[jboss-jira] [JBoss JIRA] Commented: (JBCACHE-1355) java.util.ConcurrentModificationException under load in JBoss Cache 2.0.0.GA

[Manik Surtani (JIRA)]

    [ http://jira.jboss.com/jira/browse/JBCACHE-1355?page=comments#action_12414784 ] 
            
Manik Surtani commented on JBCACHE-1355:
----------------------------------------

This is a race condition between the PLI and CLI.  Consider:

T1: attempts to lock FQN for a get() call.  FQN has been evicted, so nothing is locked.
T2: attempts to lock FQN for a put().  This is loaded by the CLI and locked by T2.
T1: now gets to the CLI and in mustLoad(), attempts to peek() into the node to see if the required keys are available.  Now FQN *does* exist, since T2 has loaded it, but T1 doesn't have any locks on it.  
T1: Calls node.getKeysDirect() to test keys and check if loading is needed.  getKeysDirect() defensively copies the keyset.  Still no locks for T1!!
T2: Now puts data into the node.  
T1: Comod exception!!

Created ConcurrentPutRemoveEvictTest in trunk for this.

> java.util.ConcurrentModificationException under load in JBoss Cache 2.0.0.GA
> ----------------------------------------------------------------------------
>
>                 Key: JBCACHE-1355
>                 URL: http://jira.jboss.com/jira/browse/JBCACHE-1355
>             Project: JBoss Cache
>          Issue Type: Bug
>      Security Level: Public(Everyone can see) 
>    Affects Versions: 2.0.0.GA
>         Environment: JDK 1.6.0_5
>            Reporter: Anton Spirkov
>         Assigned To: Manik Surtani
>            Priority: Critical
>             Fix For: 2.2.0.GA
>
>
> Concurrent Modification Exception appears under load (~500 TPS). We Add, Read and Remove same objects all the time during the tests.
> The Exception:
> java.util.ConcurrentModificationException
>         at java.util.HashMap$HashIterator.nextEntry(HashMap.java:793)
>         at java.util.HashMap$KeyIterator.next(HashMap.java:828)
>         at java.util.AbstractCollection.addAll(AbstractCollection.java:305)
>         at java.util.HashSet.<init>(HashSet.java:100)
>         at org.jboss.cache.UnversionedNode.getKeysDirect(UnversionedNode.java:433)
>         at org.jboss.cache.interceptors.CacheLoaderInterceptor.mustLoad(CacheLoaderInterceptor.java:303)
>         at org.jboss.cache.interceptors.CacheLoaderInterceptor.loadIfNeeded(CacheLoaderInterceptor.java:168)
>         at org.jboss.cache.interceptors.CacheLoaderInterceptor.invoke(CacheLoaderInterceptor.java:157)
>         at org.jboss.cache.interceptors.ActivationInterceptor.invoke(ActivationInterceptor.java:67)
>         at org.jboss.cache.interceptors.Interceptor.invoke(Interceptor.java:76)
>         at org.jboss.cache.interceptors.UnlockInterceptor.invoke(UnlockInterceptor.java:37)
>         at org.jboss.cache.interceptors.Interceptor.invoke(Interceptor.java:76)
>         at org.jboss.cache.interceptors.PessimisticLockInterceptor.invoke(PessimisticLockInterceptor.java:203)
>         at org.jboss.cache.interceptors.Interceptor.invoke(Interceptor.java:76)
>         at org.jboss.cache.interceptors.NotificationInterceptor.invoke(NotificationInterceptor.java:32)
>         at org.jboss.cache.interceptors.Interceptor.invoke(Interceptor.java:76)
>         at org.jboss.cache.interceptors.TxInterceptor.handleNonTxMethod(TxInterceptor.java:298)
>         at org.jboss.cache.interceptors.TxInterceptor.invoke(TxInterceptor.java:131)
>         at org.jboss.cache.interceptors.Interceptor.invoke(Interceptor.java:76)
>         at org.jboss.cache.interceptors.CacheMgmtInterceptor.invoke(CacheMgmtInterceptor.java:81)
>         at org.jboss.cache.interceptors.Interceptor.invoke(Interceptor.java:76)
>         at org.jboss.cache.interceptors.InvocationContextInterceptor.invoke(InvocationContextInterceptor.java:62)
>         at org.jboss.cache.CacheImpl.invokeMethod(CacheImpl.java:3939)
>         at org.jboss.cache.CacheImpl.get(CacheImpl.java:1441)
>         at org.jboss.cache.CacheImpl.get(CacheImpl.java:1415)
> Please don't hesitate to contact me for additional information. We use jboss cache at the production site, so it's quite critical for us to solve this issue. Thanks!

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