IIOP client settings that affect load balancing  Component settings

Chapter 7: Cluster Tuning

Web application settings

Web applications in a clustered deployment can provide better performance since multiple machines can handle more load than one. Clusters also provide high availability: if one machine goes off-line, clients can connect to another server in the cluster. To run your Web application in a cluster, you must configure a mechanism to support load balancing of HTTP requests, and optionally failover. For more information, see “Deploying Web applications to a cluster” in Chapter 7, “Load Balancing, Failover, and Component Availability,” in the EAServer System Administration Guide.

Chapter 5, “Web Application Tuning,” describes the Web application settings that you can tune for single-server deployments. In a clustered deployment, these additional settings affect performance:


HTTP session replication mechanism

In a clustered deployment, EAServer replicates user session data stored in HTTP sessions so that the same data is available on other servers in the cluster. Replication can use a remote database server or in-memory storage.

If using in-memory replication, EAServer replicates data between mirror pairs, that is, a pair of servers configured to share the same user session. In-memory replication can perform better than using a database, but requires more memory on each server. Specify a cache size to constrain the memory required by the cache, and specify a timeout to free up memory used by idle sessions. To set these parameters, follow the instructions in “Deploying Web applications to a cluster” in Chapter 7, “Load Balancing, Failover, and Component Availability,” in the EAServer System Administration Guide.

If using database replication, all servers in the cluster store session data in a remote database. This mechanism can perform slower than in-memory replication, but requires less memory. Also, EAServer can share a client’s session data on more than two servers. If using this technique:


Lazy session validation

In the default configuration, EAServer validates a client’s HTTP session during each request. In a clustered deployment, session validation is more resource intensive since EAServer stores the session in a database or using a replicated cache. If you enable lazy validation, EAServer validates the session only when a servlet or JSP calls ServletRequest.getSession() or ServletRequest.getSession(boolean). To enable this setting, set the com.sybase.jaguar.webapplication.lazydistributedhttpsessionvalidation Web application property to true.

Lazy validation can improve performance. However, enabling lazy authentication has the following side effects:





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