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Compaq Reliable Transaction Router User's Manual

1. MS DTC Microsoft DTC see DTC node A physical system nontransactional message A message containing data that does not contain any part of a transaction such as a broadcast or diagnostic message See transactional message partition RTR transactions can be sent to a specific database segment or partition This is data content routing and handled by RTR when so programmed in the application and specified by the system administrator A partition can be in one of three states primary standby and shadow partition properties Information about the attributes of a partition polling A processing method where the application polls for incoming messages primary The state of the partition servicing the original data store or database A primary has a secondary or shadow counterpart process The basic software entity including address space scheduled by system software that provides the context in which an image executes properties Application transaction and system information property classes Classes used for obtaining information about facilities partitions and transactions quorate Nodes roles in a facility that has quorum are quorate quorum The minimum number of routers and backends in a facility usually a majority who must be active and connected for the valid completion of processing quorum node A node defined specified in a facility as a router whose purpose is not to process
2. e You do not need to provide handling code for all messages and events e The sending and receiving of data is abstracted to a higher level with transaction controller and data classes e No buffers and links coding is needed e Internal RTR information is accessible without a need to know RTR internals Architectural Concepts 2 9 XA Support XA Support The XA interface is part of the X Open DTP Distributed Transaction Processing standard It defines the interface that transaction managers TM and resource managers RM use to perform the two phase commit protocol Resource managers are underlying database systems such as ORACLE RDBMS Microsoft SQL Server and others This interface is not used by the application programs it is only used by TM to RM exchanges to coordinate a transaction For details on using XA see the RTR C Application Programmer s Reference Manual and the RTR Application Design Guide 2 10 Architectural Concepts 3 Reliability Features Reliability in RTR is enhanced by the use of Concurrent servers Standby servers Shadow servers Callout servers Router failover Servers Note that conceptually servers can be contrasted as follows Concurrent servers handle similar transactions which access the same data partition and run on the same node Shadow servers handle the same transactions and run on different nodes Standby servers provide a node that can take over processing
3. 2 1 Concurrent server 3 1 D CPU loss 3 3 K Key range 1 16 L LAN 1 23 Link failure recovery 3 2 Load balance 1 17 Lock database 2 5 Database 2 1 2 2 locks 2 5 shared 2 5 Data model partitioned 2 5 Microsoft SQL Server 2 10 Index 1 N Network wide area 1 18 Nodes 2 2 O Object oriented 2 5 Oracle RDBMS 2 10 P Parallel execution 2 4 Partitioned data model 2 5 Processes dient 2 1 server 2 1 R RDBMS 2 10 Recovery 3 2 Reliability features 3 1 Resource manager 2 10 RM 2 10 Router 2 1 failover 3 2 layer 2 2 loss 3 3 RTR API 4 1 broadcasts 2 3 fadilities 2 3 flexibility and growth 2 3 reliability features 3 1 S Security check 1 20 Server callout 3 1 concurrent 3 1 Index 2 Server cont d shadow 3 1 spare 1 16 standby 3 1 types 3 1 Shadow server 1 17 3 1 Shared database 2 5 Spare server 1 16 SQL server 2 10 Standby server 3 1 Subscribe 2 3 T TCP IP 1 23 Three layer model 2 1 TM 2 10 TR 2 1 Transaction 2 4 integrity 2 4 replay 3 2 Transaction manager 2 10 Tunnel 1 22 Two phase commit 3 2 W WAN 1 23 Wide area network 1 18 X X Open DTP 2 10 XA interface 2 10
4. 5 The RTR Runtime Environment 000 00 eee eee 5 5 Whats Next 122222 eb date deat Regi Madre tae ead nndis 5 7 Glossary Index Examples 2 1 Objects Defined Sample 222000005 2 8 Figures eo d ded d oo obo o o o o cA 1 15 1 13 1 14 1 15 1 16 i i7 1 18 1 19 1 20 2 1 2 2 4 1 5 1 5 2 Tables 2 4 RTR Reading Path sess Rem t greed b es Client SYMDOl jase ey mex ee ee eee ues Server Symbol oe nce eee RE Pee eee eee Roles Symbols eese te REEF eed debe aed dee eee esd Facility Symbol 0 000 ee Components in the RTR Environment Two Tier Client Server Environment 5 Three Tier Client Server Environment Browser Applet Configuration 000005 RTR with Browser Single Node and Database RTR Deployed on Two Nodes 0000 eee eee RTR Deployed on Three Nodes sss Standby Server Configuration llle Transactional Shadowing Configuration Two Sites Transactional and Disk Shadowing with Standby SII CTS it a teste asthe techni i lra Aleem a ew A ae oe a ah de oe ht BP Standby ServerS 0 0 00 ccc eee Shadow Servers i 2 deus eee ga rhe kd ee ee oe ec Concurrent Servers sauma ao a me ma ae ia W eee A Callout Server seu ienicerii de aide eee eens Bank Partitioning Example aaas a aaa Standby with Partitioning ilie The
5. Concepts Objects Object Oriented Programming Table 2 1 Functional and Object Oriented Programming Compared Functional Programming Object Oriented Programming A program consists of data A program consists of a team of structures and algorithms cooperating objects The basic programming The basic programming unit is the function that unit is the dass that when when run implements an instantiated implements an algorithm object Functions operate on Objects communicate by sending elemental data types or messages data structures An application s architecture An applications architecture consists of a hierarchy of consists of objects that model functions and sub functions entities of the problem domain Objects relationships can vary In the object oriented environment a program or application is a grouping of cooperating objects The basic programming unit is the dass Instantiating or declaring an instance of a dass implements an object RTR provides object oriented programming capabilities with the C API described in the C Foundation Classes manual Objects are instances of a class In a transaction class each transaction is an object An object is an instantiated declared class Its state and behavior are determined by the attributes and methods defined in the class An object or class is defined by its State attributes e Behavior methods e Identity name at instantiation The name given
6. If one server fails the transaction in process is replayed to another server in the concurrent pool Concurrent servers are designed primarily to increase throughput and can exploit Symmetric Multiprocessing SMP systems Figure 1 17 Concurrent Servers illustrates the use of concurrent servers sending transactions to the same partition on a backend the partition A N Concurrent servers allow transactions to be processed in parallel to increase throughput Concurrent servers deal with the same database partition and may be implemented as multiple 1 18 Introduction Callout server RTR Server Types channels within a single process or as one channel in separate processes Figure 1 17 Concurrent Servers LKG 11275 98WI The callout server provides message authentication on transaction requests made in a given facility and could be used for example to provide audit trail logging A callout server can run on either backend or router nodes A callout server receives a copy of all messages in a facility Because the callout server votes on the outcome of each transaction it receives it can veto any transaction that does not pass its security checks A callout server is facility based not partition based any message arriving at the facility is routed to both the server and the callout A callout server is enabled when the facility is defined Figure 1 18 illustrates the use of a callout server that authenticates every transact
7. The dient application is executing on the frontend and the server on the backend RTR Management Station The user is called user the facility being defined is called DESIGN a client and a server are established and a test message containing the words Kathy s text today is sent from the dient to the server After the server receives this text the user on the server enters the words And this is my response System responses begin with the characters RTR Notes on the procedure are enclosed in square brackets For clarity commands you enter are shown in bold You can view the status of a transaction with the SHOW TRANSACTION command The exchange of messages you observe in executing these commands illustrates RTR activity You need to retain a similar sequence in your own designs for starting up RTR and initiating your own application You can use RTR SHOW and MONITOR commands to display status and examine system state at any time from the CLI For more information on RTR commands see the Reliable Transaction Router System Manager s Manual Note The rtr receive message command waits or blocks if no message is currently available When using the rtr receive message command in the RTR CLI use the TIME qualifier or TIMEOUT to poll for a message if you do not want your rtr_receive_message command to block RTR Interfaces 4 3 RTR Management Station The user issues the following commands on the s
8. ZKO GS015 99AI 1 Introduction This document introduces RTR and describes RTR concepts It is intended for the system manager or administrator and for the application programmer who is developing an application that works with Reliable Transaction Router RTR Reliable Transaction Router Interoperability Networking Reliable Transaction Router RTR is failure tolerant transactional messaging middleware used to implement large distributed applications with client server technologies RTR helps ensure business continuity across multivendor systems and helps maximize uptime You use the architecture of RTR to ensure high availability and transaction completion RTR supports applications that run on different hardware and different operating systems RTR also works with several database products including Oracle Microsoft Access Microsoft SQL Server Sybase and Informix For specifics on operating systems operating system versions and supported hardware see the Reliable Transaction Router Software Product Description for each supported operating system RTR can be deployed in a local or wide area network and can use either TCP IP or DECnet for its underlying network transport Introduction 1 1 RTR Continuous Computing Concepts RTR Continuous Computing Concepts 1 2 Introduction RTR provides a continuous computing environment that is particularly valuable in financial transactions for example in banki
