[openstack-dev] [nova] [placement] [operators] Optional resource asking or not?

Sylvain Bauza sbauza at redhat.com
Sun Jan 22 21:40:15 UTC 2017

Hey folks,

tl;dr: should we GET /resource_providers for only the related resources
that correspond to enabled filters ? Explanation below why even if I
know we have a current consensus, maybe we should discuss again about it.

I'm still trying to implement https://review.openstack.org/#/c/417961/
but when trying to get the functional job being +1, I discovered that we
have at least one functional test [1] asking for just the RAMFilter (and
not for VCPUs or disks).

Given the current PS is asking for *all* both CPU, RAM and disk, it's
trampling the current test by getting a NoValidHost.

Okay, I could just modify the test and make sure we have enough
resources for the flavors but I actually now wonder if that's all good
for our operators.

I know we have a consensus saying that we should still ask for both CPU,
RAM and disk at the same time, but I imagine our users coming back to us
saying "eh, look, I'm no longer able to create instances even if I'm not
using the CoreFilter" for example. It could be a bad day for them and
honestly, I'm not sure just adding documentation or release notes would
help them.

What are you thinking if we say that for only this cycle, we still try
to only ask for resources that are related to the enabled filters ?
For example, say someone is disabling CoreFilter in the conf opt, then
the scheduler shouldn't ask for VCPUs to the Placement API.

FWIW, we have another consensus about not removing
CoreFilter/RAMFilter/MemoryFilter because the CachingScheduler is still
using them (and not calling the Placement API).



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