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https://issues.apache.org/jira/browse/AMQ-3127?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12980318#action_12980318
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Stirling Chow commented on AMQ-3127:
------------------------------------
Gary, I ran the tests in org.apache.activemq.network several times and they
succeeded. If after consultation with Rob it is decided that the patch is too
broad, we could always patch just the
DiscoveryNetworkConnector/DemandForwardingBridgeSupport so that they make the
localTransport asynchronous.
-------------------------------------------------------
T E S T S
-------------------------------------------------------
Running org.apache.activemq.network.NetworkLoadTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 65.782 sec
Running org.apache.activemq.network.DemandForwardingBridgeFilterTest
Tests run: 5, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 24.859 sec
Running org.apache.activemq.network.NetworkReconnectTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 6.391 sec
Running org.apache.activemq.network.DuplexNetworkTest
Tests run: 6, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 77.36 sec
Running org.apache.activemq.network.ForwardingBridgeTest
Tests run: 4, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 8.5 sec
Running org.apache.activemq.network.SimpleNetworkTest
Tests run: 5, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 73.5 sec
Running org.apache.activemq.network.DuplexNetworkMBeanTest
Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 29.532 sec
Running org.apache.activemq.network.NetworkRemovesSubscriptionsTest
Tests run: 5, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 34.406 sec
Running org.apache.activemq.network.DemandForwardingBridgeTest
Tests run: 6, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 4.703 sec
Running org.apache.activemq.network.FailoverStaticNetworkTest
Tests run: 4, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 32.203 sec
Running org.apache.activemq.network.NetworkBrokerDetachTest
Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 22.501 sec
Results :
Tests run: 41, Failures: 0, Errors: 0, Skipped: 0
> Network bridge causes deadlock on queue/topic when message dispatch and
> consumer registration overlap.
> ------------------------------------------------------------------------------------------------------
>
> Key: AMQ-3127
> URL: https://issues.apache.org/jira/browse/AMQ-3127
> Project: ActiveMQ
> Issue Type: Bug
> Components: Broker
> Affects Versions: 5.4.2
> Reporter: Stirling Chow
> Priority: Critical
> Attachments: AMQ-3127.diff, BridgeDeadlockTest.java
>
>
> Symptom
> =======
> We have an AMQ 5.3.1 production environment with 7 brokers networked over
> HTTP using the DiscoveryNetworkConnector and SimpleDiscoveryAgent. The
> brokers share a number of topics and queues. Periodically, we have a
> catastrophic (cause still uknown) network outage that only affects the
> outbound bridges from one of the 7 brokers. The affected broker detects the
> outage, stops the existing 6 outbound bridges, and starts 6 new outbound
> bridges. Frequently, we find that the outbound bridges appear to be
> recreated properly, but messages produced by the affected broker to *some* of
> its shared queues/topics are no longer dispatched to the remote brokers.
> We have verified that the cause of this issue exists in AMQ 5.4.2.
