IT18699: MQTT channel ends unexpectedly, and FDC with NullPointerException and Probe XR013012 is generated

APAR status

• Closed as program error.

Error description

• The MQTT channel ends unexpectedly, and an FDC is generated with
  the details:
  
  | Probe Id          :- XR013012
  
  | Exception:1       :- java.lang.NullPointerException
  
  | Source            :-
  |
  |                   :- StateDump
  for:com.ibm.mq.communications.NonBlockingLis |
  |                   :- xxxxx@xxxxxx
  
  |   Throwable  :-
  |   |   Cause:1       :-  java.lang.NullPointerException
  |   |   StackTrace:1  :-  java.lang.NullPointerException
  |   |    at
  com.ibm.mq.communications.NonBlockingListener.run(NonBlockingLis
  tener.java:265)
  |   |    at java.lang.Thread.run(Thread.java:767)
  

Local fix

Problem summary

• ****************************************************************
  USERS AFFECTED:
  This issue affects users of:
  
  - The WebSphere MQ V7.5 MQXR service.
  - The IBM MQ V8.0 and V9.0 MQXR service.
  
  
  Platforms affected:
  MultiPlatform
  
  ****************************************************************
  PROBLEM DESCRIPTION:
  A MQTT client attempted to connect to the queue manager's
  telemetry (MQTT) channel. However, when the channel accepted the
  incoming server request there was an issue with it that meant
  that instead of a socket for that client being returned, a null
  object was instead. The attempt to use this when a socket was
  expected led to a NullPointerException, which caused the channel
  to end unexpectedly.
  

Problem conclusion

• The case where accepting a client connection request returns a
  null rather than a socket is now handled appropriately, and the
  channel does not end. An entry will be appended to the mqxr.log
  file indicating an InvalidSelectionKeyException to notify that
  this error has occurred and to aid in further diagnosis if
  required. The messages written to the mqxr.log look like:
  
  9/11/17 16:19:42.515  AMQCO1002E: A selection
  key=sun.nio.ch.SelectionKeyImpl@f233874a was found in an
  unexpected state.
  
  The MQTT channel continues operation as normal.
  
  ---------------------------------------------------------------
  The fix is targeted for delivery in the following PTFs:
  
  Version    Maintenance Level
  v7.5       7.5.0.9
  v8.0       8.0.0.8
  v9.0 LTS   9.0.0.3
  
  The latest available maintenance can be obtained from
  'WebSphere MQ Recommended Fixes'
  http://www-1.ibm.com/support/docview.wss?rs=171&uid=swg27006037
  
  If the maintenance level is not yet available information on
  its planned availability can be found in 'WebSphere MQ
  Planned Maintenance Release Dates'
  http://www-1.ibm.com/support/docview.wss?rs=171&uid=swg27006309
  ---------------------------------------------------------------
  

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

  WMQ BASE MULTIP

• Fixed component ID

  5724H7241

Applicable component levels