9. business exchange in a bank account might be to move money from a checking account to a savings account The complete transaction is to remove the money from the checking account and add it to the savings account A transaction that transfers funds from one account to another consists of two individual updates one to debit the first account and one to credit the second account The transaction is not complete until both actions are done If a system performing this work goes down after the money has been debited from the checking account but before it has been credited to the savings account the transaction is incomplete With transactional Introduction 1 7 RTR Terminology Nontransactional messaging Transaction ID Transaction Controller 1 8 Introduction messaging RTR ensures that a transaction is all or nothing either fully completed or discarded either both the checking account debit and the savings account credit are done or the checking account debit is backed out and not recorded in the database RTR transactions have the ACID properties An application will also contain nontransactional tasks such as writing diagnostic trace messages or sending a broadcast message about a change in a stock price after a transaction has been completed Every transaction is identified on initiation with a transaction identifier or transaction ID with which it can be logged and tracked To reinforce the use of these terms in
10. on a data partition when the primary server or node fails Callout servers run on backends or routers and receive all messages within a facility so that authentication and logging operations can be performed in parallel All servers are further described in the earlier section on RTR Terminology Reliability Features 3 1 Failover and Recovery Failover and Recovery RTR provides several capabilities to ensure failover and recovery under several circumstances Router Failover Frontend nodes automatically connect to another router if the one being used fails This reconnection is transparent to the application Routers are responsible for coordinating the two phase commit for transactions If the original router coordinating a transaction fails backend nodes select another router that can ensure correct transaction completion Backend Transactions in the process of being committed at the time of a Restart failure are recovered from RTR s disk journal Recovery could be Recovery with a concurrent server a standby server or a restarted server created when the failed backend restarts Correct ordering of the execution of transactions against the database is maintained Transaction Transaction messages which are lost in transit are resent when Message possible The frontend and backend nodes keep an in memory Replay copy of all active messages for this purpose Link Failure In the event of a communications failure RTR tries
11. rtr mt msgl msglen 19 usrhdl 0 Tid 63b01d10 0 0 0 0 2e59 43ea2002 message offset bytes text 000000 4B 61 74 68 79 27 73 20 74 65 78 74 20 74 6F 64 Kathy s text tod 000010 61 79 00 ay reason 0x00000000 RTR gt RTR REPLY TO CLIENT CHAN S And this is my response SRTR S OK normal successful completion RTR gt show transaction Frontend transactions on node NodeA in group username at Mon Aug 28 15 12 10 2000 Tid Facility FE User State 63b01d10 0 0 0 0 2e59 43ea2002 DESIGN username SENDING Router transactions on node NodeA in group username at Mon Aug 28 15 12 10 2000 63b01d10 0 0 0 0 2e59 43ea2002 DESIGN username SENDING Backend transactions on node NodeA in group username at Mon Aug 28 15 12 10 2000 63b01d10 0 0 0 0 2e59 43ea2002 DESIGN username RECEIVING RTR gt RTR_RECEIVE_MESSAGE CHAN S SRTR S OK normal successful completion channel name S msgsb msgtype rtr_mt_prepare if OK use RTR_ACCEPT_TX else use RTR REJECT TX RTR gt RTR RECEIVE MESSAGE TIME 0 RTR STOP RTR Ends example test Commands and system response at client RTR RTR START RTR SRTR S RTRSTART RTR started on node NODEA in group username RTR RTR OPEN CHANNEL CHANNEL C CLIENT fac DESIGN SRTR S OK normal successful completion RTR Interfaces 4 5 RTR Management Station RTR RTR RECEIVE MESSAGE CHANNEL C tim to get mt opened or mt closed SRTR S OK normal successful completion channel name C msgsb m
12. see the RTR C Foundation Classes manual and the RTR Application Design Guide RTR Interfaces 4 7 Application Programming Interfaces Figure 4 1 RTR Browser Interface COMPAQ Syrfem Status at 10 51 39 Ma Jan 24 20090 ETE MANAGER on aTREOcEc dei rirdespal Lj ATR Rename OK Warning SAME Facility QUORUM werfen x eme TOURMAL free spose x E MAKTITIOH Link CONNECT x Lj TRAHEACTIOH Link traffic STALLS x I Losers FLOW control eredits x i APPLICATOR PARTITIOH shehit X pes M CALL Mag outstunding x j Back TO HOME Tremactien QUEUES x Transaction REJECT S x Broadcos EVENT discards x ete additional detail about a resourses can be obtained by menitering the appropriate subsystem If viewing this page in a browser just follow one of the hyperlinks above Te customize threshold valsas te your requirements adit Iis file SYSTEM MON Sample C client Example of object creation in an RTR dient program code Create a Transaction Controller to receive incoming messages and events from a client RTRClientTransactionController pTransaction new RTRClientTransactionController Create an RTRData object to hold an ASCII message for the server RTRData pMessagel new RTRData You are pretty easy to use Send the Server a message Ju sStatus pTransaction gt SendApplicationMessage pMessagel ASSERT RTR_STS_OK sStatus Si
13. specified using RTR configuration commands RTR lets application code be completely location and configuration independent 2 2 Architectural Concepts RTR Facilities Bridge the Gap RTR Facilities Bridge the Gap Many applications can use RTR at the same time without interfering with one another This is achieved by defining a separate facility for each application When an application calls the rtr open channel routine to dedare a channel as a dient or server it specifies the name of the facility it will use See the RTR System Manager s Manual for information on how to define facilities Broadcasts Sometimes an application has a requirement to send unsolicited messages to multiple recipients An example of such an application is a commodity trading system where the clients submit orders and also need to be informed of the latest price changes The RTR broadcast capability meets this requirement Recipients subscribe to a class of broadcasts a sender broadcasts a message in this class all interested recipients receive the message RTR permits dients to broadcast messages to one or more Servers or servers to broadcast to one or more dients If a server needs to broadcast a message to another server it must open a second channel as a dient Flexibility and Growth RTR allows you to cope easily with changes in e Network demand Architectural Concepts 2 3 Flexibility and Growth e User access patt
14. the RTR System Manager s Manual A significant advantage of the partitioning shown in the bank example is that you can add more account numbers without making changes to your application you need only add another server and disk drive for the new account numbers For example Say you need to add account numbers from 90 000 to 99 999 to the basic configuration of Figure 1 19 Bank Partitioning Example You can add these accounts and bring them on line easily The system manager can change the key range with a command for example in an overnight operation or you can plan to do this during scheduled maintenance A partition can also have multiple standby servers Standby Server A node can be configured as a primary server for one key range Configurations and as a standby server for another key range This helps to distribute the work of the standby servers Figure 1 20 illustrates this use of standbys with distributed partitioning As shown in Figure 1 20 Application Server A is the primary server for accounts 1 to 19 999 and Application Server B is the standby for these same accounts Application Server B is the primary for accounts 20 000 to 39 999 and Application Server A can be the standby for these same accounts not shown in the figure For clarity account numbers are shown only for primary servers and one standby server Anonymous clients RTR supports anonymous dients that is dients can be set up in a configuration using wildcard
15. the RTR context this section briefly reviews other uses of configuration terminology A traditional two tier client server environment is based on hardware that separates application presentation and business logic the clients from database server activities The client hardware runs presentation and business logic software and server hardware runs database or data manager DM software also called resource managers RM This type of configuration is illustrated in Figure 1 6 In all diagrams all lines are bidirectional With the C API the Transaction Controller manages transactions one at a time channels messages and events Further separation into three tiers is achieved by separating presentation software from business logic on two systems and retaining a third physical system for interaction with the database This is illustrated in Figure 1 7 RTR extends the three tier model based on hardware to a multitier multilayer or multicomponent software model RTR Terminology Figure 1 6 Two Tier Client Server Environment 1 con Database Server Application Presentation and Business Logic ODBC Model LKG 11204 98WI Figure 1 7 Three Tier Client Server Environment DB Server Database Application Presentation Application Server Database Server User Interface Busin
16. this document such a system is always called a frontend or a node client classes C foundation classes used for implementing client applications commit process The transactional process by which a transaction is prepared accepted committed and hardened in the database commit sequence number CSN A sequence number assigned to an RTR commit group established by the vote window the time interval during which transaction response is returned from the backend to the router All transactions in the commit group have the same CSN and lock the database common classes C foundation classes that can be used in both client and server applications concurrent server A server process identical to other server processes running on the same node CPU Central processing unit data marshalling The capability of using systems of different architectures big endian little endian within one application data object See RTRData object deadlock Deadly embrace a situation that occurs when two transactions or parts of transactions conflict with each other which could violate the consistency ACID property when committing them to the database disk shadowing A process by which identical data are written to multiple disks to increase data availability in the event of a disk failure Used in a duster environment to replicate entire disks or disk volumes See also transactional shadowing dispatch A method in
