Prefetch limit and queue size

[ewood <wo...@ship.saic.com>]

I am running AMQ v4.1 with a network of embedded brokers (2).  My question is
what happens when the prefetch limit is reached?  Will subsequent calls to
send fail in some way?  More importantly, can I detect when the prefetch
limit has been reached from my client?  I know I can get the queue size via
JMX, but what does that size really mean?  Is that the total number enqued
minus dequed or is the number of unacknowledged messages, or some other
number.  Sorry if this is in the documentation somewhere, but I can't find
it.
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Re: Prefetch limit and queue size

[ewood <wo...@ship.saic.com>]

Thanks,

I've read the documentation and I understand what the prefetch is and how to
set it.  That wasn't really my question.

Eric



Marlon Santos wrote:
> 
> Hi, 
> 
> Try this one, http://activemq.org/site/what-is-the-prefetch-limit-for.html
> 
> HTH,
> Marlon
> 
> 
> ewood wrote:
>> 
>> I am running AMQ v4.1 with a network of embedded brokers (2).  My
>> question is what happens when the prefetch limit is reached?  Will
>> subsequent calls to send fail in some way?  More importantly, can I
>> detect when the prefetch limit has been reached from my client?  I know I
>> can get the queue size via JMX, but what does that size really mean?  Is
>> that the total number enqued minus dequed or is the number of
>> unacknowledged messages, or some other number.  Sorry if this is in the
>> documentation somewhere, but I can't find it.
>> 
> 
> 

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Re: Prefetch limit and queue size

[Marlon Santos <ms...@exist.com>]

Hi, 

Try this one, http://activemq.org/site/what-is-the-prefetch-limit-for.html

HTH,
Marlon


ewood wrote:
> 
> I am running AMQ v4.1 with a network of embedded brokers (2).  My question
> is what happens when the prefetch limit is reached?  Will subsequent calls
> to send fail in some way?  More importantly, can I detect when the
> prefetch limit has been reached from my client?  I know I can get the
> queue size via JMX, but what does that size really mean?  Is that the
> total number enqued minus dequed or is the number of unacknowledged
> messages, or some other number.  Sorry if this is in the documentation
> somewhere, but I can't find it.
> 

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Re: Prefetch limit and queue size

[James Strachan <ja...@gmail.com>]

On 11/29/06, ewood <wo...@ship.saic.com> wrote:
> I am running AMQ v4.1 with a network of embedded brokers (2).  My question is
> what happens when the prefetch limit is reached?

No more messages are dispatched to the consumer


> Will subsequent calls to
> send fail in some way?

No.

For non-persistent messaging send can sometimes block if the broker is
out of RAM (though there are options to deal with that)...

http://incubator.apache.org/activemq/slow-consumer-handling.html

also spooling to disk is coming in 4.2 etc.


> More importantly, can I detect when the prefetch
> limit has been reached from my client?

You can look at the MBeans

http://incubator.apache.org/activemq/maven/activemq-core/apidocs/org/apache/activemq/broker/jmx/SubscriptionViewMBean.html

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James
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