Clustering & Sessions

Tomcat Clustering, High Availability & Session Replication

In-memory session replication across cluster nodes, DeltaManager vs BackupManager, and cloud static membership.

High Availability

1. Standard Cluster Configuration (conf/server.xml)

Place the <Cluster> element inside the <Engine> or <Host> block to enable peer-to-peer session state replication:

<Cluster className="org.apache.catalina.ha.tcp.SimpleTcpCluster"
         channelSendOptions="8">
    <Manager className="org.apache.catalina.ha.session.DeltaManager"
             expireSessionsOnShutdown="false"
             notifyListenersOnReplication="true"/>
    <Channel className="org.apache.catalina.tribes.group.GroupChannel">
        <Membership className="org.apache.catalina.ha.mcast.McastService"
                    address="228.0.0.4"
                    port="45564"
                    frequency="500"
                    dropTime="3000"/>
        <Receiver className="org.apache.catalina.ha.tcp.nio.NioReceiver"
                  address="auto"
                  port="4000"
                  autoBind="100"
                  selectorTimeout="5000"
                  maxThreads="6"/>
        <Sender className="org.apache.catalina.ha.tcp.ReplicationTransmitter">
            <Transport className="org.apache.catalina.ha.tcp.PooledParallelSender"/>
        </Sender>
    </Channel>
</Cluster>
Webapp Prerequisite: Add <distributable/> inside your application's WEB-INF/web.xml and ensure all session attribute objects implement java.io.Serializable.