Chapter 14. Clustering

Clustering creates an illusion — it permits the deployment of application components and services to several machines while presenting only a single face to the client. There are good reasons to support this illusion. When a client requests a service, it should make no difference if the service runs on a single server or across a number of servers. The clustering abstraction provides you with a clear route to improving the performance and scalability of your applications, albeit with increased administration of hardware and network resources. WebLogic’s clustering offers three important benefits:

Scalability

A solution that allows you to create additional capacity by introducing more servers to the cluster, thereby reducing the load on existing servers.

Load balancing

The ability to distribute requests across all members of the cluster, according to the workload on each server.

High availability

A mix of features that ensure applications and services are available even if a server or machine fails. Clients can continue to work with little or no disruption in a highly available environment. WebLogic achieves high availability using a combination of features: replication, failover, and migratable services.

Clearly, WebLogic’s support for clustering impacts all aspects of J2EE development, deployment, and application security. In previous chapters, we encountered several instances in which WebLogic allows you to improve the scalability and availability of your applications: ...

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