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From Joe Fernandez <>
Subject Re: Problem with losing acks(?)
Date Mon, 13 Oct 2008 01:17:05 GMT

When creating sessions for your subscribers, what ack mode (AUTO, CLIENT, or
DUPS_OK) are you using and are your sessions transacted?

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Rick Blair wrote:
> Hi all,
> I am using ActiveMQ version 5.1 in a pub/sub system.  The broker is
> embedded
> with the publishers.  The publishers publish to 2 main topics with
> selectors.  I have many subscribers distributed on the network. The
> subscriptions are based on the selectors.  The messages are object
> messages.
>   During execution one subscriber(not always the same one) seems to stop
> sending acks.  
> In the subscriber I still see the onMessage method call being called.
> However on the broker, using jconsole looking at the subscription, the
> number of messages waiting for ack = the prefetch size and the number of
> queued messages increases.
>   This goes on until the broker memory limit hits 100% and all message
> flow
> stops. 
>  We have tried to set the policies that discard older messages, but that
> did
> not help.  The message discard count does increase to a point, then
> remains
> constant, while the enqueue count still increases.  Also at this time many
> of the stats go negative.  This very often occurs right after startup
> under
> heavy load on the producers.  Thread dumps show no threads blocked, the
> is not heavily loaded. GC does not seem to an issue.
> Any suggestions? 
> -- 
> Tìoraidh!
> Rick

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