17. ANY KIND THE ENTIRE RISK ARISING OUT OF THE USE OF THIS INFORMATION REMAINS WITH RECIPIENT IN NO EVENT SHALL COMPAQ BE LIABLE FOR ANY DIRECT CONSEQUENTIAL INCIDENTAL SPECIAL PUNITIVE OR OTHER DAMAGES WHATSOEVER INCLUDING WITHOUT LIMITATION DAMAGES FOR LOSS OF BUSINESS PROFITS BUSINESS INTERRUPTION OR LOSS OF BUSINESS INFORMATION EVEN IF COMPAQ HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES THE FOREGOING SHALL APPLY REGARDLESS OF THE NEGLIGENCE OR OTHER FAULT OF EITHER PARTY AND REGARDLESS OF WHETHER SUCH LIABILITY SOUNDS IN CONTRACT NEGLIGENCE TORT OR ANY OTHER THEORY OF LEGAL LIABILITY AND NOTWITHSTANDING ANY FAILURE OF ESSENTIAL PURPOSE OF ANY LIMITED REMEDY The limited warranties for Compaq products are exclusively set forth in the documentation accompanying such products Nothing herein should be construed as constituting a further or additional warranty This document was prepared using VAX DOCUMENT Version 2 1 Contents Preface sssssse res vii 1 Introduction Reliable Transaction Router 0 0000 ees 1 1 RTR Continuous Computing Concepts 05 1 2 RTR Terminology drca be gaa eel yeaa 1 3 RITR Server l YDeS ss a view wale bee REX Rx X e ee d 1 15 RTR Networking Capabilities llle 1 23 2 Architectural Concepts The Three Layer Model 0000 c cece eee ees 2 1 RTR Facilities Bridge the Gap 0 0 0 0 cee eee 2 3 Broadcasts c conscius hn
18. Reliable Transaction Router Getting Started Order Number AA RLE1A TE January 2001 This document introduces Reliable Transaction Router and describes its concepts for the system manager system administrator and applications programmer Revision Update Information This is a new manual Software Version Reliable Transaction Router Version 4 0 Compaq Computer Corporation Houston Texas 2001 Compaq Computer Corporation Compaq the Compaq logo AlphaServer TruCluster VAX and VMS Registered in U S Patent and Trademark Office DECnet OpenVMS and PATHWORKS are trademarks of Compaq Information Technologies Group L P Microsoft and Windows NT are trademarks of Microsoft Corporation Intel is a trademark of Intel Corporation UNIX and The Open Group are trademarks of The Open Group All other product names mentioned herein may be trademarks or registered trademarks of their respective companies Confidential computer software Valid license from Compaq required for possession use or copying Consistent with FAR 12 211 and 12 212 Commerdal Computer Software Computer Software Documentation and Technical Data for Commercial Items are licensed to the U S Government under vendor s standard commercial license Compaq shall not be liable for technical or editorial errors or omissions contained herein The information in this publication is subject to change without notice and is provided AS IS WITHOUT WARRANTY OF
19. Runtime Environment When all RTR and application components are running the RTR runtime environment contains e Client application The RTR Environment 5 5 The RTR Runtime Environment e Server application e RTR shareable image LIBRTR e RTR control process RTRACP e RTR daemon RTRD Figure 5 2 shows these components and their placement on frontend router and backend nodes The frontend router and backend can be on the same or different nodes If these are all on the same node there is only one RTRACP process Figure 5 2 RTR Runtime Environment RTRACP RTRACP RTR QRTRD COMSER RTR COMSERV RTR COMSERV Optional External Applet Not Running RTR LKG 11215 98WI 5 6 The RTR Environment What s Next Whats Next This concludes the material on RTR concepts and capabilities that all users and implementors should know For more information proceed as follows If you are Read these documents a system manager system 1 RTR Release Notes administrator or software 2 RTR Installation Guide installer 3 RTR Migration Guide if upgrading from RTR V2 to V3 4 RTR System Manager s Manual an applications or system RTR Application Design Guide management developer RTR C Foundation Classes programmer or software RTR C Application engineer Programmer s Reference Manual The RTR Environment 5 7 Glossary A few additional terms are defined in t
20. Three Layer Model sssssssssssssssn Partitioned Data Model 0 00 ees RTR Browser Interface 0 cece cee eee eee RTR System Management Environment RTR Runtime Environment eller Functional and Object Oriented Programming Compared I A x PA eee ee E ek E re T l O O ON DOD O I l _ _ lt A l k 1 18 1 45 1 14 1 15 1217 1 18 1 19 1 20 1 21 1 23 2 5 2 6 4 8 5 3 2 7 Preface Purpose of this Document The goal of this document is to assist an experienced system manager system administrator or application programmer to understand the Reliable Transaction Router RTR product Document Structure This document contains the following chapters Chapter 1 Introduction to RTR provides information on RTR technology basic RTR concepts and RTR terminology Chapter 2 Architectural Concepts introduces the RTR three layer model and explains ths use of RTR functions and programming capabilities Chapter 3 Reliability Features highlights RTR server types and failover and recovery scenarios Chapter 4 RTR Interfaces introduces the management and programming interfaces of RTR Chapter 5 The RTR Environment describes the RTR system management and runtime environments and provides explicit pointers to further reading in the RTR documentation set vii Related Documentation Additional resources in the RTR docum
21. a physical node but in RTR and in this document physical servers are called backends or nodes server classes C foundation classes used for implementing server applications shadow The state of the server process that services a copy of the data store or primary database In the context of RTR the shadow method is transactional shadowing not disk shadowing Its counterpart is primary SMP Symmetric MultiProcessing standby The state of the partition that can take over if the process for which it is on standby is unavailable It is held in reserve ready for use TPS Transactions per second transaction An operation performed on a database typically causing an update to the database Analogous in many cases to a business transaction such as executing a stock trade or purchasing an item in a store A business transaction may consist of one or more than one RTR transaction A transaction is classified as original replay or recovery depending on how it arrives at the backend Original Transadion arrived on the first attempt from the dient Replay Transaction arrived after some failure as the result of a re send from the dient that is from the dient transaction replay buffers in the RTRACP Recovery Transaction arrived as the result of a backend to backend recovery operation recovery from the journal transaction controller A transaction controller processes transactions A transaction control
22. a routing key range of values used Management with a partitioned data model and RTR data content routing Partitions exist for each range of values in the routing key for which a server is available to process transactions Redundant instances of partitions can be started in a distributed network to which RTR automatically manages the state and flow of transactions Partitions and their characterisitcs can be defined by the system manager or operator as well as within application programs RTR management functions enable the operation to manage many partition based attributes and functions induding e Creation deletion of a partition with a user specified name e Defining changing a key range definition Selecting a preferred primary node e Selecting failover precedence between local and cross site shadows e Suspending resuming operations to synchronize database backup with transaction flow e Overriding the automatic recovery procedures of RTR with manual recovery procedures for added flexibility e Specifying retry limits for problem transactions The operator can selectively inspect transactions modify states or remove transactions from the journal or the running RTR system This allows for greater operational control and enhanced management of a system where RTR is running For more details on managing partitions and their use in applications see the RTR System Manager s Manual chapter Partition Management The RTR
23. alee Aes Reha ea alee X AUR See ede ss 2 3 Flexibility and Growth 0 00 00 2 3 Transaction Integrity sien ceai ms gaa a e eaa RG e a 2 4 The Partitioned Data Model 0 00 2 5 Object Oriented Programming 0 eee 2 5 Objects ceci d DEUM Ee ie eee eee 2 7 Messages asi E L4 UR E Ge ee ees e Ca 2 8 Class Relationships llilliiilliiilllllrs 2 8 Polymorphism s carceris urei nna ees 2 9 Object Implementation Benefits 000005 2 9 XA Support iie ex xU ed Re Rd RU aye Rok d a RR iR RR a 2 10 3 Reliability Features ci T 3 1 Failover and Recovery lleeeee tee 3 2 Router Failover zu eosque Ren E hated ee eae ban ES 3 2 Recovery Scenarios leere 3 2 Backend Recovery 000 cece cette tte eee 3 3 Router Recovery uisa Cal LR aes a We ER DE E 3 3 Frontend Recovery 000 cece enn 3 3 4 RTR Interfaces RTR Management Station 0 000 cece eee 4 2 RTR Command Line Interface 000000 4 2 Browser Interface llle 4 7 Application Programming Interfaces 000 4 7 RTR Object Oriented Programming Interface 4 7 RTR C Programming Interface 0000 ee 4 9 5 The RTR Environment The RTR System Management Environment 5 1 Monitoring RTR eaa edd dene RR hex RR eU ERE bade x 5 4 Transaction Management s s s sasaaa 00 cece eee eee 5 4 Partition Management 0 000 cece eee 5
24. another it undergoes a state transition Transaction states are maintained in memory and some are stored in the RTR journal for use in recovery RTR uses three transaction states to track transaction status transaction runtime state e transaction journal state e transaction server state Transaction runtime state describes how a transaction progresses from the point of view of RTR roles FE TR BE A transaction for example can be in one state as seen from the frontend and in another as seen from the router Transaction journal state describes how a transaction progresses from the point of view of the RTR journal The transaction journal state not seen by frontends and routers managed by the backend is used by RTR for recovery replay of a transaction after a failure Transaction server state also managed by the backend describes how a transaction progresses from the point of view of the server RTR uses this state to determine if a server is available to process a new transaction or if a server has voted on a particular transaction The RTR SHOW TRANSACTION command shows transaction status and the RTR SET TRANSACTION command can be used under certain well constrained circumstances to change the state of a live transaction For more details on use of SHOW and SET commands see the RTR Systen Manager s Manual 5 4 The RTR Environment The RTR System Management Environment Partition Partitions are subdivisions of