> Cause
> =====
> Analysis of the affected broker's threads revealed a deadlock between one of
> the BrokerService threads, which was dispatching a message across an outbound
> bridge, and a transport thread (e.g., VMTransport or HTTP Reader) that was
> receiving a new subscriptions from the outbound bridge:
> Daemon Thread [BrokerService[broker1] Task] (Suspended)
> owns: Object (id=104)
> owns: Object (id=105)
> owns: Object (id=106)
> owns: Queue$3 (id=107)
> waiting for: Object (id=108)
> owned by: Daemon Thread [VMTransport] (Running)
> MutexTransport.oneway(Object) line: 40
> ResponseCorrelator.oneway(Object) line: 60
>
> DemandForwardingBridge(DemandForwardingBridgeSupport).serviceLocalCommand(Command)
> line: 738
> DemandForwardingBridgeSupport$2.onCommand(Object) line: 161
> ResponseCorrelator.onCommand(Object) line: 116
> MutexTransport(TransportFilter).onCommand(Object) line: 69
> VMTransport.dispatch(VMTransport, TransportListener, Object) line: 122
> VMTransport.oneway(Object) line: 113
> MutexTransport.oneway(Object) line: 40
> ResponseCorrelator.oneway(Object) line: 60
> ManagedTransportConnection(TransportConnection).dispatch(Command) line:
> 1249
>
> ManagedTransportConnection(TransportConnection).processDispatch(Command)
> line: 810
> ManagedTransportConnection(TransportConnection).dispatchSync(Command)
> line: 770
> QueueSubscription(PrefetchSubscription).dispatch(MessageReference)
> line: 649
> QueueSubscription(PrefetchSubscription).dispatchPending() line: 599
> QueueSubscription(PrefetchSubscription).add(MessageReference) line: 156
> Queue.doActualDispatch(List<QueueMessageReference>) line: 1798
> Queue.doDispatch(List<QueueMessageReference>) line: 1745
> Queue.pageInMessages(boolean) line: 1898
> Queue.iterate() line: 1425
> PooledTaskRunner.runTask() line: 122
> PooledTaskRunner$1.run() line: 43
> ThreadPoolExecutor$Worker.runTask(Runnable) line: 886
> ThreadPoolExecutor$Worker.run() line: 908
> Thread.run() line: 662
> Daemon Thread [VMTransport] (Suspended)
> owns: Object (id=499)
> owns: RegionBroker$1 (id=205)
> waited by: Daemon Thread [VMTransport] (Running)
> waited by: Daemon Thread [ActiveMQ Broker[broker1] Scheduler]
> (Running)
> owns: Object (id=108)
> waited by: Daemon Thread [BrokerService[broker1] Task]
> (Suspended)
> owns: URI (id=500)
> Unsafe.park(boolean, long) line: not available [native method]
> LockSupport.park(Object) line: 158
>
> ReentrantReadWriteLock$NonfairSync(AbstractQueuedSynchronizer).parkAndCheckInterrupt()
> line: 811
>
> ReentrantReadWriteLock$NonfairSync(AbstractQueuedSynchronizer).acquireQueued(AbstractQueuedSynchronizer$Node,
> int) line: 842
>
> ReentrantReadWriteLock$NonfairSync(AbstractQueuedSynchronizer).acquire(int)
> line: 1178
> ReentrantReadWriteLock$WriteLock.lock() line: 807
> Queue.addSubscription(ConnectionContext, Subscription) line: 360
> ManagedQueueRegion(AbstractRegion).addConsumer(ConnectionContext,
> ConsumerInfo) line: 290
> ManagedRegionBroker(RegionBroker).addConsumer(ConnectionContext,
> ConsumerInfo) line: 444
> ManagedRegionBroker.addConsumer(ConnectionContext, ConsumerInfo) line:
> 240
> AdvisoryBroker(BrokerFilter).addConsumer(ConnectionContext,
> ConsumerInfo) line: 89
> AdvisoryBroker.addConsumer(ConnectionContext, ConsumerInfo) line: 91
> CompositeDestinationBroker(BrokerFilter).addConsumer(ConnectionContext,
> ConsumerInfo) line: 89
> TransactionBroker(BrokerFilter).addConsumer(ConnectionContext,
> ConsumerInfo) line: 89
> BrokerService$3(MutableBrokerFilter).addConsumer(ConnectionContext,
> ConsumerInfo) line: 95
>
> ManagedTransportConnection(TransportConnection).processAddConsumer(ConsumerInfo)
> line: 550
> ConsumerInfo.visit(CommandVisitor) line: 349
>
> Specifically, a message had been produced to one of the shared queues and was
> being dispatched to a remote consumer by the BrokerService thread. In so
> doing, BrokerService had acquired the pagedInPendingDispatchLock lock from
> Queue.java:
> private void doDispatch(List<QueueMessageReference> list) throws
> Exception {
> boolean doWakeUp = false;
> pagedInPendingDispatchLock.writeLock().lock();
>
> BrokerService had sent the message to the remote broker was then
> acknowledging the local transport in DemandForwardingBridgeSupport.java:
> protected void serviceLocalCommand(Command command) {
> ...
