PK68484: MQ QUEUE CONNECTION FACTORY (QCF) HAS MQ CLIENT POOLING ENABLED BY DEFAULT

APAR status

• Closed as documentation error.

Error description

• Both WebSphere Application Server and the MQ Client provide
  connection pooling to potentially improve performance. Both
  products have included this capability because it is possible
  that each product will be used independently from the other
  product.
  
     The configuration parameter that sets this in the QCF
  configuration of the resources.xml file is
  useConnectionPooling="true"
  
  WebSphere Application Server supports other Java Message
  Service (JMS) providers. The MQ client can be used with other
  application servers or with a Java client.
  
  In this scenario, a firewall or router exists between
  WebSphere Application Server with the MQ client and the MQ
  Server that closes connections after a certain period of idle
  time. The MQ client might enter into looping behavior if the
  firewall closes a connection in the MQ client pool. In this
  case, WebSphere Application Server does not seem
  responsive. The problem that exists prevents WebSphere
  Application Server from getting a connection from the MQ Queue
  Connection Factory (QCF) connection pool. Moreover, the
  getConnection method request does not return; the application
  is "stuck" at this statement. A message does not exist in the
  WebSphere Application Server logs. In time, after all of the
  connection handles are assigned to application threads
  trying to get a connection, J2CA0020E and J2CA0045E errors will
  be logged due to a ConnectionWaitTimeoutException exception.
  
  This problem is more likely to happen if there has been a
  prolonged period of inactivity on an application.  The prolonged
  period of inactivity allows the firewall to close idle
  connections, which are not removed from the MQ client connection
  pool.
  
  A trace with the WAS.j2c=all event enabled show that
  there is a reserve() call driven by the getConnection API
  call.  This call never completes.
  
  The MQ client code enters into a loop in which it tries to
  clean up an existing connection. However, because the firewall
  has closed the connection, it cannot connect to the MQ Server
  on the connection to clean up, but it continues to try to
  connect. The MQ client calls MQOpen to complete the JMS
  createConnection.
  
  Every 10 seconds, you see an exception, such as a  InterruptedIO
  Exception. It retries 15 times, with each successive retry
  having a lower and lower timeout. It is interrupted after 10
  seconds in each case, which leads to a
  com.ibm.mq.MQInternalCommunications timed out exception.
  
  As a result of the MQOpen that fails with cc,rc=2, 2009,
  the MQ client then tries to disconnect this connection; this
  fails with cc,rc = 2, 2018.
  .
  An MQOpen is attempted again and this process repeats itself.
  [5/15/08 8:03:55:334 EDT] 00001438 JMS_WASTraceA >
  MQSESSIONClient MQOPEN Entry
  
  In summary, the issue is that the MQ client connection pooling
  is redundant and interferes with the WebSphere Application
  Server connection pooling.  The connection pool for WebSphere
  Application Server can be empty, but the MQ client connection
  pool holds open connections to the MQ Server.  When an attempt
  is made to get a new connection, the MQ client tries to use one
  of its pooled connections. However, because the firewall has
  closed the connection, the MQ client gets a SocketException
  when it tries to use it. To tune the connection pool for
  WebSphere Application Server so that it closes the connection
  before the firewall does, set the minConnections value to 0.
  Set the UnusedTimeout value to be less than the firewall
  timeout value. Set the reap timeout value so that it is often
  enough that WebSphere Application Server has a couple of
  opportunities to close the connection between the expiration of
  the UnusedTimeout value and the firewall closing the connection.
  
  The Information Center needs to document that you need to
  deselect the "Enable MQ client connection pooling" option
  for WebSphere Application Server because it has the potential
  to interfere with the WebSphere Application Server connection
  pooling.
  

Local fix

• Disable the MQ client connection pooling from the WebSphere
  Administrative Console.
  
  Change the QCF configuration to uncheck the 'enable mq
  connection pooling' box in the qcf definitions panel.
  
  http://publib.boulder.ibm.com/infocenter/wasinfo/v6r0/index.jsp?
  topic=/com.ibm.websphere.nd.doc/info/ae/ae/tmj_mqcon.html
  <http://publib.boulder.ibm.com/infocenter/wasinfo/v6r0/index.jsp
  ?topic=/com.ibm.websphere.nd.doc/info/ae/ae/tmj_mqcon.html>
  
  APAR PK46356 was included in WebSphere AppServer 6.0.2.23 and
  6.1.0.11, it corrected some problems with how the 'enable mq
  connection pooling' checkbox worked.  Prior to these versions,
  it is recommended to change the
  
  mqjms.pooling.threshold  to 0 connection and
  
  mqjms.pooling.timeout to 1800000 ms.
  
  This will have the effect of disabling the MQ client connection
  pooling, since it will set the number of pooled connections to
  0.
  

Problem summary

• ****************************************************************
  * USERS AFFECTED:  This APAR affects users of WebSphere        *
  *                  Application Server Version 6.0 and 6.1,     *
  *                  who interoperate with WebSphere MQ and who  *
  *                  have WebSphere MQ Client pooling enabled    *
  *                  by default.                                 *
  ****************************************************************
  * PROBLEM DESCRIPTION: Connections are shut down by the        *
  *                      firewall rather than cleaned up by      *
  *                      the connection pool if the following    *
  *                      conditions are true:                    *
  *                      -A firewall is being used that closes   *
  *                      idle connections.                       *
  *                      -The combined unused timeout value      *
  *                      that is configured in the connection    *
  *                      pool for the application server and     *
  *                      the mqjms.pooling.timeout value,        *
  *                      which is configured in WebSphere MQ     *
  *                      connection pooling, is greater than     *
  *                      the idle timeout configured on the      *
  *                      firewall                                *
  *                                                              *
  *                      This APAR is to document this           *
  *                      situation in the Information Center     *
  *                      and to advise users on how to avoid     *
  *                      disconnection by leaving the aged       *
  *                      timeout for connection pools set to     *
  *                      the default value of 0.                 *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  The following topics will be changed:
  
  - Configuring WebSphere MQ connection pooling
  - WebSphere MQ connection factory settings
  - WebSphere MQ topic connection factory settings
  - WebSphere MQ queue connection factory settings
  

Problem conclusion

• For the topic Configuring WebSphere MQ connection pooling, the
  following note will be added:
  "If a firewall is being used that closes idle connections, the
  total of the unused timeout configured on the WebSphere
  Application Server connection pool and the
  mqjms.pooling.timeout configured in WebSphere MQ connection
  pooling must be less than the idle timeout configured on the
  firewall to allow connections to be cleaned up by the
  connection pools, rather than being terminated by the firewall."
  
  For each of the following topics, a reference was added to
  Configuring WebSphere MQ connection pooling:
  - WebSphere MQ connection factory settings
  - WebSphere MQ topic connection factory settings
  - WebSphere MQ queue connection factory settings
  

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

Applicable component levels