25. are more fully shown in the RTR Application Design Guide RTR Interfaces 4 9 Application Programming Interfaces Sample C client code Sample C server code 4 10 RTR Interfaces Example of an open channel call in an RTR dient program status rtr open channel amp Channel Flags Facility Recipient RTR NO PEVTNUM Access RTR NO NUMSEG RTR NO PKEYSEGC if Status RTR STS OK Example of a receive message call in an RTR server program status rtr receive message amp Channel RTR NO FLAGS RTR ANYCHAN MsgBuffer DataLen RTR NO TIMOUTMS amp MsgStatusBlock if status RTR STS OK A dient can have one or multiple channels and a server can have one or multiple channels A server can use concurrent servers each with one channel How you create your design depends on whether you have a single CPU or a multiple CPU machine and on your overall design goals and implementation requirements 9 The RTR Environment The RTR environment has two parts e The system management environment e The runtime environment The RTR System Management Environment You manage your RTR environment from a management station which can be on a node running RTR or on some other node You can manage your RTR environment either from your management station running a network browser or from the command line using the RTR CLI From a managment station using a network browser processes use the http protocol for co
26. at object declaration is its identity In Example 2 1 the two dog objects King and Fifi are instances of Dog The Dog class is declared in a header Dog h file and implemented in a cpp file Architectural Concepts 2 7 Object Oriented Programming Example 2 1 Objects Defined Sample Dog h class Dog luus NO main cpp include Dog h main Dog King Dog Fifi Messages Objects communicate by sending messages This is done by calling an object s methods Some principal categories of messages are e Constructors Create objects e Destructors Delete objects e Selectors Return part or all of an object s state For example a Get method e Modifiers Change part or all of an object s state For example a Set method e terators Access multiple element objects within a container object For example an array Class Classes can be related in the following ways Relationships e Simple association One dass is aware of another class For example Dog object is associated with a Master object This is a Knows a relationship e Composition One class contains another dass as part of its attributes For example Dog objects contains Leg objects This is a Has a relationship Inheritance A child class is derived from one or more parent or base classes For example Mutt object derives from Collie object and Boxer object which both derive from Dog object This is an Is a relationship Inheritance e
27. ed node names Tunnel RTR can also be used with firewall tunneling software which supports secure internet communication for an RTR connection either dient to router or router to backend 1 22 Introduction RTR Networking Capabilities Figure 1 20 Standby with Partitioning 1 19999 Application a E Accounts A l i l l l 1 19999 EM NNNM 20000 39999 Aopo 20000 39999 Senas e 7 20000 39999 LKG 11214 98WI RTR Networking Capabilities Depending on operating system RTR uses TCP IP or DECnet as underlying transports for the virtual network RTR facilities and can be deployed in both local area and wide area networks PATHWORKS 32 is required for DECnet configurations on Windows NT Introduction 1 23 2 Architectural Concepts This chapter introduces concepts on basic transaction processing and RTR architecture The Three Layer Model RTR is based on a three layer architecture consisting of frontend FE roles backend BE roles and router TR roles The roles are shown in Figure 2 1 In this and subsequent diagrams rectangles represent physical nodes ovals represent application software and DB represents the disks storing the database and usually the database software that runs on the server Client processes run on nodes defined to have the frontend role This layer allows computing power to be provided locally at the end user site for transaction acquisition and presentation Ser
28. entation kit indude viii Document Content For all users Reliable Transacti on Router Release Notes RTR Commands For the system manager Reliable Transaction Router Installation Guide Reliable Transaction Router Systen Manager s Manual Reliable Transaction Router Migration Guide For the application programmer Reliable Transaction Router Application Design Guide Reliable Transaction Router C Foundation Classes Reliable Transaction Router C Application Programmer s Reference M anual Describes new features changes and known restrictions for RTR Lists all RTR commands their qualifiers and defaults Describes how to install RTR on all supported platforms Describes how to configure manage and monitor RTR Explains how to migrate from RTR Version 2 to RTR Version 3 OpenVMS only Describes how to design application programs for use with RTR illustrated with both the C and C interfaces Describes the object oriented C interface that can be used to implement RTR object oriented applications Explains how to design and code RTR applications using the C programming language contains full descriptions of the basic RTR API calls You can find additional information on RTR and existing implementations on the RTR web site at http www compaq com rtr Reader s Comments Compaq welcomes your comments on this guide Please send your comments and suggestions b
29. ername VOTING Router transactions on node NodeA in group username at Mon Aug 28 15 17 45 2000 63b01d10 0 0 0 0 2e59 43ea2002 DESIGN username VOTING Backend transactions on node NodeA in group username at Mon Aug 28 15 17 45 2000 63b01d10 0 0 0 0 2e59 43ea2002 DESIGN username COMMIT 4 6 RTR Interfaces RTR Management Station RTR RTR RECEIVE MESSAGE SRTR S OK normal successful completion channel name S msgtype rtr mt accepted RTR STOP RTR Browser Interface With the RTR browser interface your management station has a network browser like display from which you can view RTR status and issue RTR certain commands with a point and click operation rather than by entering commands Figure 4 1 shows one screen of the browser interface as you may view it from your management station running Microsoft Internet Explorer Not all RTR CLI commands are accessible to the browser interface only the most commonly used commands are available with the RTR browser The browser interface provides help for forms input and logging windows and navigational aids between displays Application Programming Interfaces RTR Object Oriented Programming Interface You write application programs and management applications with the RTR application programming interfaces You can use the object oriented programming interface to write C applications that use RTR For more information on the object oriented programming interface
30. erns The volume of data Since an RTR based system can be built using multiple systems at each functional layer it easily lends itself to step by step growth avoiding unused capacity at each stage With your system still up and running it is possible to e Create and delete concurrent server processes e Add or remove nodes frontend router or backend This means you do not need to provide spare capacity to allow for growth RTR also allows parallel execution This means that different parts of a single transaction can be processed in parallel by multiple servers RTR provides a comprehensive set of monitoring tools to help you evaluate the volume of traffic passing through the system This can help you respond to unexpected load changes by altering the system configuration dynamically Transaction Integrity RTR greatly simplifies the design and coding of distributed applications because with RTR database actions can be bundled together into transactions To ensure that your application deals with transactions correctly its transactions must be e Atomic e Consistent e Isolated Durable These are the ACID properties of transactions For more detail on these properties see the Reliable Transaction Router Application Design Guide 2 4 Architectural Concepts The Partitioned Data Model The Partitioned Data Model One goal in designing for high transaction throughput is reducing the time that users mus
31. erver application where RTR is running on the backend RTR Copyright Compaq Computer Corporation 1994 RTR gt set mode group SRTR I STACOMSRV starting command server on node NODEA SRTR I GRPMODCHG group changed from to username SRTR I SRVDISCON server disconnected on node NODEA RTR CREATE JOURNAL SRTR I STACOMSRV starting command server on node NODEA in group username SRTR S JOURNALINI journal has been created on device D RTR SHOW JOURNAL Journal configuration on NODEA in group username at Mon Aug 28 14 54 11 2000 Disk D Blocks 1000 RTR gt start rtr SRTR I NOLOGSET logging not set SRTR S RTRSTART RTR started on node NODEA in group username RTR CREATE FACILITY DESIGN ALL ROLES NODEA or all NODEA NODEB SRTR S FACCREATED facility DESIGN created RTR SHOW FACILITY Facilities on node NODEA in group username at Mon Aug 28 15 00 28 2000 Facility Frontend Router Backend DESIGN yes yes yes RTR rtr open server accept explicit prepare explicit chan s fac DESIGN SRTR S OK normal successful completion RTR RTR RECEIVE MESSAGE CHAN S SRTR S OK normal successful completion channel name S msgtype rtr mt opened status normal successful completion When the next command is issued RTR waits for a message from the dient 4 4 RTR Interfaces RTR Management Station RTR RTR RECEIVE MESSAGE CHAN S SRTR S OK normal successful completion channel name S msgsb msgtype
