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The Gridbus Grid Service Broker and Scheduler (2.0) User Guide

1. Optionally the location of the usercert and userkey files can also be specified as attributes of the local element in the proxyCertificate A simple username password type credential can be described as follows credentials id authl type auth gt lt auth username test password pwd gt lt credentials gt Every credential has to be given a unique id which is referred to by one or more resource elements as mentioned earlier 4 3 How to set up persistence The broker comes with a default persistence provider which saves the full broker state periodically to a mySQL database This DB database persistence provider is implemented using JDBC and hence can support any JDBC compliant database in general This section describes the procedure for configuring the broker to use persistence The procedure to enable persistence involves two steps e Installing and configuring the database e Setting the appropriate properties in the configuration file Broker properties First the user needs access to a local or remote database which has the broker database installed and configured for proper access To install the gridbus broker database the broker sql script included in the distribution can be used This will create a new database named gridbusbroker on the database server Additionally an initialisation script named init sql provided with the broker distribution needs to be run after the creation of the database Th
2. resource type Service credential prox2 gt lt service type information gt information type srbMCAT gt lt srbMCAT host srbhost cs mu oz au defaultResource defres domain dom home myhom port 9999 J gt lt information gt lt service gt lt resource gt resource type Service credential authl gt service type information gt lt information type replicaCatalog gt lt replicaCatalog replicaTop top replicaHoste hostname gridbus org lt information gt lt service gt lt resource gt amp gre Note One can observe here that the value of an attribute of a parent element generally determines which child element can be place inside it For example the type attribute of a resource element determines whether a compute storage or service child element can appear within a compute element Likewise the domain attribute of a compute element determines which of local remote becomes its child and so on This pattern is followed throughout the resource description schema Also the credential attribute of any resource element is of particular significance Its value points to the id of the credential which 1s to be used for that resource The seperation of credential and resource elements within the schema helps to specify a description where the same credential such as a proxy certificate or a username password pair is to be used for authenticating to more than one resource
3. It is common experience that such a situation is frequently seen Compute resources are servers to which the users jobs can be submitted for execution Storage resources are used to store the results of execution and hence can be considered as data sinks Service resources are those which provide generic services that can be used by the broker A compute resource is associated with a domain which can take two values local and remote Local resources could be the local computer or a cluster on which the broker is running It could be used to describe a resource which is running job management systems such as Condor PBS Alchemi The user can also optionally specify a list of queues which need to be used on the local jobmanager Remote compute resources are used to represent nodes on the grid which have a job submission interface accessible via a network So resources which run grid middleware such as Globus Unicore Alchemi etc are described here A local compute resource can described as follows resource type compute credential authl gt lt compute domain local gt local jobmanager pbs compute resource 21 The jobmanager attribute can be any of PBS Fork Alchemi Condor In case of PBS Condor on the local compute resource the broker would use the configuration of the Condor PBS client For the Alchemi manager on a local node one would need tp specify the credentials of the user No credentials wo
4. Substitute commands are used to substitute variables in strings or text files locally before sending the job to the remote side Variable objects can be created and added to a job as shown Variables are normally added as strings even though they are numeric The variable values can also refer to filenames The XPML interpreter has certain file resolver APIs which are used to resolve the physical filenames from those containing wildcard characters These need to be used so that the DataHost s and DataFiles collections used in data aware scheduling 28 are properly set up Please refer to the javadocs for further details on their usage Finally after the task is set and variables are added this job 1s added to the list of Jobs in the farming engine The broker retrieves the stdout and stderr of a job by default Any other output files generated by the job however need to be explicitly copied back to the broker node 1 e the machine running the broker Alternatively the job outputs maybe copied to some other remote location by the job as the last step after execution Servers are created using the get ComputeServer method of the ServerFactory class This creates a middleware specific compute server and returns it in the form of an instance of the generic Comput eServer abstract class The ServerFactory has various overloaded methods used to create a ComputeServer instance The least information needed is the hostname of the ComputeServer If the
5. The XPML schema is a bit texty and lengthy so a graphical representation is shown in Figs I3 4 and 15 r pm parameter 3 O emo xpml E E requirement task E 1 oo A 0 00 Figure 13 Broker XPML Schema Diagram The entire schema is not yet fully implemented in the broker The XPML interpreter is designed to be flex ible so that changes in the schema are easily accommodated It makes extensive use of the Java reflection API The entry point into the XPML interpreter is the parseXML method of the XMLReader class This loads an Interpreter class by reflection and calls its process method In this case the XomlInterpreter is loaded The interpreter processes the parameters by calling the ParameterProcessor class again using reflection which in turn reflects on each element that occurs inside a parameter element The idea here is to be easily able to add extensions to the schema while minimizing the changes that need to be made to the interpretation process So the ParameterProcessor can call one of IntegerProcessor StringProcessor GridfileProcessor etc After all the parameters are parsed the Xoml Interpreter parses the requirements and task using the RequirementProcessor and TaskProcessor The TaskProcessor also uses reflection to parse each Command So methods like processCopy processExecute processGCopy etc are called by reflection This makes it easy to add a new type
6. Winton A Grid Service Broker for Scheduling Distributed Data Oriented Applications on Global Grids in Proceedings of the 2nd Workshop on Middleware in Grid Computing MGC 04 5th ACM International Middleware Conference Middleware 2004 Toronto Canada October 2004 52 3 B Hughes S Venugopal and R Buyya Grid based Indexing of a Newswire Corpus in Proceedings of the 5th IEEE ACM International Workshop on Grid Computing GRID 2004 Pittsburgh USA IEEE Computer Society Press Los Alamitos CA USA Nov 2004 4 B Beeson S Melnikoff S Venugopal and D G Barnes A Portal for Grid enabled Physics in Proceedings of the 2005 Australasian Workshop on Grid Computing and e Research AusGrid 2005 Newcastle NSW Australia Australian Computer Society January 2005 53
7. a weather portlet a stock quote portlet and maybe a search portlet These portlets may be completely independent but are organised and presented to the user together as a single web page Portlet standards such as JSR168 enable developers to create portlets that can be plugged into any portal supporting those standards 5 3 2 Why portlets are good for us Portlets are now becoming a very popular and prominent new technology With the promotion of reusability and portability between different portlet frameworks through standards JSR168 there is definitely a strong case for the use of portlets A large number of portlet frameworks are also available to meet varying demands Within a community of web portal developers with a desire for code sharing the case for portlets just gets stronger 5 3 3 The Gridbus Broker portlets These Gridbus Broker portlets show off some of the broker s features The aim is to both provide program mers with an example of what 1s possible with the broker so that much more advanced portlets can then be developed as well as providing the community with a set of reusable portlets providing sophisticated yet simple Grid application management and execution that can be incorporated into any web portal The aim of this guide is to help deploy the example portlets and try to get them to run with Gridsphere portlet framework The portlets are JSR16 8 compliant so even though they were tested within Gridsphere they shou
8. a pre existing Tomcat installation SCATALINA HOME will be the path to Tomcat If you installed Gridsphere packaged with Tomcat then SCATALINA HOME is the path to the Gridsphere installation e Deploying the web archive Copy the gridbusbroker war web archive into the SCATALINA HOME webapps di rectory Restart Tomcat and the web archive will be automatically deployed Login to the Gridsphere portal and access the Portlet Application Manager portlet which 1s located under the Portlets submenu of the Administration menu Deploy the gridbusbroker portlet webapp as shown in Fig 5 By entering gridbusbroker in the Deploy new portlet webapp text field and clicking deploy Gridsphere becomes aware of the new portlets Create a new group and add the gridbusbroker portlets to it To access this option go to the Administration menu then to the groups submenu and then select the create new group option Fig l6 Tell Gridsphere to create a Template layout for the portlets Go to the Welcome menu and tick the box next to the gridbusbroker portlet webapp and then save as shown in Fig 7 A new menu will be displayed that will give you access to the eridbusbroker portlet webapp e Deploying the Gridsphere project using ant deploy If you have downloaded the source version of Gridsphere you can alternatively deploy the Gridsphere project version of the gridbusbroker portlets Start by
9. created by the broker The example XPML file shown above specifies a task with three commands For the grid application de scribed in the file above there are no requirements With this application description the broker creates 3 jobs with job IDs j1 j2 j3 Each job performs the same set of operations or commands as specified in the tasks section copy command has a source and a destination child element each with attributes location and file The location can take the values local and node The local value is interpreted as the machine on which the broker is executing and node is understood by the broker as the remote node on which the job is going to execute These values are substituted at runtime The mcopy and gcopy also have the same attributes 18 For the mcopy command the source location must be node the source file name can include wildcards and the destination must be a directory For the gcopy command the source and destination can be both remote so that third party transfers are possible without the broker intervening in between The gcopy currently supports the gsiftp protocol and is tailored to work with Globus only However in future versions of the broker all the protocols ftp http https gsiftp srb will be eventually supported A substitute command is meant for substitution of parameter also known as variables values in local files which are then used during local operations remote job ex
10. extracting gridbusbroker project tar into the projects sub directory of your Gridsphere source installation The projects directory gets created when you run ant new project from the Gridsphere source installation directory If the projects directory doesn t al ready exist simply create it The basic directory structure should look as follows path to Gridsphere source projects gridbusbroker pud bd reoni iay L7 META INF Se webapp build properties build xml Enter the projects gridbusbroker directory 32 sa gridsphere portal framework open source portlet jsr168 compliant Logout Welcome Hussein Gibbins Portlet Application Manager Portlet web applications 4 Portlet application Description Running Sessions Actions Mon partlet web applications Login configuration options Iv Allow users to create new accounts an the portal a Running Sessions Actions pply Changes Configure portal mail settings Enter outgoing SMTP mail host leave blank if Enter webapp name lgridbusbroker Deploy using localhost Upload Portlet WAR File E 3 Enter e mail address of the portal users can Browse receive email from this address Upload Portlet WAR Deploy new portlet webapp Figure 5 Deploy Broker Portlets Ensure SCATALINA HOME 1s correctly pointing to your Tomcat inst
11. of command to the schema and all that 1s needed would be to add a new processXXXXx method to the TaskProcessor to handle the new command The parameters are tasks parsed are then converted into variables and added to jobs which are created by the Xpml Interpreter To make the broker work with different application description schemes an interpreter for the particular description needs to be written The interpreter would ideally provide methods similar to the XMLReader 42 3 attributes name type domain ParameterType E attributes single E value E attributes m arp range Attrs from random E IIT to type altnbutes IE gap ramgeAtirs Trom range C to lype interval value select anyot O default value select onea O zm default C attributes E ar fileAttrs rotocol ie P AT A url E attributes mput a E expression Figure 14 Broker XPML Schema Diagram Contd class Currently strict interface requirements do not exist Programmers writing interpreters are encouraged to take a look at the code of the XMLReader and create classes on similar lines In future versions of the 43 subettute Figure 15 Broker XPML Schema Diagram Contd 44 broker it is planned to provide well defined interfaces to write interpreters for other application descriptions 5 4 2 Porting the broker for different low level middleware The current version of
