IZ48029: MEMORY LEAK WHEN SUBSCRIBING TO MULTICAST ENABLED TOPIC

WebSphere Message Broker V6.1 - Fix Pack 6.1.0.7

APAR status

• Closed as program error.

Error description

• Growth in the baseline memory usage is being seen over time.  It
  seems like there is rising heap usage after garbage collection.
  Testing with the multicast client, eventually the DFE abended
  with a Java Out of Memory error after about 1225 iterations.
  The same test with an XMS unicast client doesn't show any real
  increase in java heap usage and there is no trend in the heap
  use which suggests a memory leak.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All WebSphere Message Broker users of        *
  *                 Publish/Subscribe who subscribe to           *
  *                 multicast enabled topics.                    *
  ****************************************************************
  * PROBLEM DESCRIPTION: A multicast enabled topic is configured *
  *                      and deployed to the broker. Over a      *
  *                      period of time, real-time clients       *
  *                      subscribe and unsubscribe to the        *
  *                      multicast topic. This results in a      *
  *                      steady increase of the JVM heap         *
  *                      usage which eventually causes the       *
  *                      DataFlowEngine hosting the real-time    *
  *                      flow to abend due to the JVM exhausting *
  *                      its available memory.                   *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  When a real-time client application subscribes to a multicast
  enabled topic the broker creates a listener for each
  subscription that is placed. The listener that is created is
  then added to an internal list which is maintained by the
  broker. A memory leak occurs because the reference to the
  listener held in the internal list is not cleared when the
  client disconnects and unsubscribes.
  

Problem conclusion

• WebSphere Message Broker has been modified such that the
  references to the listener objects are now removed when a
  real-time client disconnects to resolve the memory leak.
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

Fix information

• Fixed component name

  MSSG BROKER AIX

• Fixed component ID

  5724J0501

Applicable component levels

• R100 PSY

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