32. ess Logic TRUM RTR provides a multicomponent software model where dients running on frontends routers and servers running on backends cooperate to provide reliable service and transactional integrity Application users interact with the dient presentation layer on the frontend node that forwards messages to the current router The router in turn routes the messages to the current appropriate backend where server applications reside for processing The connection to the current router is maintained until the current router fails or connections to it are lost Introduction 1 9 RTR Terminology All components can reside on a single node but are typically deployed on different nodes to achieve modularity scalability and redundancy for availability With different systems if one physical node goes down or off line another router and backend node takes over In a slightly different configuration you could have an application that uses an external applet running on a browser that connects to a client running on the RTR frontend Such a configuration is shown in Figure 1 8 Figure 1 8 Browser Applet Configuration PC Browser Applet RTR Frontend Web Server Process RTR Client Application LKG 11206 98WI The RTR dient application could be an ASP Active Server Page script or a process interfacing to the webserver through a standard interface such as CGI Common Gateway Interface RTR provides automatic soft
33. essaging Transaction ID Transaction controller Standby server Transactional shadowing RTR journal Partition Key range Introduction 1 3 RTR Terminology RTR Application An RTR application is user written software that executes within the confines of several distributed processes The RTR application may perform user interface business and server logic tasks and is written in response to some business need An RTR application can be written in any language commonly C or C and includes calls to RTR RTR applications are composed of two kinds of actors client applications and server applications An application process is shown in diagrams as an oval open for a client application filled for a server application Client A client is always a client application one that initiates and demarcates a piece of work In the context of RTR a client must run on a node defined to have the frontend role Clients typically deal with presentation services handling forms input screens and so on A client could connect to a browser running a browser applet or be a webserver acting as a gateway In other contexts a client can be a physical system but in RTR and in this document physical clients are called frontends or nodes You can have more than one instance of a client on a node Figure 1 1 Client Symbol C2 Server A server is always a server application one that reacts to a dient s units of work and carries them through to completi
34. faces are e The command line interface or CLI e The browser interface The application programming interfaces APIs are e The object oriented API for C programming available with RTR Version 4 0 Use this API for all new development and where appropriate for new work on existing applications An application can contain both object oriented classes and portable API calls This API can be used to implement applications on all platforms supported by RTR e TheRTR API for C programming available with RTR V3 This interface is also called the Portable API because it can be used to implement applications on all platforms supported by RTR The OpenVMS API containing OpenVMS calls available with RTR V2 This API supported on OpenVMS only is obsolete for new development While applications using this API should be rewritten in the new object oriented API to take advantage of new RTR features and capabilities they can be changed by adding object oriented classes rather than being rewritten You can use the command line interface to the API to write simple RTR applications for testing and experimentation The CLI is described in the Reliable Transaction Router System Manager s Manual Its use is illustrated in this chapter RTR Interfaces 4 1 The RTR application programming interfaces are identical on all hardware and operating system platforms that support RTR The object oriented API is fully described in the manual Reliable T
35. h as node or site outages occur Failover is automatic fault tolerant Hardware built with redundant components to ensure that processing survives component failure frontend FE the physical node in an RTR facility where the dient application runs FTP File transfer protocol inquorate Nodes roles that cannot participate in a facility s transactions are inquorate journal A file containing transactional messages used for recovery key range An attribute of a key segment for example a range A to E or F to K key segment An attribute of a partition that defines the type and range of values that the partition handles LAN Local area network link A communications path between two nodes in a network local node The node on which a C API client or server application runs The local node is the computer on which this instance of the RTR application is executing management classes C API classes used by new or existing applications to manage RTR member See facility member Glossary 5 Glossary 6 message A logical grouping of information transmitted between software components typically over network links message handler A C API derived object used in event driven processing that processes messages multichannel An application that uses more than one channel A server is usually multichannel multithreaded An application that uses more than one thread of execution in a single process
36. he Glossary to the Reliable Transaction Router Application Design Guide ACID Transaction properties supported by RTR atomicity consistency isolation durability ACP The RTR Application Control Process API Application Programming Interface applet A small application designed for running on a browser application User written software that uses employs RTR application classes The C API classes used for implementing client and server applications backend BE the physical node in an RTR facility where the server application runs bank An establishment for the custody of money which it pays out on a customer s request Glossary 1 Glossary 2 branch A subdivision of a bank perhaps in another town broadcast A nontransactional message callout server A server process used for transactional authentication channel A logical port opened by an application with an identifier to exchange messages with RTR client A dient is always a dient application one that initiates and demarcates a piece of work In the context of RTR a client must run on a node defined to have the frontend role Clients typically deal with presentation services handling forms input screens and so on A browser perhaps running an apple could connect to a web application that acts as an RTR dient sending data to a server through RTR In other contexts a client can be a physical system but in the context of RTR and in
37. inder Two facilities are shown indicated by the large double headed arrows the user accounts facility and the general ledger facility The user accounts facility uses three nodes FE TR and BE while the general ledger facility uses only two TR and BE Clients send messages to servers to ask that a piece of work be done Such requests may be bundled together into transactions An RTR transaction consists of one or more messages that have been grouped together by a client application so that the work done as a result of each message can be undone completely if some part of that work cannot be done If the system fails or is 1 6 Introduction RTR Terminology Figure 1 5 Components in the RTR Environment User Accounts Facility FE Client application General Ledger Facility LKG 11203 98WI disconnected before all parts of the transaction are done then the transaction remains incomplete Transaction A transaction is a piece of work or group of operations that must be executed together to perform a consistent transformation of data This group of operations can be distributed across many nodes serving multiple databases Applications use services that RTR provides Transactional RTR provides transactional messaging in which transactions are messaging enclosed in messages controlled by RTR Transactional messaging ensures that each transaction is complete and not partially recorded For example a transaction or
38. ion txn in a facility To authenticate any part of a transaction the callout server must vote on the transaction but does not write to the database RTR does not replay a transaction that is only authenticated Introduction 1 19 RTR Server Types Figure 1 18 A Callout Server Callout Server Application Server To Partition A LKG 11276 98WI Authentication RTR callout servers provide partition independent processing for authentication For example a callout server can enable checks to be carried out on all requests in a given facility Callout servers run on backend or router nodes They receive a copy of every transaction either delivered to or passing through the node Callout servers offer the following advantages The security check can run in parallel with the database updates thus improving response times e The security check can be run on the router hardware The security checking code is completely separated from other application code Since this technique relies on backing out unauthorized transactions it is most suitable when only a small proportion of transactions are expected to fail the security check so as not to have a performance impact 1 20 Introduction RTR Server Types Partition When working with database systems partitioning the database can be essential to ensuring smooth and untrammeled performance with a minimum of bottlenecks When you partition your database you loca
39. l shadow server can also have standby servers for greater reliability When one member of a shadow set fails RTR remembers the transactions executed at the surviving site in a journal and replays them when the failed site returns Only after all journaled transactions are recovered does the recovering site receive new online transactions Transactional shadowing is done by partition A transactional shadow configuration can have only two members of the shadow set Shadow servers are servers on separate backends which handle the same transactions in parallel on identical copies of the database Introduction 1 17 RTR Server Types Figure 1 16 shows a simple shadow configuration The main BE Server at Site 1 and the shadow server Shadow at Site 2 both receive every transaction for the data partition they are servicing Should Site 1 fail Site 2 continues to operate without interruption Sites can be geographically remote for example available at separate locations in a wide area network WAN Figure 1 16 Shadow Servers Terminals Frontends FE Routers TR Backends BE Database DB BE SITE 1 C 23 BE SITE2 C gt TR ZKO GS014 99AI Note that each shadow server can also have standby servers Concurrent server The concurrent server is an additional instance of a server application running on the same node RTR delivers transactions to a free server from the pool of concurrent servers
