[rabbitmq-discuss] Limit QueueingConsumer Memory Usage

amit bhatnagar brownspice at gmail.com
Fri Jul 10 15:23:57 BST 2009

Check out Channel.BasicQos() and set a prefetch count.

Have a look here for a good description of the prefetch:


"This command allows a consumer to choose a prefetch window that
specifies the amount of unacknowledged messages it is prepared to
receive. By setting the prefetch count to a non-zero value, the broker
will not deliver any messages to the consumer that would breach that
limit. To move the window forwards, the consumer has to acknowledge
the receipt of a message (or a group of messages). By acknowledging a
message, the consumer gains credit in the broker which makes it
eligible to receive more messages. This credit-based flow control
allows the broker to distribute work proportional to the individual
processing ability of each worker, as opposed to a simple round robin

On Jul 10, 4:32 am, Lars George <l... at worldlingo.com> wrote:
> Hi,
> I would like to use a blocking provider, but the QueueingConsumer is
> somewhat limiting as it receives whatever the queue sends and caches it
> locally, in the app servers memory. If that is a very large number then
> you can quickly run out of memory and kill the Java process with an OOME.
> Is there a way to implement a Consumer that say only receives N queue
> items before it waits until they get processed locally? I mean from the
> internal BlockingQueue and using handleDelivery() this is doable but
> then you would block the main loop in the AMPQ connection - and miss
> heart beats etc.?
> Is there a better way with this or do I have to go with a dumb while
> (true) { channel.basicGet() } loop. With that you have the issue to
> somehow gracefully handle the null delivery and not create a loop that
> consumes all CPU cycles with no actual work being done.
> Thanks,
> Lars
>  lars.vcf
> < 1KViewDownload
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