Re: [rules-users] Persistence in fireUntilHalt() loop

Marco Rietveld Mon, 19 Mar 2012 14:33:24 -0700

Alberto,

Sorry to hear that the bug isn't fixed.

Could you clarify what you mean by these points?
- Drools and JBPM have different persistence managers.
- Drools uses JTA for persistence and JBPM does not.

I was pretty sure you could specify a JTA data source in the persistence.xml that jBPM uses.

As for the persistence managers, what do you mean exactly?

Also, if you could maybe give me a github link referring to the code you're using, that would be great.

(Just to make sure, you are referring to jbpm 5, right?)

Thanks,
Marco

03/19/2012 06:23 PM, Alberto R. Galdo:

I'm afraid this bug is not resolved and doesn't have nothing to do with lazy evaluation.

We've been able to get to the source of the problem and this are the facts:

   - Drools and JBPM have different persistence managers.
   - Drools uses JTA for persistence and JBPM does not.
   - When any JPA enabled object is persisted in Drools, a transaction begins, it's EntityManager ( Hibernate ) joins the transaction and the entity gets persisted.
   - When any JPA enabled object ( in this case a ProcessInstanceInfo ) is persisted in JBPM, there are no transactions involved, and so the EntityManager ( Hibernate ) decides to delay the insert ( queuing it as there's no transaction in progress ). Then the processId never gets updated and the NPE arises.

The problem here seems to be that both Drools and JBPM manage persistence in different and incompatible ways. We've been able to modify jbpm-persistence-jpa to open a JTA transaction before persisting ProcessInstanceInfo, getting the EntityManager joining that transaction and using the current Bitronix implementation already running in Drools ( to assist persistence for their objects ) .. like so:

    public void setKnowledgeRuntime(InternalKnowledgeRuntime kruntime) {
        this.kruntime = kruntime;
        Environment env = kruntime.getEnvironment();
        Object tm = env.get( EnvironmentName.TRANSACTION_MANAGER );
        if (!(tm instanceof javax.transaction.TransactionManager)) {
            try {
            //     get Bitronix instance inside ...
                java.lang.reflect.Field field = tm.getClass().getDeclaredField("tm");
                // who says private in Java is really private ... xD
                field.setAccessible(true);
                tm = field.get(tm);
            } catch (Exception e){
                e.printStackTrace();
            }
        }
        this.txm = new JtaTransactionManager( env.get( EnvironmentName.TRANSACTION ), env.get( EnvironmentName.TRANSACTION_SYNCHRONIZATION_REGISTRY ), tm );
    }

    public void addProcessInstance(ProcessInstance processInstance) {
        ProcessInstanceInfo processInstanceInfo = new ProcessInstanceInfo( processInstance, this.kruntime.getEnvironment() );
        ProcessPersistenceContext context = ((ProcessPersistenceContextManager) this.kruntime.getEnvironment().get( EnvironmentName.PERSISTENCE_CONTEXT_MANAGER )).getProcessPersistenceContext();
        this.txm.begin();
        context.persist( processInstanceInfo );
        this.txm.commit();

I think we can agree that the previous lines of code are not the most elegant solution ( at least not for me ).

So, Is there any timeline for merging DROOLS and JBPM 5 persistence managers?

If someone gives me advice and architectural hints ( and if it is doable in a reasonable ammount of time ) I would be eager to submit a patch for this ....

Alberto R. Galdo
arga...@gmail.com
On Wed, Mar 14, 2012 at 13:56, Alberto R. Galdo <arga...@gmail.com> wrote:
Great news!

We were in the process of debugging JBPM trying to find the source of the bug ... and maybe days away from the solution ...

Is there any bug report in Jira and/or a patch we can apply without having to wait for the next release so we can quick-patch our systems?

Alberto R. Galdo
arga...@gmail.com
On Wed, Mar 14, 2012 at 13:09, Marco Rietveld <mriet...@redhat.com> wrote:
Hi Alberto,

This is a bug that has been fixed in jBPM. It had to do with lazy initialization of a JPAProcessInstanceManager field.

