"Using a point-to-point or a Topic based destination avoids this problem
since all subscribers get their own copy of every message."
Was this a typo? It would seem to me that a point-to-point is the consumer
case and this should be "Using a Topic based destination avoids this problem
since all subscribers get their own copy of every message."?
>From: Richard Monson-Haefel <[EMAIL PROTECTED]>
>Reply-To: [EMAIL PROTECTED]
>To: [EMAIL PROTECTED]
>Subject: Re: EJB 2.0 spec: Association of a message-driven bean
>Date: Wed, 25 Apr 2001 09:11:23 -0500
>
>This depends a lot on how your vendor handles clustering of MDBs. The
>specification you quoted is referring to the two different deployments
>(enterprise beans) that subscribe to the same destination. With queues,
>messages are only consumed once. So if you send a message to a queue, only
>one
>of the MDB deployments will be able to get it; the message won't be
>available
>for other MDBs. (some of this depends on transactions and how the JMS
>provider
>handles certain idiosyncrasies.) Using a point-to-point or a Topic based
>destination avoids this problem since all subscribers get their own copy of
>every message.
>
>In a clustered environment, the cluster would, ideally, ensure that only
>one
>MDB in one of the clustered servers were able to process a message from a
>Queue
>or a Topic. This is pretty easy to do with queues since they ensure that
>only
>one client can process a message anyway, which provides for natural load
>balancing between servers. With Topic based destinations, however, is more
>complicated because JMS will usually deliver all messages to all
>subscribers.
>
>To really understand how all this works you'll need to take some time to
>study
>JMS and the different message delivery protocols. Its an exciting and
>powerful
>technology but its not a simple as its API would lead you to believe.
>
>Richard
>--
>Richard Monson-Haefel
>Author of Enterprise JavaBeans, 2nd Edition (O'Reilly 2000)
>Co-Author of Java Message Service (O'Reilly 2000)
>http://www.jMiddleware.com
>
>Wei Jiang wrote:
>
> > Hi,
> >
> > Can any one clarify this for me please?
> >
> > Say, I have a message-driven bean Ear. I deploy it on each
> > server in a clustering environmen. If I send message to all
> > instances of the same bean. Will all instances of the same
> > bean get my message?
> >
> > Thanks.
> >
> > >>>>>>>>>>>>>>>>>>>>>>>>>>
> > EJB 2.0 spec:
> >
> > 14.4.9 Association of a message-driven bean with a destination
> >
> > The Deployer should avoid associating more than one message-driven bean
> > with the same JMS Queue.
> >
> > If there are multiple JMS consumers for a queue, JMS does not define how
> > messages are distribued
> > between the queue receivers.
> >
> > __________________________________________________
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> >
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