25 Empty Empty def get self Get the next item from the queue raises Queue Empty if there are no more items left nun try return self q
568. ue but do not update the channels QoS 2 14 Internals 325 Celery Documentation Release 3 0 25 The MainThread will be responsible for calling update when necessary prev None set pcount Set channel prefetch_count setting update Update prefetch count with current value celery worker consumer UNKNOWN_TASK_ERROR Received unregistered task of type s nThe message has been ign Error message for when an unregistered task is received celery worker consumer debug msg args kwargs celery worker consumer dump_body m body celery worker consumer task_reserved Add an element to a set This has no effect if the element is already present celery worker job e celery worker job f celery worker job This module defines the Request class which specifies how tasks are executed class celery worker job Request body on_ack lt function noop at 0x7fb768d6c848 gt hostname None eventer None app None connec tion_errors None request_dict None delivery_info None task None opts A request for task execution acknowledge Acknowledge task acknowledged app args connection_errors delivery_info error_msg Task name s id s raised exception exc s n Format string used to log task failure eta eventer execute loglevel None logfile None Execute the task ina trace_task Parameters e loglevel The loglevel used by the task 326 Ch
569. uest has finished e Making sure something is done by executing it asynchronously and using retries e Scheduling periodic work And to some degree e Distributed computing e Parallel execution 2 9 2 Misconceptions Does Celery really consist of 50 000 lines of code Answer No this and similarly large numbers have been reported at various locations The numbers as of this writing are e core 7 141 lines of code e tests 14 209 lines e backends contrib compat utilities 9 032 lines Lines of code is not a useful metric so even if Celery did consist of 50k lines of code you would not be able to draw any conclusions from such a number Does Celery have many dependencies A common criticism is that Celery uses too many dependencies The rationale behind such a fear is hard to imagine especially considering code reuse as the established way to combat complexity in modern software development and that the cost of adding dependencies is very low now that package managers like pip and PyPI makes the hassle of installing and maintaining dependencies a thing of the past Celery has replaced several dependencies along the way and the current list of dependencies are celery kombu Kombu is part of the Celery ecosystem and is the library used to send and receive messages It is also the library that enables us to support many different message brokers It is also used by the OpenStack project and many others validating the
570. uest txt 0 1 0 release date 2009 04 24 11 28 A M CET e Initial release 2 16 Glossary ack Short for acknowledged acknowledged Workers acknowledge messages to signify that a message has been handled Failing to acknowledge a message will cause the message to be redelivered Exactly when a transaction is considered a failure varies by transport In AMQP the transaction fails when the connection channel is closed or lost but in Redis SQS the transaction times out after a configurable amount of time the visibility_timeout apply Originally a synonym to call but used to signify that a function is executed by the current process calling Sends a task message so that the task function is executed by a worker context The context of a task contains information like the id of the task it s arguments and what queue it was delivered to It can be accessed as the tasks request attribute See Context executing Workers execute task requests idempotent Idempotence is a mathematical property that describes a function that can be called multiple times without changing the result Practically it means that a function can be repeated many times without unintented effects but not necessarily side effect free in the pure sense compare to nullipotent nullipotent describes a function that will have the same effect and give the same result even if called zero or multiple times side effect free A stronger version of idempotent request Ta
