Naming Considerations Administration Server Considerations

Clustering Best Practices 11-9

11.5 Application Deployment Considerations

Deploy clusterable objects to the cluster, rather than to individual Managed Servers in the cluster. For information and recommendations, see Deploying Applications to Oracle WebLogic Server.

11.6 Architecture Considerations

For information about alternative cluster architectures, load balancing options, and security options, see Chapter 9, Cluster Architectures.

11.7 Avoiding Problems

The following sections present considerations to keep in mind when planning and configuring a cluster.

11.7.1 Naming Considerations

For guidelines for how to name and address server instances in cluster, see Section 10.1.5, Identify Names and Addresses.

11.7.2 Administration Server Considerations

To start up WebLogic Server instances that participate in a cluster, each Managed Server must be able to connect to the Administration Server that manages configuration information for the domain that contains the cluster. For security purposes, the Administration Server should reside within the same DMZ as the WebLogic Server cluster. The Administration Server maintains the configuration information for all server instances that participate in the cluster. The config.xml file that resides on the Administration Server contains configuration data for all clustered and non-clustered servers in the Administration Servers domain. You do not create a separate configuration file for each server in the cluster. The Administration Server must be available in order for clustered WebLogic Server instances to start up. Note, however, that once a cluster is running, a failure of the Administration Server does not affect ongoing cluster operation. Singleton Services Java EE APIs used to implement singleton services include: ■ JMS Destinations, ■ JTA transaction managers ■ Cached entity beans with pessimistic concurrency control Scalability can be increased by partitioning the service into multiple instances, each of which handles a different slice of the backing data and its associated requests WebLogic Server features for increasing the availability of singleton services include: ■ Support for multiple thread pools for servers, to harden individual servers against failures ■ Health monitoring and lifecycle APIs to support detection restart of failed and ailing servers ■ Ability to upgrade software without interrupting services ■ Ability to migrate JMS servers and JTA transaction recovery services. Table 11–3 Cont. Java EE and WebLogic Support for Service Types Service Java EE Support WebLogic Server Scalability and Reliability Features for... 11-10 Using Clusters for Oracle WebLogic Server The Administration Server should not participate in a cluster. The Administration Server should be dedicated to the process of administering servers: maintaining configuration data, starting and shutting down servers, and deploying and undeploying applications. If the Administration Server also handles client requests, there is a risk of delays in accomplishing administration tasks. There is no benefit in clustering an Administration Server; the administrative objects are not clusterable, and will not failover to another cluster member if the administrative server fails. Deploying applications on an Administration Server can reduce the stability of the server and the administrative functions it provides. If an application you deploy on the Administration Server behaves unexpectedly, it could interrupt operation of the Administration Server. For these reasons, make sure that the Administration Servers IP address is not included in the cluster-wide DNS name.

11.7.3 Firewall Considerations