40. ler may have 0 or 1 transactions active at any moment in time It is through the transaction controller that messages and events are sent and received Glossary 9 Glossary 10 transactional message A message containing transactional data transactional shadowing A process by which identical transactional data are written to separate disks often at separate sites to increase data availability in the event of site failure See also disk shadowing two phase commit A database commit rollback concept that works in two steps 1 The coordinator asks each local recovery manager if it is able to commit the transaction 2 If and only if all local recovery managers agree that they can commit the transaction the coordinator commits the transaction If one or more recovery managers cannot commit the transaction then all are told to roll back the transaction Two phase commit is an all or nothing process either all of a transaction is committed or none of it is WAN Wide area network A ACID 2 4 Anonymous dient 1 22 API 4 1 Application distributed 2 4 software 2 2 Authentication 1 20 Index DECnet 1 23 Distributed applications 2 4 DTP standard 2 10 F Backend 2 1 loss 3 3 BE 2 1 Broadcast 2 3 C Facility 2 3 Failure tolerance 3 2 Fault tolerance 3 2 FE 2 1 Firewall tunneling software 1 22 Frontend 2 1 Callout server 1 20 3 1 Client anonymous 1 22 processes
41. less failover of standbys is not guaranteed Standby servers are spare servers which automatically take over from the main backend if it fails This takeover is transparent to the application Figure 1 15 shows a simple standby configuration The two backend nodes are members of a cluster environment and are both able to access the database For any one key range the main or primary server Server runs on one node while the standby server Standby runs on the other node The standby server process is running but RTR does not pass any transactions to it Should the primary node fail RTR starts passing transactions to Standby Note that 1 16 Introduction Transactional shadow server RTR Server Types one node can contain the primary servers for one key range and standby servers for another key range to balance the load across systems This allows the nodes in a duster environment to act as standby for other nodes without having idle hardware When setting up a standby server both servers must have access to the same journal Figure 1 15 Standby Servers Terminals Frontends FE Routers TR Backends BE Database DB ZKO GS013 99AI The transactional shadow server places all transactions recorded on the primary server on a second database The transactional shadow server can be at the same site or at a different site and must exist in a networked environment A transactiona
42. mmuni cati on The RTR system management environment contains four processes e The RTR Control Process RTRACP e The RTR Command Line Interface RTR CLI e The RTR Command Server Process RTRCOMSERV The RTR daemon RTRD The RTR Control Process RTRACP is the master program It resides on every node where RTR has been installed and is running RTRACP performs the following functions e Manages network links e Sends messages between nodes The RTR Environment 5 1 The RTR System Management Environment Handles all transactions and recovery RTRACP handles interprocess communication traffic network traffic and is the main repository of runtime information ACP processes operate across all RTR roles and execute certain commands both locally and at remote nodes These commands indude FACILITY SET LINK NODE SET CREATE PARTITION SHOW NODE STOP RTR RTR CLI is the Command Line Interface that Accepts commands entered locally by the system manager Sends commands to the Command Server Process RTRCOMSERV Can initiate commands on one node and execute them on another in most cases Commands executed directly by the CLI include DISPLAY DO to the local operating system MONITOR commands RECALL SET ENVIRONMENT SPAWN HELP RTR COMSERV is the Command Server Process that 5 2 The RTR Environment Receives commands from RTR Remains temporarily waiting for another command Exits automatically when idle for
43. nables the use of polymorphism 2 8 Architectural Concepts Polymorphism Object Implementation Benefits Object Oriented Programming Polymorphism is the ability of objects inherited from a common base or parent dass to respond differently to the same message This is done by defining different implementations of the same method name within the individual child class definitions For example A DogArray object DogArray OurDogs 2 refers to two element objects of class Dog the base dass King of dass Doberman is a derived or child class of Dog Fifi of dass Minipoodle is a derived or child class of Dog If in a program OurDogs n gt Bark is called in a loop then e In iteration one 1 method King Bark is called e In iteration two 2 method Fifi Bark is called King s bark does not sound likeFifi s bark because each Bark call is a separately defined method within its child object definition The virtual parent dass Dog method Bark is defined in the class definition of Dog The benefits of creating RTR solutions with C foundation dasses indude the following e Each major RTR concept is represented by its own individual foundation class Simple methods within RTR dasses transform features of RTR for streamlined solutions e Major classes include Get and Set methods for changing transaction states e Default handling code is provided for all Messages and Events where appropriate
44. nal shadow servers Introduction 1 15 RTR Server Types e Concurrent servers e Callout servers These are described in the next few paragraphs You specify server types to your application in RTR API calls RTR server types help to provide continuous availability and a secure transactional environment Standby server The standby server remains idle while the RTR primary backend server performs its work accepting transactions and updating the database When the primary server fails the standby server takes over recovers any in progress transactions updates the database and communicates with clients until the primary server returns There can be many instances of a standby server Activation of the standby server is transparent to the user A typical standby configuration is shown in Figure 1 12 Standby Server Configuration Both physical servers running the RTR backend software are assumed by RTR to connect to the same database The primary server is typically in use and the standby server can be either idle or used for other applications or data partitions or facilities When the primary server becomes unavailable the standby server takes over and completes transactions as shown by the dashed line Primary server failure could be caused by server process failure or backend node failure Standby in a The intended and most common use of a standby server is in a cluster cluster environment In a non cluster environment seam
45. nal shadowing there is no requirement that hardware the data store or the operating system at different sites be the same You could for example have one site running OpenVMS and another running Windows NT the RTR transactional commit process would be the same at each site Note Transactional shadowing shadows only transactions controlled by RTR For full redundancy to assure maximum availability a configuration could employ both disk shadowing in clusters at separate sites coupled with transactional shadowing across sites with standby servers at each site This configuration is shown in Figure 1 14 For clarity not all possible connections are shown n the figure backends running standby servers are shaded connected to routers by dashed lines Only one site the upper site does full disk shadowing the lower site is the shadow for transactions shadowing all transactions being done at the upper site 1 14 Introduction RTR Server Types Figure 1 14 Two Sites Transactional and Disk Shadowing with Standby Servers is sj BE lt gt ua u H gt Transactional E Shadowing E Standby Server or Router LKG 11212 98WI RTR Server Types In the RTR environment in addition to the placement of frontends routers and servers the application designer must determine what server capabilities to use RTR provides four types of software servers for application use e Standby servers Transactio
46. nce we have successfully finished our work tell RTR we accept the transaction pTIransaction AcceptTransaction 4 8 RTR Interfaces Application Programming Interfaces Sample C Example of object creation in an RTR server program server code void CombinationOrderProcessor StartProcessingOrdersAtoL Create an RTRKeySegment for all ASCII values between A and L uy m pkeyRange new RTRKeySegment rtr keyseg string To process strings Length of the key OffsetIntoApplicationProtocol Offset value AT Lowest ASCII value for partition L Highest ASCII value for partition StartProcessingOrders PARTITION NAMEAToL m pKeyRange Create an RTRData Oobject to hold each incoming message or event This object will be reused RTRData pDataReceived new RTRData Continually loop receiving messages and dispatching them to the handlers while true sStatus pTransaction gt Receive amp pDataReceived ASSERT RTR_STS_OK sStatus sStatus pDataReceived gt Dispatch ASSERT RTR_STS_OK sStatus RTR C You can use the C programming interface to write C applications Programming that use RTR For more information on the C programming Interface interface see the RTR C Application Programmer s Reference Manual and the RTR Application Design Guide Snippets from client and server programs using the RTR C programing API follow and
47. nfiguration Primary Server CServer gt Standby Server LKG 11210 98WI To increase transaction availability transactions can be shadowed with a shadow server This is called transactional shadowing and is accomplished by having a second location often at a different site where transactions are also recorded This is illustrated in Figure 1 13 Data are recorded in two Separate data stores or databases The router knows about both backends and sends all transactions to both backends RTR provides the server application with the necessary information to keep the two databases synchronized In the RTR environment one data store database or data file is elected the primary and a second data store is made the shadow The shadow data store is a copy of the data store kept on the primary If either data store becomes unavailable all transactions continue to be processed and stored on the surviving data store At the same time RTR makes a record of remembers all transactions stored only on the shadow data store in the RTR journal by the shadow server When the primary server and data store become available again RTR replays the transactions in the journal to the primary data store through the primary server This brings the data store back into synchronization Introduction 1 13 RTR Terminology Figure 1 13 Transactional Shadowing Configuration Primary MZ ia e Shadow Server LKG 11211 98WI With transactio