571. ueue popleft except IndexError raise self Empty Composites Similarly to exceptions composite classes should be override able by inheritance and or instantiation Common sense can be used when selecting what classes to include but often it s better to add one too many predicting what users need to override is hard this has saved us from many a monkey patch Example class Worker object Consumer Consumer def init self connection consumer_cls None self Consumer consumer_cls or self Consumer def do_work self with self Consumer self connection as consumer self connection drain_events Applications vs single mode In the beginning Celery was developed for Django simply because this enabled us get the project started quickly while also having a large potential user base In Django there is a global settings object so multiple Django projects can t co exist in the same process space this later posed a problem for using Celery with frameworks that doesn t have this limitation Therefore the app concept was introduced When using apps you use celery objects instead of importing things from celery submodules this sadly also means that Celery essentially has two API s Here s an example using Celery in single mode from celery import task from celery task control import inspect from models import CeleryStats task def write_stats_to_db stats inspect stats timeout
572. ultiprocessing pool tried to import os kill even though this is not available there Issue 450 e Fixes case where the worker could become unresponsive because of tasks exceeding the hard time limit e The task sent event was missing from the event reference e ResultSet iterate now returns results as they finish Issue 459 This was not the case previously even though the documentation states this was the expected be havior e Retries will no longer be performed when tasks are called directly using ___call1__ Instead the exception passed to ret ry will be re raised e Eventlet no longer crashes if autoscale is enabled growing and shrinking eventlet pools is still not supported e py24 target removed from tox ini 2 3 1 release date 2011 08 07 08 00 PM BST Fixes e The CEL ERY_AMOP_TASK_R ESULT_ EXPIR ES setting did not work resulting in an AMQP related error about not being able to serialize floats while trying to publish task states Issue 446 2 3 0 release date 2011 08 05 12 00 PM BST tested cPython 2 5 2 6 2 7 PyPy 1 5 Jython 2 5 2 406 Chapter 2 Contents Celery Documeniation Release 3 0 25 Important Notes e Now requires Kombu 1 2 1 e Results are now disabled by default The AMQP backend was not a good default because often the users were not consuming the results resulting in thousands of queues While the queues can be confi
573. ument to be complete and this can be resolved when calling the subtask resolves the partial add 8 2 gt gt gt res s2 delay 8 gt gt gt res get 10 Here you added the argument 8 which was prepended to the existing argument 2 forming a complete signature of add 8 2 Keyword arguments can also be added later these are then merged with any existing keyword arguments but with new arguments taking precedence gt gt gt s3 add s 2 2 debug True gt gt gt s3 delay debug False debug is now False 30 Chapter 2 Contents Celery Documeniation Release 3 0 25 As stated subtasks supports the calling API which means that e subtask apply_async args kwargs xoptions Calls the subtask with optional partial arguments and partial keyword arguments Also supports partial execution options e subtask delay args xkwargs Star argument version of apply_async Any arguments will be prepended to the arguments in the signature and keyword arguments is merged with any existing keys So this all seems very useful but what can you actually do with these To get to that I must introduce the canvas primitives The Primitives group e chain chord map e starmap chunks The primitives are subtasks themselves so that they can be combined in any number of ways to compose complex workflows Note These examples retrieve results so to try them out you need to co
574. umer queue See celery Command Line Management Utility for more information about the celeryctl program Another example using inspect 426 Chapter 2 Contents Celery Documeniation Release 3 0 25 gt gt gt from celery task control import inspect gt gt gt inspect add_consumer queue queue exchange exchange xchange_type direct routing_key key durable False auto_delete True gt gt gt inspect cancel_consumer queue e celerybeat Now logs the traceback if a message can t be sent e celerybeat Now enables a default socket timeout of 30 seconds e README introduction homepage Added link to Flask Celery 2 1 0 release date 2010 10 08 12 00 P M CEST Important Notes e Celery is now following the versioning semantics defined by semver This means we are no longer allowed to use odd even versioning semantics By our previous ver sioning scheme this stable release should have been version 2 2 e Now depends on Carrot 0 10 7 e No longer depends on SQLAIchemy this needs to be installed separately if the database result backend is used e django celery now comes with a monitor for the Django Admin interface This can also be used if you re not a Django user Update Django Admin monitor has been replaced with Flower see the Monitoring guide e If you get an error after upgrading saying AfttributeError module object has no attribute system Then this is because the c
