KEP-1748: update to stable

[dgrisonnet]

• One-line PR description:

This PR update the state of KEP-1748 to stable and set the milestone to 1.27.

We won't be able to update the status of the KEP to implemented until metrics are updated to Stable, but they first need to be BETA.

• Issue link: Expose metrics about resource requests and limits that represent the pod model #1748

• Other comments:

The graduation criteria from BETA to GA is:

Stability over two releases demonstrating cardinality is reasonable and the metrics remain valuable

The metrics have been in Kubernetes since 1.20 so although there are not exposed on the main kube-scheduler endpoint, they've been around for 7 releases already. During that period of time no cardinality explosion has been reported and the metrics are starting to be more widely used:

• Recommend kube-scheduler's metrics kube-state-metrics#1849
• Prefer kube-scheduler's resource metrics to kube-state-metrics' kubernetes-monitoring/kubernetes-mixin#815

Unit tests for the test plan have been added in kubernetes/kubernetes#94866.

[dashpole]

/lgtm

[logicalhan]

/assign

[logicalhan]

We should promote the scheduler metrics to BETA stability level as a part of graduation of this KEP to stable status, since we're presuming a certain API stability once this feature is stable.

[logicalhan]

/cc @johnbelamaric

[johnbelamaric]

Can you answer the new question as well, please? The question is written from the point of view of a node, but I suppose the same question would apply to the control plane node on which the scheduler runs.

https://github.com/kubernetes/enhancements/tree/master/keps/NNNN-kep-template#can-enabling--using-this-feature-result-in-resource-exhaustion-of-some-node-resources-pids-sockets-inodes-etc

[dgrisonnet]

I answered the new PRR questions and updated kubernetes/kubernetes#115454 to graduate the metrics to BETA.

[johnbelamaric]

/approve

[dgrisonnet]

@dashpole could you please have another look?

[dashpole]

/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

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