48. ng stock trading or passenger reservations systems RTR satisfies many requirements of a continuous computing environment Reliability Failure tolerance Data and transaction integrity e Scalability e Ease of building and maintaining applications e nteroperability with multiple operating systems RTR additionally provides the following capabilities essential in the demanding transaction processing environment Flexibility e Parallel execution at the transaction level e Potential for step by step growth e Comprehensive monitoring tools Management station for single console system management e WAN deployability RTR also ensures that transactions have the ACID properties A transaction with the ACID properties has the following attributes e Atomic e Consistent e Isolated e Durable For more details on transactional ACID properties see the discussion later in this document and in the RTR Application Design Guide RTR Terminology RTR Terminology The following terms are either unique to RTR or redefined when used in the RTR context If you have learned any of these terms in other contexts take the time to assimilate their meaning in the RTR environment The terms are described in the following order Application Client client application Server server application Channel RTR configuration Roles Frontend Router Backend Fadlity Transaction Transactional messaging Nontransactional m
49. ntend role A node that runs server applications is called a backend BE Additionally the transaction router TR contains no application software but acts as a traffic cop between frontends and backends routing transactions to the appropriate destinations The router also eliminates any need for frontends and backends to know about each other in advance This relieves the application programmer from the need to be concerned about network configuration details Introduction 1 5 RTR Terminology Figure 1 3 Roles Symbols Facility The mapping between nodes and roles is done using a facility An RTR facility is the user defined name for a particular configuration whose definition provides the role to node map for a given application Nodes can share several facilities The role of a node is defined within the scope of a particular facility The router is the only role that knows about all three roles A router can run on the same physical node as the frontend or backend if that is required by configuration constraints but such a setup would not take full advantage of failover characteristics Figure 1 4 Facility Symbol A facility name is mapped to specific physical nodes and their roles using the CREATE FACILITY command Figure 1 5 shows the logical relationship between dient application server application frontends F Es routers TRs and backends BEs in the RTR environment The database is represented by the cyl
50. on This may involve updating persistent storage such as a database file toggling a switch on a device or performing another predefined task In the context of RTR a server must run on a node defined to have the backend role In other contexts a server can be a physical system but in RTR and in this document physical servers are called backends or nodes You can have more than one instance of a server on a node Servers can have partition states such as primary standby or shadow 1 4 Introduction Channel RTR configuration Holes RTR Terminology Figure 1 2 Server Symbol e RTR expects client and server applications to identify themselves before they request RTR services During the identification process RTR provides a tag or handle that is used for subsequent interactions This tag or handle is called an RTR channel A channel is used by dient and server applications to exchange units of work with the help of RTR An application process can have one or more client or server channels An RTR configuration consists of nodes that run RTR client and server applications An RTR configuration can run on several operating systems induding OpenVMS Tru64 UNIX and Windows NT among others for the full set of supported operating systems see the title page of this document and the appropriate SPD Nodes are connected by network links A node that runs client applications is called a frontend FE or is said to have the fro
51. ransaction Router C Foundation Classes The C programming API is fully described in the Reliable Transaction Router C Application Programme s Reference Manual Both APIs are used in designs in the RTR Application Design Guide RTR Management Station RTR Command Line Interface 4 2 RTR Interfaces You can manage RTR from a node on which RTR is running from a remote node from which you send RTR commands to a node running RTR or from a browser The node where you enter commands interact with the browser or view results is your management station The command line interface CLI to the RTR API enables the programmer to write short RTR applications from the RTR command line This can be useful for testing short program segments and exploring how RTR works For example the following sequence of commands starts RTR and exchanges a message between a dient and a server To use these examples you execute RTR commands simulating your RTR client application on the frontend and commands simulating your server application on the backend Note The channel identifier identifies the application process to the ACP The dient and server process must each have a unique channel identifier In this example the channel identifier for the client is C and for the server is S Both use the facility called DESIGN The following example shows communication between a client and a server created by entering commands at a terminal keyboard
52. s dnm m sx o pL Journal Browser LKG 11208 98WI Introduction 1 11 RTR Terminology In this example the frontend with the dient and the router reside on one node and the server resides on the backend Frequently routers are placed on backends rather than on frontends A further separation of workload onto three nodes is shown in Figure 1 11 Figure 1 11 RTR Deployed on Three Nodes Browser TR fu1 4 gt gt LKG 11209 98WI This three node configuration separates transaction load onto three nodes but does not provide for continuing work if one of the nodes fails or becomes disconnected from the others In many applications there is a need to ensure that there is a server always available to access the database In this case a standby server will do the job A standby server see Figure 1 12 is a process that can take over when the primary server is not available Both the primary and the standby server access the same database but the primary processes all transactions unless it is unavailable The standby processes transactions only when the primary is unavailable At other times the standby can do other work The standby server is often placed on a node other than the node where the primary server runs 1 12 Introduction Transactional shadowing RTR Journal RTR Terminology Figure 1 12 Standby Server Co
53. sgtype rtr mt opened msglen 8 message status normal successful completion reason 0x00000000 RTR gt RTR START TX CHAN C SRTR S OK normal successful completion RTR RTR SEND TO SERVER CHAN C Kathy s text today text sent to the server SRTR S OK normal successful completion RTR gt show transaction Frontend transactions on node NodeA in group username at Mon Aug 28 15 05 43 2000 Tid Facility FE User State 63b01d10 0 0 0 0 2e59 43ea2002 DESIGN username SENDING Router transactions on node NodeA in group username at Mon Aug 28 15 06 43 2000 63b01d10 0 0 0 0 2e59 43ea2002 DESIGN username SENDING Backend transactions on node NodeA in group username at Mon Aug 28 15 06 43 2000 63b01d10 0 0 0 0 2e59 43ea2002 DESIGN username SENDING RTR RTR RECEIVE MESSAGE TIME 0 CHAN C The following lines arrive at the client from RTR after the user enters commands at the server SRTR S OK normal successful completion channel name C msgsb msgtype rtr mt reply msglen 25 usrhdl 0 tid 63b01d10 0 0 0 0 2e59 43ea2002 message offset bytes text 000000 41 6E 64 20 74 68 69 73 20 69 73 20 6D 79 20 72 And this is my r 000010 65 73 70 6F 6E 73 65 2E 00 esponse RTR gt RTR_ACCEPT_TX CHANNEL C SRTR S OK normal successful completion RTR gt show transaction Frontend transactions on node NodeA in group username at Mon Aug 28 15 17 45 2000 Tid Facility FE User State 63b01d10 0 0 0 0 2659 43ea2002 DESIGN us
54. some time The RTR System Management Environment The Command Server Process executes commands both locally and across nodes Commands that can be executed at the RTR COM SERV include START RTR e CREATE MODIFY JOURNAL SHOW LINK FACILITY SERVER CLIENT ACP must be running Application programmer commands for testing and demonstration The RTR system management environment is illustrated in Figure 5 1 Figure 5 1 RTR System Management Environment RTRACP RTRACP RTR C RTRD QRIRD COMSER COMSERV Cootiseav RTR COMSERV LKG 11216 98WI Management Station Running Browser Software The RTR Environment 5 3 The RTR System Management Environment Monitoring RTR Transaction Management RTR Monitor pictures or the RTR Monitor let you view the status and activities of RTR and your applications A monitor picture is dynamic its data periodically updated RTR SHOW commands that also let you view status are snapshots giving you a view at one moment in time A full list of RTR Monitor pictures is available in the RTR System Manager s Manual RTR Monitoring chapter and in the help file under RTR Monitoring Many RTR Monitor pictures are available using the RTR browser interface The RTR transaction is the heart of an RTR application and transaction state characterizes the current condition of a transaction As a transaction passes from one state to
