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From "Hiram Chirino" <hi...@hiramchirino.com>
Subject Re: Message queue is filled up.
Date Fri, 07 Jul 2006 16:34:18 GMT
On 7/6/06, James Strachan <james.strachan@gmail.com> wrote:
>
> On 7/7/06, Kuppe <kuppe@360t.com> wrote:
> >
> > My sincere apologies, it seems that the "Message queue is filled up"
> error
> > message is not coming from ActiveMQ at all. It is coming from my own
> > framework that is not able to process the number of messages being
> delivered
> > by ActiveMQ:)
>
> LOL! :) Thanks for letting us know - phew, there's not a bug in our
> error message reporting :)
>
>
> > Due to limitations in our previous messaging solution, I have an
> incoming
> > and outgoing queue for receiving and sending messages implemented in my
> > framework. As i am now using async dispatch and async sending, these
> queues
> > are somehow redundant. At the same time, the throughput of my framework
> also
> > seems to be somewhat limited with all the context switching and
> processing.
>
> :)
>
> > Accordingly I would like to reduce this complexity by removing my
> framework
> > queues and rely entirely on the async dispatch/send that is implemented
> in
> > ActiveMQ. Is this an approach that you would recommend?
>
> Definitely. The sync v async configuration is something you may wish
> to change over time (on a per connection/producer/consumer basis).
> e.g. for broker dispatching to consumers, doing it synchronous is
> often a bit faster as it reduces context switching, though it
> increases the chance of a slow consumer blocking other consumers for a
> little while. Leaving all this stuff to the messaging system makes it
> easier for you to tweak things (often via a URI) and remove some of
> the layers in your code.
>
>
> > At the same time, my
> > framework does offer me control as to how many threads are processing
> the
> > messages in these two receive and send queues. If I am to replace my
> > framework queues with the async functionality of ActiveMQ, i would like
> to
> > know the answer to the following two related questions;
> >
> > Q1: When using async send, is this doing the message sending in another
> > thread context?
>
> Yes



Actually no.  Async send only a single thread is used and it block only
until the message is serialized and put on the wire.  Disabling Async send
cause the send to block until the message is serialized on the wire and send
ack is received from the broker.


>  If so, is there any configuration options for limiting the
> > number of threads processing the sending of messages? What is the
> default
> > algorithm for the number of sending threads - one per session,
> producer???
>
> We use thread pools for pretty much everything now to minimise the
> number of actual threads used; we've done quite a bit of tuning in
> that regard in 4.x. (In 3.x there tended to be lots of threads created
> in a transport, session etc).


And the use of thread pools vs. using dedicated threads can be
enabled/disabled using a System property.  On the broker, out of the box we
set set it not to use ThreadPools since thread pools can add a little more
context switching overhead than if you use dedicated threads at the expense
of using more memory due to more active thread stacks.  That system property
is set like: -Dorg.apache.activemq.UseDedicatedTaskRunner=true


Whether you use sync or async in the JMS client there is typically
> (for tcp:// and vm:// at least) a thread sending and a thread
> receiving messages. All these threads are doing is streaming messages
> onto/off of a socket so there is no real reason to pool them (e.g.
> having 2 threads writing would generally be slower).
>
> Async send just means the thread doing the producer.send() doesn't
> block waiting for a response from the broker; so there's no real
> difference from the number of threads used etc; it just removes the
> latency in the send() thread.
>
>
> > Q2: In line with Q1, if i am using async dispatch, is this doing the
> message
> > dispatching in another thread context?
>
> Yes. e.g. the default in non durable topics is that the thread
> processing incoming messages from a producer will dispatch the message
> to each consumers socket. With async dispatch a thread pool is used to
> configure this.


agreed.

> If so, is there any configuration
> > options for limiting the number of threads processing the dispatching of
> > messages?
>
> There could well be - not sure off the top of my head :)


Not at the current time.

> What is the default algorithm for the number of dispatchin threads
> > - one per session, consumer???
>
> This is a broker side thing so its purely to do with how many
> consumers there are; each async dispatch consumer is a separate task
> which is added to the thread pool.


Actually on the broker side there is 1 thread per JMS connection doing the
async dispatch.

Its on the client side that all of a sessions's messages are
> dispatched to consumers in same thread (but since we use a thread pool
> if you have many sessions we may not use that many threads).



Yep. on the client side each session gets a dedicated thread too.  But these
are thread pooled by default.  But there is an option to disable
asyncSessionDispatch so that the connection thread dispatches directly to
the consumer.

--
>
> James
> -------
> http://radio.weblogs.com/0112098/
>



-- 
Regards,
Hiram

Blog: http://hiramchirino.com

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