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From Joe Fernandez <joe.fernan...@ttmsolutions.com>
Subject Re: Issue creating a distributed queue using store and forward.
Date Wed, 07 Oct 2009 18:43:49 GMT

I think that by design a message will not be forwarded to a broker that it
has already visited. 

Joe
http://www.ttmsolutions.com 


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=${broker.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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