12. or application service The task requirements and the resource information drive the discovery of resources such as computational nodes application and data resources The resource discovery module connects to the servers to find out 1f they are available and if they are suitable for the current application The broker uses credentials of the user supplied via the resource description whenever it needs to authenticate with a remote service server Once the jobs are prepared and the servers are discovered the scheduler is started The scheduler maps jobs 1 e submits jobs using the actuator component in the execution sub system to suitable servers based on its algorithm The actuator is a middleware specific component which dispatches the job to the remote grid node On receiving a job submission each server uses its associated server manager to actuate the middle ware specific job submitters also known as Agents The job monitor updates the book keeper by periodically monitoring the jobs using the services of the execution sub system Interface Resource Description A Resource Gatalog Application Description yy Broker Core Grid Information Parameter Resolver Resource Discovery E Service l Task amp Data Requiremen Network Information Service Results Execution Broker node Secure access using user s credentials and middleware supported security mechanisms Remote node Middle
13. properties in the current directory 4 2 The Broker input and configuration files The main input input and config files that are needed by the broker are as follows e The Broker properties configuration file e The XPML application description file format e The Resource description file format Each of these files and their purpose is described in the subsections below 4 2 1 The Broker properties configuration file The Broker is configured via a standard java properties file which is just a plain text file with a name value pairs one on each line The default Broker properties file supplied with the distribution is shown below Name of application description file APP DESC FILE examples calc calc xml Name of resource description file RESOURCE DESC FILE examples calc resources xml DEADLINE 30 Dec 2010 22 16 00 BUDGET 500000 00 Working directory Empty value uses the current directory LOCALDIR Maximum number of files to be processed for analysis set to 0 for all files MAX NUM FILES 3 The time interval in milliseconds for scheduler polling POLLING TIME 10000 property to specify the working environment whether command line cli or tomcat web ENV C 15 SCHEDULE default APP COST false COSTFIL costfil txt Persistence specific entries optional USE PERSISTENCE true PERSISTENCE MODE db DB DRIVER com mysql jdbc Driver DB CONNECTIONSTRING jdbc mysql localhost 3306 gridbusbroker DB USER brokeruser D
14. the Manager is not running as a web service to UNI CORE using the arcon client library to Condor and PBS using their respective command line clients This section describes the main APIs and concepts related to the common broker APIs Fig Mlbelow shows some of the main classes in the broker O org gridbus broker runfile SingleVariable T imports org gridbus broker runfile Task awe Gum be i gridbus broker farming E Job ordrandbusctrokerda mug camionoqueUep JURO org gridbus broker runfile Requirement import JobMonitor prex org gridbus broker runfile TaskCommand Server interfaces O TET o douWramies import ds a e 4 O JobWrapperFactory esse import inpr a ComputeServerManager O ServerFactory 9 org gridbus broker scheduler SchedulerFactory 9 QueueComputeServerManager imports imports imports access 9 DefaultComputeServerManager interfaces org gridbus broker scheduler Scheduler O org gridbus broker farming common queues QueueManager Figure 4 Broker UML Diagram The broker design is based on the architecture described above The main entities in the broker are Farming Engine Scheduler e Job ComputeServer Service 24 e DataHost and DataFile The farming engine is the central component which maintains the overall st
15. the broker is initialized and told to start it executing on the Grid The portlet is simple it allows the user to specify a Unix command and the number of times that they wish to execute that command Running commands like bin hostnameor bin date are usually the most interesting as they tell the user where or when the command was executed Once the command is submitted the portlet needs to 36 Create an instance of the farming engine y create a new farming engine if one doesnt already exist GridbusFarmingEngine fe GridbusFarmingEngine session getAttribute fe if fe mall 4 irv d fe new GridbusFarmingEngine catch Exception e session setAttribute fe fe PortletSession APPLICATION SCOPE Create the jobs as described in other sections of the manual according to the command and number of iterations specified Vector jobs null create the jobs based on the command and number of iterations specified by the user jobs createJobs command Integer parseInt iterations Add the jobs to the farming engine and start the broker fe setJobs jobs schedule our jobs for execution on the Grid fe schedule It should be obvious that when creating the jobs the programmer could implement the createJobs method to create jobs that do anything that the broker would usually be able to handle When referring to any files locally such as an executable that needs to be copied and executed on a re
16. the broker supports Globus 2 4 Globus 3 2 Alchemi 0 8 and Unicore 4 1 experi mental support Each of the middleware plug ins except Globus 3 2 has its own package in the broker 1 e the Globus related classes are in the org gridbus broker farming common globus package Alchemi related classes in org gridbus broker farming common alchemi and so on So to support a new middleware system one just needs to create some middleware specific classes which conform to a certain specification This section gives directions on how to implement a new middleware plug in and a brief description of the Globus implementation To support a new middleware certain middleware specific classes need to be written for the broker These include a middleware specific ComputeServer class and JobWrapper class The ComputeServer abstract class needs to be extended and all the abstract methods are to be implemented These include e discoverProperties e queryJobStatus e shutDownServer e updateStatus Each ComputeServer has an associated ComputeServerManager which is a generic middleware independent class which manages job submission to the ComputeServer using a local job buffer The discoverProperties method is called when the ComputeServerManager is started This method is meant to set the middleware specific properties and initialize any other fields in the ComputeServer sub class This method is used to set the alive status of the server Typically the server is p
17. the remote node for execution This is done by invoking the appropriate middle ware ComputeServer The ComputeServerManager has been extended to handle both stand alone grid nodes and clusters A typical submission and monitoring cycle for a job sent to a Globus node go through the following steps The Scheduler allocates 1 e submits a Job to a ComputeServer The ComputeServer puts the job in its local job buffer and informs the ComputeServerManager The ComputeServerManager creates a globus specific agent a GlobusJobWrapper and sends it to the remote machine The ComputeServerManager then asks the JobMonitor to include this job in the list of jobs it monitors on that server Since we are submitting to Globus here the ComputeServer to which the Scheduler allocates the job would actually 25 be an instance of the GlobusComputeServer class which extends the ComputeServer class The job monitor periodically queries job status by calling the GlobusComputeServer and raises status events for all jobs whose status has changed When the job is done failed the monitor stops monitoring that job Data Hosts are nodes on which data files have been stored These objects store the details of the data files that are stored on them such as their path on the disk and the protocol used to access them The Data Host objects also maintain a list of the compute resources sorted in the descending order of available bandwidth from the host Data File objects store at
18. to a public group while private groups require authorization Please make sure a valid group administrator with valid e mail is added to the group to authorize membership requests PUBLIC PRIVATE select portlets Select portlets that will be made available ta the group Users in this group will have the chance to add these portlets to their layout In addition required roles may be associated with the portlets The Gridbus Broker Monitor This is the Gridbus Broker Monitor Portlet which allows users to USER x M Portlet view monitor the status of the GBB HSER The Gridbus Broker Driver This is the Gridbus Broker Driver Portlet which allows users to run w e M Portlet the GBB o The Gridbus Broker Results This is the Gridbus Broker Results Portlet which allows users to USER s g Portlet view results generated by GBB BSEH Iv DUM credential loader MyProxy credential loader portlet USER The Gridbus Broker Resources This is the Gridbus Broker Resources Portlet which allows users M Portlet Manage resources BSE Figure 6 Create a new group for Broker Portlets 34 sa gridsphere portal framework Logout open source portlet jsr158 compliant Welcome Hussein Gibbins Welcome Administration Gridbus Broker Profile Manager Configure group membership Edit Settings for hussein Last Login Time Tuesday April 12 2005 10 16 04 PM EST Core GridSphere BE IV gridsphere SUPER
19. type of compute server is not specified it is assumed to be a Globus compute server The middleware type of a compute server is any one of the supported middleware currently GLOBUS ALCHEMI UNICORE FORK CONDOR PBS The following code snippet shows the creation of a compute server LocalProxyCredential lpc new LocalProxyCredential lpc setPassword somepassword ComputeServer cs ServerFactory getComputeServer ComputeServer GLOBUS belle cs mu oz au cs setUserCredential lpc fe addServer cs The first two lines of code set the credentials for the server This can be avoided if using a resource description file in which the credentials are specified When a compute server is created the server is not alive and the isAlive method returns false The compute server needs to be started in order to facilitate the discovery process before any of its methods can be put to good use This can be done by calling the start method The start method initiates the compute server manager and a job monitor to keep track of job submission and status updating respectively The manager performs an initialization of the compute server properties by discovering them It does so by pinging the remote node then connecting to it and querying it for certain information Once the properties are discovered the isAlive flag 1s set to true This whole process is done on a seperate thread for each server i e the start method returns im
20. with Java and users who wish to avoid this should simply initialise the broker before starting it so that the broker can pick up the existing proxy e The broker considers all paths on the local node to be relative to either its local directory or its temp directory as configured in the Broker properties This 1s mainly a problem if using the XPML to specify the application description The copy commands in the XPML assume the paths are all relative to the local directory of the broker This issue does not arise when programming the broker since an absolute path can be set using the API e The Unicore implementation is not guaranteed to work and is still shaky at best This issue will probably take a while to resolve since it involves setting up a Unicore node and detailed testing e Data aware scheduling may not be accurate when running the broker on Windows since the broker depends on Network Weather Service NWS for bandwidth data NWS is currently not available for Windows and hence the scheduling may not reflect the correctness of the algorithm 50 e The broker can only work with one SRB catalog at present This is going to be fixed when the XML based resource description 1s implemented in the next version e The full XPML schema itself is not implemented in the current version The schema is likely to be modified and enhanced The future versions of the broker will aim to implement most of the schema definitions e Globus 3 2
21. you may have regarding the Broker Relevant contact information is given below Contact Dr Rajkumar Buyya raj cs mu oz au Srikumar Venugopal srikumar cs mu oz au Krishna Nadiminti kna O cs mu oz au Hussein Gibbins hag cs mu oz au We would like to take this opportunity to acknowledge all the help and support extended to us by all the members of the GRIDS lab CSSE Department Melbourne University The Portlets section was contributed by Hussein on the basis of his experience of using the Broker with the BioGrid Portal development We would to give our special thanks to Dr Fanel Donea Theory VO Scientific Programmer Centre for Astro physics and Supercomputing Swinburne University for his comments about the broker which has helped to make this manual better than what it would have been otherwise We would also like to thank Dr Lyle Winton School of Physics University of Melbourne for his contribution to the intial thoughts over Broker design Note The latest version of this manual will be available online at http www gridbus org broker 2 0 manualv2 p References 1 R Buyya S Date Y Mizuno Matsumoto S Venugopal and D Abramson Neuroscience Instrumentation and Distributed Analysis of Brain Activity Data A Case for eScience on Global Grids Journal of Concurrency and Computation Practice and Experience 2005 Online Available http www gridbus org raj papers neurogrid ccpe pdf 2 S Venugopal R Buyya and L
