Introduce apiserver_flowcontrol_current_executing_seats metric

[MikeSpreitzer]

This is a duplicate of
apiserver_flowcontrol_request_concurrency_in_use but with a better name. Hopefully we can later remove the copy with the inferior name.

What type of PR is this?

/kind cleanup

What this PR does / why we need it:

This PR introduces the apiserver_flowcontrol_current_executing_seats metric, as a duplicate of the apiserver_flowcontrol_request_concurrency_in_use metric --- because the latter has a confusing name and I hope to delete it later.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?

The metric `apiserver_flowcontrol_current_executing_seats` has been introduced as a duplicate of `apiserver_flowcontrol_request_concurrency_in_use` because the latter has a confusing name and will be removed in a later release.

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

[MikeSpreitzer]

/cc @wojtek-t
@tkashem
/uncc @yue9944882

[jiahuif]

/assign @wojtek-t
/triage accepted

[MikeSpreitzer]

/retest

[MikeSpreitzer]

/retest

[wojtek-t]

/assign @dgrisonnet - for the review from SIG instrucmentation POV

[wojtek-t]

This LGTM, but I would like @dgrisonnet to look to for newly introduced metric.

[dgrisonnet]

IMO the safest path forward here, is to:

1. Mark apiserver_flowcontrol_request_concurrency_in_use as deprecated in 1.28
2. Continue to set apiserver_flowcontrol_request_concurrency_in_use in 1.28 so that we don't break users right away and leave them one release to update
3. We remove apiserver_flowcontrol_request_concurrency_in_use in 1.29

[dgrisonnet]

So the only additional thing I would want in this PR is to set DeprecatedVersion to "1.28.0" on the metric.

[MikeSpreitzer]

The force-push to 65e818d adds that DeprecatedVersion: "1.28.0" suggested above by @dgrisonnet .

Since #118882 is also in flight, perhaps we should mark StabilityLevel: compbasemetrics.BETA on the apiserver_flowcontrol_current_executing_seats since this metric is equal to apiserver_flowcontrol_request_concurrency_in_use and that one was suggested for promotion to BETA but we plan to delete it in 1.29.

[wojtek-t]

Since #118882 is also in flight, perhaps we should mark StabilityLevel: compbasemetrics.BETA on the apiserver_flowcontrol_current_executing_seats since this metric is equal to apiserver_flowcontrol_request_concurrency_in_use and that one was suggested for promotion to BETA but we plan to delete it in 1.29.

Let's do that in a separate PR.

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: MikeSpreitzer, wojtek-t

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• staging/src/k8s.io/apiserver/pkg/util/flowcontrol/OWNERS [MikeSpreitzer,wojtek-t]

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[wojtek-t]

Actually - wait..

/lgtm cancel

[wojtek-t]

No.. it's fine.

/lgtm

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: a3f1628ab24f8f9d3bce0b015f9abbfadb649186