Concurrent Modification on executor phases [NullPointerExeption while running relay transport for a long time]

Hi
  During Apache Synapse Iterator mediator operation for larger message
observed ,while investigating the issue found out its due to  Linked list
modification happens at different phases [1] [2] the problem
has resolved once we introduced *ConcurrentLinkedQueue  instad LinkedQueue
any thoughts on the changers....?*


At the AxisEngine

  [1]   * @throws AxisFault
     */
    private static InvocationResponse invoke(MessageContext msgContext,
boolean resuming)
            throws AxisFault {

        if (msgContext.getCurrentHandlerIndex() == -1) {
            msgContext.setCurrentHandlerIndex(0);
        }

        InvocationResponse pi = InvocationResponse.CONTINUE;

        while (msgContext.getCurrentHandlerIndex() <
msgContext.getExecutionChain().size()) {
            Handler currentHandler = (Handler)
msgContext.getExecutionChain().
                    get(msgContext.getCurrentHandlerIndex());

            try {
                if (!resuming) {
                    msgContext.addExecutedPhase(currentHandler);
                } else {
                    /* If we are resuming the flow, we don't want to add
the phase
                    * again, as it has already been added.
                    */
                    resuming = false;
                }
                pi = currentHandler.invoke(msgContext);
            }

---------------------------------------------------------------------------------------

    [2].    private static void flowComplete(MessageContext msgContext) {
        Iterator<Handler> invokedPhaseIterator =
msgContext.getExecutedPhases();

        while (invokedPhaseIterator.hasNext()) {
            Handler currentHandler = ((Handler)
invokedPhaseIterator.next());
            currentHandler.flowComplete(msgContext);
        }

        /*This is needed because the OutInAxisOperation currently invokes
        * receive() even when a fault occurs, and we will have already
executed
        * the flowComplete on those before receiveFault() is called.
        */
        msgContext.resetExecutedPhases();
    }


 a


    /**
     * Add a Phase to the collection of executed phases for the path.
     * Phases will be inserted in a LIFO data structure.
     *
     * @param phase The phase to add to the list.
     */
    public void addExecutedPhase(Handler phase) {
        if (executedPhases == null) {
            executedPhases = new LinkedList<Handler>();
        }
        executedPhases.addFirst(phase);
    }

    /**
     * Remove the first Phase in the collection of executed phases
     */
    public void removeFirstExecutedPhase() {
        if (executedPhases != null) {
            executedPhases.removeFirst();
        }
    }

43/carbon/
[2012-11-29 10:55:45,570]  INFO - TimeoutHandler This engine will expire
all callbacks after : 120 seconds, irrespective of the timeout action,
after the specified or optional timeout
Listening for transport dt_socket at address: 8888
[2012-11-29 10:55:48,369] ERROR - NativeWorkerPool Uncaught exception
java.util.ConcurrentModificationException
at java.util.LinkedList$ListItr.checkForComodification(LinkedList.java:761)
at java.util.LinkedList$ListItr.next(LinkedList.java:696)
at org.apache.axis2.engine.AxisEngine.flowComplete(AxisEngine.java:293)
at org.apache.axis2.engine.AxisEngine.receive(AxisEngine.java:182)
at
org.apache.synapse.transport.passthru.ClientWorker.run(ClientWorker.java:217)
at
org.apache.axis2.transport.base.threads.NativeWorkerPool$1.run(NativeWorkerPool.java:172)
at
java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:662)
[2012-11-29 10:55:55,462] ERROR - NativeWorkerPool Uncaught exception
java.util.ConcurrentModificationException
at java.util.LinkedList$ListItr.checkForComodification(LinkedList.java:761)
at java.util.LinkedList$ListItr.next(LinkedList.java:696)
at org.apache.axis2.engine.AxisEngine.flowComplete(AxisEngine.java:293)
at org.apache.axis2.engine.AxisEngine.receive(AxisEngine.java:182)
at
org.apache.synapse.transport.passthru.ClientWorker.run(ClientWorker.java:217)
at
org.apache.axis2.transport.base.threads.NativeWorkerPool$1.run(NativeWorkerPool.java:172)
at
java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:662)
[2012-11-29 10:55:55,484] ERROR - NativeWorkerPool Uncaught exception
java.util.ConcurrentModificationException
at java.util.LinkedList$ListItr.checkForComodification(LinkedList.java:761)
at java.util.LinkedList$ListItr.next(LinkedList.java:696)
at org.apache.axis2.engine.AxisEngine.flowComplete(AxisEngine.java:293)
at org.apache.axis2.engine.AxisEngine.receive(AxisEngine.java:182)
at
org.apache.synapse.transport.passthru.ClientWorker.run(ClientWorker.java:217)
at
org.apache.axis2.transport.base.threads.NativeWorkerPool$1.run(NativeWorkerPool.java:172)
at
java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:662)
[2012-11-29 10:55:56,040] ERROR - NativeWorkerPool Uncaught exception
java.util.ConcurrentModificationException
at java.util.LinkedList$ListItr.checkForComodification(LinkedList.java:761)
at java.util.LinkedList$ListItr.next(LinkedList.java:696)
at org.apache.axis2.engine.AxisEngine.flowComplete(AxisEngine.java:293)
at org.apache.axis2.engine.AxisEngine.receive(AxisEngine.java:182)
at
org.apache.synapse.transport.passthru.ClientWorker.run(ClientWorker.java:217)
at
org.apache.axis2.transport.base.threads.NativeWorkerPool$1.run(NativeWorkerPool.java:172)
at
java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:662)
[2012-11-29 10:55:56,263] ERROR - NativeWorkerPool Uncaught exception
java.util.ConcurrentModificationException
at java.util.LinkedList$ListItr.checkForComodification(LinkedList.java:761)
at java.util.LinkedList$ListItr.next(LinkedList.java:696)
at org.apache.axis2.engine.AxisEngine.flowComplete(AxisEngine.java:293)
at org.apache.axis2.engine.AxisEngine.receive(AxisEngine.java:182)
at
org.apache.synapse.transport.passthru.ClientWorker.run(ClientWorker.java:217)
at
org.apache.axis2.transport.base.threads.NativeWorkerPool$1.run(NativeWorkerPool.java:172)
at
java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
a



cheers,