[rabbitmq-discuss] Controlling rate of callbacks

Tue Jun 15 12:47:03 BST 2010

Hi Andreas.

You could use queue polling; if you're only going to check every 15 min 
then the slight loss in efficiency should not be a big deal. Overall I'd 
say use basic.consume if you want to consume at a fixed rate but fairly 
fast-ish, and basic.get if you want to consume very slowly or at fixed 
times.

If you want to do this with basic.consume:

* Set basic.qos with a prefetch_count of 1 (so the server will only push 
one unacked message to you at a time).

* basic.consume with no_acks turned off.

* Each time you consume, set up a timer to send the ack after 15 min or 
whenever - don't just sleep in the consume callback as this will block 
the connection.

Unfortunately I'm not very familiar with carrot so I can't give you 
direct samples.

See the recent thread "chan.flow and vm_memory_high_watermark", 
particularly here:

http://lists.rabbitmq.com/pipermail/rabbitmq-discuss/2010-June/007528.html

and here:

http://lists.rabbitmq.com/pipermail/rabbitmq-discuss/2010-June/007537.html

although the GC-related stuff shouldn't apply to you.

Cheers, Simon

On 08/06/10 09:47, Andreas Jung wrote:
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>
> We are using RabbitMQ + consumers implemented in Python on top of
> carrot and called through RabbitMQ as a callback.
> Is there some configuration option on a per-queue basis e.g. for
> controlling how or when consumers are called? For examples some queues
> must not be processed immediately but could be processed e.g. over night
> or every 15 minutes...
> Or is the recommended solution to implement arbitary logic on the
> application level and switching to queue polling?
>
> Andreas
>
>
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