575. undedSemaphore 2 gt gt gt def callback i print HELLO br i gt gt gt x acquire callback 1 HELLO 1 gt gt gt x acquire callback 2 HELLO 2 gt gt gt x acquire callback 3 gt gt gt x _waiters private do not access directly gt gt gt x release HELLO 3 acquire callback partial_args Acquire semaphore applying callback when the semaphore is ready Parameters e callback The callback to apply e partial_args partial arguments to callback clear Reset the sempahore including wiping out any waiting callbacks grow n Change the size of the semaphore to hold more values release Release semaphore This will apply any waiting callbacks from previous calls to acquire done when the semaphore was busy shrink n Change the size of the semaphore to hold less values class celery worker hub DummyLock Pretending to be a lock class celery worker hub Hub timer None Event loop object 332 Chapter 2 Contents Celery Documeniation Release 3 0 25 Parameters timer Specify custom Schedule ERR 24 Flag set on error and the fd should be read from asap READ 1 Flag set if reading from an fd will not block WRITE 4 Flag set if writing to an fd will not block add fd callback flags add_reader fd callback add_writer fd callback close args fire_timers min_delay 1 max_delay 10 max_timers 10 propagate
576. upported serialization formats 2 4 Configuration and defaults 129 Celery Documeniation Release 3 0 25 Database backend settings CELERY_RESULT_DBURI Please see Supported Databases for a table of supported databases To use this backend you need to configure it with an Connection String some examples include sqlite filename CELERY_RESULT_DBURI sqlite celerydb sqlite mysql CELERY_RESULT_DBURI mysql scott tiger localhost foo CELERY_RESULT_DBURI postgresql scott tiger localhost mydatabase oracle CELERY_RESULT_DBURI oracle scott tiger 127 0 0 1 1521 sidname See Connection String for more information about connection strings CELERY_RESULT_ENGINE_OPTIONS To specify additional SQLAIchemy database engine options you can use the CELERY_RESULT_ENGINE_OPTIONS setting echo enables verbose logging from SQLAlchemy CELERY_RESULT_ENGINE_OPTIONS echo True Short lived sessions are disabled by default If enabled they can drastically reduce performance especially on systems processing lots of tasks This option is useful on low traffic workers that experience errors as a result of cached database connections going stale through inactivity For example intermittent errors like OperationalError 2006 MySQL server has gone away can be fixed by enabling short lived sessions This
577. use a better solution and is scheduled for inclusion in the 2 0 0 release celeryd now shutdowns cleanly when receiving the SIGTERM signal celeryd now does a cold shutdown if the SIGINT signal is received Ctrl C this means it tries to terminate as soon as possible Caching of results now moved to the base backend classes so no need to implement this functionality in the base classes Caches are now also limited in size so their memory usage doesn t grow out of control You can set the maximum number of results the cache can hold using the CELERY_MAX_CACHED_RESULTS setting the default is five thousand results In ad dition you can refetch already retrieved results using backend reload_task_result back end reload_taskset_result that s for those who want to send results incrementally celeryd now works on Windows again Warning If you re using Celery with Django you can t use project settings as the settings module name but the following should work S python manage py celeryd settings settings Execution messaging TaskPublisher send_task now incorporates all the functionality apply_async previously did Like converting countdowns to eta so celery execute apply_async is now simply a convenient front end to celery messaging TaskPublisher send_task using the task classes default options 456 Chapter 2 Contents Celery Documeniation Release 3 0 25
578. used New in this version you can also change the time limits for a task at runtime using the time_limit remote control command gt gt gt from celery task import control gt gt gt control time_limit tasks sleeptask soft 60 hard 120 reply True workerl example com ok time limits set successfully Only tasks that starts executing after the time limit change will be affected Note Soft time limits will still not work on Windows or other platforms that do not have the SIGUSRI1 signal e Redis backend configuration directive names changed to include the CELERY_ prefix Old setting name Replace with REDIS_HOST CELERY_REDIS_HOST REDIS_PORT CELERY_REDIS_PORT REDIS_DB CELERY_REDIS_DB REDIS_PASSWORD_ CELERY_REDIS_PASSWORD The old names are still supported but pending deprecation e PyPy The default pool implementation used is now multiprocessing if running on PyPy 1 5 e celeryd multi now supports pass through options Pass through options makes it easier to use celery without a configuration file or just add last minute options on the command line Example use celeryd multi start 4 Ge 2 broker host amqp example com broker vhost celery disable_rate_limits yes 408 Chapter 2 Contents Celery Documeniation Release 3 0 25 Fixes celerybeat Now retries establishing the connection Issue 419 celeryctl New li
