[occm] Add Openstack server hostId as k8s node label

[chess-knight]

Is this a BUG REPORT or FEATURE REQUEST?:

/kind feature

What happened:
This issue follows a discussion in kubernetes-sigs/cluster-api-provider-openstack#1605, as a request to automatically label nodes with underlying hostId information, so e.g. workload can be scheduled on different physical hosts. It can be used as a topology differentiator when all other topology labels are the same.

Anything else we need to know?:
Issue kubernetes/cloud-provider#67 is closed and potentially resolved by kubernetes/kubernetes#123223 so now based on comment kubernetes/cloud-provider#67 (comment), AdditionalLabels with hostId information can be added to InstanceMetadata:

cloud-provider-openstack/pkg/openstack/instancesv2.go

Lines 136 to 142 in dab0f06

	return &cloudprovider.InstanceMetadata{
	ProviderID: i.makeInstanceID(&server.Server),
	InstanceType: instanceType,
	NodeAddresses: addresses,
	Zone: server.AvailabilityZone,
	Region: i.region,
	}, nil

This information should be available in the server struct AFAIK, so there should not be too much work I think now.

One potential issue that I see is live migration, e.g. see #1801, where occm will have to update the label because hostId will change.

Environment:

• openstack-cloud-controller-manager(or other related binary) version:
• OpenStack version:
• Others:

[dulek]

This seems like a valid request from my point of view. @mdbooth, what do you think?

@chess-knight: Are you planning to contribute implementation?

[dulek]

@gryf, @stephenfin: This sounds like a low hanging fruit you can grab to get up to speed with CPO code.

[zetaab]

is hostid really available to normal user in openstack? I do not have access now to openstack, but if I remember correctly normal user cannot see that?

[chess-knight]

According to our research in SovereignCloudStack/issues#540, hostId should be available for all users. You can see e.g. in the nova code, that it is supported from API version 2.62 https://opendev.org/openstack/nova/commit/c2f7d6585818c04e626aa4b6c292e5c2660cb8b3. hostId is different from host. The host is available only to admins but hostId is a hash of (project_id + host) so it can be available to all.

[zetaab]

actually I can see both hostId and host_id which has same value. Perhaps that label could be added if it exists. This can be added in https://github.com/kubernetes/cloud-provider-openstack/blob/master/pkg/openstack/instancesv2.go#L136-L142 as AdditionalLabels https://github.com/kubernetes/cloud-provider/blob/d2f5e75a5fd6d31f75b1519fe20879b1ab5347b8/cloud.go#L300