Handling Concurrent Requests in jPOS Participant

[Trịnh Vĩnh Khang]

I have a problem that I need help with: if two requests enter the same participant, will there be any issue? If one of them calls close or tow of them calls , will it affect the other?
i have a exception "ConcurrentModificationException" in class class="org.jpos.transaction.Close" when two requests in one participant index but other idle. 
Thanks all 

[Mark Salter]

Can you share the stacktrace, so we can see what is throwing the ConcurrentModificationException and where?

Can you share the source of the Participant or share a link to it?

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Mark

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[Trịnh Vĩnh Khang]

yes i have a exception with hibernate in 

I don’t know whether having two requests come in at the same time like this causes any problems:

=======================================================

TIMESTAMP: Tue Oct 07 03:51:30 GMT 2025

paticipant-9:idle:69397 (java.util.ConcurrentModificationException)
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TIMESTAMP: Tue Oct 07 03:51:31 GMT 2025

paticipant-9:idle:69398 (no error).  

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</info> *** PANIC - TX not null - RESPONSE OMITTED *** </exception> at java.base/java.lang.Thread.run(Thread.java:840) at org.jpos.transaction.TransactionManager.run(TransactionManager.java:335) at org.jpos.transaction.TransactionManager.commit(TransactionManager.java:531) at org.jpos.transaction.TransactionManager.commit(TransactionManager.java:599) at org.jpos.transaction.Close.commit(Close.java:34) at org.jpos.transaction.Close.closeDB(Close.java:47) at org.hibernate.engine.transaction.internal.TransactionImpl.commit(TransactionImpl.java:101) at org.hibernate.resource.transaction.backend.jdbc.internal.JdbcResourceLocalTransactionCoordinatorImpl$TransactionDriverControlImpl.commit(JdbcResourceLocalTransactionCoordinatorImpl.java:281) at org.hibernate.resource.transaction.backend.jdbc.internal.JdbcResourceLocalTransactionCoordinatorImpl.access$300(JdbcResourceLocalTransactionCoordinatorImpl.java:40) at org.hibernate.resource.transaction.backend.jdbc.internal.JdbcResourceLocalTransactionCoordinatorImpl.beforeCompletionCallback(JdbcResourceLocalTransactionCoordinatorImpl.java:183) at org.hibernate.engine.jdbc.internal.JdbcCoordinatorImpl.beforeTransactionCompletion(JdbcCoordinatorImpl.java:449) at org.hibernate.internal.SessionImpl.beforeTransactionCompletion(SessionImpl.java:2425) at org.hibernate.internal.SessionImpl.flushBeforeTransactionCompletion(SessionImpl.java:3290) at org.hibernate.internal.SessionImpl.managedFlush(SessionImpl.java:489) at org.hibernate.internal.SessionImpl.doFlush(SessionImpl.java:1407) at org.hibernate.event.service.internal.EventListenerGroupImpl.fireEventOnEachListener(EventListenerGroupImpl.java:107) at org.hibernate.event.internal.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:40) at org.hibernate.event.internal.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:344) at org.hibernate.engine.spi.ActionQueue.executeActions(ActionQueue.java:475) at java.base/java.util.LinkedHashMap.forEach(LinkedHashMap.java:721) at org.hibernate.engine.spi.ActionQueue.lambda$executeActions$1(ActionQueue.java:478) at org.hibernate.engine.spi.ActionQueue.executeActions(ActionQueue.java:602) at java.base/java.util.Collections$UnmodifiableCollection$1.next(Collections.java:1055) at java.base/java.util.ArrayList$Itr.next(ArrayList.java:967) at java.base/java.util.ArrayList$Itr.checkForComodification(ArrayList.java:1013) java.util.ConcurrentModificationException <exception name="null">

Thanks Mark

Vào lúc 21:12:56 UTC+7 ngày Thứ Tư, 22 tháng 10, 2025, Mark Salter đã viết:

[Mark Salter]

You did not include any detail/source for your Close Participant?

As a brief aside for context/interest...

       For the two transactions that are being processed at the same time...

•  are they duplicates/identical , or for different cards/transaction types? 
  
• anything interesting about the pair?

Hibernate is reporting the failure and perhaps using a single Hibernate Session in two threads could be the issue - hence wondering about the database work for the transactions and if/how they might be colliding at a specific level, or simply if a Session per Transaction is needed - seems likely.

-- 

Mark

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[Alejandro Revilla]

This logs are difficult to read, but based on what you say, I believe your problem could be related to this:

   https://jpos.org/blog/2020/09/badsharedmemories

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@apr

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