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| Disable duplicate COA COD messages on subscriptions |
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| mtagarrobang |
 Posted: Thu Apr 21, 2022 4:21 am Post subject: Disable duplicate COA COD messages on subscriptions |
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Newbie
Joined: 21 Apr 2022
Posts: 2
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Hi!
Is there any way to disable COA COD report mesages on one or more subscriptions for the same Topic? The publisher publish a message for a Topic with report options COA COD, all subscriptions for this topic send back COA COD messages (n) times as (n) subscribers, but only a COA COD pair is requiered.
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| fjb_saper |
| Posted: Thu Apr 21, 2022 7:29 am Post subject: |
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Grand High Poobah
Joined: 18 Nov 2003
Posts: 20756
Location: LI,NY
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Have you tried asking for COA only?
And why would you ask for COA/COD on pub/sub? 
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| bruce2359 |
| Posted: Thu Apr 21, 2022 7:35 am Post subject: |
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Poobah
Joined: 05 Jan 2008
Posts: 9469
Location: US: west coast, almost. Otherwise, enroute.
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Pub/Sub model allows for 0, 1 or more publishers, and 0, 1 or more subscribers - usually neither aware of each other. What purpose/requirement does COA/COD address?
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| hughson |
| Posted: Thu Apr 21, 2022 10:59 am Post subject: Re: Disable COA COD messages on subscriptions |
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Padawan
Joined: 09 May 2013
Posts: 1959
Location: Bay of Plenty, New Zealand
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| mtagarrobang wrote: |
| ... but only a COA COD pair is required. |
So your application doesn't care once it has received the first COA COD pair. It could throw the rest away.
Alternatively, you could look into other ways of achieving what the COA COD pair does for you. Could you tell us why the publishing app uses the COA COD report? One guess might be that it is using it to determine whether there are any subscribers at all? If that was the reason, you could instead use MQPMO_WARN_IF_NO_SUBS_MATCHED.
Let us know the aim and we may be able to help further.
Cheers,
Morag
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Morag Hughson @MoragHughson
IBM MQ Technical Education Specialist
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| bruce2359 |
| Posted: Thu Apr 21, 2022 11:22 am Post subject: |
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Poobah
Joined: 05 Jan 2008
Posts: 9469
Location: US: west coast, almost. Otherwise, enroute.
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Much has been discussed here regarding the value of COA and COD. IMHO, not much, especially in pub/sub app design model.
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I like deadlines. I like to wave as they pass by.
ב''ה
Lex Orandi, Lex Credendi, Lex Vivendi. As we Worship, So we Believe, So we Live. |
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| mtagarrobang |
| Posted: Mon Apr 25, 2022 5:56 am Post subject: |
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Newbie
Joined: 21 Apr 2022
Posts: 2
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Thank you for all responses.
The application will deal with the first pair of COA/COD report messages.
Addtionally there is an issue with the MgsID and CorreI ID, the values from the original message need to be passed to the COA/COD reply message.
Report options:
MQRO_PASS_CORREL_ID
MQRO_PASS_MSG_ID
Publish/Subscribe attribute:
Destination Correl ID is set to '000000000000000000000000000000000000000000000000' (48 zeros) so the CorrelId set by the publishing application is maintained in the copy of the message delivered to the subscription, then copied to the COA/COD reply message (MQRO_PASS_CORREL_ID).
Is there any way to maintain the MsgID set by the publishing application and copy it to the COA/COD reply? (The MsgID is not maintained in the copy of the message delivered to the subscription and not copied to the COA/COD reply message (MQRO_PASS_MSG_ID)
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| bruce2359 |
| Posted: Mon Apr 25, 2022 3:16 pm Post subject: |
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Poobah
Joined: 05 Jan 2008
Posts: 9469
Location: US: west coast, almost. Otherwise, enroute.
