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From Gary Tully <>
Subject Re: Issue creating a distributed queue using store and forward.
Date Fri, 09 Oct 2009 13:10:23 GMT
just in case you have not seen it, you may find some of the detail in
the the following old thread relevant to your investigation.

2009/10/8 Eric Van Dewoestine <>:
> Thanks for the link. Did you try applying that patch? If so did it
> resolve your issue?
> I'll give the patch a shot, but the note in the ticket regarding
> failures for large message counts and Joe's warnings make me a little
> apprehensive.  I'll update my findings as soon as I get a chance to
> test it out.
> On Thu, Oct 8, 2009 at 10:17 AM, farshad <> wrote:
>> Hi Eric,
>> I think you and I have run into the same problem.  Please check below.
>> Farshad
>> Eric Van wrote:
>>> ActiveMQ 5.3.0_SNAPSHOT (Sep 8th according to the snapshots listing)
>>> I'm running into an issue with the store and forward feature of
>>> activemq, which I using in an attempt to create a highly available
>>> distributed queue.  I'm trying to figure out if the issue is a
>>> misconfiguration on my part, expected behavior of activemq, or a bug.
>>> The summary of the problem is that given 2 brokers, B1 and B2, which
>>> each have one consumer, C1 and C2, which are subscribed to the same
>>> queue.  If I stop a consumer on one of the brokers, the pending
>>> messages from that broker are not always forwarded to the other broker
>>> which still has a consumer, leading to those messages getting
>>> indefinitely stuck.
>>> The steps I use to reproduce this scenario are as follows (Note: all
>>> producing and consuming is performed over the stomp transport):
>>> Couple notes about the consumers:
>>> - they have a prefetchSize of 40
>>> - the processing of messages can take some time, so for the purposes
>>>   of this exercise, I've created a simple consumer that sleeps for 10
>>>   seconds before sending the message ack (using client-individual ack
>>>   mode)
>>> 1. start both brokers (B1 and B2). The consumers (C1 and C2) are not
>>>    yet running.
>>> 2. produce a few thousand messages to B1
>>>    Note: B1 now has a few thousand pending messages and B2 has 0.
>>> 3. start consumer C2 (listing for messages from B2)
>>>    Note: messages are are successfully received and begin processing
>>>    (monitoring the brokers shows pending messages decreasing). Now B2
>>>    has all the pending messages and B1 has 0.
>>> 4. start consumer C1 (listing for messages from B1)
>>>    Note: no messages are received, which is another issue I have since
>>>    B2 now has thousands of pending messages which C1 could help
>>>    process, but instead sits idle while C2 is forced to handle all the
>>>    messages.
>>> 5. stop consumer C2
>>>    Note: now I have thousands of messages sitting on B2 and 0 on B1
>>>    where a C1 is alive and ready to handle them.  So at this point,
>>>    despite having a consumer running, thousands of messages are stuck
>>>    in the queue.
>>> 6. stop consumer C1
>>>    Note: now I have no consumers.  Stopping and restarting C1 has no
>>>    effect on the pending messages sitting on B1's queue.
>>> 7. stop both brokers
>>> 8. start B1, then start B2
>>> 9. start C1
>>>    Note: now all messages have migrated from B2 to B1 and C1 is again
>>>    processing messages.
>>> So after step 5, the only way to recover from the stuck messages is to
>>> restart the brokers.
>>> Below is my current connector config which I have on both brokers.
>>> I've tried playing with the various properties of the connector, but
>>> it seems as though no matter what I try the above scenario continues
>>> to occur.
>>> <networkConnector
>>>     name="default-nc"
>>>     uri="multicast://default?group=${}"
>>>     dynamicOnly="true"
>>>     networkTTL="25"
>>>     suppressDuplicateQueueSubscriptions="true"/>
>>> So, is this an activemq bug? Am I mis-using activemq? Is there some
>>> other way to achieve a highly available distributed queue?
>>> Any help in this regard is greatly appreciated.
>>> --
>>> eric
>> --
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> --
> eric


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