Add flagz endpoint for apiserver

[richabanker]

What type of PR is this?

/kind feature

What this PR does / why we need it:

Adds a /flagz endpoint for kube-apiserver

Which issue(s) this PR fixes:

kubernetes/enhancements#4828

Special notes for your reviewer:

Does this PR introduce a user-facing change?

Adds a /flagz endpoint for kube-apiserver endpoint

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

• KEP : https://github.com/kubernetes/enhancements/blob/master/keps/sig-instrumentation/4828-component-flagz/README.md

Snippet of response returned by

curl -k --cert /etc/kubernetes/pki/apiserver-kubelet-client.crt --key /etc/kubernetes/pki/apiserver-kubelet-client.key https://localhost:6443/flagz

kube-apiserver flags
Warning: This endpoint is not meant to be machine parseable, has no formatting compatibility guarantees and is for debugging purposes only.

advertise-address=192.168.8.2
contention-profiling=false
enable-priority-and-fairness=true
profiling=true
authorization-mode=[Node,RBAC]
authorization-webhook-cache-authorized-ttl=5m0s
authorization-webhook-cache-unauthorized-ttl=30s
authorization-webhook-version=v1beta1
default-watch-cache-size=100
delete-collection-workers=1
enable-garbage-collector=true
encryption-provider-config-automatic-reload=false
etcd-cafile=/etc/kubernetes/pki/etcd/ca.crt
etcd-certfile=/etc/kubernetes/pki/apiserver-etcd-client.crt
etcd-compaction-interval=5m0s
etcd-count-metric-poll-period=1m0s
etcd-db-metric-poll-interval=30s
etcd-healthcheck-timeout=2s
etcd-keyfile=/etc/kubernetes/pki/apiserver-etcd-client.key
etcd-prefix=/registry
etcd-readycheck-timeout=2s
etcd-servers=[https://127.0.0.1:2379]
lease-reuse-duration-seconds=60
storage-media-type=application/vnd.kubernetes.protobuf
watch-cache=true

[richabanker]

/remove-sig cli
/remove-sig network
/remove-sig node

/remove-area kubelet
/remove-area kube-proxy
/remove-area kubectl

[sttts]

It's very likely o.OIDC.areFlagsConfigured. That func is bound to the fs argument of the AddFlags method. And because this PR calls opts.Flags() another time, areFlagsConfigured is wrong. So it is not this PR that is wrong, but it just uncovers the hack in AddFlags, mutating the receiver, which is should not do.

[richabanker]

It's very likely o.OIDC.areFlagsConfigured. That func is bound to the fs argument of the AddFlags method. And because this PR calls opts.Flags() another time, areFlagsConfigured is wrong. So it is not this PR that is wrong, but it just uncovers the hack in AddFlags, mutating the receiver, which is should not do.

Created #128674 for a partial fix for the OIDC flags. With this, the TestOIDC test was passing with the flagz changes.

[liggitt]

/approve

[richabanker]

/test pull-kubernetes-integration

[dgrisonnet]

/lgtm

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: 6e30f852399771f58bb2d52a175af52a481e9759

[richabanker]

/hold
until #125577 merges

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: dgrisonnet, liggitt, richabanker, sttts

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• cmd/kube-apiserver/OWNERS [liggitt,sttts]
• pkg/controlplane/OWNERS [liggitt,sttts]
• pkg/features/OWNERS [dgrisonnet,liggitt,sttts]
• plugin/pkg/auth/authorizer/OWNERS [liggitt]
• staging/src/k8s.io/apiserver/OWNERS [liggitt,sttts]
• staging/src/k8s.io/component-base/zpages/OWNERS [dgrisonnet,liggitt]
• test/featuregates_linter/test_data/OWNERS [dgrisonnet,liggitt,sttts]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[dgrisonnet]

/lgtm

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: aae9d3dcdd951de2a40b516d01d8c7621e5c6f2c

[richabanker]

/unhold
since #125577 is now merged

[wendy-ha18]

Hi @richabanker @dgrisonnet
Appreciate all of your efforts with this PR!!
A gentle reminder that the code freeze has started 02:00 UTC Friday November 8th 2024 . Please make sure this has both lgtm and approved labels ASAP, and file an Exception.

[richabanker]

@wendy-ha18 lgtm label was added an hour ago, and the approve tag was added much before. Do I still need to file an exception?

[wendy-ha18]

Hi @richabanker, IOM no you don't need to file Exception. I saw this PR in merging queue are now with a milestone. PR can be merged with milestone after code freeze.