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https://issues.apache.org/activemq/browse/AMQ-349?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Rob Davies reassigned AMQ-349:
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Assignee: Rob Davies
> Misbehaving consumer can affect message delivery to other consumers for a
> given topic.
> --------------------------------------------------------------------------------------
>
> Key: AMQ-349
> URL: https://issues.apache.org/activemq/browse/AMQ-349
> Project: ActiveMQ
> Issue Type: Bug
> Components: Broker
> Affects Versions: 3.1
> Environment: Solaris, JDK 1.4
> Reporter: Kevin Yaussy
> Assignee: Rob Davies
> Fix For: 5.0.0
>
>
> If you have a supplier publishing to a topic, with two consumers both
> consuming that topic, a problem with one of the consumers can eventually stop
> message flow to the other consumer. The consumer-problem is specifically
> categorized as some sort of freeze-up, such that the broker eventually blocks
> on the socket write to that consumer. The freeze-up could be the process
> itself (perhaps a problem with the JVM), the network, or perhaps the machine
> that the consumer is running on panics and goes away.
> Once the socket becomes blocked, the broker will queue (upto
> maxOutstandingMessages) to the consumer. The properly behaving consumer
> continues to receive events at this point. However, once the queue size
> reaches maxOutstandingMessages, the broker (the session dispatcher thread for
> the given topic) will block on the PooledExecutor.execute method. This now
> prohibits any further message delivery for the given topic to the properly
> behaving consumer.
> I'm wondering why the "waitWhenBlocked" policy on the PooledExecutor is used?
> These are NON_PERSISTENT messages, so what would be the problem with
> potentially using one of the discard policies, such as
> "discardOldestWhenBlocked" (or "discardWhenBlocked")? Seems like one of
> these two policies should be used by default, and the "waitWhenBlocked" would
> be a configurable option. Our preference would be to use
> "discardOldestWhenBlocked". I changed TcpTransportServerChannel.java to use
> "discardOldestWhenBlocked", which gave us our desired functionality.
> From our point of view, having the broker affect all consumers on behalf of
> one misbehaving one is bad. So, what might we be missing with regards to
> using "discardOldestWhenBlocked"?
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