55. t wait for shared resources While many elements of a transaction processing system can be duplicated one resource that must be shared is the database Users compete for a shared database in three ways e For use of the disk e For locks on database records e For the CPU resources needed to access the database This competition can be alleviated by spreading the database across several backend nodes each node being responsible for a subset of the data or partition RTR enables you to implement this partitioned data model shown roughly in Figure 2 2 where the database has three partitions RTR routes messages to the correct partition on the basis of an application defined key For a more complete description of partitioning as provided with RTR see the Reliable Transaction Router Application Design Guide Object Oriented Programming The C foundation classes map traditional RTR functional programming concepts into an object oriented programming model Using the power and features of these foundation dasses requires a basic understanding of the differences between functional and object oriented programming concepts Table 2 1 compares the worlds of functional programming and object oriented programming Architectural Concepts 2 5 Object Oriented Programming Figure 2 2 Partitioned Data Model Terminals Frontends FE Routers TR Backends BE Database DB ZKO GS012 99AI 2 6 Architectural
56. te different parts of your database on different disk drives to spread both the physical storage of your database onto different physical media and to balance access traffic across different disk controllers and drives For example in a banking environment you could partition your database by account number as shown in Figure 1 19 A partition is a segment of your database Figure 1 19 Bank Partitioning Example iy ee eae Appn i iServer BE LKG 11213 98WI Key range Once you have decided to partition your database you use key ranges in your application to specify how to route transactions to the appropriate database partition A key range is the range of data held in each partition For example the key range for the first partition in the bank partitioning example goes from 00001 to 19999 You can assign a partition name in your application program or have it set by the system manager Note that sometimes the terms key range and partition are used as synonyms in code examples and samples with RTR Introduction 1 21 RTR Server Types but strictly speaking the key range defines the partition A partition has both a name its partition name and an identifier generated by RTR the partition ID The properties of a partition callout standby shadow concurrent key segment range can be defined by the system manager with a CREATE PARTITION command For details of the command syntax see
57. the C API RTRData dass which when called interprets the contents on the RTRData object and calls an appropriate handler to process the data The handler chosen to process the data is the handler registered with the transaction controller This method is used with the event driven receive model DTC Microsoft Distributed Transaction Coordinator Glossary 3 Glossary 4 endian The byte ordering of multibyte values Big endian high order byte at starting address little endian low order byte at starting address event RTR or application generated information about an application or RTR event driven A processing model in which the application receives messages and events by registering handlers with the transaction controller These handlers are derived from the C foundation dass message and event handler classes event handler A C API derived object used in event driven processing that processes events facility The mapping between nodes and roles used by RTR and established when the facility is created facility manager A C API management class that creates and deletes facilities facility member A defined entity within a facility A facility member is a role and node combined Can be a dient router or server failover The ability to continue operation on a second system when the first has failed or become disconnected failure tolerant Software that enables an application to continue when failures suc
58. to reconnect Recovery the link or links until it succeeds Recovery Scenarios This section describes how RTR recovers from different hardware and software failure For additional information on failure and recovery scenarios see the RTR Application Design Guide 3 2 Reliability Features Backend Recovery Router Recovery Frontend Recovery Recovery Scenarios If standby or shadow servers are available on another backend node operation of the rest of the system will continue without interruption using the standby or shadow server If a backend processor is lost any transactions in progress are remembered by RTR and later recovered either when the backend restarts or by a standby if one is present Thus the distributed database is brought back to a transaction consistent state If a router fails and another router node is available all in progress transactions are transparently re routed by the other router System operation will continue without interruption If a frontend is lost e All transactions committed but not completed on the frontend node at the time of failure will be completed e All transactions started but not committed on the frontend node at the time of failure will be aborted Reliability Features 3 3 4 RTR Interfaces RTR provides interfaces for management and application programmi ng You manage RTR with a management interface from the RTR management station The management inter
59. transactions but to ensure that quorum negotiations are possible quorum threshold The minimum number of routers and backends in a facility required to achieve quorum roles Roles are defined for each node in an RTR configuration based on the requirements of a specific facility Roles are frontend router or backend Glossary 7 Glossary 8 rollback When a transaction has been committed on the primary database but cannot be committed on its shadow the committed transaction must be removed or rolled back to restore the database to its pre transaction state router The RTR role that manages traffic between RTR clients and servers RTR configuration The set of nodes disk drives and connections between them used by RTR RTR environment The RTR run time and system management areas RTRData object An instance of the C API RTRData class This object contains either a message or an event It is used for both sending and receiving data between client and server applications secondary See shadow Server A server is always a server application or process one that reacts to a client application s units of work and carries them through to completion This may involve updating persistent storage such as a database file toggling the switch on a device or performing another pre defined task In the context of RTR a server must run on a node defined to have the backend role In other contexts a server may be
60. ver processes represented by Server in Figure 2 1 run on nodes defined to have the backend role This layer Allows the database to be distributed geographically e Permits replication of servers to cope with either network node or site failures e Allows computer resources to be added to meet performance requirements Architectural Concepts 2 1 The Three Layer Model Figure 2 1 The Three Layer Model Terminals Frontends FE Routers TR Backends BE Database DB B ZKO GS011 99Al e Allows performance or geographic expansion while protecting the investments made in existing hardware and application software The router layer contains no application software unless running callout servers This layer reduces the number of logical network links required on frontend and backend nodes It also decouples the backend layer from the frontend layer so that configuration changes in the frequently changing user environment have little influence on the transaction processing and database backend environment The three layer model can be mapped to any system topology More than one role may be assigned to any particular node For example on a system with few frontends the router and frontend layers can be combined in the same nodes During application development and test all three roles can be combined in one node The nodes used by an application and their configuration roles are
61. ware failure tolerance and failure recovery in multinode environments by sustaining transaction integrity in spite of hardware communications application or site failures Automatic failover and recovery of service can exploit redundant or underutilized hardware and network links As you modularize your application and distribute its components on frontends and backends you can add new nodes identify usage bottlenecks and provide redundancy to increase availability Adding backend nodes can help divide the transactional load and distribute it more evenly For example you could have a single node configuration as shown in Figure 1 9 RTR with Browser Single Node and Database A 1 10 Introduction RTR Terminology single node configuration can be useful during development but would not normally be used when your application is deployed Figure 1 9 RTR with Browser Single Node and Database Browser TR i NE mn LKG 11207 98WI When creating the configuration used by an application and defining the nodes where a facility has its frontends routers and backends the setup must also define which nodes will have journal files Each backend in an RTR configuration must have a journal file to capture transactions when other nodes are unavailable When applications are deployed often the backend is separated from the frontend and router as shown in Figure 1 10 Figure 1 10 RTR Deployed on Two Node
62. y email to rtrdoc compaq com Please indude the document title date from title page order number section and page numbers in your message For produc information send email to rtr compaq com Conventions Reading Path This manual adopts the following conventions Convention Description New term User input Terms and titles FE TR BE New terms are shown in bold when introduced and defined All RTR terms are defined in the glossary at the end of this document or in the supplemental glossary in the RTR Application Design Guide User input and programming examples are shown in a monospaced font Boldface monospaced font indicates user input Terms defined only in the glossary are shown in italics when presented for the first time Italics are also used for titles of manuals and books and for emphasis RTR frontend RTR transaction router or router RTR backend The reading path to follow when using the Reliable Transaction Router information set is shown in Figure 1 Cover SPD Release letter p Notes Getting Started System Manager Application Programmer Installation Appleen Guide Guido v If V2 to V3 v e SSS 7 e C Application Visum Migration Programmer s See Manual ele Reference Classes Manual AQ Commands LL Tutorial

Compaq Reliable Transaction Router User's Manual

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