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| Sequence messages across a cluster? |
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| pavdaddy72 |
 Posted: Wed Jan 07, 2015 6:41 am Post subject: Sequence messages across a cluster? |
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Newbie
Joined: 07 May 2014
Posts: 6
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How can I ensure that messages remain in sequence across a cluster? Does the sequence node accomplish this or is there further administration work that needs to be setup?
Long story short, we're trying to figure out if we can keep messages in sequence across a cluster of brokers. For example, if a flow was running on 2-4 brokers, can we use sequence nodes to mainatin order. Or is there a different way to accomplish this?
Obviously, any other ideas to meet the same requirement are useful too.
Unable to find any IBM links or docs that talk about maintaining sequence over clusters. Thanks,
Jason |
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| fjb_saper |
| Posted: Wed Jan 07, 2015 6:53 am Post subject: |
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Grand High Poobah
Joined: 18 Nov 2003
Posts: 20756
Location: LI,NY
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Well there is a kind of round about way.
You need to set the default bind on open property to GROUP.
Then you need to send all the messages that need sequencing in the same group... and to use a re-sequencing node on the broker...
Basically your cluster represents a bunch of threads to which you are going to dispatch work in a round robin manner. Nobody cares about the order and you have no control because you are processing the different threads in parallel...
Setting the default bind to group AND sending the messages as a group allows you to send all the messages in the group to the same "thread". But there is no guarantee that they will arrive in order on the thread...
Hence the potential need to re-sequence at arrival point.
And you need to give a lot of thought about how you are going to handle out of sequence messages...., and what represents a new sequence rather than the continuation of an existing one?
How do you handle a sequence that skips a number between 2 quiet intervals???
Have fun 
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MQ & Broker admin |
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| mqjeff |
| Posted: Wed Jan 07, 2015 8:46 am Post subject: |
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Grand Master
Joined: 25 Jun 2008
Posts: 17447
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You would use a single Sequence node to assign a sequence to each message.
You would then fan the messages across the cluster for processing.
You would then use a single REsequence node to emit the messages in the proper sequence.
This is essentially a fan-out/fan-in process.
If you want to ensure that Message 2 is always processed after message 1 and before message 3, you can't process them on different servers.
Unless you want to do something dumb like use Global Cache to implement a lock. |
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