22. 36 5 3 8 The Gridbus Broker Resources Portlet 0 37 530 The Gridbus Broker Monitor Portlet aoaaa a 39 a 40 RD eee ee eee es 41 5 4 5 Authentication mechanisms 0 6 0 cee ee ee ek ee ee 6 TROUBLESHOOTIN 7_KNOWN ISSUES LIMITATIONS 8 FUTURE DEVELOPMENT PLANS 9 CONCLUSION AND ACKNOWLEDGMENTS 50 50 51 52 1 INTRODUCTION 1 1 Grid Computing A Grid 1s a type of parallel and distributed system that enables the sharing selection and aggregation of geographically distributed autonomous resources dynamically at runtime depending on their availability capability performance cost and users quality of service requirements It should be noted that Grids aim at exploiting synergies that result from cooperation ability to share and aggregate distributed computational capabilities and deliver them as service The next generation of scientific experiments and studies popularly called as e Science is carried out by large collaborations of researchers distributed around the world engaged in analysis of huge collections of data generated by scientific instruments Grid computing has emerged as an enabler for e Science as it permits the creation of virtual organizations that bring together communities with common objectives Within a community data collections are stored or replicated on distributed resources to enhance storage capability or efficiency of access In such an environment scientists n
23. B PWD somepasswordhere 14 NWS NAME SERVER belle cs mu 0z au Log4j Properties I I E A na Root Logger Appenders Levels commented out since cog outputs f everything too which we dont want log4j rootLogger FATAL RL log4j logger org gridbus broker INFO stdout DB log4j logger org gridbus broker test DEBUG stdout log4j logger org gridbus broker persistence INFO log4j logger org gridbus broker xpml INFO log4j appender stdout org apache log4j ConsoleAppender log4j appender stdout layout org apache log4j PatternLayout Pattern to output the caller s file name and line number log4j appender stdout layout ConversionPattern 5p F L m n log4j appender DB org apache log4j RollingFileAppender log4j appender DB File brokerLogs broker log log4j appender RL org apache log4j RollingFileAppender log4j appender RL File brokerLogs rootlogger log log4j appender DB MaxFileSize 1000KB log4j appender RL MaxFileSize 1000KB Keep one backup file log4j appender DB MaxBackupIndex 1 log4j appender DB layout org apache log4j PatternLayout log4j appender DB layout ConversionPattern d Sp t SF L m n log4j appender RL layout org apache log4j PatternLayout Oo log4j appender RL layout ConversionPattern p t c m n oe F oo L In the Broker properties config file show above the broker is configured to look for the application description file
24. JobWrapper is the object that performs the actual process of sending the job to the remote node and executing it there The methods that need to be implemented are e execute e terminate 45 The execute method typically reads in a Job and iterates through all its commands and variables It then performs appropriate operations such as creating scripts etc to actually execute the commands in a job s task Before executing any command on the remote node a temporary directory should be created for each instance of the broker The name of this directory is of the form GB2 lt brokerID gt Each job is expected to create a sub directory inside this broker temp directory on the node All the commands specified in the RunFile package are expected to be implemented in some way Support for accessing data from remote datahosts like SRB for example also should be provided The jobwrapper is expected to copy back the standard output and standard error of each job as two seperate files with names of the form stdout jobID and stderr jobID The brokers JobMonitor associated with each ComputeServer checks for the existence of these files before reporting the job s status as DONE The copy back of the standard out and error are to be implemented such that they are the last things the job does on the remote node The job itself 1s submitted to the remote node in batch mode and a handle to the running job is returned and set via the setJobHandle m
25. The Gridbus Grid Service Broker and Scheduler 2 0 User Guide Krishna Nadiminti Srikumar Venugopal Hussein Gibbins Rajkumar Buyya Grid Computing and Distributed Systems GRIDS Laboratory Department of Computer Science and Software Engineering The University of Melbourne Australia Email kna srikumar hag raj 9 cs mu oz au RECO www gridbus org broker Contents ON xx oko 4e X 3 X e XOU x EOS Y se 4 ARA x R 3 3 93 3 5 30x 3 4 PEE 4 ILLA eee eee ee ade p es toaeaen 6 er ea TS 8 9 2 1 Requirements a 9 2 1 1 Broker side 1 e On the machine running the broker a a a a 9 ee ee ABEAbaaDERA REU RES hese aaa 10 ued bas BAe ewe eee Ar A e A 10 ETTI SLARLLD SI THE BR KER 11 11 12 13 Using the broker on the CLI with various flags 2 a a a a 13 PF 14 42 The Brokerpropertes configuration fill le 14 ee kr ur ee eee 17 42 3 The Resource descrptonfild a ee 19 rr re rr re re 23 5 PROGRAMMER ID 24 51 Design and Implementation 0 0 aa a 24 52 Using the broker in vour own applications 1 a a ee 26 5 3 Usine the broker in a web portal portlets 0 30 5 3 1 What are DOI efs eee ko eRe ee we DEERE ERDEe 9 RS AE 31 5 3 2 Whvportletsaresoodforusg RR 3l 5 3 3 The Gridbus Broker portlet oaoa aa a cce 31 er re eee eer 31 ee ee ee epee eee sura 33 I epee ene eee eee hee eeee
26. User Name hussein Locale Ed English a s Be JSF Tutorial Full Name Hussein Gibbins Fr jsrtutorial portlets USER Email fhag esmu oz au Mrica amp ddis Ababa DP OGCE OGCE USER Address hag des mu 0z au Timezone Africa Algiers mes ESB SR Africa Asmera Gridbus E ERU MEIN USER Organization GRIDS Lab Als amaka Broker portlets Save _Save Configure messaging service Update password Messaging Service Sendmessagesto au o password Figure 7 Configure Broker Portlets group 35 MyProxy Credential Loader Portlet User not Authenticated Username hussein Password oo MyProxy hostname ay Proxy part 7512 load Figure 8 MyProxy Portlet GSSCredential cred null MyProxy myproxy null Pi connect to myproxy server myproxy new MyProxy host Integer parseInt port EA get the credential for this user cred myproxy get username password 3600 ff store credential in session in application scope so other portlets can use it Session setAttribute userCred cred PortletSession APPLICATION SCOPE 5 3 7 The Gridbus Broker Driver Portlet org gridbus broker examples portlets gridbusbroker GBBDriver java Gridbus Broker Driver Portlet Specify command and number of iterations Unis command binzdate Iterations o ruri Figure 9 GBB Driver Portlet The driver portlet is where the majority of the code which uses the broker API is Here
27. a broker configuration file Broker properties 1s found the configuration specified in that file will be loaded Otherwise a default set of values will be loaded The default values for the broker configuration are shown below ENV DEADLINE 1 day BUDGET Long MAX VALUE LOCALDIR System getProperty user dir SCHEDULE default TEMPDIR PM USE PERSISTENCE false PERSISTENCE MODE dp 26 DB DRIVER com mysql jdbc Driver DB CONNECTIONSTRING DB USER DB PWD we POLLING_TIME MAX_NUM_FILES OL O default logger properties root logger log45 log45 log45 log45 log45 log45 rootLogger FATAL RL appender appender appender appender appender RL org apache log4j RollingFileAppender Ri File e prokertogs rootlodger 106 RL MaxFileSize 1000KB RL layout org apache log4j PatternLayout RL layout ConversionPattern Sp t c m n F L Broker specific logs log45 log45 log45 log45 log45 log45 log45 log45 log45 log45 log45 log45 log45 appender appender appender appender appender appender appender appender appender logger org gridbus broker DEBUG stdout DB logger org gridbus broker test DEBUG stdout logger org gridbus broker persistence INFO logger org gridbus broker xpml INFO stdout org apache log4j ConsoleAppender stdout layout org apache log4j PatternLay
28. above The broker database design 1s shown in Fig The design has the Broker table central to all other entities in the database There is one record for each run of the broker in this table The other tables store information about the main broker components ComputeServers Jobs Tasks Variables Datahosts Datafiles all linked with the unique broker id All the tables are updated periodically by the scheduler by calling the store method in the farming engine If a database doesn t suit one s needs for persistence it is a simple task to write a persistence provider for the broker by simply implementing the Reader and Writer interfaces The recovery process involves reviving the broker to a state that was last recorded on persistent storage The unique broker instance id 1s a required input for this mode of operation The recovery follows the steps outlined below e read and create the broker instance the state object associated with the given 1d e populate the state object with the configuration properties used prior to the failure e create the servers from the saved state e create the datahosts and datafile objects from the saved state e create the variables task and jobs in that order from the saved state e start up the manager and monitor threads associated with each compute server e recover the jobs which are already running on the grid re query status and recover job outputs e resume scheduling of jobs which are not subm
29. allation and run the com mand ant deploy This will deploy the gridbusbroker portlets Restart the Tomcat server and then follow steps starting from the third step from Deploying the web archive Now that the broker demo portlets are accessible it is time to see what each of them does and how they have been implemented 5 3 6 The MyProxy Portlet org gridbus broker examples portlets gridbusbroker GetMyProxy java By default a user will not be authorised to interact with any of the broker portlets yet this is because they need a valid proxy so that work can be done out on the Grid assuming the user wants to execute on Globus nodes So initially the user will only have access to the MyProxy portlet The MyProxy portlet will allow users to specify the location of a MyProxy server as well as the username and password of a proxy stored at that location The portlet will retrieve the proxy and make it available to the rest of the portlets by putting it into the session note that the object must be put into application scope or else it won t be found by other portlets This proxy or user credentials will be later passed to the broker in order for it to authenticate to other Grid resources 33 Portlet Group Manager um Group information Enter group name Gridbus Broker Enter a brief description of group idbus broker portlets Group visibility Select if group should be public or private Anyone can add themselves
30. ass to start the broker in the simplest case as shown below tryl Create a new Farming Engine GridbusFarmingEngine fe new GridbusFarmingEngine Set the Application description file fe setAppDescriptionFile calc xml Set the Resource description file fe setResourceDescriptionFile resources xml Call the initialise method to setup jobs and servers fe init Start scheduling fe schedule 12 The schedule method returns immediately after starting the scheduling To wait for results monitor jobs use the following loop ET while fe isSchedulingComplete kcatch Exception e e printStackTrace The samples provided with the broker distribution show some common ways in which the broker can be invoked from a java program or a jsp application The Programmers Manual section has a more detailed explanation of how to use the common broker APIs Programmers who want to use the APIs are suggested to first read through the User Manual section and then go on to the Programmers Manual section which has more detailed explanation of the broker architecture and common APIs The last section of the Pro erammers Manual also has descriptions of how to extend the broker s APIs and build upon them to suit your needs 4 END USER GUIDE 4 1 Using the broker on the CLI with various flags The broker provides the following usage options on the command line gridbus broker mode startUpM
31. ate of the broker at all times It is the glue that binds all the components together It acts as a container for the job and server collections It is the component that interacts with external applications and initiates the scheduling The farming engine can be considered as the broker s in memory database as it holds the broker s current state at any point of time If using persistence the farming engine keeps saving its state periodically to a persistence storage The scheduler is a middleware independent component which maps jobs to nodes on the grid It doesn t need to worry about lower level details and can schedule jobs based on metrics which do not depend on the underlying platform The broker comes with three built in schedulers e economy based scheduler DBScheduler e data aware scheduler DataScheduler e economy and data aware scheduler DBDataScheduler For more details on ue scheduler algorithms pa refer to the Gridbus Broker paper at A Jobis an ET T a unit of work assigned to a node As described in previous sections it consists of Variables and a Task A variable holds the designated parameter value for a job A variable can hold a range of values or a set of values or a single value in which case it is called a single variable A task is the description of what has to be done by the job It is composed of a set of commands There are three types of commands Copy Command Execute Command and Substitute Command The Copy comma
