Overview of Session Persistence and Failover

Communications Server provides high availability session persistence through failover of HTTP/SIP session data and stateful session bean (SFSB) session data. Failover means that in the event of an server instance or hardware failure, another server instance takes over a distributed session.

Requirements

A distributed session can run in multiple Sun GlassFish Communications Server instances, if:

• Each server instance has access to the same session state data. Communications Server provides the following types of high availability storage for HTTP/SIP session and stateful session bean data:

  • In-memory replication on other servers in the cluster. In-memory replication is enabled by default with the cluster profile.

    The use of in-memory replication requires the Group Management Service (GMS) to be enabled. For more information about GMS, see Group Management Service.

    If server instances in a cluster are located on different machines, ensure that the following prerequisites are met:

    • To ensure that GMS and in-memory replication function correctly, the machines must be on the same subnet.

    • To ensure that in-memory replication functions correctly, the system clocks on all machines in the cluster must be synchronized as closely as possible.

• Each server instance has the same distributable web application deployed to it. The web-app element of the web.xml deployment descriptor file or the sip-app element of the sip.xml deployment descriptor file must contain the distributable element.

• The web application uses high-availability session persistence. If a non-distributable web application is configured to use high-availability session persistence, the server writes an error to the log file.

• The web application must be deployed using the deploy or deploydir command with the --availabilityenabled option set to true. For more information on these commands, see deploy(1) and deploydir(1).