[openstack-dev] [nova][placement][ironic] Progress on custom resource classes

Matt Riedemann mriedem at linux.vnet.ibm.com
Fri Dec 2 20:14:11 UTC 2016

On 12/2/2016 11:10 AM, Jay Pipes wrote:
> Ironic colleagues, heads up, please read the below fully! I'd like your
> feedback on a couple outstanding questions.
> tl;dr
> -----
> Work for custom resource classes has been proceeding well this cycle,
> and we're at a point where reviews from the Ironic community and
> functional testing of a series of patches would be extremely helpful.
> https://review.openstack.org/#/q/topic:bp/custom-resource-classes+status:open
> History
> -------
> As a brief reminder, in Newton, the Ironic community added a
> "resource_class" attribute to the primary Node object returned by the
> GET /nodes/{uuid} API call. This resource class attribute represents the
> "hardware profile" (for lack of a better term) of the Ironic baremetal
> node.
> In Nova-land, we would like to stop tracking Ironic baremetal nodes as
> collections of vCPU, RAM, and disk space -- because an Ironic baremetal
> node is consumed atomically, not piecemeal like a hypervisor node is.
> We'd like to have the scheduler search for an appropriate Ironic
> baremetal node using a simplified search that simply looks for node that
> has a particular hardware profile [1] instead of searching for nodes
> that have a certain amount of VCPU, RAM, and disk space.
> In addition to the scheduling and "boot request" alignment issues, we
> want to fix the reporting and account of resources in an OpenStack
> deployment containing Ironic. Currently, Nova reports an aggregate
> amount of CPU, RAM and disk space but doesn't understand that, when
> Ironic is in the mix, that a significant chunk of that CPU, RAM and disk
> isn't "targetable" for virtual machines. We would much prefer to have
> resource reporting look like:
>  48 vCPU total, 14 used
>  204800 MB RAM total, 10240 used
>  1340 GB disk total, 100 used
>  250 baremetal profile "A" total, 120 used
>  120 baremetal profile "B" total, 16 used
> instead of mixing all the resources together.
> Need review and functional testing on a few things
> --------------------------------------------------
> Now that the custom resource classes REST API endpoint is established
> [2] in the placement REST API, we are figuring out an appropriate way of
> migrating the existing inventory and allocation records for Ironic
> baremetal nodes from the "old-style" way of storing inventory for VCPU,
> MEMORY_MB and DISK_GB resources towards the "new-style" way of storing a
> single inventory record of amount 1 for the Ironic node's
> "resource_class" attribute.
> The patch that does this online data migration (from within the
> nova-compute resource tracker) is here:
> https://review.openstack.org/#/c/404472/
> I'd really like to get some Ironic contributor eyeballs on that patch
> and provide me feedback on whether the logic in the
> _cleanup_ironic_legacy_allocations() method is sound.
> There are still a couple things that need to be worked out:
> 1) Should the resource tracker auto-create custom resource classes in
> the placement REST API when it sees an Ironic node's resource_class
> attribute set to a non-NULL value and there is no record of such a
> resource class in the `GET /resource-classes` placement API call? My gut
> reaction to this is "yes, let's just do it", but I want to check with
> operators and Ironic devs first. The alternative is to ignore errors
> about "no such resource class exists", log a warning, and wait for an
> administrator to create the custom resource classes that match the
> distinct Ironic node resource classes that may exist in the deployment.

Seems to me that if you had to go to the work of setting the 
node.resource_class field in Ironic already, then Nova could be helpful 
and just auto-create the custom resource class to match that if it 
doesn't exist. That's one less manual step that operators need to deal 
with to start using this stuff, which seems like goodness.

> 2) How we are going to modify the Nova baremetal flavors to specify that
> the flavor requires one resource where the resource is of a set of
> custom resource classes? For example, let's say I'm have an Ironic
> installation with 10 different Ironic node hardware profiles. I've set
> all my Ironic node's resource_class attributes to match one of those
> hardware profiles. I now need to set up a Nova flavor that requests one
> of those ten hardware profiles. How do I do that? One solution might be
> to have a hacky flavor extra_spec called
> "ironic_resource_classes=CUSTOM_METAL_A,CUSTOM_METAL_B..."  or similar.
> When we construct the request_spec object that gets sent to the
> scheduler (and later the placement service), we could look for that
> extra_spec and construct a special request to the placement service that
> says "find me a resource provider that has a capacity of 1 for any of
> the following resource classes...". The flavor extra_specs thing is a
> total hack, admittedly, but flavors are the current mess that Nova has
> to specify requested resources and we need to work within that mess
> unfortunately...
> The following patch series:
> https://review.openstack.org/#/q/topic:bp/custom-resource-classes+status:open
> contains all the outstanding patches for the custom resource classes
> work. Getting more eyeballs on these patches would be super. If you are
> an Ironic operator that has some time to play with the new code and
> offer feedback and testing, that would be super awesome. Please come
> find me, cdent, bauzas, dansmith, mriedem, edleafe and others on IRC to
> chat, or feel free to email this message back.
> Thanks in advance,
> -jay
> [1] Or set of related hardware profiles.
> [2] https://review.openstack.org/#/c/391959/
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Matt Riedemann

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