32. broker s installation directory for nix lt broker install dir gt gb2 0 a examples calc calc xml r examples calc resources xml for Windows C lt broker install dir gt gb2 0 bat a examples calc calc xml r examplesicalciresources xml where broker install dir refers to the directory where the broker is installed This will now start the broker and there should be some output scrolling by which informs the user about what the broker is doing For more detailed description about available command line options flags please refer to the User Manual section If invoked via the command line the broker is always a non interactive program This behaviour can be altered to suit the user s needs by using the broker APIs in programs built on top of the broker The next section has some information about how to do that 3 2 Application Programming Interface API The Gridbus broker is designed to be very flexible and extensible It is targeted at both basic usage and customisation by providing programmers the ability to access most of the common APIs which are used internally Starting from the current version v 2 0 the full functionality of the XPML files are available for programmatic access via the API This makes it easy to integrate the broker into your own programs Using the broker in your programs is as simple as copying the gridbroker jar into a place where the libraries for your program are located and invoking a single cl
33. brokerID is the unique ID of the broker generated for each run Inside this directory is one directory for each job that gets submitted to the remote node Inside each job s temp directory on the remote node are all its files inputs and outputs Normally the broker deletes the temp directories on the remote node after it completes execution on the node The shell files on the local side are also deleted However if the logger is set to DEBUG level then these shell files and remote directories are left alone to assist in debugging This section has hopefully helped you to gain a reasonable understanding of the broker APIs to get started on working with the broker You are encouraged to have a look at the full java docs for the broker at http www gridbus org broker 2 0 docs 5 3 Using the broker in a web portal portlets The previous section provided in depth instructions on how to integrate the broker into Java applications by making use of the broker API This section will build on that knowledge and walk through an example of how the broker could be used within a portlet environment highlighting any interesting details along the way This guide assumes the programmer has some experience working with a portlet framework such as 30 Gridsphere and with portlet development 5 3 1 What are portlets Portlets are reusable Web components that are used to compose web portals A news oriented portal may make use of a news article portlet
34. d SRB optimisation of selection of SRB datahosts and multiple SRB federations e Programmer support Cleaner and enhanced APIs for easier programmability The broker APIs available as a set of loosely coupled Web services so that programs written in any language can take advantage of the services of the Gridbus resource broker A plug in for the Eclipse development environment to facilitate programming with and extend ing the broker User friendly GUI Web based tools 51 starting the broker job monitoring browsing and analysing the broker database and execution logs generation and modification of XPML and resource description XML e Others Improved performance scalability and robustness Advanced scheduling algorithms Support for Grid Marker Directory service VO directories and other information services as Community Authorization Service CAS Support for grid economy model via GridBank Ability to invoke any webservice using the broker dynamically at runtime XML based persistence for removing dependence on an external RDBMS 9 CONCLUSION AND ACKNOWLEDGMENTS This manual attempts to explain the design of the Gridbus Broker how to install configure and use it The programmer s manual aims to help programmers use the broker in their own programs and how to extend the broker to tailor it to various situations The Gridbus Broker team would be very happy to an swer any queries that
35. de i e On the machine running the broker e Java Virtual Machine 1 4 2 more info http www java com e Valid certificates properly set up if using remote Globus nodes By default the certificates are places in the USER HOME globus directory where lt USER_HOME gt is the user s home directory for a user belle on a Unix machine this would be home belle globus for a user belle on a Windows NT 2000 XP machine this would be C Documents and Settings belle globus For more information on how to acquire and setup x 509 certificates please consult http www globus orgd securitv vi l certs htmll e Additionally some ports on the local node should be configured to be open so that the jobs can connect back to the broker Please refer to the globus documentation for more details e Optional Components Condor v 6 6 9 submit and execute packages Required if running jobs on a local cluster man aged by a Condor system more info ht tp www cs wisc edu condor downloads OpenPBS v 2 3 Portable Batch System Required 1f running jobs on a local cluster managed by a PBS system more info Network Weather Service NWS v 2 8 client tools Required if running applications that access remote datahosts more info Note NWS client tools are only available for nix Grid applications that need remote data can still be run using the broker on Windows however optimal selection of datahosts 1s not assured sinc
36. e the absence of NWS will mean the broker cannot get that information by itself We are working on some way to avoid workaround this dependency in future versions of the broker SCommands Client tools v 3 x for SRB Storage Resource Broker Required if running applica tions that need to access SRB data more info http www sdsc edu srb scommands index html access to a MySQL v 3 x and above database server installation either on the machine on which the broker is installed or a remote machine Required if using the persistence feature of the broker Recommended if you want more robust failure recovery options The broker will not be able to recover from crashes if persistence 1s disabled 2 1 2 Remote Grid node side For a compute resource e Middleware installation which 1s one of Globus 2 4 more info Globus 3 2 with the pre WS globus gatekeeper and gridftp services running Alchemi 0 8 Cross platform manager more info Unicore Gateway 4 1 experimental support within the broker more info Condor 6 6 90http www cs wisc edu condor downloads e Optional Components on a compute resource SRB SCommands Client tools v 3 x Required if running applications that need to access SRB data For a data host one of the following services should be running e SRB v 3 x OR e Globus GridFTP service Additionally the user should have permissions to access the remote resources In case of G
37. ecution Typically the values of the parameters are determined at runtime and there could be scenarios in which certain input text files need to be tailored for each job using these parameter values Any of the parameters can be used as a variable in the files used in a substitute command by pre fixing to the parameter name So the parameter X is the variable X A substitute command has source and destination file names and a location attribute which must be local The following is an example of a substitute command substitute location local gt source file input gt destination file input jobname lt substitute gt In the substitute command shown above the destination element itself has another variable jobname which refers to the job s unique id So after substitution the input file is tailored to each job and saved as input jl input j2 etc for each job Requirements Certain jobs need a particular environment during execution This environment needs to be setup before the job actually starts executing on the remote node For this purpose the Requirements element is provided It can be used to specify a set of initialisation tasks and in the future conditions Requirements are of two types node and job A node requirement is a set of tasks conditions that need to be satisfied before a node can be used for submission of jobs So a node requirement is performed by the broker before any jobs are submit
38. eed to have the ability to carry out their studies by transparently accessing distributed data and computational resources This is where the concept of resource brokers comes into picture 1 2 Resource Brokers A Resource on a grid could be any entity that provides access to a service This could range from Com pute servers to databases scientific instruments applications and the like In a heterogeneous environment like a grid resources are generally owned by different people communities or organizations with varied administration policies and capabilities Naturally obtaining and managing access to these resources is not a simple task Resource Brokers aim to simplify this process by providing an abstraction layer to users who just want to get their work done In the field of Grids and distributed systems resource brokers are soft ware components that let users access heterogeneous resources transparently without having to worry about availability access methods security issues and other policies The Gridbus resource broker is a resource broker designed with the aim of solving these issues in a simple way 1 3 Gridbus Broker The Gridbus broker is designed to support both computational and data grid applications For example it has been used to support composition and deployment of neuroscience compute intensive applications and High Energy Physics Belle Data Grid applications on Global Grids The architecture of the broker has emphas
39. en running the broker on the command line this is an option that is mandatory The relative absolute path to the resource description file When running the broker on the command line this is an option that is mandatory The deadline to be used in economy based scheduling The deadline is specified in the format dd MMM yyyy HH mm ss The cost of accessing a resource i e price Per Job used in economy based scheduling The Working directory which the broker can use to find input files An Empty value means the current directory is used The Maximum number of files to be processed for during data aware applications Set to O for all files This is mainly used for testing The recommended value is 0 The time interval in milliseconds for scheduler polling Default 10000 if not given The property to specify the working environment whether command line CLI or Tomcat WEB Default CLI The type of scheduling to use Default is cost time optimized economy scheduler Possible values cost time costtime costdata timedata true false Specifies whether to use an additional cost for accessing an application This feature is currently not fully supported and is used in an experimental scheduler optional The name of the file specifying the application cost of network links during data aware scheduling This property is not fully supported and is used in an experimental scheduler optional true false S
40. eter gt element as shown lt parameter name infile type gridfile domain file gt title protocol srb mode block url srb lt db 7jar 7 gt fil PLOLOCOL Lin mode block url ney SsomedirecEeory someotnerd1reclory abe six gt tile protocole srb mode block url sre samole examole gGridtile stdouti 7 gt lt parameter gt An application can have only one task with any number of commands in any order Tasks A task consists of commands such as copy gcopy mcopy execute substitute etc e A copy gcopy mcopy command specifies a copy operation to be performed Each of the copy commands has a source and destination file specified The gcopy supports copying files to and from remote locations The mcopy command can copy complete directories and supports use of the wild card character e An execute command is where actual execution happens The execute command specifies an exe cutable to be run on the remote node It also specifies any arguments to be passed to the command on the command line e A substitute command specifies a string substitution inside a text file This operation is used to substitute the names of user defined variables for example Parameter names can be used as variables with a pre fixed Apart from this certain special default variables are also defined such as OS which specifies the Operating system on the remote node jobname which refers to the job ID of a Job
41. ethod of the job The execute method is also expected to initiate the monitoring of the job set its submitted time stamp remote directory and job handle for the job job getServer startMonitoring job job setJobSubmittedTimestamp job setRemoteDir set the remote dir here job setJobHandle some job handle object obtained from the middleware The execute method therefore returns immediately after sending the job to the remote node and starting execution Since the job is expected to be submitted in batch mode it doesn t wait till the job returns from the node Note In case the middleware doesn t yet support the submission of batch jobs and can only execute jobs interactively the JobWrapper for the middleware may still try to associate some job handle with it and return immediately after the execute method by starting the interactive job on a seperate thread This approach 1s followed in the implementation of the middleware plug in for Alchemi v 0 8 The terminate method is provided for any job specific clean up operations that may need to be done on the remote side The terminate method is called by the JobMonitor after the job is reported done or failed As an example the Globus implementation 1s briefly described The Globus implementation uses the Cog kit v 1 2 for submission and management of jobs on a Globus node The same set of classes are used for both Globus v 2 4 and Globus v 3 2 The GlobusComputeServer class exte
42. her location on the system 5 3 9 The Gridbus Broker Monitor Portlet org gridbus broker examples portlets gridbusbroker GBBMonitor java Gridbus Broker Monitor Portlet WW Ready Waiting E Running E Done all Failed I Unknown refresh Figure 11 GBB Monitor Portlet 39 The broker API provides the programmer with the ability to get all of the jobs and query their status infor mation Using this a simple monitor can be created to report the status of each of the jobs being run Collection jobs new Vector jobs TesgetJobs The collection of the jobs then needs to be sent to the view the JSP for format ng where each job will be queried for its status The broker s overall status can also be queried to determine whether it is stopped running failed finished or complete check the overall status of the broker if fe isSchedulingFailed status failed else if fe isSchedulingFinished status finished else status running More advanced things can be done like checking which server 1s executing which job cancel jobs restart any jobs which may have failed and so on What the programmer decides to do with all the information and flexibility provided by the broker 1s left to the imagination Now the broker has finished executing but how can the user really tell that the commands were successfully run on the remote nodes 5 3 10 The Gridbus Broker Results Portlet o
