[hibernate-issues] [Hibernate-JIRA] Commented: (EJB-457) ConcurrentModificationException when initializing unrelated EntityManagerFactories in two different threads

[Kenneth Flynn (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/EJB-457?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=33693#action_33693 ] 

Kenneth Flynn commented on EJB-457:
-----------------------------------

Okay, somehow I pressed enter before typing the rest of the issue.  Rest of the description here,..

When I create two EntityManagerFactories in two different threads, I get the stacktrace below.  It looks like I'm determining the persistence provider implementations twice at the same time; the static set in the Persistence class is not thread safe; in particular findAllProviders() fails if it is called concurrently.  In this case, the use of the persistence api in the two different threads is completely unrelated--they are using different persistence units, different dbs, etc.  This seems like a use case that should be supported?

[java] java.util.ConcurrentModificationException
     [java]         at java.util.HashMap$HashIterator.nextEntry(HashMap.java:793)
     [java]         at java.util.HashMap$KeyIterator.next(HashMap.java:828)
     [java]         at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:51)
     [java]         at com.darkcorner.minotaur.sa.redline.RedlineDatabaseControl.ensureRunning(RedlineDatabaseControl.java:101)
     [java]         at com.darkcorner.minotaur.sa.redline.RedlineService.restartService(RedlineService.java:316)
     [java]         at com.darkcorner.harmonice.ServiceHandler.callRestart(ServiceHandler.java:241)
     [java]         at com.darkcorner.harmonice.ServiceHandler.access$000(ServiceHandler.java:56)
     [java]         at com.darkcorner.harmonice.ServiceHandler$RestartTask.run(ServiceHandler.java:63)
     [java]         at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441)
     [java]         at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
     [java]         at java.util.concurrent.FutureTask.run(FutureTask.java:138)
     [java]         at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:98)
     [java]         at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:207)
     [java]         at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
     [java]         at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
     [java]         at java.lang.Thread.run(Thread.java:619)


> ConcurrentModificationException when initializing unrelated EntityManagerFactories in two different threads
> -----------------------------------------------------------------------------------------------------------
>
>                 Key: EJB-457
>                 URL: http://opensource.atlassian.com/projects/hibernate/browse/EJB-457
>             Project: Hibernate Entity Manager
>          Issue Type: Bug
>          Components: EntityManager
>    Affects Versions: 3.4.0.GA
>            Reporter: Kenneth Flynn
>
> I get the following:

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