BEA Weblogic Interview Question:

Does WebLogic JMS support clustering?

Submitted by: Administrator

WebLogic JMS supports cluster-wide, transparent access to destinations from any server in the cluster. 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.

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.

You can configure multiple JMS servers on the various nodes in the cluster as long as you give them different names. You can assign destinations to the various JMS servers.

One problem to be aware of is the propagation delay in replicating entries in JNDI. If you have an MDB deployed on one node but reference a destination on another node, the deployment may fail with a javax.naming.NamingException exception. The problem occurs because the server is not synced up to the JNDI from the remote server (JMS server) yet, so the JNDI lookup of destination as part of MDB deployment will fail. One workaround is for each MDB to reference a local destination. Another approach is deploy the MDBs after the server boots (plus a delay for JNDI propagation). To get around losing messages before the MDB is deployed, use durable subscribers. This problem is fixed for MDBs in WLS 6.1, where the MDB will be deployed and reconnection will be retried until the destination is available. Note that this is still a problem for EJBs in general that try to reference a non-local JMS destination.
Submitted by: Administrator