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Message-ID: <ec6e67fd0704160046i6a8a2cc6hf10ddb16b62f53f3@mail.gmail.com>
Date: Mon, 16 Apr 2007 08:46:03 +0100
From: "James Strachan" <james.strachan@gmail.com>
To: users@activemq.apache.org
Subject: Re: messageListener, ASYNC, and threads in "onMessage()"
In-Reply-To: <10002299.post@talk.nabble.com>
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References: <10002299.post@talk.nabble.com>

A JMS provider will only invoke a MessageListener on a JMS
MessageConsumer by one thread at once. Indeed; a JMS provider will
invoke the MessageListener on all MessageConsumer's in a given Session
by a single thread at once.


On 4/15/07, robr <rowntreerob@yahoo.com> wrote:
>
> i read the post at :
> http://www.nabble.com/-activemq-user--two-threads-per-session-tf476901s2354.html#a1298138
> which suggests an extra thread around the onMessage dispatcher. We have
> occaisional issues in the scope of our 3.1 implementation of "onMessage()"
> that could be cause by non-thread-safe code on a file Access. These could be
> issues that only come up when the broker gets very busy as they affect only
> 5 - 10% of our message flow.
>
> I dont completely understand whether there are , in fact , multiple threads
> that call onMessage? The javax.jms api says there is only 1.
> http://java.sun.com/javaee/5/docs/api/javax/jms/MessageListener.html
>
> Other posts suggest that when using listeners and ASYNC that you should be
> prepared to have a 2nd onMessage call dispatched before the prior call has
> finished. So , your call stak from onMessage should be thread-safe.
>
> I've decided to review the code and to make sure that we are not throwing
> exceptions in the scope of "onMessage" and to protect the obvious objects in
> case there is m-thread issue... but i dont really know...
>
> comments appreciated
> --
> View this message in context: http://www.nabble.com/messageListener%2C-ASYNC%2C-and-threads-in-%22onMessage%28%29%22-tf3579500s2354.html#a10002299
> Sent from the ActiveMQ - User mailing list archive at Nabble.com.
>
>


-- 

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