43. her ways of authentication the UserCredential class would need to be extended and appropriate mechanism is to be implemented As the broker is ported to more middleware it will also support other authentication mechanisms as needed 6 TROUBLESHOOTING This section has some information on troubleshooting the broker It will be kept up to date online at http www gridbus org broker 2 0 manual e If you get a ClassNotFoundException while running the broker please make sure the broker jar and all other jar libraries are in the classpath e When using the broker in Gridsphere portlets running on Windows the system user dir is set to C windows system32 since the portlet container runs as the SYSTEM user So the broker temporary directory is created in the config Vsystemprofile subdirectory of the Windows sys tem directory 7 KNOWN ISSUES LIMITATIONS As with any software made by anyone the broker has its own limitations Some of the most obvious ones are listed here e The broker expects Globus certificates to be in their default directories So the usercert pem and userkey pem need to be located in the globus directory in the user s home directory The next version of the broker will have APIs in the GridProxyUtil class to specify the globus cert locations to override this default behaviour e The grid proxy utility in the broker uses the libraries in the Cog Kit and Java which echo password to the stdout This 1s an inherent problem
44. ilt in mechanisms for job status monitoring and updating of job statistics such as active jobs completed jobs failed jobs etc Once the scheduling is started the jobs get sub mitted to remote nodes and as their status changes the JobMonitor for each server updates the status and the scheduler updates the statistics The JobMonitor uses events to signal JobListeners about statusChanged events for jobs To receive job status events the JobListener interface needs to be implemented The broker has a built in logging system that uses the Apache log4j APIs When the broker is used via the command line or the APIs it creates a log file called broker log in a temporary directory created for each run of the broker The temporary directory is of the form DBxxxxxxxxxxxxxx where the x s are obtained from the current date time stamp In this temp directory are all the files generated by the broker and the jobs it schedules The broker logs are useful for reviewing the broker output messages and debugging Each job produces an stdout jobid and a stderr lt jobid gt file containing the standard output and error There is also one shell file per job in the directory This is the file that actually gets executed on the remote node Apart from these files there are also any other outputs files generated copied back by the job itself On the remote node each invocation of the broker creates a temporary directory that looks like GB2 lt brokerID gt where
45. inged and queried for information in this method If this method fails it is assumed that the server cannot be contacted and it will not be considered to be alive Only servers which are alive are used during scheduling The prepareJob method is meant to set the middleware specific JobWrapper for the job and also set the server for the job The queryJobStatus is used to query the status of a job executing on the remote node It receives the job handle argument as a generic Java Object Using the job handle the queryJobStatus is meant to find out the status of the job interpret its meaning and map it to one of the generic status codes defined in the Job class The status codes defined are all integers and the quer yJobStatus is expected to return an integer The shutDownServer method is provided for any middleware specific clean up procedures which need to be performed once for each server before closing down the broker The updateStatus method is meant for updating the status field of the ComputeServer This is provided for future use even though the current version of the broker doesn t really use the status field The broker mainly checks the isAlive method to determine the server status In addition some of the methods of the ComputeServer can be overridden if the default implementation doesn t suffice for a middleware specific server The other part of a middleware plug in involves creating a class that implements the JobWrapper inter face The
46. iption is obviated A service resource can be of two types information services and application services Information services are typically entities which provide information about other resources or services These could be LDAP directories web services data catalogs etc Currently supported service types include the SRB MCAT and the Replica Catalog Application services provide applications hosted on nodes that can be accessed as a service The example below shows the definition of a SRB Metadata Catalog This is modelled as an information service which can be queried to extract data about available SRB storage resources and files located on them resource type service credential prox2 gt lt service type information gt information type srbMCAT gt lt srbMCAT host srbhost cs mu oz au defaultResource defres domain dom home myhom port 9999 y gt lt information gt lt service gt lt resource gt A credentials entry describes the user s authentication information that is used to access the services provided by a grid resource Credentials can be of the following types x 509 based proxy certificates simple username password pairs MyProxy saved proxies or keystores A proxy credential can be described as follows credentials id proxl type proxyCertificate gt lt proxyCertificate source local gt 22 lt local password proxyPwd gt lt local gt JproxyCertificate credentials
47. is on simplicity extensibility and platform independence It is implemented in Java and provides transparent access to grid nodes running various middleware The main design principles of the broker include e Assume Nothing about the environment No assumptions are made anywhere in the Broker code as to what to expect from the Grid resource except for one that the resource provides atleast one way of submitting a job and if running a flavour of Unix will provide atleast a POSIX shell Also no assumption is made about resource availability throughout an execution The implications of this principle have a huge impact throughout the broker such as The broker has no close integration with any of the middleware it supports It uses the mini mum set of services that are required to run a job on a resource supported by the middleware Advantages of this are In a Grid with multiple resources configured differently the broker tries to make use of ev ery resource possible by not imposing a particular configuration requirement For example in the case of Globus 2 4 all 1s required 1s that the GRAM service be set up properly on the resource The broker can run jobs on resources with different middleware at the same time The broker need not be refactored if there 1s a new version of the middleware The broker is able to handle gracefully jobs and resources failing throughout an execution The job wrapper and job monitor code is writ
48. is sets up some initial values in the database and prepares it for use by the broker It is recommended to create a seperate user login on the database server for enabling access to this database The second step is to set the following properties in the broker config file for example USE PERSISTENCE true PERSISTENCE MODE db DB DRIVER com mysql jdbc Driver DB CONNECTIONSTRING jdbc mysql somehost cs mu oz au 3306 gridbusbroker DB USER brokeruser DB PWD gridbus In the above example the broker is configured to use the db or database persistence provider Currently this is the only provider the broker supports The DB DRIVER specifies the JDBC driver class to used to connect to the database The DB CONNECTIONSTRING specifies the string used to connect to the database server The DB USER DB PWD set the username and password for the database login To disable persistence just set the USE PERSISTENCE property to false 23 5 PROGRAMMER S GUIDE 5 1 Design and Implementation The Gridbus broker has been implemented in Java so that it can be used from the command line deployed in Web enabled environments such as Tomcat driven portals and portlets and also be used as an API within other programs built on top of the services provided by the broker It interfaces to nodes running Globus using the Java Commodity Grid CoG Kit to Alchemi nodes using the Alchemi Cross Platform Manager Interface or the Alchemi command line client if
49. itted 5 4 5 Authentication mechanisms As the broker supports various middleware it also naturally supports the different ways of authenticating to resources on behalf of the user Currently the following methods of authentication with resources are implemented e x 509 proxy certificates generated locally e x 509 proxies stored in MyProxy which can be retrieved by the broker e Simple authentication using a username password pair 48 Gridbus Broker Database Design Diagram DataHost DataFile dhid datahostID datafFileID pathonHast username dtstamp brakerProps i DataFile status Computes broker ID taskObject coud Mm type brokerID name serverMame hosEName huid status brakerID pricePercPLISec eventID pricePerJob sourcell contactString dtstamp History brokerID serverID taskID jebMame status Job Varia r am Iis me variableID remoteDir jobID Event Type handle server ype euid OS tvpe ENT SOUrCE Variable iagram D ign Broker Database Des 16 igure F 49 e Keystore based authentication The x 509 proxies are used for Globus resources and GSI enabled SRB systems Keystores are used for Unicore nodes while Alchemi nodes are supplied with a username password pair for authentication The UserCredential class and its subclasses represent the various credentials that handle authen tication to remote grid nodes To be able to support ot
50. l for Iterator it resources iterator it hasNext cs ComputeServer it next if cs getServerID compareTo req getParameter serverID 0 cs startup break 38 This loop finds which resource needs to be started and then calls the compute server s startup method The portlet may return before the resource s status has been updated so a refresh may be required to update the display A resource can also be stopped during execution The implementation is the same but the shutdown method is called instead of startup Another way to specify to the broker which resources it should use is by using the resource list file as discussed earlier in the manual One could imagine allowing users to upload a resource list and then passing that onto the broker Another option would be to read a resource list that already exists on the server s file system There is an example resource list in the directory gridbusbroker webapp files config resources xml Here is code that can be used to load that file load the description of compute servers froma file String resourceDesc getPortletContext getRealPath files config resources xml fe setResourceDescriptionFile resourceDesc Of most interest here is the following call getPortletContext getRealPath files config resources xml This allows the programmer to refer to resources contained within the web application s directory structure Otherwise Java may look in some ot
51. ld be portable to other frameworks 5 3 4 Pre requisites This guide assumes that the programmer has a working installation of Gridsphere ht tp www gridsphere org This means that you ll also have an installation of Jakarta Tomcat http jakarta apache org tomcat If this has not already done it should be installed before continuing It should be noted that due to the need for GSI security the machine running the portal needs to know about the CA certificates of any Grid resources that will be used Globus cog will look for certificates 1n the globus directory under the current user s user directory both windows or nix Make sure all required CA certificates are located in the appropriate place taking into consideration the user under which Gridsphere is executing as In the case of the author who is running Gridsphere in Windows XP the directory was C WINDOWS system32 config systemprofile globus certificates On a Windows 2000 machine this could be something like C Documents and Settings Default User globus certificates Under nix it would be something like home hag globus certificates 31 5 3 5 Deploying and installing the broker portlets with Gridsphere Next deploy the set of portlets according to the instructions for the portlet framework being used Two ways you can do this in Gridsphere are described below Note If you have downloaded the source version of Gridsphere and have deployed Gridsphere into
52. lobus the user s credentials should be mapped to an account on the remote node Please consult the administrator of the resource for more details 2 2 Installation process Installing the broker 1s a simple process The broker 1s distributed as a tar gz and a zip archive that can be downloaded from http www gridbus org broker 2 0 gridbus broker 2 0 tar gz orhttp www gridbus org broker 2 0 gridbus broker 2 0 zip The installation just involves unzipping the files to any directory and optionally setting the PATH environment variable to include the broker executable script gb2 0 or gb2 0 bat depending on your OS Following are the steps to be fol lowed e Unzip the archive to the directory where you want to install the broker In case of Windows you can use Winzip if you download the zip file or WinRar for the tar gz In case of nix run the command o bar axvt gridbusbroker 2 tgf gz e The following directory structure is created under the main gridbus broker2 0 directory 10 lt broker install directory gt bui contains the broker executable binary docs broker API docs examples example files for using the broker d dog all the libraries needed to run the broker manual manual to install and run the broker sho the broker source code xml the xml schemas used by the inputs to the broker e Change DB HOME variable in the gridbus broker2 0 bin classpath rc file to point to the directory where yo