We'll be releasing a new jBPM version sometime soon (synchronous with Drools, I think). The bug is fixed in there.

Regards,
Marco

03/08/2012 11:32 AM, Alberto R. Galdo:
Hi,

We're running an application that uses Drools + JBPM 5 + Drools integration our set-up can be seen as:

Some rule fires and creates a JBPM process ( a fact gets inserted into drools using "kcontext.getKnowledgeRuntime().startProcess("testProcess")" ). We have a problem with the persistence of this processes. Persistence is implemented with JPA and JTA. Our application runs with fireUntilHalt() and when a process is launched from the consequence of any of the rules the persistence of the process fails. If the application runs with fireAllRules(), the persistence works like a charm.

The error shown is as follow:

Exception in thread "Thread-5" Exception executing consequence for rule "Run Process" in com.sample: java.lang.NullPointerException

at org.drools.runtime.rule.impl.DefaultConsequenceExceptionHandler.handleException(DefaultConsequenceExceptionHandler.java:39)

at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:1101)

at org.drools.common.DefaultAgenda.fireNextItem(DefaultAgenda.java:1029)

at org.drools.common.DefaultAgenda.fireUntilHalt(DefaultAgenda.java:1229)

at org.drools.common.AbstractWorkingMemory.fireUntilHalt(AbstractWorkingMemory.java:754)

at org.drools.common.AbstractWorkingMemory.fireUntilHalt(AbstractWorkingMemory.java:730)

at org.drools.command.runtime.rule.FireUntilHaltCommand$1.run(FireUntilHaltCommand.java:50)

at java.lang.Thread.run(Thread.java:662)

Caused by: java.lang.NullPointerException

at org.jbpm.persistence.processinstance.JPAProcessInstanceManager.addProcessInstance(JPAProcessInstanceManager.java:44)

at org.jbpm.process.instance.AbstractProcessInstanceFactory.createProcessInstance(AbstractProcessInstanceFactory.java:36)

at org.jbpm.process.instance.ProcessRuntimeImpl.startProcess(ProcessRuntimeImpl.java:182)

at org.jbpm.process.instance.ProcessRuntimeImpl.createProcessInstance(ProcessRuntimeImpl.java:154)

at org.jbpm.process.instance.ProcessRuntimeImpl.startProcess(ProcessRuntimeImpl.java:135)

at org.jbpm.process.instance.ProcessRuntimeImpl.startProcess(ProcessRuntimeImpl.java:130)

at org.drools.common.AbstractWorkingMemory.startProcess(AbstractWorkingMemory.java:1074)

at org.drools.impl.StatefulKnowledgeSessionImpl.startProcess(StatefulKnowledgeSessionImpl.java:301)

at com.sample.Rule_Run_Process.defaultConsequence(Rule_Run_Process.java:9)

at com.sample.Rule_Run_ProcessDefaultConsequenceInvoker.evaluate(Unknown Source)

at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:1091)

... 6 more

The problem is in this function:

public void addProcessInstance(ProcessInstance processInstance) {

ProcessInstanceInfo processInstanceInfo = new ProcessInstanceInfo( processInstance, this.kruntime.getEnvironment() );

ProcessPersistenceContext context

= ((ProcessPersistenceContextManager) this.kruntime.getEnvironment()

.get( EnvironmentName.PERSISTENCE_CONTEXT_MANAGER ))

.getProcessPersistenceContext();

// @PrePersist added to ProcessInstanceInfo because of this

context.persist( processInstanceInfo );

((org.jbpm.process.instance.ProcessInstance) processInstance).setId( processInstanceInfo.getId() );

processInstanceInfo.updateLastReadDate();

internalAddProcessInstance(processInstance);

}

We think after that persist sentence, the entity manager would have to run a flush sentence for the process instance is inserted into database and get the ID.

Greets.
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-- jBPM/Drools developer Utrecht, the Netherlands

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jBPM/Drools developer
Utrecht, the Netherlands

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Re: [rules-users] Persistence in fireUntilHalt() loop

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