PI05266: Infinite loop until transaction timeout causes high CPU when using HTTP session replication.

APAR status

• Closed as program error.

Error description

• When retrieving timed out sessions to inform the
  application when a HTTP session has timed out in the grid,
  there was a logic error that caused the code to get into an
  infinite loop until the transaction retrieving the HTTP
  sessions times out.  The exception stack from an FFDC report on
  the grid server when this happens looks like the following:
  
  com.ibm.websphere.objectgrid.TransactionTimeoutException
  com.ibm.ws.objectgrid.SessionImpl.unexpectedThrowable 2220
  Exception =
  com.ibm.websphere.objectgrid.TransactionTimeoutException
  Source = com.ibm.ws.objectgrid.SessionImpl.unexpectedThrowable
  probeid = 2220
  Stack Dump =
  com.ibm.websphere.objectgrid.TransactionTimeoutException:
  Maximum time limit 45000ms for transaction exceeded for
  C489B813-0141-4000-E000-D2360A444716
  at
  com.ibm.ws.objectgrid.SessionImpl.checkTransactionActiveAndBegin
  IfNeeded(SessionImpl.java:2543)
  at
  com.ibm.ws.objectgrid.SessionImpl.mapPreInvoke(SessionImpl.java:
  3394)
  at
  com.ibm.ws.objectgrid.ObjectMapImpl.removeAll(ObjectMapImpl.java
  :1001)
  at
  com.ibm.ws.xs.sessionmanager.EvictedAgent.processAllEntries(Evic
  tedAgent.java:102)
  at
  com.ibm.ws.objectgrid.datagrid.EntryAgentCommand.executeCommand(
  EntryAgentCommand.java:317)
  at
  com.ibm.ws.objectgrid.AbstractDistributedCommand.run(AbstractDis
  tributedCommand.java:43)
  at
  com.ibm.ws.objectgrid.thread.ThreadPoolRunnable.run(ThreadPoolRu
  nnable.java:46)
  at
  java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoo
  lExecutor.java:897)
  at
  java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExe
  cutor.java:919)
  at java.lang.Thread.run(Thread.java:736)
  

Local fix

• n/a
  

Problem summary

• ****************************************************************
  * USERS AFFECTED:  Users of eXtreme Scale using the HTTP       *
  *                  session replication function.               *
  ****************************************************************
  * PROBLEM DESCRIPTION: When the data grid invalidates a        *
  *                      session instead of the web container,   *
  *                      the processor usage can increase due to *
  *                      an infinite loop.                       *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  When the eXtreme Scale invalidates HTTP sessions if a session
  table does not exist the web container or more sessions are in a
  web container than the size of the session table.  The client
  must
  be informed when a session is invalidated.  When iterating over
  the evicted sessions to report back to the client, a logic error
  was corrected.  This logic error attempts to lock the same entry
  until the transaction times out. This loop increased processor
  usage because nothing was causing the thread to pause.
  

Problem conclusion

• An interim fix is available for this APAR.
  

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

  WS EXTREME SCAL

• Fixed component ID

  5724X6702

Applicable component levels

• R711 PSY

     UP

• R850 PSY

     UP

• R860 PSY

     UP