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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