579. ust be manually enabled The CELERYD_FORCE_EXECV setting has been added to solve a problem with deadlocks that originate when threads and fork is mixed together CELERYD_FORCE_EXECV True This setting is recommended for all users using the processes pool but especially users also using time limits or a max tasks per child setting e See Python Issue 6721 to read more about this issue and why resorting to execv is the only safe solution Enabling this option will result in a slight performance penalty when new child worker processes are started and it will also increase memory usage but many platforms are optimized so the impact may be minimal Considering that it ensures reliability when replacing lost worker processes it should be worth it e It s already the default behavior on Windows e It will be the default behavior for all platforms in a future version 2 11 2 Optimizations e The code path used when the worker executes a task has been heavily optimized meaning the worker is able to process a great deal more tasks second compared to previous versions As an example the solo pool can now process up to 15000 tasks second on a 4 core MacBook Pro when using the pylibrabbitmq transport where it previously could only do 5000 tasks second e The task error tracebacks are now much shorter e Fixed a noticeable delay in task processing when rate limits are enabled 2 11
580. utines conditional expressions and enhanced try blocks the code base now contains so many 2 4 related hacks and workarounds it s no longer just a compromise but a sacrifice If it really isn t your choice and you don t have the option to upgrade to a newer version of Python you can just continue to use Celery 2 2 Important fixes can be backported for as long as there is interest e celeryd Now supports Autoscaling of child worker processes The autoscale option can be used to configure the minimum and maximum number of child worker processes autoscale AUTOSCALE Enable autoscaling by providing max_concurrency min_concurrency Example autoscale 10 3 always keep 3 processes but grow to 10 if necessary e Remote Debugging of Tasks celery contrib rdb is an extended version of pdb that enables remote debugging of pro cesses that does not have terminal access Example usage from celery contrib import rdb from celery task import task task def add x y result x y rdb set_trace lt set breakpoint return result func celery contrib rdb set_trace sets a breakpoint at the current location and creates a socket you can telnet into to remotely debug your task The debugger may be started by multiple processes at the same time so rather than using a fixed port the debugger will search for an available port starting from the base port 6900 by default The base port can be c
581. ve group result for later retrieval using restore Example gt gt gt result save gt gt gt result GroupResult restore group_id serializable class celery result ResultBase Base class for all results class celery result ResultSet results app None kwargs Working with more than one result Parameters results List of result instances add result Add AsyncResult as a new member of the set Does nothing if the result is already a member app None clear Remove all results from this set completed_count Task completion count Returns the number of tasks completed discard result Remove result from the set if it is a member If it is not a member do nothing failed Did any of the tasks fail Returns True if one of the tasks failed 1 e raised an exception forget Forget about and possible remove the result of all the tasks get timeout None propagate True interval 0 5 See join This is here for API compatibility with AsyncResult in addition it uses join_native ifavailable for the current result backend 2 13 API Reference 255 Celery Documentation Release 3 0 25 iter_native timeout None interval None Backend optimized version of iterate New in version 2 2 Note that this does not support collecting the results for different task types using different backends This is currently only supported by the amqp Redis and cache re
