Yuriy Sidelnikov created AMQ-4561:
-------------------------------------
Summary: Deadlock in DemandForwardingBridgeSupport class if
ConsumerInfo message has arrived before BrokerInfo message.
Key: AMQ-4561
URL: https://issues.apache.org/jira/browse/AMQ-4561
Project: ActiveMQ
Issue Type: Bug
Components: Broker
Affects Versions: 5.7.0, 5.6.0
Reporter: Yuriy Sidelnikov
To establish connection a spoke broker sends some special messages to the hub:
• BrokerInfo
• ConnectionInfo
• SessionInfo
• ProducerInfo
• ConsumerInfo
In return hub sends exactly the same set of messages:
• BrokerInfo
• ConnectionInfo
• SessionInfo
• ProducerInfo
• ConsumerInfo
All messages are sent asynchronously so message order is not guaranteed.
However BrokerInfo message has to be delivered BEFORE ConsumerInfo message to
the spoke broker because:
1. ConsumerInfo processing logic is depended on some information provided in
BrokerInfo message so spoke broker side has lock on it.
2. All incoming messages are processed in the same thread including reading
from tcp/nio stream.
Short excerpt from DemandForwardingBridgeSupport class:
private void startLocalBridge() throws Throwable { BrokerInfo message
processing
…..
localStartedLatch.countDown();
}
And ConsumerInfo message processing part has the lock:
case ConsumerInfo.DATA_STRUCTURE_TYPE:
localStartedLatch.await();
So if ConsumerInfo message has been received before BrokerInfo message the
consuming thread will be in dead lock:
Name: ActiveMQ NIO Worker 13
State: WAITING on java.util.concurrent.CountDownLatch$Sync@150b06b
Total blocked: 1 Total waited: 3
Stack trace:
sun.misc.Unsafe.park(Native Method)
java.util.concurrent.locks.LockSupport.park(LockSupport.java:156)
java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:811)
java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireSharedInterruptibly(AbstractQueuedSynchronizer.java:969)
java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireSharedInterruptibly(AbstractQueuedSynchronizer.java:1281)
java.util.concurrent.CountDownLatch.await(CountDownLatch.java:207)
org.apache.activemq.network.DemandForwardingBridgeSupport.serviceRemoteCommand(DemandForwardingBridgeSupport.java:534)
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