allocation candidates db backend can handle traits but the HTTP front end is not turned on

[Chris Dent]

The code for /allocation_candidates is set up to be able to process a 'required' parameter alongside the 'resources' parameter. This results in a collection of RequestGroups which are used by the AllocationCandidates code in nova/objects/resource_provider.py

But we can't request traits on /allocation_candidates because the json schema does not allow the 'required' parameter.

Adding that results in a system that appears to work modulo at least one issue:

* AllocationCandidates._get_by_requests raised ValueError on an unknown trait. It should probably raise TraitNotFound, which should be caught in the allocation_candidates handler. (There's also a raw ValueError related to sharing providers).

Of course this doesn't address the nested situation, but that's in progress elsewhere.

I have some wip code that demonstrates making it work, others should feel free to leap on this though as I will be out of touch for the next 4 days.

[OpenStack Infra (hudson-openstack)]

Related fix proposed to branch: master
Review: https://review.openstack.org/534886

[OpenStack Infra (hudson-openstack)]

Change abandoned by Chris Dent (<email address hidden>) on branch: master
Review: https://review.openstack.org/534886
Reason: Alex is doing this properly at Change-Id: Id821b5b2768dcc698695ba6570c6201e1e9a8233

[Chris Dent (cdent)]

Apparently this was mostly expected, but not fully documented, so going to invalidate the bug.

https://review.openstack.org/#/c/535642/