I have been working through the code with a debugger, it looks like this method
call in SingleSessionCommandService is what causes it to behave as if its
single threaded:
public synchronized <T> T execute(Command<T> command) {
The method is synchronized, which I don't understand - but maybe that is why it
is called SingleSessionCommandService. I have tried to work around this by
creating a new session every time I need to start a new process but this causes
hibernate exceptions of this form:
2010/08/31 10:15:58.469{UTC} [AssertionFailure] [ProcessStarterThread-8]:
ERROR: : an assertion failure occured (this may indicate a bug in Hibernate,
but is more likely due to unsafe use of the session)
org.hibernate.AssertionFailure: null id in
org.drools.persistence.processinstance.ProcessInstanceInfo entry (don't flush
the Session after an exception occurs)
at
org.hibernate.event.def.DefaultFlushEntityEventListener.checkId(DefaultFlushEntityEventListener.java:82)
at
org.hibernate.event.def.DefaultFlushEntityEventListener.getValues(DefaultFlushEntityEventListener.java:190)
at
org.hibernate.event.def.DefaultFlushEntityEventListener.onFlushEntity(DefaultFlushEntityEventListener.java:147)
at
org.hibernate.event.def.AbstractFlushingEventListener.flushEntities(AbstractFlushingEventListener.java:219)
at
org.hibernate.event.def.AbstractFlushingEventListener.flushEverythingToExecutions(AbstractFlushingEventListener.java:99)
at
org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:50)
at org.hibernate.impl.SessionImpl.flush(SessionImpl.java:1206)
at
org.hibernate.impl.SessionImpl.managedFlush(SessionImpl.java:375)
at
org.hibernate.ejb.AbstractEntityManagerImpl$1.beforeCompletion(AbstractEntityManagerImpl.java:1057)
at
bitronix.tm.BitronixTransaction.fireBeforeCompletionEvent(BitronixTransaction.java:430)
at
bitronix.tm.BitronixTransaction.commit(BitronixTransaction.java:173)
at
bitronix.tm.BitronixTransactionManager.commit(BitronixTransactionManager.java:104)
at
org.drools.persistence.session.JtaTransactionManager.commit(JtaTransactionManager.java:164)
at
org.drools.persistence.session.SingleSessionCommandService.execute(SingleSessionCommandService.java:281)
at
org.drools.command.impl.CommandBasedStatefulKnowledgeSession.startProcess(CommandBasedStatefulKnowledgeSession.java:193)
at
org.drools.command.impl.CommandBasedStatefulKnowledgeSession.startProcess(CommandBasedStatefulKnowledgeSession.java:184)
at
drools.test.PersistenceTest.startProcess(PersistenceTest.java:93)
at drools.test.PersistenceTest.access$1(PersistenceTest.java:92)
at drools.test.PersistenceTest$1.run(PersistenceTest.java:67)
at java.lang.Thread.run(Thread.java:619)
So I am wondering if what I am trying to do is even supported?
From: [email protected]
[mailto:[email protected]] On Behalf Of Puigdomenech, David
Sent: 31 August 2010 08:17
To: Rules Dev List
Subject: Re: [rules-dev] A drools flow persistence example thatbehaves strangely
Greg,
First of all, thank you very much for you test example.
Answering your question:
"My question is why when I change the code from running without persistence to
running with persistence does it become "single threaded"? You can see by
toggling the persistence variable in the top of the test file that when
persistence is enabled each flow will complete before the next one begins yet
without persistence they run in parallel."
We think the problem is that all the threads are waiting for getting the
connection, because of there is only one connection it becomes a shared
resource.
What do you thing about?
Thanks,
David.
David Puigdomènech Blancas
Dpto. I+D Desarrollo
Logister, S.A. - GRIFOLS
Polígon Llevant
C/Palou, 6
08150 Parets del Vallès
Tel: + 34 93 571 02 78
Fax: + 34 93 571 02 94
P Do you need to print this message? Let's protect the environment.
De: [email protected]
[mailto:[email protected]] En nombre de Chrystall, Greg
Enviado el: viernes, 27 de agosto de 2010 18:14
Para: Rules Dev List
Asunto: Re: [rules-dev] A drools flow persistence example thatbehaves strangely
You can download it here:
http://dl.dropbox.com/u/2634115/drools-test.zip
You can just import that project into an eclipse workspace and run the unit
test, the database should start when you do.
I am away until Tuesday next week, if you have any questions I will answer them
then.
Thanks,
Greg
From: [email protected]
[mailto:[email protected]] On Behalf Of Puigdomenech, David
Sent: 27 August 2010 16:20
To: Rules Dev List
Subject: Re: [rules-dev] A drools flow persistence example that behaves
strangely
Please, could you be so kind to put the whole test project on an http server.
I was trying to persist the flow in a PostgreSQL database but I was receiving
some Bitronix errors.
Have ever of you persist a flow in a database different from h2?
Thank at all.
David Puigdomenech
De: [email protected]
[mailto:[email protected]] En nombre de Chrystall, Greg
Enviado el: viernes, 27 de agosto de 2010 16:45
Para: Rules Dev List
Asunto: [rules-dev] A drools flow persistence example that behaves strangely
I have written a test based as much as possible on the Drools Flow 5.1
Persistence Documentation. You can see the code here:
http://pastebin.com/33QXK4iU
And I have attached my eclipse project but without the jars as its too big, if
anyone wants a zip of the whole project ready to run, I can put it on an http
server for you.
My question is why when I change the code from running without persistence to
running with persistence does it become "single threaded"? You can see by
toggling the persistence variable in the top of the test file that when
persistence is enabled each flow will complete before the next one begins yet
without persistence they run in parallel.
Any advice on what I am doing wrong or whether persistence simply does not
support what I want to do is much appreciated.
Greg
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