That was the big thing I was missing - channels can be subscribed to more
than one queue! Thank you so much, that was a nice breakthrough.

On Tue, Oct 11, 2011 at 2:19 AM, Matthias Radestock

On 11/10/11 02:48, Adam Rabung wrote:

I am trying to implement a work queue in RabbitMQ. I have several
machines that will act as worker pools for consuming my queues. I would
like each job to be processed only once. Some jobs
have environmental requirements, ie must be executed on a machine with
an SSD. Not all worker pools will meet these requirements. A first
approach would be to have a queue for every permutation of requirements:
"No Requirements", "Requires SSD", "Requires Certificate", etc and have
each worker pool subscribe to all queues which it can handle.
That is a sound approach.

A majority of the jobs will have no requirements, so many worker pools
will be underutilized.
As you say, the worker pools would subscribe to all the queues with
combinations of requirements they can handle. That includes the "No
Requirements" queue. The subscriptions can be active *simultaneously*, so
work in the "No Requirements" queue would be round-robin routed to all
workers, jobs in the "Require SSD" queue will be routed to all workers that
have SSDs, etc.

If each worker uses a single channel with a basic.qos prefetch setting of 1
and subscribes to all the relevant queues on that channel, it will be fed
work items one at a time from the subset of all these queues that have
messages in them. There's some logic at the server that ensures this is
reasonably fair, though you will most likely find that queues which can be
handled by many workers drain faster than others.


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postedOct 11, '11 at 1:48a
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