Server Affinity for Distributed JMS Destinations Initial Context Affinity and Server Affinity for Client Connections

5-12 Using Clusters for Oracle WebLogic Server

5.3.1 Server Affinity for Distributed JMS Destinations

Server affinity is supported for JMS applications that use the distributed destination feature; this feature is not supported for standalone destinations. If you configure server affinity for JMS connection factories, a server instance that is load balancing consumers or producers across multiple members of a distributed destination will first attempt to load balance across any destination members that are also running on the same server instance. For detailed information on how the JMS connection factorys Server Affinity Enabled option affects the load balancing preferences for distributed destination members, see How Distributed Destination Load Balancing Is Affected When Using the Server Affinity Enabled Attribute in Configuring and Managing JMS for Oracle WebLogic Server.

5.3.2 Initial Context Affinity and Server Affinity for Client Connections

A system administrator can establish load balancing of JMS destinations across multiple servers in a cluster by configuring multiple JMS servers and using targets to assign them to the defined WebLogic Servers. Each JMS server is deployed on exactly one WebLogic Server and handles requests for a set of destinations. During the configuration phase, the system administrator enables load balancing by specifying targets for JMS servers. For instructions on setting up targets, see Section 10.2.11, Configure Migratable Targets for Pinned Services. For instructions on deploying a JMS server to a migratable target, see Section 10.2.16, Deploying, Activating, and Migrating Migratable Services. A system administrator can establish cluster-wide, transparent access to destinations from any server in the cluster by configuring multiple connection factories and using targets to assign them to WebLogic Servers. Each connection factory can be deployed on multiple WebLogic Servers. Connection factories are described in more detail in ConnectionFactory in Programming JMS for Oracle WebLogic Server. The application uses the Java Naming and Directory Interface JNDI to look up a connection factory and create a connection to establish communication with a JMS server. Each JMS server handles requests for a set of destinations. Requests for destinations not handled by a JMS server are forwarded to the appropriate server. WebLogic Server provides server affinity for client connections. If an application has a connection to a given server instance, JMS will attempt to establish new JMS connections to the same server instance. When creating a connection, JMS will try first to achieve initial context affinity. It will attempt to connect to the same server or servers to which a client connected for its initial context, assuming that the server instance is configured for that connection factory. For example, if the connection factory is configured for servers A and B, but the client has an InitialContext on server C, then the connection factory will not establish the new connection with A, but will choose between servers B and C. If a connection factory cannot achieve initial context affinity, it will try to provide affinity to a server to which the client is already connected. For instance, assume the Note: To provide persistent store for failover of JMS and JTA pinned services, you might consider using high-availability clustering software such as VERITAS Cluster Server, which provides an integrated, out-of-the-box solution for WebLogic Server based applications. Some other recommended high-availability software solutions include SunCluster, IBM HACMP, or the equivalent. Load Balancing in a Cluster 5-13 client has an InitialContext on server A and some other type of connection to server B. If the client then uses a connection factory configured for servers B and C it will not achieve initial context affinity. The connection factory will instead attempt to achieve server affinity by trying to create a connection to server B, to which it already has a connection, rather than server C. If a connection factory cannot provide either initial context affinity or server affinity, then the connection factory is free to make a connection wherever possible. For instance, assume a client has an initial context on server A, no other connections and a connection factory configured for servers B and C. The connection factory is unable to provide any affinity and is free to attempt new connections to either server B or C.

5.4 Load Balancing for JDBC Connections