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mattfarney
PostPosted: Thu Jan 19, 2012 3:02 pm    Post subject: Reply with quote

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mqjeff wrote:
It's naught to do with internals.

QALIASes only override the ObjectQname on an MQOpen, they don't affect the ObjectQmgrName.

Cause, you know, they only have another queue name in them, not a qmgr name as well... if they had a qmgr name, they'd be a qremote, not a qalias.


So, a remoteQ writing to a local alias ends up with the realQMName (from the QR) so the alias look up fails since it only looks on the specified QM; while a local write to the alias (not specifying the qmname) ends up with no qm name, so the cluster resolution kicks in?

-mf
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bruce2359
PostPosted: Thu Jan 19, 2012 5:45 pm    Post subject: Reply with quote

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mattfarney wrote:

So, a remoteQ writing to a local alias ends up with the realQMName (from the QR) so the alias look up fails since it only looks on the specified QM; while a local write to the alias (not specifying the qmname) ends up with no qm name, so the cluster resolution kicks in?

What?! This is not very technical, and makes little sense.

Name resolution is always done on the local qmgr where any app does an MQOPEN. The qmgr looks for local object definitions for a matching object name in this order:
1) QLocal
2) QModel
3) QAlias
4) QRemote
If no object by that name exists, then the qmgr looks in the repositories (PR, then FR) or a cluster definition that matches the name being resolved.

[edit]
If the object name resolves to a transmission queue, the message traverses the network and ends up at the receiving end of the channel. There the MCA drives name resolution on the RQMName, and then the RQName (from the XQH), as above.
[/edit]
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mattfarney
PostPosted: Fri Jan 20, 2012 9:21 am    Post subject: Reply with quote

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We are not talking about first level name resolution. Both the QRemote and the direct open calls can find the alias on the gateway. Only the local write to the Qalias will resolve to remote cluster objects.

I'm trying to figure out why it works this way so that I can keep that in mind when dealing with my clusters moving forward.

-mf
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bruce2359
PostPosted: Fri Jan 20, 2012 9:28 am    Post subject: Reply with quote

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mattfarney wrote:
We are not talking about first level name resolution.

What exactly and precisely are we talking about here?

mattfarney wrote:
Only the local write to the Qalias will resolve to remote cluster objects.

Please, oh please, use WMQ technical terminology. There is no such thing as a local write.

MQPUTs create messages, but do not drive name resolution.

Local object definitions, including QAlias definitions, may or may not resolve to cluster objects.

What is the point your are trying to make here?
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fjb_saper
PostPosted: Fri Jan 20, 2012 1:27 pm    Post subject: Reply with quote

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IIRC the point he was trying to make was following:

Moving msgs from qmgr A to qmgr C, C being in a cluster and A not:
  • If your remote queue on A points to an alias queue on C and the alias queue on C points to a cluster q not present on C you get an error.
  • If instead the queue on C is a remote Q (with blank qmgr name) the call will resolve correctly...

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mattfarney
PostPosted: Fri Jan 20, 2012 5:10 pm    Post subject: Reply with quote

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In the simplest possible terms,

How does MQ decide where to look when resolving a QAlias TARGQ in a clustered environment?

As a likely follow-on, why is this different if the message comes from outside the cluster?

If a QM in the cluster and a QM outside of the cluster write to the same object, I would expect the same result and that is *NOT* what happens.

-mf
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bruce2359
PostPosted: Fri Jan 20, 2012 5:15 pm    Post subject: Reply with quote

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fjb_saper wrote:
IIRC the point he was trying to make was following:

Moving msgs from qmgr A to qmgr C, C being in a cluster and A not:
  • If your remote queue on A points to an alias queue on C and the alias queue on C points to a cluster q not present on C you get an error.
  • If instead the queue on C is a remote Q (with blank qmgr name) the call will resolve correctly...

So, you're saying that non-cluster qmgr A sends a message into cluster qmgr C, for delivery of a message outside cluster C (like qmgr D)? C is a hub.

If this is the case, then there will need to be a QR definition on C that resolves the queue-name and/or qmgrname (from XQH) to the leaving-the-cluster xmitq. Like this definition:
DEFINE QREMOTE(Q3.ALIAS) RNAME(Q3) XMITQ(D)


Unless I've completely lost the thread of this post, which is likely.
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fjb_saper
PostPosted: Fri Jan 20, 2012 11:52 pm    Post subject: Reply with quote

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bruce2359 wrote:

So, you're saying that non-cluster qmgr A sends a message into cluster qmgr C, for delivery of a message outside cluster C (like qmgr D)? C is a hub.


I believe MattFarney had both C and D in the cluster. In C he had an alias queue pointing to D.

His point was that if connected to C you can post and see no problem.
If you send the message from A and target the alias Q on C you get an error...?
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mqjeff
PostPosted: Sun Jan 22, 2012 6:35 am    Post subject: Reply with quote

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fjb_saper wrote:
bruce2359 wrote:

So, you're saying that non-cluster qmgr A sends a message into cluster qmgr C, for delivery of a message outside cluster C (like qmgr D)? C is a hub.


I believe MattFarney had both C and D in the cluster. In C he had an alias queue pointing to D.

His point was that if connected to C you can post and see no problem.
If you send the message from A and target the alias Q on C you get an error...?


Yes, this was my point about aliases only applying to the ObjectQName, not the ObjectQmgr name. If you send the message from A to C, then when it arrives on C, the queue name is going to get overriden by the qalias resolved value, but the qmgr name is still going to be pointing to C. And then the message won't get delivered, because the qalias points to a queue that's shared in the cluster on D, not local to C.
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