On 06/02/2015 07:25 PM, Chris Friesen wrote:
On 06/02/2015 02:36 PM, Andrew Laski wrote:
There used to be a project that I think was looking for an API like
this to
provide a reservation system, Climate or Blazar or something. There
was brief
talk of providing something like it for that use case, but the idea
was put on
the backburner to wait for the scheduling rework that's occurring.
The question in my mind is should the claim requests be in the Nova
API or come
from a scheduler API. And I tend to think that they should come from a
scheduler API.
Who owns the resources, nova or the scheduler?
In many cases only nova-compute can resolve races (resource tracking of
specific CPU cores, specific PCI devices, etc. in the face of parallel
scheduling) so unless we're going to guarantee no races then I think
claim requests should be a nova API call, and it should go all the way
down to nova-compute to make sure that the resources are actually claimed.
That's actually how the system works today. And, IMHO, it's inefficient.
The nova-compute node should be the final arbiter of whether a request
for resources can be properly fulfilled by the hypervisor, however, the
scheduler should be the thing that "owns" resource usage records for the
partition of resource providers that the scheduler process is
responsible for.
I think the claim IDs should be returned from the scheduler API instead
of created within the nova-compute manager.
Best,
-jay
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