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From "James Strachan" <>
Subject Re: handling slow consumers on non-persistent topics and AMQ-688
Date Tue, 04 Jul 2006 13:04:07 GMT
BTW AMQ-792 is now fixed - details here...

so the only real pending issue so far that I'm aware of for dealing
with slow consumers is AMQ-791 (spooling to disk)...

Unless folks have any other use cases or requirements?

On 7/3/06, James Strachan <> wrote:
> While perusing JIRA I spotted this issue again...
> I know its an issue close to folks at Amazon's hearts.
> Dealing with slow consumers is a fascinating problem for a messaging
> system; its quite a tricky problem :). Here's some background on the
> issue...
> together with the currently supported features - to allow messages to
> be discarded on slow consumers using a pluggable algorithm...
> Now for all consumers we fill up prefetch buffers as quickly as possible...
> so there's always a buffer of messages per consumer. For non-durable
> topics once these messages are written to a socket they are evicted
> from RAM; so we already have some support for slow consumers.
> I wanted to start a discussion on both AMQ-688 and to see if folks had
> other requirements for handling slow consumers & to try decide what
> features & stragegies we should add next in this area.
> One of the first requirements folks ask for is that rather than
> blocking permanently the non-persistent topic engine until RAM is
> cleared, that at a certain threshhold we start spooling to disk. I've
> raised a separate JIRA issue for this specific feature request...
> Another issue some folks have hit in the past is that for high
> performance and to minimise context switches in the broker, we tend to
> use the current thread in the broker to dispatch to all the
> non-durable topic consumers so a slow/blocked consumer can appear to
> 'block' the producer.
> I've raised this issue to track that feature
> I just wondered if folks had any other issues or requirements with the
> whole slow consumers and non-durable topics they'd like to discuss? Is
> there any requirements we won't have covered if the above two JIRAs
> are fixed
> --
> James
> -------



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