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| Using Pub/Sub to send grouped messages in a clustered env |
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| dwitherspoon |
 Posted: Thu Oct 28, 2004 12:10 pm Post subject: Using Pub/Sub to send grouped messages in a clustered env |
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Acolyte
Joined: 09 Dec 2003
Posts: 59
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Hi folks,
If I wanted to send lots of files to lots of receivers, and break them up into chunks (an MQ group of messages), is it reasonable that I could do that using Pub/Sub in a clustered environment?
I am guaranteed of having multiple subscribers to the same topic (for load-balancing and failover). I've done some pub/sub stuff before using JMS, but I don't have a way of requiring that all the messages in a group come to the same receiver, that they don't start being delivered to the receiver until they've all landed, and to get them in the same order. Since these would be files, I'd really want to have that level of control. But I'm not sure how that work through pub/sub.
I'd appreciate some sage advice, as I think my project is about to take a turn down a dark road! 
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| jefflowrey |
| Posted: Thu Oct 28, 2004 12:21 pm Post subject: |
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Grand Poobah
Joined: 16 Oct 2002
Posts: 19981
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If you use pub/sub, and you have multiple subscribers to the same topic, then *all* messages for that topic will go to *all* subscribers.
So every subscriber will get every file.
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| EddieA |
| Posted: Thu Oct 28, 2004 12:31 pm Post subject: |
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Jedi
Joined: 28 Jun 2001
Posts: 2453
Location: Los Angeles
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I don't think it will with JMS, because that doesn't have the required control over the Group options.
If you can live without JMS, then why don't you try publishing a message with the Group options set, and check at the Subscription queue to see if they "survive" through the Broker.
If they do, then all you need to do is Publish, using the Group, and code your Subscribers to use the Complete Group option.
If you must use JMS, then you are into building your own "Group" information in the Properties. 
Cheers,
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Eddie Atherton
IBM Certified Solution Developer - WebSphere Message Broker V6.1
IBM Certified Solution Developer - WebSphere Message Broker V7.0 |
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| EddieA |
| Posted: Thu Oct 28, 2004 12:34 pm Post subject: |
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Jedi
Joined: 28 Jun 2001
Posts: 2453
Location: Los Angeles
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But I also spotted:
| Quote: |
| using Pub/Sub in a clustered environment |
This might cause you some problems, if there is more than a single copy of a Subscription queue. You will have no control (well, not easily) over which one each message in the Group is sent to.
Cheers,
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Eddie Atherton
IBM Certified Solution Developer - WebSphere Message Broker V6.1
IBM Certified Solution Developer - WebSphere Message Broker V7.0 |
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| dwitherspoon |
| Posted: Fri Oct 29, 2004 5:21 am Post subject: |
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Acolyte
Joined: 09 Dec 2003
Posts: 59
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Thanks for all this info! I read on a older post that the STREAM underlying the pub/sub mechanisms cannot be a clustered queue. Not sure why. Can anyone confirm whether that is the case, and if so why?
Thanks all!
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| EddieA |
| Posted: Fri Oct 29, 2004 7:13 am Post subject: |
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Jedi
Joined: 28 Jun 2001
Posts: 2453
Location: Los Angeles
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I don't have a copy handy, but if you pull the PDF for the original SupportPac Pub/Sub Broker, and search for Cluster, it has a section on which queues cannot be clustered.
Plus, as I pointed out earlier, if any of the Subscribers receive the information on a Cluster Q, then you have to think what happens when different Publications go to different copies of the Subscriber Q.
Cheers,
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Eddie Atherton
IBM Certified Solution Developer - WebSphere Message Broker V6.1
IBM Certified Solution Developer - WebSphere Message Broker V7.0 |
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| bower5932 |
| Posted: Fri Oct 29, 2004 7:24 am Post subject: |
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Jedi Knight
Joined: 27 Aug 2001
Posts: 3023
Location: Dallas, TX, USA
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| Without knowing for a fact, I'd guess that the stream queue can't be clustered because it contains state. It is where things go that the broker needs to know about. If messages were just round-robining around the cluster, brokers wouldn't know what is going on regarding publishes and subscribes. |
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