topic Re: Parallel Gateway and asynchronous continuations in Alfresco Archive

Parallel Gateway and asynchronous continuations

filipearaujo — Sat, 29 Oct 2011 00:47:07 GMT

Hi,I'm trying to create a parallel gateway with three sequence flows with destination a service task with asynchronous continuation.But unfortunately it gives me this exceptionct 29, 2011 2:12:11 AM org.activiti.engine.impl.interceptor.CommandContext closeSEVERE: Error while closing command contex

Re: Parallel Gateway and asynchronous continuations

trademak — Sat, 29 Oct 2011 15:32:35 GMT

Hi,

I've just answered a post on the forum with the same exception: see http://forums.activiti.org/en/viewtopic.php?f=6&t=2596
How did you test this?

Best regards,

Re: Parallel Gateway and asynchronous continuations

filipearaujo — Sun, 30 Oct 2011 18:07:15 GMT

Yes i've seen it, but the given solution ("retrying") it's not the solution i'm looking for. I'm testing this in the:

- eclipse plugin 5.8 (activiti.cfg.xml)

 <bean id="processEngineConfiguration" class="org.activiti.engine.impl.cfg.StandaloneInMemProcessEngineConfiguration">
  <property name="databaseSchemaUpdate" value="true"/>
      <!– job executor configurations –>
  <property name="jobExecutorActivate" value="true" />
 </bean>

- engine 5.8

With this workflow:

[img]http://dl.dropbox.com/u/175705/Screen%20shot%202011-10-30%20at%206.03.10%20PM.png[/img]

With A,B and C asynchronous, I want to start the 3 tasks at the same time and when the 3 finish their job, task D is executed. It's a simple example.

Re: Parallel Gateway and asynchronous continuations

trademak — Mon, 31 Oct 2011 08:31:20 GMT

Hi,

You're right. The parallel gateway / async continuation combination seems to the problem.
We'll look into this.

Thanks,

Re: Parallel Gateway and asynchronous continuations

meyerd — Wed, 02 Nov 2011 08:38:54 GMT

We lack support for exclusive jobs.

What happens is that 3 jobs are created and executed by the job executor concurrently. The job executor has a thread pool to which it delegates the actual execution of the jobs. So in this case 3 threads are going to execute one service task each. To do this, they check out the ExecutionEntity in three different transactions. Now there is a race condition: whichever of the transactions is first will be able to commit, the other ones fail.

So this is both expected and unexpected behavior: form the point of view of engine-persistence it is expected, from the point of view of the user it is maybe unexpected.

Update:
I moved the discussion about how to handle this to the developer forum:
http://forums.activiti.org/en/viewtopic.php?f=4&t=2652&start=0