This builds on the ProviderTree work in the compute driver and
resource tracker to take the supported capabilities from a driver and
turn those into standard traits on the compute node resource provider.
This is a simple way to expose in a REST API (Placement in this case)
what a compute node, via its driver, supports.
This is also something easy that we can do in lieu of a full-blown
compute capabilities REST API in nova, which we've talked about for
years but never actually done anything about.
We can later build on this to add a request filter which will mark
certain types of boot-from-volume requests as requiring specific
capabilities, like for volume multiattach and tagged devices.
Any traits provided by the driver will be automatically added during
startup or a periodic update of a compute node:
https://pasteboard.co/I3iqqNm.jpg
Similarly any traits later retracted by the driver will be
automatically removed.
However any traits associated with capabilities which are
inappropriately added to or removed from the resource provider by the
admin via the Placement API will not be reverted until the compute
service's provider cache is reset.
The new call graph is shown in this sequence diagram:
https://pasteboard.co/I25qICd.png
Co-Authored-By: Adam Spiers <aspiers@suse.com>
Related to blueprint placement-req-filter
Related to blueprint expose-host-capabilities
Change-Id: I15364d37fb7426f4eec00ca4eaf99bec50e964b6
7ce265ebc5