582. ved dependency to simplejson Cache Backend Re establishes connection for every task process if the Django cache backend is mem cached libmemcached Tyrant Backend Now re establishes the connection for every task executed release date 2009 06 08 01 07 P M CET The Periodic WorkController now sleeps for 1 second between checking for periodic tasks to execute release date 2009 06 08 01 07 PM CET celeryd Added option discard Discard delete all waiting messages in the queue celeryd The wakeup after option was not handled as a float release date 2009 06 08 01 07 PM CET The PeriodicTask worker is now running in its own thread instead of blocking the TaskController loop Default QUEUE_WAKEUP_AFTER has been lowered to 0 was 0 3 2 15 History 469 Celery Documentation Release 3 0 25 0 3 0 release date 2009 06 08 12 41 P M CET VERY IMPORTANT Pickle is now the encoder used for serializing task arguments so be sure to flush your task queue before you upgrade IMPORTANT TaskSet runQ now returns a celery result TaskSetResult instance which lets you inspect the status and return values of a taskset as it was a single entity IMPORTANT Celery now depends on carrot gt 0 4 1 The celery daemon now sends task errors to the registered admin emails To turn off this feature set SEND_CELERY_TASK_ERROR_EMAILS to False in your settings py Thanks to Gr goire Cachet You can now run the celery daemon by
583. vel kwargs task_is_eager self request is_eager NEW self request args NEW self request kwargs In addition the following methods now automatically uses the current context so you don t have to pass kwargs manually anymore task retry task get_logger task update_state e Eventlet support This is great news for I O bound tasks To change pool implementations you use the P poo1 argument to celeryd or globally using the CELERYD_POOL setting This can be the full name of a class or one of the following aliases processes eventlet gevent For more information please see the Concurrency with Eventlet section in the User Guide Why not gevent For our first alternative concurrency implementation we have focused on Eventlet but there is also an experimental gevent pool available This is missing some features notably the ability to schedule ETA tasks Hopefully the gevent support will be feature complete by version 2 3 but this depends on user demand and contributions e Python 2 4 support deprecated We re happy H H H H Hsad to announce that this is the last version to support Python 2 4 2 15 History 417 Celery Documeniation Release 3 0 25 You are urged to make some noise if you re currently stuck with Python 2 4 Complain to your package maintainers sysadmins and bosses tell them it s time to move on Apart from wanting to take advantage of with statements coro
584. verts them to seconds celery utils timeutils remaining start ends_in now None relative False debug False Calculate the remaining time for a start date and a timedelta e g how many seconds left for 30 seconds after start Parameters e start Start datetime e ends_in The end delta as at imedelta e relative If enabled the end time will be calculated using delta_resolution i e rounded to the resolution of ends_in e now Function returning the current time and date defaults to datetime utcnow celery utils timeutils timedelta_seconds delta Convert datetime timedelta to seconds Doesn t account for negative values celery utils timeutils to_ute dt Converts naive datetime to UTC celery utils timeutils weekday name Return the position of a weekday 0 7 where 0 is Sunday Example gt gt gt weekday sunday weekday sun weekday mon 0 0 L celery utils compat e celery utils compat l celery utils compat Compatibility implementations of features only available in newer Python versions celery utils compat chain_from_iterable chain from_iterable iterable gt chain object Alternate chain contructor taking a single iterable argument that evaluates lazily celery utils compat format_d i celery utils serialization e celery utils serialization j 2 14 Internals 381 Celery Documentation Release 3 0 25
585. w tried to handle broken PID files Added a Django test runner to contrib that sets CELERY_ALWAYS_EAGER True for testing with the database backend Added a CELERY_CACHE_BACKEND setting for using something other than the django global cache backend Use custom implementation of functools partial curry for Python 2 4 support Probably still problems with running on 2 4 but it will eventually be supported Prepare exception to pickle when saving RETRY status for all backends SQLite no concurrency limit should only be effective if the database backend is used 0 8 0 release date 2009 09 22 03 06 PM CEST Backward incompatible changes e Add traceback to result value on failure Note If you use the database backend you have to re create the database table celery_taskmeta Contact the Mailing list or IRC channel for help doing this e Database tables are now only created if the database backend is used so if you change back to the database backend at some point be sure to initialize tables django syncdb python celeryinit Note This is only applies if using Django version 1 1 or higher e Now depends on carrot version 0 6 0 e Now depends on python daemon 1 4 8 Important changes e Celery can now be used in pure Python outside of a Django project This means celery is no longer Django specific For more information see the FAQ entry Zs Celery for Django only 464 Cha
