[jboss-jira] [JBoss JIRA] Resolved: (JBAS-4075) JBossCacheManager.findLocalSessions concurrency issue

[Brian Stansberry (JIRA)]

     [ http://jira.jboss.com/jira/browse/JBAS-4075?page=all ]

Brian Stansberry resolved JBAS-4075.
------------------------------------

    Resolution: Done

As Hany noted, the oswego concurrent.jar's ConcurrentHashMap's values() method returns a collection whose toArray() method isn't thread safe.

For 4.2 and trunk I fixed this by switching to the java.util.concurrent.ConcurrentHashMap, which doesn't have this problem.

For Branch_4_0 I copy off the collection using its thread safe iterator and then create the array from the copy.

> JBossCacheManager.findLocalSessions concurrency issue
> -----------------------------------------------------
>
>                 Key: JBAS-4075
>                 URL: http://jira.jboss.com/jira/browse/JBAS-4075
>             Project: JBoss Application Server
>          Issue Type: Bug
>      Security Level: Public(Everyone can see) 
>          Components: Clustering
>    Affects Versions: JBossAS-4.0.5.GA, JBossAS-5.0.0.Beta1, JBossAS-4.0.4.GA
>         Environment: SLES 9, SP3.
> JBOSS 4.0.5.GA
>            Reporter: Hany Mesha
>         Assigned To: Brian Stansberry
>             Fix For: JBossAS-5.0.0.Beta2, JBossAS-4.2.0.CR1, JBossAS-4.0.5.SP1 
>
>
> When running a load test on a JBoss Cluster I see the following exception
> 2007?02?06 14:23:58,231 ERROR
> [org.jboss.web.tomcat.tc5.session.JBossCacheManager:processExpires]
> processExpires: failed with exception: java.util.NoSuchElementException
> java.util.NoSuchElementException
>         at
> EDU.oswego.cs.dl.util.concurrent.ConcurrentHashMap$HashIterator.next(ConcurrentHashMap.java:1131)
>         at java.util.AbstractCollection.toArray(AbstractCollection.java:176)
>         at
> org.jboss.web.tomcat.tc5.session.JBossCacheManager.findLocalSessions(JBossCacheManager.java:851)
>         at
> org.jboss.web.tomcat.tc5.session.JBossCacheManager.processExpires(JBossCacheManager.java:1188)
>         at
> org.jboss.web.tomcat.tc5.session.JBossManager.backgroundProcess(JBossManager.java:817)
>         at
> org.apache.catalina.core.ContainerBase.backgroundProcess(ContainerBase.java:1284)
>         at
> org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1569)
>         at
> org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1578)
>         at
> org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1578)
>         at
> org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.run(ContainerBase.java:1558)
>         at java.lang.Thread.run(Thread.java:595)
> Upon further investigation and looking at the source code of JBossCacheManager in 4.0 branch, the method findLocalSessions() suffers from concurrency issue when calling java.util.AbstractCollection.toArray(Object[] array) which is not thread safe.

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