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| when is published message deleted |
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| WBI_user |
 Posted: Tue Mar 08, 2005 1:08 pm Post subject: when is published message deleted |
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Partisan
Joined: 07 Aug 2001
Posts: 386
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If all I have are non-durable subscribers, will MQ keep the message at all after it has given the published message to whichever subscriber is connected at the time ?
If that is the case should the subscribers queue be always empty ? |
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| bower5932 |
| Posted: Tue Mar 08, 2005 2:35 pm Post subject: |
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Jedi Knight
Joined: 27 Aug 2001
Posts: 3023
Location: Dallas, TX, USA
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It depends. There is a concept of a retained publication that the broker retains to give to a subscriber that is new to a topic. It is a WMQ concept. If you are strictly in the JMS world, you shouldn't see any messages laying around.
Of course, I've seen a lot of people who don't have anybody subscribed only to find out that they left some durable subscribers hanging around. |
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| malammik |
| Posted: Tue Mar 08, 2005 7:37 pm Post subject: |
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Partisan
Joined: 27 Jan 2005
Posts: 397
Location: Philadelphia, PA
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Unless the publication is retained or if the publication message had expiry set on it, broker will discard the publication after all subscribers had received the message. You can subscribe to a special $SYS/foo/bar topic that broker will publish messages to when publication is expired.
_________________
Mikhail Malamud
http://www.netflexity.com
http://groups.google.com/group/qflex |
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| WBI_user |
| Posted: Tue Mar 08, 2005 8:34 pm Post subject: |
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Partisan
Joined: 07 Aug 2001
Posts: 386
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Thanks for the response. I am talking strictly MQ PUB/SUB, not using event broker or WBI message borker.
You said " Unless the publication is retained or if the publication message had expiry set on it, broker will discard the publication after all subscribers had received the message"
How does the publisher know that there will be new subscriber for the topic ?
If there is no new subscriber, the broker admin person is responsible for cleaning up these retained publication , Am I right
How is retain publication specified ?
If expiry time is specified, the broker will not throw away the published message until it expires. Is that right ?
"... retain publication...It is a WMQ concept"
Do you mean that retain publication is not part of JMS pub/sub ? |
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| bower5932 |
| Posted: Wed Mar 09, 2005 7:21 am Post subject: |
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Jedi Knight
Joined: 27 Aug 2001
Posts: 3023
Location: Dallas, TX, USA
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| WBI_user wrote: |
How does the publisher know that there will be new subscriber for the topic ?
If there is no new subscriber, the broker admin person is responsible for cleaning up these retained publication , Am I right
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The broker has no way of knowing if there will be a new subscriber for a topic. It is 'stuck' having to hang onto the message.
| WBI_user wrote: |
How is retain publication specified ?
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Check out the Publish/Subscribe User's Guide. There is a parameter that you specify at publish time indicating that the message should be retained. You have to also be careful that you don't mix retained and non-retained messages on the same topic.
| WBI_user wrote: |
If expiry time is specified, the broker will not throw away the published message until it expires. Is that right ?
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Correct.
| WBI_user wrote: |
"... retain publication...It is a WMQ concept"
Do you mean that retain publication is not part of JMS pub/sub ? |
Retained publications are NOT part of JMS. |
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