Memory-to-memory topology: Peer-to-peer function

The basic peer-to-peer (both client and server function, or both mode) topology is the default configuration and has a single replica. However, you can also add additional replicas by configuring the replication domain.

In this basic peer-to-peer topology, each server Java Virtual Machine (JVM) can:

Host the Web application leveraging the HTTP session
Send out changes to the HTTP session that it owns
Receive backup copies of the HTTP session from all of the other servers in the cluster

This configuration represents the most consolidated topology, where the various system parts are collocated and requires the fewest server processes. When using this configuration, the most stable implementation is achieved when each node has equal capabilities (CPU, memory, and so on), and each handles the same amount of work.

Session hot failover

A new feature called session hot failover has been added to this release. This feature is only applicable to the peer-to-peer mode. In a clustered environment, session affinity in the WebSphere Application Server plug-in routes the requests for a given session to the same server. If the current owner server instance of the session fails, then the WebSphere Application Server plug-in routes the requests to another appropriate server in the cluster. For a cluster configured to run in the peer-to-peer mode this feature causes the plug-in to failover to a server that already contains the backup copy of the session, therefore avoiding the overhead of session retrieval from another server containing the backup.

You must upgrade all WebSphere Application Server plug-in instances that front the Application Server cluster to version 6.0 to ensure session affinity when using the peer-to-peer mode.

Related reference
Replication domain collection