[jboss-jira] [JBoss JIRA] Commented: (JBPM-1071) Possible problem in concurrent signalling from multiple threads

[Jiri Pechanec (JIRA)]

    [ http://jira.jboss.com/jira/browse/JBPM-1071?page=comments#action_12383167 ] 
            
Jiri Pechanec commented on JBPM-1071:
-------------------------------------

Hi,
the exception throws is
org.jbpm.JbpmException: couldn't execute org.jbpm.command.SignalCommand at 715c2843
	at org.jbpm.command.impl.CommandServiceImpl.execute(CommandServiceImpl.java:73)
	at org.jpbm.exploratory.Signalist.run(Signalist.java:30)
Caused by: org.jbpm.JbpmException: couldn't signal token 'Token(/)' : node 'EndState(end-state1)' doesn't have a default transition
	at org.jbpm.graph.exe.Token.signal(Token.java:138)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:585)
	at org.hibernate.proxy.pojo.cglib.CGLIBLazyInitializer.invoke(CGLIBLazyInitializer.java:157)
	at org.jbpm.graph.exe.Token$$EnhancerByCGLIB$$9af9b4e6.signal(<generated>)
	at org.jbpm.command.SignalCommand.execute(SignalCommand.java:91)
	at org.jbpm.command.impl.CommandServiceImpl.execute(CommandServiceImpl.java:71)
	... 1 more

Which means that other threads are isgnalling process when it is in the end state.
But this is not a problem I am trying to point out.
The problem is that the same node is executed 4 times from different threads and all changes made are successfully comitted.
IMHO the correct semantics is that only one thread executes each action (each node). The rest of threads will either throw something like concurrent access exception or will be used to signal in the next wait states.
According to content of the exception I can pretty accurately suppose that
4 threads executed Action 2, commited
3 threads executed transition to end state, probably committed
13 threads failed as there is no next transition
What I suppose is to have
1 thread executed Action 2, commited
3 thread executed Action 2, fail and rollback
1 thread executed transition to end state,  committed
2 threads executed transition to end state,  fail and rollback
13 threads failed as there is no next transition
or
1 thread executed Action 2, commited
1 thread executed transition to end state,  committed
18 threads failed as there is no next transition




> Possible problem in concurrent signalling from multiple threads
> ---------------------------------------------------------------
>
>                 Key: JBPM-1071
>                 URL: http://jira.jboss.com/jira/browse/JBPM-1071
>             Project: JBoss jBPM
>          Issue Type: Bug
>          Components: Core Engine
>    Affects Versions: jBPM jPDL 3.2.2
>         Environment: Linux  2.6.21-1.3228.fc7 #1 SMP Tue Jun 12 14:56:37 EDT 2007 x86_64 x86_64 x86_64 GNU/Linux
> MySQL 5.0.22
>            Reporter: Jiri Pechanec
>         Assigned To: Tom Baeyens
>            Priority: Critical
>         Attachments: expl.tar.gz
>
>
> Attached is a simple test case that
> 1) Deploys process definition with two nodes
> 2) Starts the process instance that will go to the wait state on first node
> 3) Starts 20 threads that tries concurrently signal the same process instance
> 4) The second node writes a record to the database
> The test case needs to be executed multiple times to see the incorrect behaviour.
> This is an example of run output
> Isol 8
> Action 1
> Action 2
> Action 2
> Action 2
> Action 2
> Action 2 1
> Action 2 1
> Action 2 1
> Action 2 1
> Signalist 5
> Signalist 6
> Signalist 8
> Signalist 12
> Signalist 7
> Signalist 13
> Signalist 14
> Signalist 15
> Signalist 9
> Signalist 16
> Signalist 17
> Signalist 18
> Signalist 4
> Success 7
> Failure 13
> Explanation of the outcome
> 4 threads successfully executed the node action including database operation. All database opeartion were comitted (4 new records were created)
> 3 threads successfully executed the signal operation but no real action was performed
> 13 threads attempted to execute the signal operation but ended with an exception

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