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From "Jamie McCrindle" <jamiemccrin...@gmail.com>
Subject Re: Flow control on a recursive system, guidelines?
Date Fri, 29 Dec 2006 18:53:15 GMT
Hi Francesco,

I might not be understanding your problem correctly but there should
be some solutions available if you can't move to 4.2 straight away:

1. use consumer.receive instead of a messagelistener on L1 so that you
can explicitly control the volume of messages that it passes on to q2.
you can heuristically throttle it with a Thread.sleep between
consumption of a message and sending it to q2.

2. if the heuristic method doesn't work (because you're not maximising
throughput), have L2 inform L1 when it's finished processing messages.

3. Use the JMX api's to find out how many messages are in q2 to throttle L1

If you want more consumers on L1, use something like the Executors from Java 5.0

?

cheers,
j.


On 12/29/06, drvillo <f.vivoli@gmail.com> wrote:
>
> Hi all
>
> I have been trying to get a stable configuration for over a month now, but
> I keep encountering a variety of issues[1] that reduces everything to an
> unutilizable
> system.
> I have now built a simpler system, which perhaps exposes the same behavior,
> it is just a pipeline of two queues
>
> seeds--->q1--->L1--->q2--->L2
>
> what happens is that when L1 receives a message it sends a number of
> messages to q2.
> I run tests changing the number of messages to be sent to q1 and the number
> of
> messages to be forwarded by L1 to q1 (toSend and toForward respectively)
>
> A first scenario representing a real use case is having toSend small (1-10)
> and toForward
> big(10k-100k)
>
> A first observation is that if using kaha persistence everything eventually
> stops, when the broker
> starts to be too full[2] of messages, having the attached dump. Thus I'm
> using the default
> jdbc persistence.
>
> A general behavior that I've seen is that if toSend is big (10k) then no
> flow control
> seems to take place, as L2 eventually stops receiving messages when the
> broker
> runs out of memory (when not using an usagemanageer), or the heap space is
> exahusted
> (when setting it to something like 1Gb).
> In this case I'd expect that sends to L1 are slowed down, to allow L2 to
> consume the (more) messages
> that are arriving. but this doesn't happen, seeds are kept being sent at the
> same rate.
>
> On the other hand having toSend<<toForward makes all the messages to be
> delivered,
> but after some time everything slows awfully down (1msg/second maybe...),
> mainly because
> the jvm is garbage collecting all the time (the heap space is being all used
> up).
>
>
> Basically I need some way to slow down the first producer so that the whole
> system is not flooded
> with messages that then I can barely consume.
> My question then is, how should I configure the destination and broker
> memory limits, and eventually
> the prefetch values so that I don't either run out of memory or end up with
> a frozen system?
>
> Setting higher memory limits causes the JVM to need a bigger heap space
> (which makes it less stable
> in uncontrolled environments) but keeping them low seems that prevents the
> broker
> to send more messages at some point (again [1]). On the other side, being
> everything in the
> same VM, I don't know if it's better to set prefetch limits higher or lower,
> as pending messages
> have to be stored somewhere, either on the broker or on the consumer...
> Reading about slow consumers[3] doesn't point me to any option, I can't
> discard messaging.
> So I end up considering implementing a sort of timing between sends, or
> waiting for
> message spooling, which I read should come with 4.2...
>
>
> Sorry for the long message, but it's hard to express all of the above, there
> are probably too
> many options to be considered.
> Any help, guideline or hint would be most apreciated, it seems that this
> project is not
> going to be released ever:(
> For the interested is http://www.ripe.net/info/stats/hostcount/hostcount++/
>
>
> Thanks everybody,
> Francesco
>
> [1]: http://www.nabble.com/Consumer-Deadlock-tf2014492.html#a5536571
> [2]: I haven't got any measure for too full, but I'd say something like 800k
> messages,
> with an heap space of 128Mb
> [3]:  http://activemq.org/site/slow-consumer-handling.html
> http://www.nabble.com/file/5167/kahadump.log kahadump.log
> --
> View this message in context: http://www.nabble.com/Flow-control-on-a-recursive-system%2C-guidelines--tf2894291.html#a8086394
> Sent from the ActiveMQ - User mailing list archive at Nabble.com.
>
>

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