53. m scheduler for the broker Every scheduler that works with the broker must inherit from the Scheduler class The schedule method is where the algorithm is implemented The scheduler works with the jobs and servers collections and uses methods in the ComputeServer and Job class to find out information about a server or a job The DataHost and DataFile classes are used in data aware scheduling where the scheduler takes into account the effect of moving data around the grid etc The implementation of the schedule method depends entirely on the algorithm chosen The only thing that needs to be taken care of is to check whether a server is alive or not before submitting a job to it using the i sAlive method The schedulers included with the broker are all polling based schedulers which iterate through the entire list of jobs ad servers to select the best server that can execute a job For each poll the jobs which are still UNSUBMITTED are submitted to a suitable server if one 1s found The submission itself doesn t depend on any middleware specific operations as that is handled by the middleware plug ins The submitJob method of the ComputeServer class is used to submit a job to a server Apart from the schedule method the scheduler may choose to override the updateStats method to update the statistics for jobs and servers The farming engine selects a scheduler based on its algorithm type The SchedulerFactory class is used by the farming engine
54. mediately However the farming engine makes sure the start method is called on all servers before starting scheduling So in effect it is not necessary to call this method explicitly if the jobs are to scheduled to servers To begin scheduling jobs the schedule method needs to be called on the farming engine This will get the scheduler defined in the Broker properties file if 1t exists or the default scheduler otherwise There are two ways to override this behaviour One of them is to set the SCHEDULE property of the BrokerProperties class The possible values for this are cost time costtime costdata timedata default The alternate method is to explicity set the scheduler for the farming engine using the SchedulerFactory class The follow ing code shows how to do this l simply call the schedule method to invoke the default scheduler the scheduler defined in the BrokerProperties fe schedule OR 29 2 set the scheduling type algorithm in the BrokerProperties before calling the schedule method for cost optimizing scheduler BrokerProperties setProperty SCHEDULE cost fe schedule OR 3 explicitly create a scheduler object and set the farming engine s scheduler Scheduler s SchedulerFactory getScheduler cost fe fe setScheduler s te schedulet s The schedule method of the farming engine starts the scheduler on a seperate thread and returns imme diately The broker provides bu
55. mote node it may be handy to make use of the PortletContext getRealPath java lang String path method This method will help avoid hard coding absolute paths in portlets Well now the broker is running and the user s command is being run over the Grid well not exactly The broker doesn t know what resources to use yet Luckily there is a portlet that allows the user to specify their resources 5 3 8 The Gridbus Broker Resources Portlet org gridbus broker examples portlets gridbusbroker GBBResources java The job of this portlet is to tell the broker which resources to run on Here the user can add any resources they want to be a part of their Grid Remember that the proxy will need to be valid on any resource that is identified in order for the broker to be able to access it on the user s behalf When a new resource is submitted by the user the portlet needs to make sure there is an instance of the farming engine or else there will be nothing to add the resource to Doing this allows resources to be added before starting execution via the Driver portlet 1f fe nul 4 try 37 Gridbus Broker Resources Portlet Currently available resources Name T manira cs mu oz au globus belle cs mu az au 1 refresh Figure 10 GBB Resources Portlet fe new GridbusFarmingEngine catch Exception e session setAttribute fe fe PortletSession APPLICATION SCOPE Since the broker is already running resource
56. named calc xml in the examples calc directory relative to the current directory from where the broker is executing The resource description option points to the resources xml in the same directory in this case Note The file names are case sensitive or not depending on each operating system nix es are case sensitive Win9x is not Win NT 2000 XP preserves case but ignores them when reading accessing the files It is advised in general to pay attention to the case of the name of these files always and set the values accordingly The Broker properties config file has two sections One dealing with the Broker configuration The other deals with the lo4j logger configuration which is used by the user for logging output The Broker configuration file ignores the lines starting with a H and considers them as comments Please note that the options are all specified in upper case and the broker is particular about the case sensitivity The configuration options available are described in the tables shown in Fig 15 Broker properties Configuration APP DESC FILE RESOURCE DESC FILE DEADLINE BUDGET LOCALDIR MAX NUM FILES POLLING TIME ENV SCHEDULE APP COST COSTFIL USE MARKET DIR Persistence specific entries optional USE PERSISTENCE PERSISTENCE MODE DB DRIVER DB CONNECTIONSTRING DB USER DB PWD The relative absolute path to the XPML application description file that the broker will use Wh
57. nd instructs the broker to copy a file from the source to the destination It can be used for either copying the files from the broker host to the remote node or vice versa A Multiple Copy MCopy is a special case of the CopyCommand which instructs the broker to copy multiple files as described with a wildcard etc A GCopy command provides the ability to copy from one node to another node without the broker intervening in between The GCopy is currently supported only by the Globus middleware plug in The ComputeServer class describes a node on the grid and holds the properties for that node eg its middleware architecture OS etc It is a middleware independent entity and as been extended for differ ent middleware like Globus Alchemi Unicore Condor PBS and also to allow forking jobs on the local node Each ComputeServer has an associated JobMonitor and ComputeServerManager which are also middleware independent A ComputeServer also has an associated UserCredential object which stores the credentials of the user for accessing services provided by that ComputeServer The JobMonitor is responsible for monitoring the execution of all jobs submitted to the remote node corre sponding to this ComputeServer The ComputeServerManager is the component that manages the job submission It uses a local buffer for this purpose and when the job needs to be submitted to the remote node it creates an middleware specific agent and sends this agent to
58. nds the ComputeServer class and implements the abstract methods queryJobStatus discoverProperties shutDownServer and updateStatus It also stores the user s proxy that is used for job submission by the GlobusJobWrapper The queryJobStatus method queries the job on the remote side using the Gram class of the Cog Kit The following are the job status mappings for Globus GramJob STATUS STAGE IN Job SUBMITTED GramJob STATUS ACTIVE Job ACTIVE GramJob STATUS UNSUBMITTED Job UNSUEMITIED GramJob STATUS PENDING Job PENDING GramJob STATUS_FATLED Job FATLED Any other status is mapped to Job UNKNOWN The queryJobStatus is called periodically on a job by the JobMonitor once every polling inter val which is determined by the broker configuration The GlobusComputeServer implements the 46 discoverProperties by querying the MDS on the remote node The information returned by the query 1s used to set the properties for the compute server If the discover properties fails or the remote node cannot be contacted or ping ed then the isAlive flag is set to false The updateStatus is implemented to do nothing specific for Globus currently The GlobusJobWrapper implements the JobWrapper interface and performs all the steps mentioned above in the description of the implementation of the execute method A standard nix shell script is created which includes nix shell commands to implement the various commands in the Runf ile package For ex am
59. needs The Gridbus broker is an open source effort and any help from the community to improve the broker fix bugs add new features etc 1s always welcome Contributions enhancements to the broker code may be 4 included in future distributions after being tested by the broker development team The v 2 0 distribution ships with all the source code and this section describes the design main groups of APIs from the point of view of a developer wanting to contribute towards the broker development The following information applies to those who want to modify the broker source code to suit their needs for example write custom schedulers middleware plug ins application description interpreters etc for the broker 5 4 1 Application Interfaces Application Description Interpreter APIs The first step before running any grid application would be to describe it in some form This step basically involves capturing the requirements and codifying them in a format that can be interpreted by the broker The design of the broker allows it to work with different application descriptions so long as there are appropriate interpreters which convert the description into objects that the broker works with i e the application description 1s mapped to the broker s core objects such as jobs servers datahosts datafiles etc The default application description system based on XML 1s provided with the broker is XPML Extensible Parametric Modeling Language
60. ode brokerID lt ID gt appdesc XPML file name bc BrokerProperties file name resources resources xml or resource list file name help h Displays help on using the Broker on the command line This option cannot be used in combination with any other option test t Tests the Broker installation and configuration This option cannot be used in combination with any other option version v Displays the Broker version number This option cannot be used in combination with any other option mode m Sets the start up mode of the Broker This option can take the following values cli recover If ommitted it defaults to cli command line If the mode is set to recover then brokerID option is mandatory The Broker looks to recover that broker instance whose brokerID is given in the brokerID option Currently the broker supports RDBMS based persistence So the database connection information needs to be specified in the Broker configuration file i e Broker properties for recovery mode to work appdesc a Specifies the app description file to use This option overrides the APP DESC FILE setting in the Broker properties config file resources r Specifies the resource description file This option overrides the RESOURCE DESC FILE setting in the Broker properties config file 13 brokerconfig bc Specifies the Broker configuration file to use If ommitted the broker looks for a config file named Broker
61. ortletConfig getPortletContext getRealPath files results fe getBrokerID The results are then copied into a unique directory based on the broker s ID This way each run will put results in a new directory resultsDir mkdirs gt File files tempDir listFiles for int i 0 i lt files length i if files i getName startsWith output File newFile new File resultsDir getAbsolutePath files i getName files i renameTo newFile Now all the results will be copied over to a directory relative to the web portal so they can be easily accessed The only problem is that the copying only happens when the portlet is reloaded This means that if the portlet is never reloaded then the files will never actually be copied This 1s just one solution to the problem Another solution could involve starting a new thread to monitor the broker s output directory and copy results as soon as they appear Programmers should also be aware that any output from an execution output files from an executable can be accessed like this not only the stdout Well that s it This is just an example of what is possible Hopefully this has demonstrated how easily the broker can be integrated into portals To Grid enable a legacy application with a portlet interface the programmer needs to just modify the Driver and Results portlets to suit the needs of the application 5 4 Modifying or Enhancing the broker code to suit your
62. out stdout layout ConversionPattern 5p F L m n DB org apache log4j RollingFileAppender DB Pile brokerLogs broker log DB MaxFileSize 1000KB DB MaxBackupIndex 10 DB layout org apache log4j PatternLayout Q DB layout ConversionPattern d p t F L m n After creating the farming engine the next step is to setup the jobs and servers This can be done in two ways One way is to create jobs from an application description file currently only the XPML format is supported The other way to create jobs is to use the Task and Command APIs which give the programmer more flexibility Similarly servers can be setup using a resource list file supplied to the farming engine or using the ServerFactory APIs To setup jobs and servers using an application and resource description files use the following fe setAppDescriptionFile calc xml fe setResourceDescriptionFile resources xml Ie lnit Note Use the init method of the farming engine only when supplying the application and resource de scription files The init method fails if these files are not given The init method itself calls the two methods initResources and initJobs 1n that order This order is to be maintained strictly if the initResources initJobs methods are explicitly called by another program This is because the initResources sets up the broker with services which are queried for example to find out the datahos