586. with acks_late if that level of reliability is required Can I schedule tasks to execute at a specific time Answer Yes You can use the eta argument of Task apply_async Or to schedule a periodic task at a specific time use the celery schedules crontab schedule behavior from celery schedules import crontab from celery task import periodic_task periodic_task run_every crontab hour 7 minute 30 day_of_week mon def every monday _morning print This is run every Monday morning at 7 30 How do I shut down celeryd safely Answer Use the TERM signal and the worker will finish all currently executing jobs and shut down as soon as possible No tasks should be lost 2 9 Frequently Asked Questions 183 Celery Documentation Release 3 0 25 You should never stop ce leryd with the KILL signal 9 unless you ve tried TERM a few times and waited a few minutes to let it get a chance to shut down As if you do tasks may be terminated mid execution and they will not be re run unless you have the acks_late option set Task acks_late CELERY_ACKS_LATE See also Stopping the worker How do I run celeryd in the background on platform Answer Please see Running the worker as a daemon 2 9 8 Django What purpose does the database tables created by django celery have Several database tables are created by default these relate to e Monitoring When you use the django admin monitor
587. xamples celery list bindings NOTE For RabbitMQ the management plugin is required args bindings list_bindings management run what None _ kw sortpri 0 celery bin celery load_extension_commands namespace celery commands celery bin celery main argv None class celery bin celery migrate app None no_color False stdout lt open file lt stdout gt mode w at Ox7fb76c556150 gt stderr lt open file lt stderr gt mode w at Ox7fb76c5561e0 gt show_reply True Migrate tasks from one broker to another Examples celery migrate redis localhost amqp guest localhost celery migrate django redis localhost NOTE This command is experimental make sure you have a backup of the tasks before you continue args lt source_url gt lt dest_url gt on_migrate_task state body message option_list lt Option at 0x7fb762af2a70 q quiet gt lt Option at 0x7fb762af2098 C no color gt lt Option at 0x7fb7 run args kwargs sortpri 0 class celery bin celery multi app None no_color False stdout lt open file lt stdout gt mode w at 0x7fb76c556150 gt stderr lt open file lt stderr gt mode w at Ox7fb76c5561e0 gt show_reply True Start multiple worker instances get_options respects_app_option False run_from_argv prog_name argv sortpri 0 class celery bin celery purge app None no_color
588. xceptions was raised propagates No 50 Chapter 2 Contents Celery Documeniation Release 3 0 25 REVOKED Task has been revoked propagates Yes Custom states You can easily define your own states all you need is a unique name The name of the state is usually an uppercase string As an example you could have a look at abortable tasks which defines its own custom ABORTED state Use update_state to update a task s state from celery import current_task celery task def upload files filenames for i file in enumerate filenames current_task update_state state PROGRESS meta current i total len filenames Here I created the state PROGRESS which tells any application aware of this state that the task is currently in progress and also where it is in the process by having current and total counts as part of the state metadata This can then be used to create e g progress bars Creating pickleable exceptions A rarely known Python fact is that exceptions must conform to some simple rules to support being serialized by the pickle module Tasks that raise exceptions that are not pickleable will not work properly when Pickle is used as the serializer To make sure that your exceptions are pickleable the exception MUST provide the original arguments it was instantiated with in its args attribute The simplest way to ensure this is to have the exception call Exception __init__
589. xed compatibility with Ubuntu s minimal Dash shell Issue 1387 208 Chapter 2 Contents Celery Documeniation Release 3 0 25 Fix contributed by monkut e Task apply ALWAYS_EAGER now also executes callbacks and errbacks Issue 1336 e Worker The worker shutdown signal was no longer being dispatched Issue 1339 j e Python 3 Fixed problem with threading Event Fix contributed by Xavier Ordoquy e Python 3 Now handles io UnsupportedOperation that may be raised by file fileno in Python 3 e Python 3 Fixed problem with qualname e events State Now ignores unknown event groups e MongoDB backend No longer uses deprecated safe parameter Fix contributed by rfkrocktk The eventlet pool now imports on Windows e Canvas Fixed regression where immutable chord members may receive arguments Issue 1340 Fix contributed by Peter Brook e Canvas chain now accepts generator argument again Issue 1319 e celery migrate command now consumes from all queues if no queues specified Fix contributed by John Watson 2 12 7 3 0 19 release date 2013 04 17 04 30 00 P M BST e Now depends on billiard 2 7 3 28 e A Python 3 related fix managed to disable the deadlock fix announced in 3 0 18 Tests have been added to make sure this does not happen again e Task retry policy Default max_retries is now 3 This ensures clients will not be hanging while the broker is down Note You can set a longer
