[jboss-user] [Clustering/JBoss] - Re: Session Replication - Concurrency Problems?

jyoonyang do-not-reply at jboss.com
Tue Jul 10 21:29:51 EDT 2007

I'm seeing similar issue.

"bstansberry at jboss.com" wrote : 
  | Everyone else -- is anyone seeing this problem with sticky sessions enabled and working properly?  You have to use sticky sessions.

Why does sticky session need to enabled?  We have sticky session false and want to replicate the session.

We see this error when we repeatedly log in and out using the same browser.

I did printDetail on JMS console TomcatClusteringCache 

When I log in, I see the following in both nodes.

  |     /localhost
  |       /myapp
  |         /s6YGpkbACWfDPVre4sMcqQ**
  | VERSION: 3
  | s6YGpkbACWfDPVre4sMcqQ**: [B at 5e43ee

After logging out, I see the same in both nodes, except that the VERSION is bumped up to 4.

I tried logging in and out repeatedly, until I run into the error.  
ERROR [org.jboss.web.tomcat.tc5.session.JBossCacheService] externalizeSession(): exception occurred externalizing session SessionBasedClusteredSession[id: s6YGpkbACWfDPVre4sMcqQ**.worker1 lastAccessedTime: 1184115870097 version: 13 lastOutdated: 0]
  | java.lang.NullPointerException
  |         at org.springframework.webflow.execution.FlowSessionImpl.writeObject(FlowSessionImpl.java:156)
  |         at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  |         at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
  |         at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
  |         at java.lang.reflect.Method.invoke(Method.java:585)
  | ...

Followed by
WARN  [org.jboss.web.tomcat.tc5.session.CacheListener] Possible concurrency problem: Replicated version id 13 matches in-memory version for session s6YGpkbACWfDPVre4sMcqQ**

Here is tc5-cluster jboss-service.xml settings

  | <attribute name="ClusterName">Tomcat-${jboss.partition.name:Cluster}</attribute>
  | <attribute name="IsolationLevel">REPEATABLE_READ</attribute>
  | <attribute name="CacheMode">REPL_ASYNC</attribute>

Any idea?

Thanks in advance,

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