nova/releasenotes/notes/placement-claims-844540aa7bf52b33.yaml
Jay Pipes 23c4eb3438 claim resources in placement API during schedule()
Adds logic to call the placement API's PUT /allocations/{consumer_uuid}
when selecting hosts in the filter scheduler's _schedule() method.

We only attempt the claim of resources if and only if the scheduler
driver uses allocation candidates (i.e. it isn't the caching scheduler)
and the conductor has passed in a list of instance UUIDs (otherwise,
there's no way to allocate in the placement API).

Change-Id: Ifc5cf482209e4f6f4e3e39b24389bd3563d86444
blueprint: placement-claims
2017-07-27 17:56:28 -07:00

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YAML

---
other:
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The filter scheduler will now attempt to claim a number of
resources in the placement API after determining a list of
potential hosts. We attempt to claim these resources for each instance
in the build request, and if a claim does not succeed, we try this
claim against the next potential host the scheduler selected. This
claim retry process can potentially attempt claims against a large
number of hosts, and we do not limit the number of hosts to attempt
claims against. Claims for resources may fail due to another scheduler
process concurrently claiming resources against the same compute node.
This concurrent resource claim is normal and the retry of a claim
request should be unusual but harmless.