590. xtra arguments to celeryd oe LERYD_OPTS time limit 300 concurrency 8 will be replaced with the nodename ERYD_LOG_FILE var log celery n log Et et ERYD_PID_FILE var run celery n pid Workers should run as an unprivileged user CELE CELE RYD_USER celery RYD_GROUP celery Name of the projects settings module export DJANGO_SETTINGS_MODULE MyProject settings Available options CELERYD_NODES Node names to start CELERYD_OPTS Additional arguments to celeryd see celeryd help for a list CELERYD_CHDIR Path to change directory to at start Default is to stay in the current directory CELERYD_PID_FILE Full path to the PID file Default is var run celeryd n pid CELERYD_LOG_FILE Full path to the celeryd log file Default is var log celeryd n log CELERYD_LOG_LEVEL Log level to use for celeryd Default is INFO CELERYD_MULTI Path to the celeryd multi program Default is celeryd multi You can point this to a virtualenv or even use manage py for django CELERYCTL Path to the celeryctl program Default is celeryctl You can point this to a virtualenv or even use manage py for django CELERYD_USER User to run celeryd as Default is current user CELERYD_GROUP Group to run celeryd as Default is current user Init script celerybeat Usage etc init d celerybeat start stop restart Configuration file etc default cel
591. y Beanstalk MongoDB CouchDB and in memory Consistent error handling with introspection The ability to ensure that an operation is performed by gracefully handling connection and channel errors Message compression zlib bzip2 or custom compression schemes This means that ghettog is no longer needed as the functionality it provided is already available in Celery by default The virtual transports are also more feature complete with support for exchanges direct and topic The Redis transport even supports fanout exchanges so it is able to perform worker remote control commands e Magic keyword arguments pending deprecation The magic keyword arguments were responsibile for many problems and quirks notably issues with tasks and decorators and name collisions in keyword arguments for the unaware It wasn t easy to find a way to deprecate the magic keyword arguments but we think this is a solution that makes sense and it will not have any adverse effects for existing code The path to a magic keyword argument free world is the celery decorators module is deprecated and the decorators can now be found in celery task The decorators in celery task disables keyword arguments by default All examples in the documentation have been changed to use celery task This means that the following will have magic keyword arguments enabled old style from celery decorators import task task def add x y x xkw
592. y as it doesn t matter if a task is registered twice If you don t want your task to be automatically registered you can set the abstract attribute class MyTask Task abstract True 458 Chapter 2 Contents Celery Documeniation Release 3 0 25 By using abstract only tasks subclassing this task will be automatically registered this works like the Django ORM If you don t want subclasses to be registered either you can set the autoregister attribute to False Incidentally this change also fixes the problems with automatic name assignment and relative im ports So you also don t have to specify a task name anymore if you use relative imports e You can no longer use regular functions as tasks This change was added because it makes the internals a lot more clean and simple However you can now turn functions into tasks by using the task decorator from celery decorators import task task def add x y return x y See also Tasks for more information about the task decorators e The periodic task system has been rewritten to a centralized solution This means celeryd no longer schedules periodic tasks by default but a new daemon has been introduced celerybeat To launch the periodic task scheduler you have to run celerybeat celerybeat Make sure this is running on one server only if you run it twice all periodic tasks will also be executed twice If you only have one worker server you
