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On Apr 12, 2019, at 12:02 PM, Pierre Riteau <pierre at stackhpc.com> wrote:
> 
> I am not sure how placement fits into this. If Ironic starts using
> placement for its allocation API, as it is mentioned in
> https://storyboard.openstack.org/#!/story/2004341, we would figure out
> a way for Blazar to put a hold on reservable nodes, so that users
> allocating directly with Ironic could only request from a
> non-reservable pool of nodes. Blazar would create Ironic allocation on
> behalf of users as described above. The question of allocation
> enforcement is also critical in this scenario.

As was mentioned earlier in this thread, placement does not have a concept of time, except for “right now”. In other words, you cannot say “allocate this resource to this consumer next Tuesday at 1400UTC, and then delete that allocation after 48 hours”.

At an earlier PTG (Dublin?) we spoke of different ways around this. One was creating an aggregate for Blazar-controlled resources, and then somehow forbidding other services from using those resources. Another was allocating the resources to Blazar so that no one else could use them, and then Blazar would use a two-step process (release the resource; allocate it to the consumer) when the actual usage begins. Neither is ideal, but they do get around the time-agnostic nature of placement.

-- Ed Leafe