Broker stops delivering messages to some consumers
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Key: AMQ-1333
URL: https://issues.apache.org/activemq/browse/AMQ-1333
Project: ActiveMQ
Issue Type: Bug
Components: Broker
Affects Versions: 4.1.0
Environment: WinXP
Reporter: Vadim Pesochinskiy
Priority: Critical
Fix For: 4.1.2
This is a clone of AMQ-1251 to put the fix into 4.1.2. I think there is a
serious synchronization issue here.
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I have around 40 consumers taking messages from a single queue. After awhile 1
or 2 consumers stop receiveing any messages. Going to JMX and stopping
corresponding connection causes re-connect and messages are delivered again.
I reproduced it twice in QA enviroment and now it happened in production. I
tried to instrument the code and set the log in debug, but that changed timing
and I failed to reproduce it after the changes.
I suspect that runtime association b/w Queue and Consumer objects is lost on
the Broker side.
One of the suspects is the empty catch block in the RoundRobinDispatchPolicy
(line 64) class. It is possible that the CopyOnWrite array list is messed up
and it fails when removed consumer is added back.
BTW CopyOnWrite list is good when you mostly read, but not so good when you
write for every message delivery and empty catch blocks are bad in any case.
if (firstMatchingConsumer != null) {
// Rotate the consumer list.
try { consumers.remove(firstMatchingConsumer);
consumers.add(firstMatchingConsumer); } catch (Throwable bestEffort) {
}
}
This issue now occurs on a very slow and busy machine after consumer gets a
dozen of messages it stops getting others.
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