63. pecifies whether to use the Grid Market Directory The current version of the broker has the Grid Market Directory disabled It is expected to be supported in a future version true false Specifies whether to use persistence in the broker The broker saves its state to persistent storage only if this option is set to true Name of the persistence provider Currently only the database provider is supported To use the DB provider set this to db The fully qualified name of the java database driver class for example for mySQL use com mysal jdbc Driver The jdbc url connection string eg jdbc mysql hostname port gridbusbroker for the database gridbusbroker The username of the database user The password of the database user we are working on storing the password in an encrypted fashion instead of clear text Network weather service specific entries optional NWS NAMESERVER The hostname of 1g Network Weather Service Name Server Figure 3 Broker properties Configuration 4 2 2 The XPML application description file format XPML eXtensible Parametric Modelling Language is an XML based language which is used by the broker to create jobs Simply put an XPML application description file is an XML file with special elements as defined in the XMLSchema that comes with the broker XPML supports description of parameter sweep application execution model in which the same application is run for different values of inpu
64. ple copying files is achieved by using g1obus url copy on the remote node and starting up a GASS server locally one GassServer is started for each GlobusComputeServer SRB support is built in by the use of SCommands which are a command line client interface to SRB A NodeRequirement s job is implemented in a similar way except that it doesn t have its own job directory inside the broker s temp directory on the remote node All the jobs create symbolic links to all files in the broker temp directory which is the parent of each job directory on the remote node After the shell script is created the job RSL is generated and the job is submitted using Gram A handle is obtained and set for the job and the job monitor is informed to start monitoring this job The terminate method in the GlobusJobWrapper just deletes the shell file which is stored locally However the shell file is not deleted if the broker is run in debug mode set using the logger level to DEBUG 5 4 3 Schedulers The scheduler is a middleware independent component and is only concerned with allocating jobs to re sources based on its internal algorithm The design of the broker therefore allows anyone to write their own scheduler to implement a custom algorithm Each scheduler is a class in the org gridbus broker scheduler package The broker currently ships with three schedulers DBScheduler DataScheduler and the DB DataScheduler This section describes the way to write a custo
65. rg gridbus broker examples portlets gridbusbroker GBBResults java Gridbus Broker Results Portlet Results of execution will be listed here Output 0 output 1 Output z output 3 output output 5 output output output output refresh Figure 12 GBB Results Portlet This portlet displays and allows the user to download the stdout generated by each of the iterations The content of output 4 is shown below 40 This job is running on host belle cs mu oz au Executing command bin date Wed Apr 13 01 10 56 EST 2005 GBX 0 Command done Copying file home bellegrid GB2 6AC7C2AB FFCO E7AE AA4E8 ED23BACEB122 DB1113318673296 4 stdout 4 to https 129 250 34 16 3259 brokerLogs DBl111331908391140 o Utp ut 4 The destination is https 128 250 34 16 3259 brokerLogs DB1113318391140 output 4 Note On windows there is a known issue with the broker having trouble copying files to an absolute path locally This is due to globus GASS using https URIs and the inability to specify a drive letter as part of that URI in windows Because of this the outputs are copied over from the broker s working directory into a directory where they can be accessed by the web portal whenever the results portlet 1s refreshed First the source and destination for the copy need to be set move results from brokers temp directory to results directory File tempDir new File fe getTempDirectory File resultsDir new File getP
66. s e services A sample resource description 1s shown below lt xml version 1 0 encoding UTF 8 gt lt xgr 1 xmlns xsi http www w3 org 2001 XMLSchema instance xsi noNamespaceSchemaLocation ResourceDescriptionSchema xsd credentials id proxl type proxyCertificate gt proxyCertificate source local gt local password proxyPwd gt lt local gt lt proxyCertificate gt lt credentials gt credentials id prox2 type proxyCertificate gt lt proxyCertificate source myProxy gt myProxy password test username test host myownserver org lt proxyCertificate gt lt credentials gt credentials id authl type auth gt lt auth username test password pwd gt lt credentials gt credentials id ksl type keystore gt lt keystore file somefile password pwd gt lt credentials gt resource type compute credential authl gt lt compute domain local gt local jobmanager pbs gt lt local gt lt compute gt lt resource gt resource type compute credential proxl gt lt compute domain remote gt lt remote middleware globus gt globus hostname belle cs mu oz au globus remote compute resource resource type compute credential ks1 gt compute domain remote gt remote middleware unicore lt unicore gatewayURL ssl hostname cs mu oz au gt 20 lt remote gt lt compute gt lt resource gt
67. s a range element inside it The range child element has from and to and step attributes which specify the starting ending and step values of the range e A file domain parameter specifies a gridfile which is the url of a remote grid file A gridfile url can have embedded wildcards which are resolved to the actual physical file names by the broker file resolver A gridfile url currently supports the url protocols lfn srb Note The name of the child element must match with the value of the domain attribute of the parameter element A grid application can any number of parameters The number of jobs created is the product of 17 the number of all possible values for each parameter In the example show above parameter X ranges from 1 to 3 The second parameter has a constant value 0 So the number of jobs created is 3 x 1 3 jobs since the first parameter can take 3 possible values and the second parameter can have one possible value In case gridfile type parameters are used the number of jobs can be ascertained only at runtime since the broker has to actually resolve the file names to physical files before creating one job for each file A gridfile parameter can be defined as shown below parameter name infile type gridfile domain file gt lt P be pr rocol srb mode block tei Stb db lt j ar lt parameter gt For multiple gridfiles multiple lt file gt elements are placed within the lt param
68. s are now being added on the fly Adding resources to the broker is simple and is detailed elsewhere in the manual Within a portal it is the same just get the hostname from the form and add it to the farming engine Note that the default compute server type is globus and the ProxyCredential 1s given the credential that was previously retrieved from MyProxy if req getParameter type compareTo globus 0 ProxyCredential pc new ProxyCredential pc setProxy GSSCredential session getAttribute userCred ComputeServer cs ServerFactory getComputeServer req getParameter host fe addserver cs When adding resources prior to starting the broker with a farmingEngine schedule the call to schedule will automatically initialize and start all available resources If the resources have been added after scheduling has started as with the path of this guide each resource will have to be started manually When a resource is added the portlet will show that the resource is in the stopped state and there will be a start button beside it The user must click on the start button to start the resource Starting the resource will allow the broker to identify the resource as being active and will then start giving it work to do If an invalid resource is supplied the startup will fail get the current set of compute servers and set the selected server to alive Collection resources fe getServers ComputeServer cs nul
69. s behaviour can be modified by change the settings in the Broker properties configuration file When running the broker on the command line it needs the following inputs e The Application Description The Application description is provided to the broker as an XPML file which describes the grid application The value for this input can be any absolute or relative path The broker distribution comes with some sample app description files found in the examples directory For example examples calc calc xml e The Resource Description The Resource description specifies the available resources and describes their attributes The broker is pointed to the location of the resource list file which contains the re source description in a xml format The resource description file has a description of the resources that are to be used by the broker for executing the grid application The broker distribution has a sample 11 set of resources which are used by us for testing In almost all cases this file may have to be modified to specify the resources the user has access to For example examples calc resources xml The following instructions assume the broker is being started from the directory where it was installed since it uses relative paths to refer to the broker input files It also assumes that the PATH variable includes the broker binary To run the broker with the default configuration the following command is used at the command prompt from the
70. sability extensibility and flexibility The architecture of the broker is shown in Fig The broker can be thought of as a system composed of three main sub systems e the application interface sub system e the core sub system e he execution sub system Home Node Portal Condor Alchemi Gridbus M Broker AAA naa Data Store The Gridbus broker works with middleware such as Globus UNICORE Alchemi JobManagers such as Condor PBS Data catalogs and also Data storage systems such as the Replica Catalog and SRB Figure 1 Broker Block Diagram The input to the broker is an application description which consists of tasks and the associated parameters with their values and a resource description which could be in the form of a file specifying the hosts available or an information service which the broker queries At the application interface sub system there is the application and resource decription The app description interpreter and the resource discovery module convert these inputs into entities called jobs and servers with which the broker works internally in the core sub system job is an abstraction for a unit of work assigned to a node It consists of a task and variables A variable holds the designated parameter value for a job which are obtained from the process of interpreting the application description A server represents a node on the grid which could provide a compute storage information
71. sed application description format e Support for data sources managed by systems such as Storage Resource Broker SRB and the Globus Replica Catalog e Support for queuing systems such as PBS on clusters e Persistence to enable failure management and recovery of an executing grid application e Extensibility the broker is engineered to support extensions in the form of custom schedulers mid dleware plug ins application description interpreters and persistence providers e Platform independence which is a natural consequence of a java implementation The Gridbus broker comes with a default application description interpreter for a language called XPML eXtensible Parametric Modeling Language which is designed to describe dynamic parameter sweep appli cations on distributed systems in a declarative way As such the broker can easily execute parameter sweep applications on the grid A parameter sweep application is one in which there is a program which operates on multiple sets of data and each instance of the running program is independent of the other instances Such applications are inherently parallel and can be readily adapted to distributed system For more information about research on grids and distributed systems please refer to 1 4 Gridbus Broker Architecture The Gridbus broker follows a service oriented architecture and is designed on object oriented principles with a focus on the idea of promoting simplicity modularity reu
72. support will require pre WS components on the remote node A complete GT3 2 support using the managed job submission services will be offered in the next version 8 FUTURE DEVELOPMENT PLANS The Gridbus Broker is a project in continuous development As part of the Gridbus project it aims to implement the innovations that come out of the research work performed by the members of the GRIDS lab Below 1s a brief about the current plans about the future development path of the broker The list below mainly deals with new features Obviously there will be work going on to rid the broker of its current limitations and also improvement in existing features e Middleware Support for Globus toolkit 4 0 and complete support for v 3 2 using grid service model Support for other middleware low level services such as Clarens NorduGrid CondorG XGrid etc Implementing a middleware simulator to run applications on simulated grid nodes using GridSim Application Description Interfaces and Programming models Extensions to XPML to include enumerated types conditions and loops input validation Support for new application description languages and programming models such as Grid su perscalar ASSIST GAT BPeL4WS A new Grid thread application programming model for creating distributed applications that run on a global grid Data services Improved support for SRB Storage Resource Broker datahosts including GSI enable
