IBM Software Group ® WebSphere ® Support Technical Exchange Transactions in WebSphere Process Server Lalitha Chandran

IBM Software Group WebSphere ® Support Technical Exchange 2 of 34 Agenda Module A Module B Same Transaction

IBM Software Group WebSphere ® Support Technical Exchange 3 of 34 Agenda  Transactions  Invocation Styles  Qualifiers  Asynchronous behaviors affecting Transaction boundary  Examples  References  Q&A 1

IBM Software Group WebSphere ® Support Technical Exchange 4 of 34 Transactions  What is transaction?  Motivation behind transactions  Real-world Example: Transfer of Money  Begin Debit Account A Credit Account B Update history log  End 2

IBM Software Group WebSphere ® Support Technical Exchange 5 of 34 Terminology  Global transaction and Local transaction  Transaction Boundary  Commit/Rollback  Container Managed Transaction (CMT)  Bean Managed Transaction (BMT)

IBM Software Group WebSphere ® Support Technical Exchange 6 of 34 IQA

IBM Software Group WebSphere ® Support Technical Exchange 7 of 34 Invocation Styles  What is invocation style?  Invocation Style  Synchronous  Asynchronous  Effect on transactions Component A Component B

IBM Software Group WebSphere ® Support Technical Exchange 8 of 34 Invocation Styles  Synchronous invocation  The source and the target are executed in the same thread  No further processing in caller  Asynchronous invocation  The source and the target are executed in the different thread  Further processing occurs Component A Component B Component A Component B Request Response Request Response

IBM Software Group WebSphere ® Support Technical Exchange 9 of 34 Asynchronous Invocation  Asynchronous invocation is like snail mail, they are delivered and the sender can continue with other jobs.  Once the receiver receives the mail, it is processed. If required, the response is sent later. Component A Component B TX 1TX 2 The message in the queue is not visible unless the transaction within which it was “put” is committed. 3

IBM Software Group WebSphere ® Support Technical Exchange 10 of 34 Expected Behavior  Parameters affecting invocation style  Preferred Interaction Style  Request response or one-way operations  Target and Source component  API Calls  How the Source target in invoked 4

IBM Software Group WebSphere ® Support Technical Exchange 11 of 34 Examples: Microflow Invocation Styles

IBM Software Group WebSphere ® Support Technical Exchange 12 of 34 Actual Behavior  Turn on the trace SCA.*=fine  Execute the invocation  Search in the trace file for "Processing interaction: " Synchronous: Processing interaction: [invoke,getAccount] {MyModule}MyServiceRequestor.component#MyServiceInterfacePartner => {MyModule}MyServiceProvider.component Asychronous: Processing interaction: [invokeAsync,getAccount] {MyModule}MyServiceRequestor.component#MyServiceInterfacePartner => {MyModule}MyServiceProvider.component

IBM Software Group WebSphere ® Support Technical Exchange 13 of 34 IQAIQA

IBM Software Group WebSphere ® Support Technical Exchange 14 of 34 Qualifiers  Types of qualifiers Implementation Qualifiers Interface Qualifiers Reference Qualifiers 5

IBM Software Group WebSphere ® Support Technical Exchange 15 of 34 Transaction qualifiers  Four Transaction related Qualifiers Transaction (global) Component AComponent B TX Suspend Transaction (false) Join Transaction (true)

IBM Software Group WebSphere ® Support Technical Exchange 16 of 34 Transaction qualifiers  Asynchronous Invocation (commit|call) Component A Component B TX 1TX 2

IBM Software Group WebSphere ® Support Technical Exchange 17 of 34 Transaction qualifiers  Asynchronous Invocation (commit|call) Component A Component B TX 1TX 2 Asynchronous Invocation = Commit

IBM Software Group WebSphere ® Support Technical Exchange 18 of 34 Transaction qualifiers  Asynchronous Invocation (commit|call) Component A Component B TX 1TX 2 Asynchronous Invocation = Call

IBM Software Group WebSphere ® Support Technical Exchange 19 of 34 IQA

IBM Software Group WebSphere ® Support Technical Exchange 20 of 34 Asynchronous implementations  Java™ Component (POJO) that implements the ServiceAsyncImpl interface  Long running business process  Human tasks  JMS import  MQ import

