How to implement session replication in Tomcat?

In Tomcat, session replication can be achieved by configuring a cluster environment. The following are the steps to implement session replication.

1. Group of items or individuals gathered together.

<Engine name="Catalina" defaultHost="localhost">
    ...
    <Cluster className="org.apache.catalina.ha.tcp.SimpleTcpCluster">
        <Manager className="org.apache.catalina.ha.session.DeltaManager"
            expireSessionsOnShutdown="false"
            notifyListenersOnReplication="true"/>
        <Channel className="org.apache.catalina.tribes.group.GroupChannel"/>
        <Valve className="org.apache.catalina.ha.tcp.ReplicationValve"
            filter=""/>
        <Valve className="org.apache.catalina.ha.session.JvmRouteBinderValve"/>
        ...
    </Cluster>
</Engine>

1. Configure session management: Specify the class of the session manager within the element, such as using the DeltaManager class to enable session replication.
2. Configure the cluster communication channel: Specify the class for the cluster communication channel within the element, such as using the GroupChannel class for cluster communication.
3. Configure a replication valve: Specify the class for the replication valve in the element, for example, use the ReplicationValve class to implement session replication.
4. Set up load balancing: If a load balancer is used to distribute requests to nodes in a Tomcat cluster, session stickiness can be configured in the load balancer to ensure that a user’s request is sent to the same Tomcat node.

Once the configuration process is completed as described above, the Tomcat cluster environment will be able to achieve session replication. This means that when there are changes to session data on one Tomcat node, these changes will be synchronized to other Tomcat nodes, thus enabling session replication.