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From "James Strachan" <james.strac...@gmail.com>
Subject Re: detaching message group affinity
Date Mon, 19 Jun 2006 16:09:34 GMT
On 6/19/06, Sanjiv Jivan <sanjiv.jivan@gmail.com> wrote:
> On 6/19/06, James Strachan <james.strachan@gmail.com> wrote:
> >
> >
> > > Who is the owner of the "JMSXGroupID" to broker mapping? Is it the JMS
> > > Connection or a JMSSession? I need to send messages by different Message
> > > Groups from the same client application. I would like to understand if I
> > > need to create separate JMS Connections for each message group based
> > > conversation, or separate JMS Sessions would suffice. A quick look at
> > the
> > > source seems to indicate that Message Groups are held at the JMS
> > connection
> > > level (ActiveMQConnectionMetaData). Can you confirm?
> >
> > A broker manages Message Groups for its consumers. Its nothing to do
> > with connections per se - its purely a mapping of JMSXGroupID to
> > message consumer in a broker.
>
>
> A consumer being the value in JMSReplyTo?

Not necessarily - a consumer being some POJO created via
Session.createMessageConsumer().

But if the consumers are using temporary queues/topics then they are
nearly the same thing.


> I guess what I'm having difficulty
> understanding is where is the correlation between a single message with "
> message.setIntProperty("JMSXGroupSeq", 0);" to MessageGroupID being made. Is
> it based on JMSReplyTo value provided by the producer sending the message?


If someone is sending a message and they want to 'close' a message
group, they set the JMSXGroupSeq header along with the JMSXGroupID
header.

If some other node who is not a JMS sender wants to close a message
group, you could always just send a dummy message.


> What is the expected behaviour in such a scenario (this is related to issue
> AMQ-760): A network of 2 brokers has been set up. A client sends several
> messages to MG1 and MG2 which are received by SERVER1 and SERVER2
> respectively. The client process terminates (ie the JMSConenction,
> session etc are destroyed). The client comes up an send messages to MG1 and
> MG2. Is is guaranteed that MG1 and MG2 go to the designated servers from the
> previous run (SERVER1 and SERVER2 respectively).

Message groups is a broker-side thing; the only thing which affects
which consumer is associated with a message group is

* when the consumer is closed (e.g. as a result of a Connection
close), its message groups are put back in the pool to be re-assigned
to a consumer

* if the message group is explicitly closed by a message containing a
JMSXGroupId and a JMSXGroupSeq of value 0

-- 

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

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