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From "anish pathadan" <anishpatha...@gmail.com>
Subject Re: [jira] Commented: (AMQ-1126) The Resource Adapter ignores the JMSXGroupID when dispatching to MDBs
Date Thu, 16 Aug 2007 07:17:56 GMT
The concept of JMSXGroupId comes into picture only if there is multiple
message listeners (consumers).In this case if the MDB container is the sole
consumer then it is mdb containers choice on how to process the received
messages.Also I cannot see the advantages of processing the messages having
same JMSXGroupId in a single MDB instance.I think this issue will get more
response if it is posted on JBoss/OpenEJB forum as it is more related to MDB
container implementation than an active mq issue.

correct me if I am wrong anywhere.

On 8/14/07, John Robinson (JIRA) <jira@apache.org> wrote:
>
>
>    [
> https://issues.apache.org/activemq/browse/AMQ-1126?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_39929]
>
> John Robinson commented on AMQ-1126:
> ------------------------------------
>
> Page 31, section 3.5.9 of the JMS Specification states:
>
> JMSXGroupID and JMSXGroupSeq are standard properties clients should use if
> they want to group messages. All providers must support them.
>
> So I guess the real question is, what does it mean to support it?
>
> I agree that the MDB container is the listener, and that it is free to
> dispatch messages to to which ever MDB instance it chooses.
>
> However, what I think is broken is that it is dispatching them in
> parallel.  That is, it should, in my opinion, be handing out one message at
> a time, and not handing out another one until the first message is
> acknowledged, or its transaction is committed, for example.  In other words,
> it should finish one before sending another.
>
> If it does not do this, then grouping has no semantic meaning or purpose
> with MDBs, at least that I can divine.
>
> I would further point out that, in my opinion, the container is free to
> dispatch any one message, without respect to order, so long as the sequence
> number was not set.  If the sequence number and the group number are set,
> then the container should be handing a single MDB a single message for that
> group in the order defined by the sequence number.
>
> Right now, when grouping and sequence numbers are used with MDBs, the
> messages are dispatched in sequence, but because the container does not wait
> for the first one to finish before dispatching the second one, the messages
> end up being processed simultaneously, and thread/execution priority
> determines which one finish first.
>
> For example, if you have a message that takes a long time to process (call
> it message A) and a message that takes a short amount of time to process
> (call it message B), and you group them and sequence them so that A is first
> and B is second, then with MDBs it is quite likely that B (the shorter one)
> will finish first.  I think, based on my understanding, that the container
> should dispatch message A, wait until it is 'complete', and then dispatch
> message B.
>
> Whether they go to the same, or a different, MDB instances is really moot,
> and shouldn't matter a whit.
>
> In my opinion part of the problem is that the spec is very vague on what,
> exactly, is meant by 'support' with respect to these two attributes.
>
> I would love to hear from others on this subject.
>
> -John
>
>
> > The Resource Adapter ignores the JMSXGroupID when dispatching to MDBs
> > ---------------------------------------------------------------------
> >
> >                 Key: AMQ-1126
> >                 URL: https://issues.apache.org/activemq/browse/AMQ-1126
> >             Project: ActiveMQ
> >          Issue Type: Bug
> >          Components: JCA Container
> >    Affects Versions: 4.0.1
> >         Environment: Java 1.4.2_08
> > JBoss 4.0.4
> > ActiveMQ 4.0.1
> >            Reporter: John Robinson
> >
> > Integrate AMQ into JBoss using the data source, and resource
> adapter.  Create an outbound queue and an MDB with a pool size of
> 100.  Dispatch several messages to the outbound queue, setting the
> JMSXGroupID property on the message to be the same value each time.  In the
> MDB's onMessage method print out the MDBs toString (don't override toString)
> and you should see something that looks like:
> > OutQueueProcessorBean@19a7266
> > Observe two things:
> > a) Many messages are processed in parallel
> > b) Many different values will occur after the @ in the above message,
> denoting that more than on MDB instance is being handed messages.
> > The correct behavior would be to dispatch messages with the same group
> id to the same MDB instance in sequence.  This would allow messages from
> different groups to be processed in parallel, but messages in any one group
> would be processed serially, in the order in which they were placed into the
> queue.
>
> --
> This message is automatically generated by JIRA.
> -
> You can reply to this email to add a comment to the issue online.
>
>


-- 
Best Regards,
Anish Pathadan

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