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| senMQ |
 Posted: Fri Aug 24, 2007 11:39 am Post subject: Message priority |
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Acolyte
Joined: 14 Aug 2006
Posts: 66
Location: Palo Alto, CA
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| We are planning to set up higher message priority for messages sent by one of our application. In a clustered environment, would these messages zip through the cluster transmit queue before other messages. Also, I anticipate a very high volume of messages of this type. So, does that ean that it is going to slow down the other messages? |
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| PeterPotkay |
| Posted: Fri Aug 24, 2007 12:00 pm Post subject: |
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Poobah
Joined: 15 May 2001
Posts: 7722
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yes and yes, if you have so many of them that the channels are always sending the higher priority ones and only occasionally catch up to the point where there are no other hi priority messages so they finally get to the lower priority ones.
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Peter Potkay
Keep Calm and MQ On |
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| hin3407 |
| Posted: Thu Sep 06, 2007 7:14 am Post subject: |
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Centurion
Joined: 17 Oct 2006
Posts: 120
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Actually, that is not necessarily true. Higher priority messages will not be sent across a channel faster than those that are lower priority, iff there is a backlog of messages on the XMITQ. If the XMITQ does not backup, than higher priority messages will not arive any faster.
Additionally, on the consuming side. If the dequeue rate is just as fast as the enqueue rate, than again, message priority is irrelevant. It will only occur if the dequeue rate is slower than the dequeue rate.
Cheers.
hin3407 |
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| PeterPotkay |
| Posted: Thu Sep 06, 2007 7:28 am Post subject: |
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Poobah
Joined: 15 May 2001
Posts: 7722
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| hin3407 wrote: |
| Higher priority messages will not be sent across a channel faster than those that are lower priority, iff there is a backlog of messages on the XMITQ. |
Yes they will.
| hin3407 wrote: |
| If the XMITQ does not backup, than higher priority messages will not arive any faster. |
Correct. FIFO in action.
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Peter Potkay
Keep Calm and MQ On |
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| jefflowrey |
| Posted: Thu Sep 06, 2007 7:28 am Post subject: |
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Grand Poobah
Joined: 16 Oct 2002
Posts: 19981
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Messages dequeued from a queue that has been opened to return messages in Priority Order will be delivered off the queue in order of priority.
The next message delivered is always the first message in the queue with the highest priority.
This applies for messages coming off of the XMITQ as well. I believe it is well documented that the MCA reads the XMITQ in priority order.
If the XMITQ is completely empty, and the channel batch size is small enough or the batch interval is small enough, then messages may get shipped across the channel in FIFO order - because there is never more than one message on the queue when the MCA issues an MQGet.
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I am *not* the model of the modern major general. |
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| hin3407 |
| Posted: Thu Sep 06, 2007 7:31 am Post subject: |
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Centurion
Joined: 17 Oct 2006
Posts: 120
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Your first comment is not correct. Show me evidence of where that would be true and false.
The only way that would be false, is if there is a backlog of messages on the xmitq, otherwise, message priority is irrelevant. |
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| hin3407 |
| Posted: Thu Sep 06, 2007 12:57 pm Post subject: |
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Centurion
Joined: 17 Oct 2006
Posts: 120
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| yup, that sums up everything i said. |
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| PeterPotkay |
| Posted: Thu Sep 06, 2007 4:38 pm Post subject: |
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Poobah
Joined: 15 May 2001
Posts: 7722
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hin3407, what I said is correct and agrees with what Jeff said.
You wrote:
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Higher priority messages will not be sent across a channel faster than those that are lower priority, iff there is a backlog of messages on the XMITQ.
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That is wrong. If there is a backlog, higher priority mesages WILL be sent across first.
senmq asked:
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We are planning to set up higher message priority for messages sent by one of our application. In a clustered environment, would these messages zip through the cluster transmit queue before other messages.
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And I said yes. "before other messages" In this case I took "other messages" to mean lower priority messages in the XMITQ a.k.a there is a backlog on the XMITQ. Otherwise those "other messages" don't exist yet or are sitting in local queues and are irrelevant.
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Peter Potkay
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| jefflowrey |
| Posted: Thu Sep 06, 2007 5:19 pm Post subject: |
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Grand Poobah
Joined: 16 Oct 2002
Posts: 19981
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I think, to be fair..
what I said properly sums up what hin3407 thought hin3407 said... and not what was actually written.
I tend to do this kind of thing a lot myself - where somehow betwixt brain and fingers, the words get jumbled or the sentences get jumbled.
For example, I nearly typed "hin037" rather than "hin3407".
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| hin3407 |
| Posted: Thu Sep 06, 2007 6:41 pm Post subject: |
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Centurion
Joined: 17 Oct 2006
Posts: 120
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okay, you are summarizing everything i said.
btw.... "iff" means, if and only if, not "if"
So read that again, and its everything you said.
cheers. |
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