> if (!message.isResponseRequired()) {
>
> // If the message was originally sent using async
> // send, we will preserve that QOS
> // by bridging it using an async send (small
> chance
> // of message loss).
> try {
> remoteBroker.oneway(message);
> localBroker.oneway(new MessageAck(md,
> MessageAck.INDIVIDUAL_ACK_TYPE, 1));
> Since localBroker was a synchronous VMTransport, BrokerService had to then
> acquire the write mutex in MutexTransport.java:
> public void oneway(Object command) throws IOException {
> synchronized (writeMutex) {
> next.oneway(command);
> }
> }
> So the dispatching thread (BrokerService) had acquired
> Queue.pagedInPendingDispatchLock was trying to acquire
> MutexTransport.writeMutex.
> At the same time, a new remote consumer was being registered through the same
> outbound bridge through which the aforementioned dispatch was ocurring. The
> bridge's remote transport listener thread (in this example, VMTransport) was
> adding the subscription through DemandForwardingBridgeSupport.java:
> protected void addSubscription(DemandSubscription sub) throws IOException
> {
> if (sub != null) {
> localBroker.oneway(sub.getLocalInfo());
> }
> }
> Again, localBroker is synchronous, so the VMTransport thread acquired
> MutexTransport.writeMutex. Registration of consumers to a queue is
> synchronized with the dispatching of messages, as shown in Queue.java:
> public void addSubscription(ConnectionContext context, Subscription sub)
> throws Exception {
> super.addSubscription(context, sub);
> // synchronize with dispatch method so that no new messages are sent
> // while setting up a subscription. avoid out of order messages,
> // duplicates, etc.
> pagedInPendingDispatchLock.writeLock().lock();
> So the remote transport listening thread (VMTransport) had acquired
> MutexTransport.writeMutex and was trying to acquire
> Queue.pagedInPendingDispatchLock, thus creating a deadlock with BrokerService.
> Solution
> ======
> Deadlock can be avoided by making the local transport asynchronous, which
> would allow the remote transport listener thread to acquire the
> MutexTransport.writeMutex, but then offload the acquisition of
> Queue.pagedInPendingDispatchLock to its peer listening thread. We've
> included a unit test that passes with this change.
> There is no clear reason why the local transport is asynchronous. This is
> enforced by BrokerService.java when it starts the network connectors:
> protected void startAllConnectors() throws Exception {
> ....
> URI uri = getVmConnectorURI();
> Map<String, String> map = new HashMap<String,
> String>(URISupport.parseParameters(uri));
> map.put("network", "true");
> map.put("async", "false");
> This change was made by the following checkin, but no rational was given:
> Revision: 553094
> Author: rajdavies
> Date: 11:33:48 PM, July 3, 2007
> Message:
> set async=false for network connectors
> ----
> Modified :
> /activemq/trunk/activemq-core/src/main/java/org/apache/activemq/broker/BrokerService.java
> Addendum
> =========
> We've included a unit test that demonstrates the deadlock 100% of the time on
> our systems. Since this is a timing issue, you may need to run the unit test
> several times to create the deadlock. Also note that three specific
> configurations must exist to create the deadlock:
> 1) The bridge must have conduit subscriptions disabled; this is so that there
> can be an existing subscription across the bridge to which messages are being
> dispatched while at the same time another subscription is being added.
> 2) The bridge must be configured to dispatch synchronously; this is so that
> message subscriptions are are dispatched by the same thread that accesses the
> queue.
> 3) The message producers must be transactionalized; this is so that the
> message dispatches require a response by the dispatch thread (i.e.,
> BrokerService).
> If any of these conditions is not present, deadlock (at least through this
> recreation) does not occur.
>
>
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>
> Through further testing
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