IT16587: MQ CLASSES FOR JAVA AND CLASSES FOR JMS APPLICATION THREADS HANG AFTER CHANNEL QUIECSED

APAR status

• Closed as program error.

Error description

• An application using the WebSphere MQ classes for JMS is
  connecting to a queue manager using the CLIENT transport, and is
  receiving messages from a queue by calling the method:
  
  MessageConsumer.receive()
  
  While the application is running, the WebSphere MQ channel that
  the application is using to connect to the queue manager is
  quiesced. When this happens, the call to the method:
  
  MessageConsumer.receive()
  
  never returns and no exceptions are thrown. A Javacore taken
  when the issue occurs shows that the application thread is
  blocked in the method RemoteSession.exchangeTSH().
  

Local fix

Problem summary

• ****************************************************************
  USERS AFFECTED:
  This issue affects two categories of user:
  
  1. Users of:
  
  - The WebSphere MQ V7.5 classes for Java who have an interim fix
  for APAR IT05967 installed.
  - The IBM MQ V8.0.0.3 (or later) classes for Java.
  - The IBM MQ V9.0.0.0 classes for Java.
  
  who have applications that connect to a WebSphere MQ queue
  manager using the CLIENT transport, and put or get messages from
  either queues or topics.
  
  2. Users of:
  
  - The WebSphere MQ V7.5 classes for JMS, who have an interim fix
  for APAR IT05967 installed.
  - The IBM MQ V8.0.0.3 (or later) classes for JMS
  - The IBM MQ V9.0.0.0 classes for JMS
  
  - The WebSphere MQ V7.5 resource adapter, who have an interim
  fix for APAR IT05967 installed.
  - The IBM MQ V8.0.0.3 (or later) resource adapter
  - The IBM MQ V9.0.0.0 resource adapter
  
  who have applications that connect to a queue manager using the
  CLIENT transport and WebSphere MQ messaging provider normal
  mode,, and put or get messages from either queues or topics.
  
  
  Platforms affected:
  MultiPlatform
  
  ****************************************************************
  PROBLEM DESCRIPTION:
  When either of the mqsc commands:
  
  STOP CHANNEL()
  STOP CHANNEL() MODE(QUIESCE)
  
  are issued against a queue manager, the queue manager will
  perform a controlled shutdown of all of the instances of the
  channel specified. In order to do this, it will contact all of
  the WebSphere MQ Clients that are currently using an instance of
  that channel, informing them that the channel is being quiesced.
  The WebSphere MQ Clients will then perform the following
  behaviour:
  
  - All applications that are currently using that channel
  instance, who are in the middle of getting or putting a message
  at the time the command was run and have specified the
  MQGetMessageOption MQGMO_FAIL_IF_QUIESCE or the
  MQPutMessageOption MQPMO_FAIL_IF_QUIESCE should have the get or
  put operations interrupted with an error containing reason code
  2202 (MQRC_CONNECTION_QUIESCING).
  
  - All applications that are currently using that channel
  instance, who are in the middle of getting or putting a message
  at the time the command was run and have not specified the
  MQGetMessageOption MQGMO_FAIL_IF_QUIESCE or the
  MQPutMessageOption MQPMO_FAIL_IF_QUIESCE should be allowed to
  carry on using the channel instance as normal.
  
  - Any new applications that try to connect to the queue manager
  using that channel, or any additional threads inside existing
  applications which try to create a new connection to a queue
  manager using an instance of that channel, should be unable to
  connect and will receive an error containing WebSphere MQ Reason
  Code 2537 (MQRC_CHANNEL_NOT_AVAILABLE).
  
  APAR IT05967 introduced some new logic into the WebSphere MQ
  classes for Java and classes for JMS to ensure that this
  processing was carried out correctly. However, as a result of
  this change, a small timing window was introduced which would
  prevent the notification from being passed to an application
  thread which was waiting to receive data from the queue manager.
  As a result of this, the thread would block until the
  application was shut down, even though it had specified either
  the MQGetMessageOption MQGMO_FAIL_IF_QUIESCE or the
  MQPutMessageOption MQPMO_FAIL_IF_QUIESCE.
  
  Javacores taken at the time of the issue would show that the
  application thread was blocked in the method
  RemoteSession.exchangeTSH(). An example of the call stack for a
  thread that was getting messages from the queue manager when the
  issue occurred is shown below:
  
     java.lang.Object.wait()
  at java.lang.Object.wait()
  at com.ibm.mq.jmqi.remote.impl.RemoteSession.exchangeTSH()
  at
  com.ibm.mq.jmqi.remote.impl.RemoteProxyQueue.requestMessagesReco
  nnectable()
  at
  com.ibm.mq.jmqi.remote.impl.RemoteProxyQueue.requestMessages()
  at com.ibm.mq.jmqi.remote.impl.RemoteProxyQueue.flushQueue()
  at com.ibm.mq.jmqi.remote.impl.RemoteProxyQueue.proxyMQGET()
  at
  com.ibm.mq.jmqi.remote.api.RemoteFAP.jmqiGetInternalWithRecon()
  at com.ibm.mq.jmqi.remote.api.RemoteFAP.jmqiGetInternal()
  at com.ibm.mq.jmqi.internal.JmqiTools.getMessage()
  at com.ibm.mq.jmqi.remote.api.RemoteFAP.jmqiGet()
      :    :    :    :    :    :    :    :    :    :    :    :
     :    :
  

Problem conclusion

• The WebSphere MQ classes for Java and classes for JMS have been
  updated to ensure that if a notification is received from a
  queue manager indicating that a channel is being quiesced. then
  all application threads using that channel instance which have
  specified either the MQGetMessageOption MQGMO_FAIL_IF_QUIESCE or
  the MQPutMessageOption MQPMO_FAIL_IF_QUIESCE will be interrupted
  and receive a JMSException containing WebSphere MQ reason code
  2202 (MQRC_CONNECTION_QUIESCING).
  
  ---------------------------------------------------------------
  The fix is targeted for delivery in the following PTFs:
  
  Version    Maintenance Level
  v7.5       7.5.0.8
  v8.0       8.0.0.7
  v9.0 CD    9.0.2
  v9.0 LTS   9.0.0.1
  
  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