Configuring Message Listener Service in a Cluster can Cause Unequal Workload Distribution on all Releases of V5.0
 Technote (troubleshooting)
 
Problem(Abstract)
In all releases of WebSphere® Application Server V5.0, two or more application servers can be configured in a cluster with the same listener port, listening on the same queue, defined on each server. This can cause unequal workload distribution between the message-driven beans (MDBs) defined on each application server. Failover will work, so if one application server is stopped, the MDB on the other will process the incoming messages. However, when both servers are running, it is possible that only one of the MDBs will process the messages on the target queue.
 
Cause
There are several possible causes of this behavior, including:
  • The rate at which messages appear on the queue

  • The complexity of the MDB

  • The current workload on the machine
 
Resolving the problem
In the configuration described above, only one MDB will pick up the incoming messages if:
  • The messages are all placed on the queue at the same time or

  • They are placed on the queue at a very slow rate (for example, less than ten messages per second, although the exact rate will depend on the complexity of the MDB and the workload of the machine being used).

If the rate is increased (usually to more than ten messages per second), the messages should be distributed between the MDBs on all servers in the cluster. Even in this scenario, an even distribution of the messages is not guaranteed because the two listeners will compete for messages on the queue.

For these reasons, the recommendation is that only one listener port and one MDB be configured to listen on a queue.

 
 
Cross Reference information
Segment Product Component Platform Version Edition
Application Servers Runtimes for Java Technology Java SDK
 
 


Document Information


Product categories: Software > Application Servers > Distributed Application & Web Servers > WebSphere Application Server > Java Message Service (JMS)
Operating system(s): Windows
Software version: 5.0
Software edition:
Reference #: 1154178
IBM Group: Software Group
Modified date: Dec 9, 2003