PM67540: JAVA.UTIL.CONCURRENTMODIFICATIONEXCEPTION IN POOLMANAGER

8.5.0.1: WebSphere Application Server V8.5 Fix Pack 1
8.5.0.2: WebSphere Application Server V8.5 Fix Pack 2

APAR status

• Closed as program error.

Error description

• Sometimes when tracing is enabled and the server is under
  load the following exception may be thrown
  
  java.util.ConcurrentModificationException
    at java.util.Hashtable$HashIterator.next(Hashtable.java:192)
    at
  java.util.Hashtable$HashEnumIterator.next(Hashtable.java:702)
    at
  com.ibm.ejs.j2c.PoolManager.toString2(PoolManager.java:5110)
    at com.ibm.ejs.j2c.PoolManager.reserve(PoolManager.java:2646)
    at com.ibm.ejs.j2c.PoolManager.reserve(PoolManager.java:2567)
    at
  com.ibm.ejs.j2c.ConnectionManager.allocateMCWrapper(ConnectionMa
  nager.java:1544)
    at
  com.ibm.ejs.j2c.ConnectionManager.allocateConnection(ConnectionM
  anager.java:1027)
    at
  com.ibm.ws.rsadapter.jdbc.WSJdbcDataSource.getConnection(WSJdbcD
  ataSource.java:642)
    at
  com.ibm.ws.rsadapter.jdbc.WSJdbcDataSource.getConnection(WSJdbcD
  ataSource.java:609)
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED:  All users of IBM WebSphere Application      *
  *                  Server Liberty Profile                      *
  ****************************************************************
  * PROBLEM DESCRIPTION: A ConcurrentModificationException is    *
  *                      thrown when getConnection is called     *
  *                      on a datasource or connection factory.  *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  The Application Server's PoolManager class uses the iterator
  of a Hashtable that is accessed in multiple threads without
  synchronizing on the Hashtable. So the hashtable can be updated
  on one thread while the iterator is being used on the other
  resulting in the
  java.util.ConcurrentModificationException.
  

Problem conclusion

• The PoolManager class has been modified to use a
  ConcurrentHashMap which will not throw a
  java.util.ConcurrentModificationException on multithreaded
  usage.
  
  The fix for this APAR is currently targeted for inclusion in
  fix pack 8.5.0.1. Please refer to the Recommended Updates page
  for delivery information:
  http://www.ibm.com/support/docview.wss?rs=180&uid=swg27004980
  

Temporary fix

Comments

APAR Information

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

  PM66241

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

Fix information

• Fixed component name

  LIBERTY PROFILE

• Fixed component ID

  5724J0814

Applicable component levels

• R850 PSY

     UP