[wildfly-dev] Transaction synchronization between threads

[Cheng Fang]

On 2/4/14, 10:09 AM, Scott Marlow wrote:
> What is it that you are trying to exactly?  Does thread 2 need to be 
> started only after a user app starts a job?  Or could thread 2 be from 
> a background pool that is waiting for a job to run? Depending on what 
> you want to do, I think the answer is different.
>
the job execution task needs to be submitted to execution service as 
part of transaction/thread 1.  So I guess we could buffer up the 
submitted task and don't actually submit it to the underlying execution 
service till afterCompletion is called with committed status.  I think 
we can achieve that in wildfly-batch integration module.  Will check 
with James.

Thanks,
Cheng
> On 02/04/2014 09:49 AM, Cheng Fang wrote:
>> A jberet user reported JBERET-29
>> <https://issues.jboss.org/browse/JBERET-29> (Foreign key constraint
>> step_execution_jobexecutionid_fkey fails when using Postgresql on
>> WildFly, and we are trying to fix it by jberet 1.0.0.Final.  The problem
>> happens when user app starts a job within a transaction (e.g., CMT EJB),
>> jberet inserts JobExecution into database (thread 1 & transaction 1),
>> and then spawn a jberet-batch thread to run the job (thead 2 &
>> transaction 2).  Sometimes T2 tries to access db before T1 is committed,
>> hence the error reported by the user.
>>
>> What's the common approach for solving this kind of problem?  I suppose
>> other WildFly components may also have this issue and probably already
>> solved.  Using transaction synchronization is a cleaner solution than
>> polling db, but I'm not sure about its full implication. Ideally, I
>> don't want to use system level JTA API like TransactionManager or
>> Synchronization in jberet proper, but probably we can implement it in
>> WildFly jberet integration.
>
> If you want to create a thread after the JTA transaction completes, 
> you could key that off of the 
> Synchronization.afterCompletion(Status).  See 
> http://docs.oracle.com/javaee/5/api/javax/transaction/TransactionSynchronizationRegistry.html
>
>>
>> Thanks,
>> Cheng
>>
>>
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>