Hello,
I'm running Tomcat 8.0.15 with Java 1.8.0_25 on Ubuntu 14.04. We have 5
instances that are all setup with session clustering as follows:
<Cluster className="org.apache.catalina.ha.tcp.SimpleTcpCluster">
<Manager className="org.apache.catalina.ha.session.DeltaManager"
stateTransferTimeout="5" />
<Channel className="org.apache.catalina.tribes.group.GroupChannel">
<Membership className="org.apache.catalina.tribes.membership.McastService"
address="${multicast}" />
</Channel>
</Cluster>
-Dmulticast=228.0.0.4
To help prevent accidental misconfigurations that have occurred in the past, I
decided to implement monitoring on the session replication by checking the JMX
mbean Catalina/Manager/<host>/<context>/activeSessions attribute. Most of the
time the values for the 5 instances are all within 1 or 2 of each other. Over
the weekend we consistently had one instance that had more sessions than the
other 4. It began with 102 sessions where every other instance had 95. Over
the next 36 hours as more sessions were expiring over the weekend, the
difference grew to 49 vs 29. Eventually it resynced and now they all report
the same active session count. My question is, does anyone know why this would
happen, and if this can be expected is there a better way to monitor session
replication to ensure that there isn't one instance that isn't being replicated
to? I believe this only happens on weekends when most sessions are expiring
and very few are being created but I may be wrong.
Thank you,
Peter
