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From <Juergen.Schumac...@empolis.com>
Subject Concurrent execution of extension activities (RE: Problem with flow and extension activities)
Date Tue, 14 Apr 2009 13:14:50 GMT
Hi Tammo,

> -----Original Message-----
> From: Tammo van Lessen [mailto:tvanlessen@gmail.com]
> Sent: Thursday, April 02, 2009 4:17 PM
> Subject: Re: AW: Problem with flow and extension activities
>
> That's true. If you need a concurrent execution of extension activities
> you'd need to implement the abstract class for async extensions, fork
> your own thread and call the ExtensionContext.complete method once your
> processing has finished. In this case the run method can finish before
> the processing is done and the navigation continues.

I tried this with ODE 2.0 beta2 and put the complete code of my extension activity 
execution in a Runnable to be executed in an own thread, but it doesn't work yet.
The code is basically like this:

class MyExtensionActivity extends AbstractAsyncExtensionOperation {

  static java.util.concurrent.Executor executor = Executors.newCachedThreadPool();

  void run(...) {
    executor.execute(new Runnable() {
      public void run() {
	  // extension activity code: 
        // read variables from ext context
        // do something
	  // write variables to ext context
	  // complete ext context
      }
    }
  }
}

For in-memory=true there is an exception when I try to complete the ExtensionContext:

java.lang.NullPointerException
	at org.apache.ode.jacob.vpu.JacobVPU.activeJacobThread(JacobVPU.java:203)
	at org.apache.ode.jacob.vpu.ChannelFactory$ChannelInvocationHandler.invoke(ChannelFactory.java:89)
	at $Proxy42.completed(Unknown Source)
	at org.apache.ode.bpel.rtrep.v2.ExtensionContextImpl.complete(ExtensionContextImpl.java:147)

So the actual execution of the extension code has worked in this case.

For in-memory=false I get an exception when trying to read a variable in my separate thread:
 
java.lang.NullPointerException
	at org.apache.ode.dao.jpa.ProcessInstanceDAOImpl.getScope(ProcessInstanceDAOImpl.java:231)
	at org.apache.ode.bpel.engine.BpelRuntimeContextImpl.fetchVariableData(BpelRuntimeContextImpl.java:354)
	at org.apache.ode.bpel.rtrep.v2.RuntimeInstanceImpl.fetchVariableData(RuntimeInstanceImpl.java:155)
	at org.apache.ode.bpel.rtrep.v2.ExtensionContextImpl.readVariable(ExtensionContextImpl.java:90)
	at org.apache.ode.bpel.rtrep.v2.ExtensionContextImpl.readVariable(ExtensionContextImpl.java:108)

which means that the DAO impl cannot find it's associated JPA entity manager anymore. 
So it seems I cannot access the variables in the extension context in this case. 

And then there's another exception on completeWithFault() that looks similar to the above:

Exception in thread "pool-2-thread-3" java.lang.NullPointerException
	at org.apache.ode.jacob.vpu.JacobVPU.activeJacobThread(JacobVPU.java:203)
	at org.apache.ode.jacob.vpu.ChannelFactory$ChannelInvocationHandler.invoke(ChannelFactory.java:89)
	at $Proxy40.completed(Unknown Source)
	at org.apache.ode.bpel.rtrep.v2.ExtensionContextImpl.completeWithFault(ExtensionContextImpl.java:162)

It doesn't matter if my extension activities are actually called from within a <flow>
or not. 
It also didn't change anything to let my extension implementation extend AbstractAsyncExtensionOperation

instead of just implementing ExtensionOperation (I also did not find anything in the ODE code,
where they 
are treated differently). Or have there been changes since 2.0-beta2 that make this work?


Or is there just something I am missing or that I have misunderstood? (-; 

Thanks for your patience, 
Juergen.


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