73. t parameters often expressed as ranges A simple application description file is shown below lt xml version 1 0 encoding UTF 8 gt xpml xmlns xsi http www w3 org 2001 XMLSchema instance xsi noNamespaceSchemaLocation XMLInputSchema xsd lt parameter name X type integer domain range gt range from type step anterval 1 7 gt lt parameter gt lt parameter name time_base_value type integer domain single gt lt single value 0 gt lt parameter gt lt task type main gt lt COpy gt source locations local file cale gt destination locatione node rrirteetoate copy execute location node gt command valuez calc arg value X gt arg value Stime base value execute copy source locatrone node file output gt destination location local file output Sjobname gt ey CODY task xpml An XPML app description consists of three sections parameters tasks and requirements Param eters Each parameter has a name type and domain and any additional attributes Parameters can be of various types including integer string gridfile and belong to a domain such as single range or file e A single domain parameter specifies a variable with just one value which is of the type specified in the type attribute of the parameter element e A range domain specifies a parameter which can take a range of values A range domain parameter ha
74. ted to it This 1s done once and only once for each node A job requirement is also a set of tasks conditions which are to be performed once for each job Job requirements are currently not implemented in v 2 0 of the broker Requirements can be specified as follows requirement type node lt anything that can go inside a task element can go here lt requirement gt The type can be node or job As mentioned only node 1s currently supported for this version The requirements element can have any number of commands in any order It is similar to the task element in that respect The XPML language is undergoing improvements and refinements It is planned to include more advanced features like if conditions loops enumerated range gt lists etc in future versions For those interested a detailed description of the XPML language schema and the interpretation process is given in the Programmer s manual section 4 23 5 The Resource description file The Resource description file is just an xml file describing the resources that can be used by the broker and their properties as defined in the resource description schema that comes with the broker The Resource 19 description can be used to describe two types of entities resources and credentials to access the resources A resource as defined currently can be of three types e compute resources e storage resource which function as data sink
75. ten to handle every failure status possible The scheduler does not fail if a resource drops out suddenly The failure of the broker itself 1s taken care of by the recovery module if persistence has been configured e Client centric design The scheduler has just one target that is to satisfy the users requirements especially if the deadline and budget are supplied Even in the absence of these the scheduler strives to get the jobs done in the quickest way possible Thus resources are evaluated by the scheduler depending on how fast or slow they are executing the jobs submitted by the broker In keeping with Principle 1 the broker also does not depend on any metrics supplied by the resource it does its own monitoring e Extensibility is the key In Grid environments transient behaviour 1s not only a feature of the resources but also of the middle ware itself Rapid developments in this still evolving field have meant that middleware goes through many versions and unfortunately interface changes are a norm rather than the exception Also chang ing requirements of Grid users require that the broker itself be flexible enough for adding new features or extending old ones Thus every possible care has been taken to keep the design modular and clean The advantages due to this principle Extending broker to support new middleware is a zip Requires implementation of only three interfaces For more details refer to Programming sec
76. tion Getting broker to recognize the new information sources 1s also easy The differences in middleware are invisible to the upper layers such as the scheduler and vice versa Thus any changes made in one part of the code remain limited to that section and are im mediately applicable For example after adding a new middleware the scheduler is immediately able to use any resource using that middleware XPML is extensible Adding any new constructs is easy using the same reflection framework see Programming Section You could also do away with XPML altogether and implement your own favorite interface to describe applications Figlilshows the block diagram of the broker The main features of the Gridbus Broker version 2 are e Discovery of resources on the grid e Transparent Access to computational resources running middleware such as Globus 2 4 Globus 3 2 pre WS Alchemi 0 8 and Unicore 4 1 queuing systems such as Condor 6 6 9 OpenPBS 2 3 This includes support for all basic services like Job scheduling and execution for batch jobs Job monitoring and status reporting Gathering output of completed jobs and directing it to user defined locations Note Unicore Condor PBS support is experimental e Economy based scheduling with built in algorithms for cost time and cost time optimizations e Data aware scheduling which considers network bandwidths and proximity of data to Computational resources e XML ba
77. to get the appropriate scheduler 5 4 4 Persistence providers The broker s persistence feature is designed to provide scalability and fail safe operation The persistence model involved dumping the entire state and execution history of the running broker periodically to persistent 47 storage so that the broker can be revived to its original state in case of a crash or a failure on the broker side The broker is able to be restarted from its last known state and continue executing without much loss in terms of CPU time taken by the jobs that were being executed on the grid The broker recovery process also takes care that finished jobs should not have to be run again This feature becomes especially important when considering real world scenarios and grid economy The persistence model provided is designed to use any persistence storage provider such as a database the local file system etc The Reader and Writer interfaces define a base set of APIs that need to be implemented by any persistence provider The State class derives from the farming engine and is meant to represent the frozen state of the broker at any point of time The default persistence provide that comes with the broker uses a relational database The Reader and Writer interfaces are implemented by the DBReader and DBWriter classes using the generic JDBC APIS The database persistence feature is expected to work with any JDBC compliant RDBMS and has been tested with mySQL v 3 22 and
78. tributes of input files that are required for an application such as size and location A Data File object links to the different Data Hosts that store that file Overall the broker is designed to be a loosely coupled set of components working together The classes in the broker can be grouped into the following main categories e Application description Interpreters e Middleware support e Schedulers e Persistence providers e Other support utils and modules By extending the classes in each group the broker can transparently support many different app description formats schedulers middleware etc For more information on how to develop one or more these components please refer to the section Modifying or Enhancing the broker to suit your needs 5 2 Using the broker in your own applications This section expands on the brief description given in section 3 2 about how to program the broker and use its services in your own application Since the main APIs are already described in the sections above we begin here by looking at some simple examples of the usage of the broker API in a java program The first step in invoking the broker is to create an instance of the Farming Engine This can be achieved by the following code snippet Create a new Farming Engine GridbusFarmingEngine fe new GridbusFarmingEngine This creates the farming engine sets its configuration properties and also configures the default logging options If
79. ts and datafiles needed by the jobs in an application 27 To use the APIs to create jobs Job currentJob new Job currentJob setJobID 51 Create commands Command to Copy the program CopyCommand copy new CopyCommand copy setoource true workingDIR calco true copy setDestination false calc true Command to execute the program ExecuteCommand exec new ExecuteCommand TaskCommand EXECUTE CMD exec setExecutable calc exec addArgument X exec addArgument Stime base value Command to collect the results CopyCommand results new CopyCommand results setSource false output true results setDestination true output currentJob getJobID true Task task new Task task addCommand copy task addCommand exec task addCommand results currentJob setTask task currentJob addVariable new SingleVariable X 1 currentJob addVariable new SingleVariable Stime base value 0 fe addJob currentJob First a new Job object is created job object is associated with Variables and a Task which has any number of commands which can have commands such as Copy GCopy MCopy Execute and Substitute For copy commands Copy MCopy GCopy the source and destination file names need to be set The ExecuteCommand class can be used to execute programs on the remote node As shown above the executable and arguments need to be set for the ExecuteCommand
80. u have installed the broker e Additionally it is recommended to have the directory gridbus broker2 0 bin added to the system PATH variable For example for a Bash shell S export PATH PATH lt broker install directory gt bin e Test the installation by running the broker from a shell S gb2 0 test If you see a message confirming that the configuration is ok congratulations You have successfully installed the gridbus broker on your machine This however only confirms that you have met the basic requirements on your machine to run the broker To be sure that all the features of the broker are functional you will have to make sure the remote resources you have access to are set up properly If the test shows any error messages please refer to the Troubleshooting section of this manual 3 GETTING STARTED USING THE BROKER The Broker can be used as a stand alone command line program or it can be used in your own Java programs or portals This section describes the use of the Gridbus Broker in both modes 3 1 Command Line Interface CLI running the broker as a stand alone program The broker can be invoked from the command line just like any other java program The broker distribution comes with a shell script and a batch file for Windows which just sets the correct classpath and then calls the broker with any command line args passed to it In this mode the broker outputs its messages to both the console and a log file by default Thi
81. uld be needed to fork jobs on the local node however the attribute still needs to be provided for the sake of complete conformance with the schema To describe a remote globus node a description similar to the following 1s used resource type compute credential prox2 gt compute domain remote gt remote middleware globus gt globus hostname manjra csimu oz adu versron 3 2 75 remote compute resource In the above resource description the node manjra cs mu oz au is specified to be running globus v 3 2 and uses the credential identified by the string prox2 This would be the id of a proxy type credential defined elsewhere in the resource description file Similarly other compute resources can be described as defined in the schema A storage resource is a data sink where the user can opt to store the results of execution of a grid applica tion Currently this feature 1s not fully supported by the broker Hence a full description of this element is not given here The user is referred to the schema for more information A future broker version will have an expanded description and implementation of storage resources Note Data sources are discovered by the broker at runtime using the application description which contains file parameters and information catalog services defined as service elements in the resource description Hence the need for explicitly specifying data sources in the resource descr
82. ware Eg Globus UNICORE Alchemi Condor PBS lt gt Remote Data User Process Eg SRB GridFTP source Figure 2 Broker Architecture As they jobs get completed the agents take care of clean up and gathering the output of the jobs The scheduler stops after all the jobs have been scheduled The scheduling policy determines whether failed jobs are restarted or ignored Once all scheduling is complete the broker waits till all jobs are either completed or failed before exiting 1 5 Sample Applications of the Broker The Gridbus Broker has been used in Grid enabling many scientific applications successfully in collabora tion with various institutions worldwide Some of these are listed below e Neuroscience Brain Activity Analysis 1 School of Medicine Osaka University Japan e High Energy Physics 2 School of Physics University of Melbourne e Finance Portfolio analysis Complutense University of Madrid Spain e Natural Language Engineering 3 Dept of Computer Science University of Melbourne e Astrophysics 4 School of Physics University of Melbourne It has been also been utilised in serveral Grid demonstrations including the 2003 IEEE ACM SuperComput ing Conference SC 2003 HPC Challenge demonstration The programmer s perspective of the broker design and implementation including the extensibility features are described in detail in the section 2 INSTALLATION 2 1 Requirements 2 1 1 Broker si

The Gridbus Grid Service Broker and Scheduler (2.0) User Guide

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