I am evaluating the case of using sticky sessions with Session replication in tomcat. From my initial evaluation, I thought that if we enable Session replication, then session started in one tomcat node will be copied to all other tomcat nodes and thus we do not need sticky session to continue sessions and the request can be picked up by any node.
But it seems that session replication is in general used with sticky sessions, otherwise the session id needs to be changed whenever the request goes to some other node. ref: http://tomcat.apache.org/tomcat-6.0-doc/cluster-howto.html#Bind_session_after_crash_to_failover_node
Can anyone explain what is the real use of session replication if you have to enable sticky session? Because then you would be unnecessarily copying the session on each node, when the request with a given session id is always going to the same node. It could be beneficial in case of a node crashing, but then that does not happen frequently and using session replication only for that seems like an overkill.
As Mindas explained it before :
When you use loadbalancing it means you have several instances of tomcat and you need to divide loads.