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

[Kariem Hussein (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HHH-3006?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_29765 ] 

Kariem Hussein commented on HHH-3006:
-------------------------------------

I might be wrong, but I think the problem is that the Throwable should not be catched. Instead a null pointer exception would be sufficient according to the comment. Or am i totally wrong on that? According to SVN this change was introduced in 3.2.3, which would match Remi's observation. We upgraded from a 3.1.x version.

3.2.2:
http://anonsvn.jboss.org/repos/hibernate/core/tags/v322/src/org/hibernate/jdbc/AbstractBatcher.java

3.2.3 - 3.2.6
http://anonsvn.jboss.org/repos/hibernate/core/tags/v323/src/org/hibernate/jdbc/AbstractBatcher.java
http://anonsvn.jboss.org/repos/hibernate/core/tags/v324/src/org/hibernate/jdbc/AbstractBatcher.java
http://anonsvn.jboss.org/repos/hibernate/core/tags/v325/src/org/hibernate/jdbc/AbstractBatcher.java
http://anonsvn.jboss.org/repos/hibernate/core/tags/v326/src/org/hibernate/jdbc/AbstractBatcher.java

Sorry, no links from fisheye: I could not find a URL with nice annotations.

> 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
>         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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