No subject

added at the end of MigrateRsc() with comments why that is done:
/* migrate 'then' action also needs anything that the stop needed to
have completed too */
/* migrate 'then' action also needs anything that the start needed to
have completed too */

May be that function is a good place too do that?

Vladislav

> 
> The migration operations don't actually get calculated by the policy
> engine. All moves are calculated as "stop/start" internally and then at
> the end of all the calculations we attempt to detect when we can migrate
> based on the final graph.
> 
> -- Vossel
> 
>> At the other hand, migration is a very special operation I'd say. It
>> is
>> not a stop on one node and start on another one, but a magical move
>> of
>> resource. It was running on one node and oops, it runs on another. It
>> does neither stop nor start, does not allocate or free resources. It
>> just appears in a different place.
>> Most common example of resource migration is live VM migration.
>> And last part of migration (actual switch to another node) is done
>> almost atomically nowadays. VM just appears on a different node.
>>
>> Another example of a "real life" migration (not in clusters) would be
>> remote desktop, where you start application on a remote server being
>> at
>> work, then you come home, connect to that desktop and see your
>> application. You do not stop and do not start it. You just see that
>> your
>> window is "migrated" to another place.
>>
>> For pacemaker this could be illustrated with some resource agent
>> which
>> manages some external entity which exists "somewhere". And "resource
>> is
>> running on node A" just means that that entity is managed from node
>> A.
>> It does not run there, it is just managed from there. In my case that
>> entity is a pacemaker ticket. It exists everywhere in the cluster,
>> but
>> is granted or revoked by a script (resource agent) running on one
>> node.
>> I do not want that ticket to be ever touched without my explicit
>> command. I just allow to migrate the management point.
>>
>> So, from my PoV, term "migration" does not assume any start or stop
>> operations. And advisory ordering (which applies to simultaneous
>> start
>> or stop of two different resources) should not be honored because
>> only
>> one resource is actually starting/stopping. Do I miss something here?
>>
>> Best,
>> Vladislav
>>
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> 
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