[rules-users] Multithreading work items

Mon Apr 26 09:47:29 EDT 2010

Alan, couldn't you have achieved this using a Split and Join?

2010/4/26 <Alan.Gairey at tessella.com>

>
> Interesting. What you've described Pedro is similar to what I'm trying to
> achieve, and also relates to some earlier posts I made to the list (title:
> 'Drools Flow: Problem with constraint in (Wait) State node').
>
> I have a process that launches independent sub flows; these independent sub
> flows execute on separate threads. I then want the original process to
> "block" until all the subflows have finished, and to then continue.
> In order to achieve this, I've done the following:
>
> - Each process (both the main flow and each sub flow) is executed by a
> separate stateful knowledge session.
> - When a sub flow is started, it inserts a fact into the working memory of
> the session for the original process.
> - When a sub flow finishes, it updates a fact in the working memory of the
> session for the original process to "signal" its completion.
> - After launching the sub flows, the original process contains a (wait)
> state node; the constraint for this node is designed to block until all
> facts in its memory are in the "signalled" state.
>
> I've attached an example project that illustrates what I'm trying to
> achieve. The constraint on the wait state node is currently as follows:
>
> (and forall(SimpleFact(complete == true)) exists(SimpleFact()))
>
> I'd be interested to know from someone who understands rule syntax better
> than me as to why this seems to work when other attempts (see my earlier
> posts) failed.
>
> I still have two problems though:
>
> 1) The above constraint appeared to work OK with an earlier 5.1 snapshot
> build (from a couple of months back). However, using the latest successful
> build from trunk (#3845), the Action node after the wait state node isn't
> executed. Given that 5.1.M2 is supposed to be imminent, I'm worried. Does
> anyone know why this no longer works?
>
> 2) If I try to enable JPA-based state persistence, using the Bitronix
> transaction manager, then when I try to insert a fact into the  working
> memory of the session for the original process from a separate thread, I get
> the following error:
>
> bitronix.tm.internal.BitronixRollbackException: transaction was marked as
> rollback only and has been rolled back
>         at
> bitronix.tm.BitronixTransaction.commit(BitronixTransaction.java:153)
>         at
> bitronix.tm.BitronixTransactionManager.commit(BitronixTransactionManager.java:96)
>         at
> org.drools.persistence.session.SingleSessionCommandService.execute(SingleSessionCommandService.java:258)
>         at
> org.drools.command.impl.CommandBasedStatefulKnowledgeSession.insert(CommandBasedStatefulKnowledgeSession.java:306)
>         at
> com.test.InsertWorkItemHandler$1.insertFact(InsertWorkItemHandler.java:52)
>         at
> com.test.InsertWorkItemHandler$1.run(InsertWorkItemHandler.java:40)
>         at java.lang.Thread.run(Thread.java:619)
> java.lang.RuntimeException: Could not rollback transaction
>         at
> org.drools.persistence.session.SingleSessionCommandService.execute(SingleSessionCommandService.java:283)
>         at
> org.drools.command.impl.CommandBasedStatefulKnowledgeSession.insert(CommandBasedStatefulKnowledgeSession.java:306)
>         at
> com.test.InsertWorkItemHandler$1.insertFact(InsertWorkItemHandler.java:52)
>         at
> com.test.InsertWorkItemHandler$1.run(InsertWorkItemHandler.java:40)
>         at java.lang.Thread.run(Thread.java:619)
> Caused by: java.lang.IllegalStateException: no transaction started on this
> thread
>         at
> bitronix.tm.BitronixTransactionManager.rollback(BitronixTransactionManager.java:103)
>         at
> org.drools.persistence.session.SingleSessionCommandService.execute(SingleSessionCommandService.java:278)
>         ... 4 more
>
> Any help anyone can provide would be very much appreciated. Thank you.
>
> Regards,
>
> Alan
>
>
>
>
>  *Pedro Maria Buitrago Mantilla <pmbtgun at gmail.com>*
> Sent by: rules-users-bounces at lists.jboss.org
>
> 23/04/2010 14:38
>  Please respond to
> Rules Users List <rules-users at lists.jboss.org>
>
>   To
> Rules Users List <rules-users at lists.jboss.org>
> cc
>   Subject
> Re: [rules-users] Multithreading work items
>
>
>
>
> Each of the sub flows requires final user design. Mauricio thanks very
> much.
>
> PEDRO BUITRAGO
> Bogotá, Colombia
>
>
> 2010/4/22 Mauricio Salatino <*salaboy at gmail.com* <salaboy at gmail.com>>
> yes.. sounds more like a normal java problem than Drools FLow problem. I
> think that your solution is the correct one because it handle internally the
> multithreaded requierements and then it continue the business process
> normally.
>
>
> 2010/4/22 Pedro Maria Buitrago Mantilla <*pmbtgun at gmail.com*<pmbtgun at gmail.com>>
>
>
> The idea is to run multiple independent sub flows. Each of the sub flows
> requires approximately 2 minutes to complete, so parallel processing is
> required. Once all the sub flows have completed their tasks is necessary to
> collect all the results and process them. This implies that the workflow
> should not end until it collects all information submitted by the sub flows.
>
> For now, I think to create, with JMS, a queue in jboss receive the name of
> each sub flow, create your own KnowledgeBase run each subflow as a separate
> workflow and delivers the results. Finally, some components will take all
> the results (from a database of another jms queue and process and again
> another component start another workflow to process all results.
>
>
> PEDRO BUITRAGO
> Bogotá, Colombia
>
>
> 2010/4/22 Mauricio Salatino <*salaboy at gmail.com* <salaboy at gmail.com>>
>
> can you describe a little bit your use case?
> I'm not sure about what you want to achieve.
>
> 2010/4/21 Pedro Maria Buitrago Mantilla <*pmbtgun at gmail.com*<pmbtgun at gmail.com>
> >
> In general, I meet that for resolve the topic of multithreading it's
> required to implement another thread over a work item.
>
> How does the asynchronic task  can modified a variable of Knowledgebase?
>
> Can you give me an example?
>
> Pedro Buitrago
>
>
>
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