[rabbitmq-discuss] Limit QueueingConsumer Memory Usage

Fri Jul 10 18:17:14 BST 2009

Having said this, I am wondering if it makes sense to use a
QueueingConsumer on a channel that has a basicQos of 1? Would I be
safe to use a DefaultConsumer here instead?

On Jul 10, 8:23 am, amit bhatnagar <brownsp... at gmail.com> wrote:
> Check out Channel.BasicQos() and set a prefetch count.
>
> Have a look here for a good description of the prefetch:http://hopper.squarespace.com/blog/2009/1/26/work-distribution-in-rab...
>
> fta:
>
> "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
> mechanism."
>
> 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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