Graduate sysctls to GA

[wgahnagl]

What type of PR is this?

/ kind feature

What this PR does / why we need it:

graduates sysctls to GA

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?

sysctls is now GA and locked to default

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

[KEP]: https://github.com/kubernetes/enhancements/tree/master/keps/sig-node/34-sysctl-fields#graduation  

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[k8s-ci-robot]

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[ehashman]

/kind feature
/sig node
/ok-to-test
/priority important-soon
/triage accepted

[ehashman]

/lgtm

/hold
I think I'm a feature approver now, want to give node a chance to take a look

/assign @derekwaynecarr

[ehashman]

/test pull-kubernetes-e2e-kind

[wgahnagl]

/retest

[ehashman]

This LGTM, the only real difference from #99263 is that PR removes the feature gates.

I don't understand why that wouldn't happen in the release where the feature gates actually get removed; otherwise, if for some reason we want to turn it back off the reverts would be very messy. What is the point of going through the step to lock the feature gate to true and not just remove it entirely if we're going to remove all the codepaths in advance of removal? cc @dims

[ehashman]

/lgtm

[pacoxu]

/lgtm
🎉 for your first PR

[pacoxu]

A small comment on PR description part, additional documentation for KEP link should be like https://github.com/kubernetes/kubernetes/blame/master/.github/PULL_REQUEST_TEMPLATE.md#L66

- [KEP]:  link

[mrunalp]

/approve

[ehashman]

/assign @liggitt

[liggitt]

/approve

for removal of locked GA feature gate checking in API helpers.

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ehashman, liggitt, mrunalp, pacoxu, wgahnagl

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

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Needs approval from an approver in each of these files:

• pkg/api/OWNERS [liggitt]
• pkg/features/OWNERS [ehashman,liggitt]
• pkg/kubelet/OWNERS [liggitt,mrunalp]

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[liggitt]

What is the point of going through the step to lock the feature gate to true and not just remove it entirely if we're going to remove all the codepaths in advance of removal?

Feature gates are user-visible in the CLI invocation. Locking to true at GA lets us simplify the code while giving deployments that opted into the feature early and are explicitly enabling it time to adjust their invocations to drop the explicit enable.

https://kubernetes.io/docs/reference/using-api/deprecation-policy/#deprecating-a-feature-or-behavior tried to describe this (but I acknowledge it is confusing):

Feature gates are intended to cover the development life cycle of a feature - they are not intended to be long-term APIs. As such, they are expected to be deprecated and removed after a feature becomes GA or is dropped.

As a feature moves through the stages, the associated feature gate evolves. The feature life cycle matched to its corresponding feature gate is:

• Alpha: the feature gate is disabled by default and can be enabled by the user.
• Beta: the feature gate is enabled by default and can be disabled by the user.
• GA: the feature gate is deprecated (see "Deprecation") and becomes non-operational.
• GA, deprecation window complete: the feature gate is removed and calls to it are no longer accepted.

[ehashman]

/hold cancel

Thanks @liggitt ! @dims also put together kubernetes/community#5545