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| jaykarthi |
 Posted: Mon Jan 09, 2006 1:46 am Post subject: How to see message availability??? |
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Newbie
Joined: 28 Dec 2005
Posts: 6
Location: Chennai, India.
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When I run a publisher application using JMS with Websphere MQ.6 and no subscriber applications are running(yet to get started)
1. What will happen to the Message sent by the publisher?
2. If it will be residing in the Queue then how can I see or check whether a message is published and also the message using Websphere MQ explorer or MQ command?
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| jefflowrey |
| Posted: Mon Jan 09, 2006 4:20 am Post subject: Re: How to see message availability??? |
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Grand Poobah
Joined: 16 Oct 2002
Posts: 19981
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| jaykarthi wrote: |
| 1. What will happen to the Message sent by the publisher? |
It's discarded. Unless it's a retained publication.
But don't use retained publications unless you have to.
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| jaykarthi |
| Posted: Mon Jan 09, 2006 9:10 pm Post subject: |
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Newbie
Joined: 28 Dec 2005
Posts: 6
Location: Chennai, India.
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If that is the case, then what is the difference between having it as retained publication and having a dead letter queue(my understanding is that DLQs retain the failed delivery messages)? Clarify me on this.
Thanks for the earlier reply.
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| jefflowrey |
| Posted: Tue Jan 10, 2006 4:22 am Post subject: |
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Grand Poobah
Joined: 16 Oct 2002
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It is not my understanding that non-retained publications for topics with no registered subscribers will end up on the Dead Letter Queue.
It is my understanding that these publications will be deleted.
I have been known to be wrong before.
Again, don't use retained publications unless there's a very specific business case for using them. And then think twice about that business case and see if there is another way to solve it.
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| mvic |
| Posted: Wed Jan 11, 2006 2:47 am Post subject: |
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Jedi
Joined: 09 Mar 2004
Posts: 2080
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| jaykarthi wrote: |
| what is the difference between having it as retained publication and having a dead letter queue(my understanding is that DLQs retain the failed delivery messages)? |
In MQ's JMS you don't get to control all of the fine details of the usage of the MA0C command messages. The controls, such as they are, are all on the subscribe, rather than the publish.
On the publish, MQ's JMS doesn't use the MA0C facility of retained publications.
You do get to choose whether to create a durable or non-durable subscriber. If non-durable, then the subscription only lives, at maximum, for the life of the app/connection. If durable, then messages will be stored for the app even if it stops running. For the durable subscriber, you do have to explicitly unsubscribe when you no longer want to receive messages.
The DLQ is only used when a message is unprocessable. The full rules on this are complex - but are documented
http://publib.boulder.ibm.com/infocenter/wmqv6/v6r0/topic/com.ibm.mq.csqzaw.doc/jms77a4.htm
(Scroll down to the section entitled "Handling poison messages") |
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| jefflowrey |
| Posted: Wed Jan 11, 2006 4:19 am Post subject: |
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Grand Poobah
Joined: 16 Oct 2002
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Actually, I think you only get retained publications when you use Message or Event Broker as your pub/sub engine, not the plain broker that is shipped with MQ as of 5.3.8 (and that used to be MA0C).
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