Oracle Web Cache as a Software Load Balancer

9-24 Oracle Fusion Middleware High Availability Guide When you add a cache to the cluster, the cache-specific information of the new cluster member is added to the configuration of the cache cluster. Then, Oracle Web Cache synchronizes the configuration to all members of the cluster. Because adding a new member changes the relative capacity of each Web cache, Oracle Web Cache uses the information about capacity to recalculate which cluster member owns which content. When cache cluster members detect the failure of another cluster member, the remaining cache cluster members automatically take over ownership of the content of the failing member. When the cache cluster member is reachable again, Oracle Web Cache again reassigns the ownership of the content. When you remove a Web cache from a cache cluster, the remaining cache cluster members take over ownership of the content of the removed member. In addition, the configuration information about the removed member is deleted from the configuration and the revised configuration is synchronized with the remaining cache cluster members. See Section 9.3.3.2, Configuring a Cache Cluster for instructions on configuring a cache cluster.

9.3.2.5 Oracle Web Cache as a Software Load Balancer

You can configure a special mode of Oracle Web Cache that enables you to use Oracle Web Cache solely as a software load balancer of HTTP traffic. This configuration mode is useful to: ■ Manage low-volume, departmental, or test Web sites ■ Manage traffic in the DMZ between a hardware load balancer and an application using Oracle Portal or Oracle Single Sign-On This mode does not cache any content or provide support for the following features: ■ Compression: Oracle Web Cache ignores all compression settings. ■ Request filtering: Oracle Web Cache ignores any configure request filters and rules. ■ ESI: Oracle Web Cache does not assemble ESI content. ■ Cache hierarchies: If you plan to configure two caches in a cache hierarchy, then you should not configure one of the caches as a load balancer. You can deploy a single Oracle Web Cache server as a load balancer. However, this deployment makes the Oracle Web Cache server a single point of failure for your application. You can instead configure a cache cluster with multiple Oracle Web Cache servers in conjunction with operating system load balancing capabilities. Take note of the capacity changes mentioned earlier in this section. In this mode, you can configure Oracle Web Cache to load balance HTTP traffic in front of an application using ESI or in front of another Oracle Web Cache. The Oracle Web Cache load balancer does not process ESI content or participate in hierarchical caching. For example, a typical Oracle Portal deployment has a built-in Oracle Web Cache used for ESI assembly. For these configurations, do not configure the Oracle Web Cache used for ESI assembly as a load balancer. If you require other Oracle Web Cache features, such as caching or compression support, do not configure this mode. Instead, configure a hardware load balancer or operating system load balancing support, and use the load balancing feature to manage requests to origin servers. See Section 9.3.3.3, Configure Oracle Web Cache as a Software Load Balancer for instructions on configuring this mode. Configuring High Availability for Web Tier Components 9-25

9.3.3 Configuring Oracle Web Cache High Availability Solutions