Hey Nova-istas, While I was hacking on  I was considering how to approach the fact that we now need to track one more thing (NUMA node utilization) in our resources. I went with - "I'll add it to compute nodes table" thinking it's a fundamental enough property of a compute host that it deserves to be there, although I was considering Extensible Resource Tracker at one point (ERT from now on - see ) but looking at the code - it did not seem to provide anything I desperately needed, so I went with keeping it simple.
So fast-forward a few days, and I caught myself solving a problem that I kept thinking ERT should have solved - but apparently hasn't, and I think it is fundamentally a broken design without it - so I'd really like to see it re-visited. The problem can be described by the following lemma (if you take 'lemma' to mean 'a sentence I came up with just now' :)): """ Due to the way scheduling works in Nova (roughly: pick a host based on stale(ish) data, rely on claims to trigger a re-schedule), _same exact_ information that scheduling service used when making a placement decision, needs to be available to the compute service when testing the placement. """ This is not the case right now, and the ERT does not propose any way to solve it - (see how I hacked around needing to be able to get extra_specs when making claims in , without hammering the DB). The result will be that any resource that we add and needs user supplied info for scheduling an instance against it, will need a buggy re-implementation of gathering all the bits from the request that scheduler sees, to be able to work properly. This is obviously a bigger concern when we want to allow users to pass data (through image or flavor) that can affect scheduling, but still a huge concern IMHO. As I see that there are already BPs proposing to use this IMHO broken ERT ( for example), which will surely add to the proliferation of code that hacks around these design shortcomings in what is already a messy, but also crucial (for perf as well as features) bit of Nova code. I propose to revert  ASAP since it is still fresh, and see how we can come up with a cleaner design. Would like to hear opinions on this, before I propose the patch tho! Thanks all, Nikola  https://blueprints.launchpad.net/nova/+spec/virt-driver-numa-placement  https://review.openstack.org/#/c/109643/  https://review.openstack.org/#/c/111782/  https://review.openstack.org/#/c/89893 _______________________________________________ OpenStack-dev mailing list OpenStackemail@example.com http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev