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Session Replication

Session Replication with Hazelcast Enterprise is a container specific module where no application change is required to enable session replication for JEE Web Applications.

Features

  1. Seamless Tomcat 6,7 integration
  2. Sticky + Non-Sticky sessions supported
  3. Tomcat failover
  4. Deferred write for performance boost

Deployments

Client-Server Deployment

In this deployment type, Tomcat instances work as clients to an existing Hazelcast Cluster.

Features:

  • Existing Hazelcast cluster is used as the Session Replication Cluster.
  • Offload Session Cache from Tomcat to Hazelcast Cluster.
  • The architecture is completely independent. Complete reboot of Tomcat instances.

Configuration:

  1. Set clientOnly property as true (optional, default is false).
  2. Set mapName property (optional, configured map for special cases like WAN Replication, Eviction, MapStore, etc.).
  3. Configure Hazelcast client via hazelcast.client.config system property or by putting hazelcast-client.xml into classpath.
  4. Add hazelcast-client-<version>.jar and hazelcast-sessions-tomcat6-<version>.jar to $CATALINA_HOME/lib/ folder.

Sample Configuration

<Context>
  <Manager className="com.hazelcast.session.HazelcastSessionManager" clientOnly="true" mapName="sessionMap"/>
</Context>

P2P Deployment

This launches embedded Hazelcast Node in each server instance.

Features

This type of deployment is the simplest approach. You can just configure your Tomcat and launch. There is no need for an external Hazelcast cluster.

Configuration

  1. Set mapName property (optional, configured map for special cases like WAN Replication, Eviction, MapStore, etc.).
  2. Configure Hazelcast client via hazelcast.config system property or by putting hazelcast.xml into classpath.
  3. Add hazelcast-<version>.jar and hazelcast-sessions-tomcat6-<version>.jar to $CATALINA_HOME/lib/ folder.

Sample Configuration

<Context>
  <Manager className="com.hazelcast.session.HazelcastSessionManager" mapName="sessionMap"/>
</Context>

Session Affinity

Sticky Sessions (default)

Sticky Sessions are used to improve the performance since the sessions do not move around the cluster.

Request goes always to the same instance where the session was firstly created. By using a sticky session, you eliminate session replication problems mostly, except for the failover cases. In case of failovers, Hazelcast helps you not lose existing sessions.

Non-Sticky Sessions

Non-Sticky Sessions are not good for performance because you need to move session data all over the cluster every time a new request comes in.

However, with Non-Sticky caches, load balancing might be super easy as some load increasing case you can distribute the request to the least used Tomcat instance. Hazelcast supports Non-Sticky Sessions as well.

Supported Containers

  • Tomcat 6.0.39
  • Tomcat 7.0.54