Web container clustering and failover

 

As mentioned before, a WebSphere environment may include several HTTP server instances. Each HTTP server is configured to run the WebSphere HTTP plug-in in its process. Each request coming into the Web server is passed through this plug-in, which uses its configuration information to determine if the request should be routed to WebSphere, and if so, which Web container the request should be routed to (see Figure 9-1). These Web containers may be running on the same machine as the HTTP server, a different machine, or a combination of the two.

In WebSphere V5, several new functions have been added to enhance WebSphere plug-in failover and recovery: Server weight: Minimizes unavailability due to overloading (refer to Chapter 5, Plug-in workload management and failover for more information on server weights). Ordered cluster server failover: Eliminates the problem that two cluster servers may be selected as the session failover target concurrently. Primary server and backup server lists: Provides one more level of failover support. Non-blocking connection: Reduces the impact of operating system's TCP/IP keep-alive timeout. Memory-to-memory session replication: Enhances session data availability.

The Web container failover support in WebSphere V5 is provided by three mechanisms: WebSphere Web container server cluster, which creates server process redundancy for failover support. The workload management routing technique built into the WebSphere Web server plug-in. It controls the routing of client requests among redundant server processes. Session management and failover mechanism, which provides HTTP session data for redundant server processes.

Figure 9-1 WAS (Web container) high availability

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WebSphere is a trademark of the IBM Corporation in the United States, other countries, or both.

 

IBM is a trademark of the IBM Corporation in the United States, other countries, or both.