[rabbitmq-discuss] Strictly sequential queue processing with round-robin consumers

Eugene Kirpichov ekirpichov at gmail.com
Wed Jul 13 11:30:40 BST 2011

No, IIRC qos doesn't do that. It will still roundrobin, but it will
not stop roundrobining to a particular consumer until you accumulate
100000 unacked messages there.

2011/7/13 Lee Henson <lee.m.henson at gmail.com>:
> Hi
> This question is based on a hypothetical situation that I am going to do my
> absolute best to avoid. I fully expect a "don't do that, it's a bad idea"
> response. But just for arguments sake, I'd like to know whether such a
> scenario is possible with rmq. Forewarned is forearmed, as they say..... :D
> The scenario would be a durable persistent queue Q with n consumers C1, C2,
> .. Cn. The queue should round-robin messages off to each consumer but only
> delivering the next message to the next consumer when the previous consumer
> has ACKed or REJECTed the last one. If the previous consumer failed in some
> way, then that message should be delivered to the next consumer immediately
> instead of delivering the next message in the queue. In this fashion, a
> guaranteed order of processing could be relied upon and it would be
> fault-tolerant with respect to consumers.
> The only possible solution I could think of was setting the qos.prefetch to
> a huge number, say 1000000. As I understand it, that will deliver 1000000
> messages to one consumer before it starts delivering them to the next.
> Any thoughts?
> Cheers
> Lee
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Eugene Kirpichov
Principal Engineer, Mirantis Inc. http://www.mirantis.com/
Editor, http://fprog.ru/

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