[hibernate-issues] [Hibernate-JIRA] Commented: (HHH-3006) ConcurrentModificationException in AbstractBatcher results in infinite loop

[Steve Ebersole (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HHH-3006?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_30429 ] 

Steve Ebersole commented on HHH-3006:
-------------------------------------

Just heard from some JTA folks.  Apparently this can be an issue due to transaction timeouts depending on how the TM implements timeout "reaping".  JBossTM, for example, will reap timed out transaction in a background thread.

So the simple fix here would be to account explicitly for CME in these 2 cleanups and just break from the corresponding loops in the case of CME.  Since we are explicitly handling this condition for the case of JTA, we can assume that the DataSource will handle any resource releasing...

> ConcurrentModificationException in AbstractBatcher results in infinite loop
> ---------------------------------------------------------------------------
>
>                 Key: HHH-3006
>                 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-3006
>             Project: Hibernate3
>          Issue Type: Bug
>          Components: core
>    Affects Versions: 3.2.5
>         Environment: Hibernate 3.2.5.ga
> MySQL 5.0.42
>            Reporter: Stefan Hauk
>            Assignee: Steve Ebersole
>            Priority: Minor
>             Fix For: 3.2.x, 3.3.0.CR2
>
>         Attachments: batcherinfinitelooptest.zip, batcherinfinitelooptest.zip
>
>
> Here is a piece of code from org.hibernate.jdbc.AbstractBatcher's closeStatements() method:
> Iterator iter = resultSetsToClose.iterator();
> while ( iter.hasNext() ) {
> 	try {
> 		logCloseResults();
> 		( (ResultSet) iter.next() ).close();
> 	}
> 	catch (SQLException e) {
> 		// no big deal
> 		log.warn("Could not close a JDBC result set", e);
> 	}
> 	catch (Throwable e) {
> 		// sybase driver (jConnect) throwing NPE here in certain cases
> 		log.warn("Could not close a JDBC result set", e);
> 	}
> }
> resultSetsToClose.clear();
> In case there is a ConcurrentModificationException thrown when iterating over the resultSetsToClose HashSet the exception will be caught by the catch(Throwable) clause. However, the iteration may continue infinitely because of the corrupted HashSet. This pegs one CPU and logs the following stack trace over and over again:
> 28/11 20:16:50 WARN AbstractBatcher [resin-tcp-connection-myserver:6001-15] Could not close a JDBC result set
> java.util.ConcurrentModificationException
> at java.util.HashMap$HashIterator.nextEntry(HashMap.java:841)
> at java.util.HashMap$KeyIterator.next(HashMap.java:877)
> at org.hibernate.jdbc.AbstractBatcher.closeStatements(AbstractBatcher.java:314)
> at org.hibernate.jdbc.ConnectionManager.cleanup(ConnectionManager.java:382)
> at org.hibernate.jdbc.ConnectionManager.close(ConnectionManager.java:324)
> at org.hibernate.impl.SessionImpl.close(SessionImpl.java:298)
> at org.springframework.orm.hibernate3.SessionFactoryUtils.closeSession(SessionFactoryUtils.java:774)
> at org.springframework.orm.hibernate3.support.OpenSessionInViewFilter.closeSession(OpenSessionInViewFilter.java:252)
> at org.springframework.orm.hibernate3.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:183)
> at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:75)
> at com.caucho.server.dispatch.FilterFilterChain.doFilter(FilterFilterChain.java:70)
> at com.caucho.server.cache.CacheFilterChain.doFilter(CacheFilterChain.java:188)
> at com.caucho.server.webapp.WebAppFilterChain.doFilter(WebAppFilterChain.java:178)
> at com.caucho.server.dispatch.ServletInvocation.service(ServletInvocation.java:229)
> at com.caucho.server.hmux.HmuxRequest.handleRequest(HmuxRequest.java:419)
> at com.caucho.server.port.TcpConnection.run(TcpConnection.java:389)
> at com.caucho.util.ThreadPool.runTasks(ThreadPool.java:492)
> at com.caucho.util.ThreadPool.run(ThreadPool.java:425)
> at java.lang.Thread.run(Thread.java:595)
> The catch(Throwable) block was added in Hibernate 3.2.3 if I saw that correctly. Apparently the reason was to catch a NPE thrown by a sybase driver here, but catching Throwable catches more than that and produces this side-effect.
> Now I do realize that the ConcurrentModificationException might be caused by not using Hibernate in a correct way, but I haven't determined the cause for it yet. However, I do think that Hibernate should fail more gracefully than it currently does.

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