IBM Software Group WebSphere ® Support Technical Exchange 21 of 34 Sync-over-Async switch  When an asynchronous invocation is invoked synchronously, a transaction boundary is introduced Component A Component B TX 1 TX 2 Request Response 6

IBM Software Group WebSphere ® Support Technical Exchange 22 of 34 Asynchronous hop reduction  An asynchronous import binding is invoked asynchronously  An asynchronous export invokes another component asynchronously Component A MQ Export MQ Import When invoking a component asynchronously it is expected for a message to be placed in a queue and a transaction boundary to be introduced. For performance optimization reasons, this asynchronous hop is eliminated. This would change the nature of the invocation to a synchronous one. Eliminating the transaction boundaries. Now the import or the export will execute in the same transaction as Component A. 6

IBM Software Group WebSphere ® Support Technical Exchange 23 of 34 Example: MQ Import  Scenario  POJO invokes MQ import  Requirement  Import and POJO should execute in the same transaction  Reminder: MQ Import is an asynchronous implementation

IBM Software Group WebSphere ® Support Technical Exchange 24 of 34 Example: MQ Import POJO MQ Import Synchronous Synch-over-Asynch Swith Since both the POJO and MQ import need to be part of same transaction, POJO would need to invoke the MQ import synchronously. But since MQ Import is an asynchronous implementation, the call will not remain a synchronous one Instead the synch-over-asynch switch will trigger and create a transaction boundary TX 1 TX 2

IBM Software Group WebSphere ® Support Technical Exchange 25 of 34 Example: MQ Import POJO MQ Import Asynchronous Synchronous Lets try invoking the MQ import in an asynchronous manner. But due to the asynchronous hop reduction, the call does not remain an asynchronous one The asynchronous hop would eliminate a would be transaction boundary. The POJO and MQ import execute in the same transaction as required.

IBM Software Group WebSphere ® Support Technical Exchange 26 of 34 Example: Deadlock  Asynchronous Deferred Response Component A Component B Response Request

IBM Software Group WebSphere ® Support Technical Exchange 27 of 34 Example: Deadlock  Scenario: Request and response are located within the same transaction  Asynchronous Invocation = Commit Component A Component B Response Request Transaction boundary 1 Put of the message 3 Commit of transaction 2 Receive a response 1 is waiting for 3 3 is waiting for 2 2 is waiting for 1 6

IBM Software Group WebSphere ® Support Technical Exchange 28 of 34 Example: Deadlock  Asynchronous Invocation = Call, but this can cause an issue with duplicate messages.  Review the article (6) in the references section for correct usage of this invocation style.

IBM Software Group WebSphere ® Support Technical Exchange 29 of 34 Example: CICS  Global Transaction, Local Transaction Containment (LTC) and Resource Manager Local Transaction GT1GT2GT3 LTC RMLT1 LTC Enterprise Information Systems, Relation databases or JMS queues/topics

IBM Software Group WebSphere ® Support Technical Exchange 30 of 34 Example: CICS  Requirement: No active J2EE transaction while the Java EE Connector Architecture (JCA) Adapter for CICS is called  Set the Resolver attribute to Application in the Enterprise JavaBeans (EJB) deployment descriptor CICS Import Join Transaction (false) 7 8

IBM Software Group WebSphere ® Support Technical Exchange 31 of 34 Summary IQA

IBM Software Group WebSphere ® Support Technical Exchange 32 of 34 References  1 TransactionsTransactions  2 An introduction to transactionsAn introduction to transactions  3 SCA asynchronous invocation patterns in depthSCA asynchronous invocation patterns in depth  4 Invocation StylesInvocation Styles  5 QualifiersQualifiers  6 Asynchronous processing in WebSphere Process ServerAsynchronous processing in WebSphere Process Server  7 ECI_EXTEND_MODE in JCA Adapter for CICSECI_EXTEND_MODE in JCA Adapter for CICS  8 WebSphere and CICSWebSphere and CICS

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IBM Software Group WebSphere ® Support Technical Exchange 34 of 34 Questions and Answers