IT44567: MFT agents generate FFDCs containing a NullPointerException, and monitors stop triggering, after upgrading to 9.3.0.10

APAR status

• Closed as program error.

Error description

• An IBM MQ 9.3 Managed File Transfer (MFT) agent has been
  configured with the agent property:
  
  monitorMaxResourcesInPoll
  
  set to the value of 10. A resource monitor defined on the agent
  has been configured to poll a directory every 30 seconds and
  trigger on:
  
  - Files that end in *.xml
  - And have a size that remains unchanged for 1 poll.
  
  When the agent is running MQ MFT 9.3.0.6, the monitor runs as
  expected and triggers on any XML files that it finds have
  remained unchanged for 1 poll.
  
  However, after the agent is upgraded to use MQ MFT 9.3.0.10, the
  monitor sometimes fails to trigger and generates an FFDC file
  containing a java.lang.NullPointerException. An example of the
  FFDC is shown below:
  
  ---------------------------------------------------------
  ..........
  Level:      p930-010-230816
  Time:       07/09/2023 14:42:32:756 EDT
  Thread:     43 (pool-4-thread-1)
  Class:      com.ibm.wmqfte.monitor.management.MonitorWork
  Method:     generateFFDC
  Probe:      FFDC_005
  Cause:      java.lang.NullPointerException
  java.lang.NullPointerException
    at
  com.ibm.wmqfte.monitor.resource.MonitorResourceItems.<init>(Moni
  torResourceItems.java:101)
    at
  com.ibm.wmqfte.monitor.matcher.MonitorMatcher.executeWorker(Moni
  torMatcher.java:484)
    at
  com.ibm.wmqfte.monitor.management.MonitorWork.buildListOfResourc
  esUsingWorkerThread(MonitorWork.java:753)
    at
  com.ibm.wmqfte.monitor.management.MonitorWork.buildListOfResourc
  es(MonitorWork.java:636)
    at
  com.ibm.wmqfte.monitor.management.MonitorWork.execute(MonitorWor
  k.java:387)
    at
  com.ibm.wmqfte.monitor.management.MonitorImpl.run(MonitorImpl.ja
  va:171)
    at
  com.ibm.wmqfte.monitor.management.MonitorTimerTask.run(MonitorTi
  merTask.java:78)
    at
  java.util.concurrent.Executors$RunnableAdapter.call(Executors.ja
  va:522)
    at
  java.util.concurrent.FutureTask.runAndReset(FutureTask.java:319)
    at
  java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFuture
  Task.access$301(ScheduledThreadPoolExecutor.java:191)
    at
  java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFuture
  Task.run(ScheduledThreadPoolExecutor.java:305)
    at
  java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExec
  utor.java:1160)
    at
  java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExe
  cutor.java:635)
    at java.lang.Thread.run(Thread.java:825)
  ..........
  ---------------------------------------------------------
  

Local fix

Problem summary

• ****************************************************************
  USERS AFFECTED:
  This issue affects two categories of user:
  
  Category 1:
  --------------
  Users of MQ 9.3.0.10  and 9.3.3 CD Managed File Transfer (MFT)
  who have an agent configured with the agent property:
  
  monitorMaxResourcesInPoll
  
  set in the agent.properties file.
  
  Category 2:
  --------------
  Users of MQ 9.3.0.10 and 9.3.3 CD MFT who have queue resource
  monitors defined on an agent, where the monitor is configured to
  trigger on complete message groups, or individual messages not
  in a group.
  
  
  Platforms affected:
  MultiPlatform
  
  ****************************************************************
  PROBLEM DESCRIPTION:
  When an IBM MQ Managed File Transfer resource monitor performs a
  poll, it will collect a list of items that match its trigger
  condition using one of two methods:
  
  Method 1:
  --------------
  When an agent has the:
  
  moniorMaxResourcesInPoll
  
  property set, any directory resource monitors that are defined
  on it will use an internal Worker Thread to collect the list of
  items that match its trigger condition. Queue resource monitors
  that have been configured to trigger on complete message groups,
  or individual messages not in a group, will also use a Worker
  Thread.
  
  Method 2:
  --------------
  If an agent does not have the property:
  
  moniorMaxResourcesInPoll
  
  set, then any directory resource monitors running within it will
  collect the list of items that match the trigger condition on
  the monitor's main thread. The same mechanism is used by queue
  resource monitors that are configured to trigger on a non-empty
  queue.
  
  
  Now, as part of the work on APAR IT43806
  (https://www.ibm.com/support/pages/apar/IT43806), some
  additional trace statements were added to allow IBM Support to
  diagnose how a resource monitor was managing its history.
  Unfortunately, this inadvertently changed some of the logic in
  the Worker Thread (mentioned in Method 1 above) so that it could
  use an uninitialized variable when working out what to remove
  from a monitor's history. When this happened, the monitor would
  stop triggering and generate an FFDC containing the following
  information:
  
  ---------------------------------------------------------
  ..........
  Class:      com.ibm.wmqfte.monitor.management.MonitorWork
  Method:     generateFFDC
  Probe:      FFDC_005
  Cause:      java.lang.NullPointerException
  java.lang.NullPointerException
    at
  com.ibm.wmqfte.monitor.resource.MonitorResourceItems.<init>(Moni
  torResourceItems.java:101)
    at
  com.ibm.wmqfte.monitor.matcher.MonitorMatcher.executeWorker(Moni
  torMatcher.java:484)
    at
  com.ibm.wmqfte.monitor.management.MonitorWork.buildListOfResourc
  esUsingWorkerThread(MonitorWork.java:753)
    at
  com.ibm.wmqfte.monitor.management.MonitorWork.buildListOfResourc
  es(MonitorWork.java:636)
    at
  com.ibm.wmqfte.monitor.management.MonitorWork.execute(MonitorWor
  k.java:387)
    at
  com.ibm.wmqfte.monitor.management.MonitorImpl.run(MonitorImpl.ja
  va:171)
    at
  com.ibm.wmqfte.monitor.management.MonitorTimerTask.run(MonitorTi
  merTask.java:78)
    at
  java.util.concurrent.Executors$RunnableAdapter.call(Executors.ja
  va:522)
    at
  java.util.concurrent.FutureTask.runAndReset(FutureTask.java:319)
    at
  java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFuture
  Task.access$301(ScheduledThreadPoolExecutor.java:191)
    at
  java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFuture
  Task.run(ScheduledThreadPoolExecutor.java:305)
    at
  java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExec
  utor.java:1160)
    at
  java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExe
  cutor.java:635)
    at java.lang.Thread.run(Thread.java:825)
  ..........
  ---------------------------------------------------------
  

Problem conclusion

• To resolve this issue, MQ Managed File Transfer (MFT) has been
  updated so that resource monitor Worker Threads use the correct
  internal variable when removing items from a monitor's history.
  This ensures that the history is updated correctly, and prevents
  the NullPointerException reported in this APAR from occurring.
  
  ---------------------------------------------------------------
  The fix is targeted for delivery in the following PTFs:
  
  Version    Maintenance Level
  v9.3 LTS   9.3.0.15
  v9.x CD    9.3.5
  
  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

  MQ BASE V9.3

• Fixed component ID

  5724H7291

Applicable component levels