Hello, I have a working Tomcat 8.0.15 cluster with 3 members with the BackupManager as session manager. The session replication is mostly working except in a few cases. In those cases, I get the following error:
09-Apr-2015 12:16:58.369 SEVERE [Tribes-Task-Receiver-6]
org.apache.catalina.tribes.tipis.AbstractReplicatedMap.messageReceived Unable
to apply diff to key:3B286B4C7CA060163A00988969D21923
java.lang.NullPointerException
at
org.apache.catalina.ha.session.DeltaSession.applyDiff(DeltaSession.java:164)
at
org.apache.catalina.tribes.tipis.AbstractReplicatedMap.messageReceived(AbstractReplicatedMap.java:664)
at
org.apache.catalina.tribes.group.GroupChannel.messageReceived(GroupChannel.java:293)
at
org.apache.catalina.tribes.group.ChannelInterceptorBase.messageReceived(ChannelInterceptorBase.java:81)
at
org.apache.catalina.tribes.group.interceptors.TcpFailureDetector.messageReceived(TcpFailureDetector.java:112)
at
org.apache.catalina.tribes.group.ChannelInterceptorBase.messageReceived(ChannelInterceptorBase.java:81)
at
org.apache.catalina.tribes.group.ChannelInterceptorBase.messageReceived(ChannelInterceptorBase.java:81)
at
org.apache.catalina.tribes.group.interceptors.ThroughputInterceptor.messageReceived(ThroughputInterceptor.java:89)
at
org.apache.catalina.tribes.group.ChannelInterceptorBase.messageReceived(ChannelInterceptorBase.java:81)
at
org.apache.catalina.tribes.group.ChannelCoordinator.messageReceived(ChannelCoordinator.java:260)
at
org.apache.catalina.tribes.transport.ReceiverBase.messageDataReceived(ReceiverBase.java:240)
at
org.apache.catalina.tribes.transport.nio.NioReplicationTask.drainChannel(NioReplicationTask.java:206)
at
org.apache.catalina.tribes.transport.nio.NioReplicationTask.run(NioReplicationTask.java:97)
at
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
I was able to replicate the problem with a scenario in the application, but I
was not able to understand the underlying problem.
This happens when the user is making a very specific request and this request
arrives on a Tomcat where his session is not stored, forcing the Tomcat to
fetch the session elsewhere.
The 3 tomcats are on the same network with a very low network latency.
Does anybody has some advice on how to debug this problem?
For now, I got around it with sticky sessions on mod_jk, but I find this very
unsatisfactory.
Thank you in advance for your help,
//Théo
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