Re: Deadlock.

Andrus Adamchik Tue, 12 Dec 2006 05:06:27 -0800

John,

After staring at the stack trace a bit longer, I think I have abetter idea of what's going on (although JVM thread dumps are stillbetter as they show all the locks owned by each thread :-)). You areusing nested DataContexts contexts and while a child commits toparent, parent is being refreshed via an event, resulting in adeadlock. Could you possibly open a bug report? We may implement asimilar solution - sending an event in a separate thread.


http://issues.apache.org/cayenne/

Thanks
Andrus


On Dec 11, 2006, at 2:39 PM, Andrus Adamchik wrote:

Do you have a full thread dump printed by JVM? From these twothreads I can't figure out the nature of a deadlock.
Thanks
Andrus

On Dec 8, 2006, at 2:22 PM, John Gunning wrote:
Hi there,


I am experiencing a deadlock issue which looks similar
to CAY-297. I understand CAY-297 was fixed in release
1.1 but I am using version 1.2.1 and the deadalock
issue arises. When I set
"cayenne.DataRowStore.remote.notify" to false the
issue does not arise. However, I need this set to true
so that remote web services can be notified. I'm also
extending the Cayenne EventBridge class. I attach the
stack traces of the deadlocking threads as well as the
processMessage and sendExternalEvent methods of the
EventBridge extension. Any ideas anyone?...


Thanks in advance,

John Gunning.
Send instant messages to your online friends http://uk.messenger.yahoo.com Deadlock found :-"JMS Session Delivery Thread" Id=31 in BLOCKED on[EMAIL PROTECTED]
     owned by EventDispatchThread-3 Id=15
at org.objectstyle.cayenne.access.ObjectStore.registerDiff(ObjectStore.java:200)atorg.objectstyle.cayenne.access.ObjectStore.recordObjectCreated(ObjectStore.java:152)at org.objectstyle.cayenne.access.DataContext.registerNewObject(DataContext.java:922)at org.objectstyle.cayenne.access.ChildDiffLoader.nodeCreated(ChildDiffLoader.java:110)at org.objectstyle.cayenne.graph.NodeCreateOperation.apply(NodeCreateOperation.java:73)at org.objectstyle.cayenne.graph.CompoundDiff.apply(CompoundDiff.java:133)at org.objectstyle.cayenne.access.ObjectStoreGraphDiff.apply(ObjectStoreGraphDiff.java:155)at org.objectstyle.cayenne.access.DataContext.onContextFlush(DataContext.java:1215)at org.objectstyle.cayenne.access.DataContext.onSync(DataContext.java:1194)at org.objectstyle.cayenne.access.DataContext.flushToParent(DataContext.java:1261)at org.objectstyle.cayenne.access.DataContext.commitChanges(DataContext.java:1165)atcom.bbcnews.mps.transcode.TranscodeProcessor.triggerTranscodes(TranscodeProcessor.java:265)atcom.bbcnews.mps.transcode.TranscodeProcessor.processRequestMessage(TranscodeProcessor.java:237)at com.bbcnews.mps.transcode.TranscodeProcessor.processMessage(TranscodeProcessor.java:148)at com.bbcnews.jms.MessageListenerProxy.onMessage(MessageListenerProxy.java:134)
    at progress.message.jimpl.Session.rbB_(Unknown Source)
    at progress.message.jimpl.QueueSession.run(Unknown Source)
    at progress.message.jimpl.ep.run(Unknown Source)
"EventDispatchThread-3" Id=15 in BLOCKED on[EMAIL PROTECTED]
     owned by JMS Session Delivery Thread Id=31
atorg.objectstyle.cayenne.access.ObjectStore.processSnapshotEvent(ObjectStore.java:813)atorg.objectstyle.cayenne.access.DataContextMergeHandler.graphChanged(DataContextMergeHandler.java:131)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(UnknownSource)
    at java.lang.reflect.Method.invoke(Unknown Source)
at org.objectstyle.cayenne.util.Invocation.fire(Invocation.java:240)at org.objectstyle.cayenne.event.EventManager$Dispatch.fire(EventManager.java:433)at org.objectstyle.cayenne.event.DispatchQueue.dispatchEvent(DispatchQueue.java:182)at org.objectstyle.cayenne.event.DispatchQueue.dispatchEvent(DispatchQueue.java:94)at org.objectstyle.cayenne.event.EventManager.dispatchEvent(EventManager.java:372)at org.objectstyle.cayenne.event.EventManager.postEvent(EventManager.java:343)atorg.objectstyle.cayenne.access.DataContext.fireDataChannelChanged(DataContext.java:1731)atorg.objectstyle.cayenne.access.ObjectStore.processSnapshotEvent(ObjectStore.java:842)at org.objectstyle.cayenne.access.ObjectStore.snapshotsChanged(ObjectStore.java:804)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(UnknownSource)
    at java.lang.reflect.Method.invoke(Unknown Source)
at org.objectstyle.cayenne.util.Invocation.fire(Invocation.java:240)at org.objectstyle.cayenne.event.EventManager$InvocationDispatch.fire(EventManager.java:452)at org.objectstyle.cayenne.event.EventManager$DispatchThread.run(EventManager.java:499) public voidprocessMessage(final WrappedMessage message) {
                if (!(message instanceof CayenneNotificationMessage)) {
                        LOG.error("Not a valid notication message class: "
                                        + message.getClass().getName());
                }

                LOG.debug("Received a notification message");
                try {
                        final String vmID = ((CayenneNotificationMessage) 
message)
                                        .getRuntimeId();

                        LOG.debug("My VM: " + VM_ID);
                        LOG.debug("Event VM: " + vmID);
                        if (VM_ID.equals(vmID)) {
                                LOG.debug("... from the same VM!");
                                return;
                        }
final CayenneEvent event = (CayenneEvent)((CayenneNotificationMessage) message)
                                        .getEvent();
                        if (event != null) {
                                LOG.debug("... processing the event");
                                onExternalEvent(event);
                        }
                } catch (Exception e) {
                        LOG.error("Random notification exception: "
                                        + e.getLocalizedMessage());
                }
        }
protected void sendExternalEvent(final CayenneEvent localEvent)throws JMSException {
                LOG.debug("Sending an event");
final CayenneNotificationMessage message = newCayenneNotificationMessage();
                message.setRuntimeId(VM_ID);
                message.setEvent(localEvent);
                sendProxy.sendMessageToTopic(message, topicName);
                LOG.debug("Sent the event");
        }

Re: Deadlock.

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