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| mtagarrobang wrote: |
| The application will deal with the first pair of COA/COD report messages. |
No, the requesting app must deal with every reply if it created a request message. And, the requesting app must also deal with every COA and COD message if it asked for them. AFIK, there is no configuration that specifies "only one COA/COD, please."
| mtagarrobang wrote: |
Addtionally there is an issue with the MgsID and CorreI ID, the values from the original message need to be passed to the COA/COD reply message.
Report options:
MQRO_PASS_CORREL_ID
MQRO_PASS_MSG_ID
Publish/Subscribe attribute:
Destination Correl ID is set to '000000000000000000000000000000000000000000000000' (48 zeros) so the CorrelId set by the publishing application is maintained in the copy of the message delivered to the subscription, then copied to the COA/COD reply message (MQRO_PASS_CORREL_ID).
Is there any way to maintain the MsgID set by the publishing application and copy it to the COA/COD reply? (The MsgID is not maintained in the copy of the message delivered to the subscription and not copied to the COA/COD reply message (MQRO_PASS_MSG_ID)
thanks |
You appear to misunderstand COA/COD functionality.
COA messages are created by down network MQ receiver-end message channel agents; COD messages are created by down network qmgrs.
The requesting (MQPUTting) app usually requests a new and unique message id (PMO_NEW_MSGID), and populates the ReplyToQueue and ReplyToQueueManager fields in the MQMD. The CorrelId field in the request message is not used by the MQPUTting app, so CorrelId of zeros is no surprise.
The replying (MQGETting app), recognizing that the message is a request message will need to copy the inbound MsgId to the CorrelId field of outbound reply message, AND MQPUT the reply message to the ReplyToQueue and ReplyToQueueManager specified in the request message.
Again, it is unusual (not contemplated in the design and implementation) for publishers to want/need COAs or CODs or replies from subscribers.
_________________
I like deadlines. I like to wave as they pass by.
ב''ה
Lex Orandi, Lex Credendi, Lex Vivendi. As we Worship, So we Believe, So we Live.
Last edited by bruce2359 on Mon Apr 25, 2022 6:55 pm; edited 1 time in total |
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| bruce2359 |
| Posted: Mon Apr 25, 2022 3:30 pm Post subject: |
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Poobah
Joined: 05 Jan 2008
Posts: 9469
Location: US: west coast, almost. Otherwise, enroute.
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Moved to API support forum.
_________________
I like deadlines. I like to wave as they pass by.
ב''ה
Lex Orandi, Lex Credendi, Lex Vivendi. As we Worship, So we Believe, So we Live. |
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| hughson |
| Posted: Tue Apr 26, 2022 2:45 am Post subject: |
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Padawan
Joined: 09 May 2013
Posts: 1959
Location: Bay of Plenty, New Zealand
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| mtagarrobang wrote: |
There is an issue with the MgsID and CorreI ID, the values from the original message need to be passed to the COA/COD reply message.
Report options:
MQRO_PASS_CORREL_ID
MQRO_PASS_MSG_ID
Publish/Subscribe attribute:
Destination Correl ID is set to '000000000000000000000000000000000000000000000000' (48 zeros) so the CorrelId set by the publishing application is maintained in the copy of the message delivered to the subscription, then copied to the COA/COD reply message (MQRO_PASS_CORREL_ID). |
Well done for finding this! A lot of people don't. This is the correct way to flow the CorrelId from the publisher to the subscriber.
| mtagarrobang wrote: |
| Is there any way to maintain the MsgID set by the publishing application and copy it to the COA/COD reply? (The MsgID is not maintained in the copy of the message delivered to the subscription and not copied to the COA/COD reply message (MQRO_PASS_MSG_ID) |
Since many messages are generated as a result of a publish, each of these generated messages is given a unique MsgID. None of the subscriber copies of the message contains the MsgId from the publisher. There is no option to change this behaviour.
You might find the following blog post a good summary: IBM MQ Little Gem #31: Publisher's CorrelId
Cheers,
Morag
_________________
Morag Hughson @MoragHughson
IBM MQ Technical Education Specialist
Get your IBM MQ training here!
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