593. y app control j celery app control Client for worker remote control commands Server implementation is in celery worker control class celery app control Control app None 242 Chapter 2 Contents Celery Documeniation Release 3 0 25 class Mailbox namespace type direct connection None clock None accept None Node hostname None state None channel None handlers None abcast command kwargs call destination command kwargs timeout None callback None channel None cast destination command kwargs connection None exchange None exchange_fmt s pidbox get_queue hostname get_reply queue multi_call command kwargs timeout 1 limit None callback None channel None namespace None node_cls alias of Node oid reply exchange None reply exchange_fmt reply s pidbox reply queue type direct Control add_consumer queue exchange None exchange_type direct routing_key None op tions None kwargs Tell all or specific workers to start consuming from a new queue Only the queue name is required as if only the queue is specified then the exchange routing key will be set to the same name like automatic queues do Note This command does not respect the default queue exchange options in the configuration Parameters e queue Name of queue to start consuming from e exchange Optional name of exchange e exchange_typ
594. y default tick Run a tick that is one iteration of the scheduler Executes all due tasks update_from_dict dict_ exception celery beat SchedulingError An error occured while scheduling a task class celery beat Service max_interval None schedule_filename None scheduler_cls None app None get_scheduler lazy False scheduler scheduler_cls alias of PersistentScheduler start embedded_process False stop wait False sync 2 14 Internals 351 Celery Documentation Release 3 0 25 celery backends e celery backends j celery backends Backend abstract factory did I just say that and alias definitions celery backends default_backend lt celery backends cache CacheBackend object at 0x7fb767118c10 gt deprecated alias to current_app backend celery backends get_backend_by_url backend None loader None celery backends get_backend_cls args kwargs Get backend class by name alias celery backends base e celery backends base I celery backends base Result backend base classes e BaseBackend defines the interface e BaseDictBackend assumes the fields are stored in a dict e KeyValueStoreBackend is a common base class using K V semantics like _get and _put class celery backends base BaseBackend args kwargs Base backend class EXCEPTION_STATES frozenset 7 FAILURE RETRY REVOKED READY_STATES frozenset FAILURE
595. y delay the redelivery of lost tasks in the event of a power failure or forcefully terminated workers Periodic tasks will not be affected by the visibility timeout as this is a concept separate from ETA countdown You can increase this timeout by configuring a transport option with the same name BROKER_TRANSPORT_OPTIONS visibility_timeout 43200 The value must be an int describing the number of seconds e Monitoring events as used by flower and other tools are global and is not affected by the virtual host setting 2 2 Getting Started 13 Celery Documeniation Release 3 0 25 This is caused by a limitation in Redis The Redis PUB SUB channels are global and not affected by the database number Using SQLAIchemy Installation Configuration Celery needs to know the location of your database which should be the usual SQLAIchemy con nection string but with sqla prepended to it BROKER_URL sqlatsqlite celerydb sqlite This transport uses only the BROKER_URL setting which have to be an SQLAIchemy database URI Please see SQLAIchemy Supported Databases for a table of supported databases Here s a list of examples using a selection of other SQLAIchemy Connection String s sqlite filename BROKER_URL sqlatsqlite celerydb sqlite sqlatmysql scott tiger localhost foo BROKER_URL sqlatpostgresql scott tiger localhost mydatabase
596. y threads Pool implementation using threads class celery concurrency threads NullDict dict None kwargs class celery concurrency threads TaskPool args kwargs on_apply target args None kwargs None callback None accept_callback None _ on_start on_stop celery beat e celery beat j celery beat The periodic task scheduler celery beat EmbeddedService args kwargs Return embedded clock service Parameters thread Run threaded instead of as a separate process Default is False class celery beat PersistentScheduler args kwargs close get_schedule info known_suffixes db dat bak dir persistence lt module shelve from usr lib python2 7 shelve pyc gt schedule set_schedule schedule 2 14 Internals 349 Celery Documentation Release 3 0 25 setup_schedule sync class celery beat ScheduleEntry name None task None last_run_at None to tal_run_count None schedule None args kwargs options relative False An entry in the scheduler Parameters e name see name e schedule see schedule e args see args e kwargs see kwargs e options see options e last_run_at see last_run_at e total_run_count see total_run_count e relative Is the time relative to when the server starts args None Positional arguments to apply is_due See is_due kw

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