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From "Martin Ritchie (JIRA)" <qpid-...@incubator.apache.org>
Subject [jira] Created: (QPID-1431) Client can fail to notify all framelisteners
Date Wed, 05 Nov 2008 12:21:44 GMT
Client can fail to notify all framelisteners
--------------------------------------------

                 Key: QPID-1431
                 URL: https://issues.apache.org/jira/browse/QPID-1431
             Project: Qpid
          Issue Type: Bug
          Components: Java Client
    Affects Versions: M3, M2.1
            Reporter: Martin Ritchie
            Assignee: Martin Ritchie
            Priority: Critical
             Fix For: M4


Summary:

Due to our desire to reduce synchronization on the client it is possible to fail to notify
a client of an exception state.
As highlighted by the two thread processes below, the _frameListeners can be updated such
that the notification fails to take place.

Thread 1.						Thread 2.

Synchronous Op.(Commit, Create...) 		Error Occurs
AMQProtocolHandler				AMQProtocolHandler		
  syncWrite(frame)				  propagateExceptionToFrameListeners(error)
    writeCommandAndWait(frame,listener)		

      synchronize(_frameListeners) 	 	     if (_frameListeners.isEmpty())
        frameListener.add(listener)              _frameListeners.iterator();

This is due to our use of CopyOnWrite lists. As the Exception handler is propagating the exception
a new syncWait can occur, which will fail as the connection is closed. There is a question
of why the socket write does not fail but that may be because the close has not yet occurred.

Suggested change:

All uses of the _frameListeners should be synchronized and the syncWrite should check to see
if the connection is closed before allowing the adding the listener. Throwing any exception
that has already been set.

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