Promote kubelet graceful node shutdown to beta

[bobbypage]

What type of PR is this?

/kind feature

What this PR does / why we need it:

Promoting kubelet graceful node shutdown to beta.

• Change the feature gate from alpha to beta and enable it by default
  • Update a few of the unit tests due to feature gate being enabled by default
• Small refactor in nodeshutdown_manager which adds featureEnabled function (which checks that feature gate and that kubeletConfig.ShutdownGracePeriod > 0).
  • Use featureEnabled() to exit early from shutdown manager in the case that the feature is disabled
• Update kubelet config defaulting to be explicit that ShutdownGracePeriod and ShutdownGracePeriodCriticalPods default to zero and update the godoc comments.

With this feature now in beta and the feature gate enabled by default, to enable graceful shutdown all that will be required is to configure ShutdownGracePeriod and ShutdownGracePeriodCriticalPods in the kubelet config. If not configured, they will be defaulted to zero, and graceful shutdown will effectively be disabled.

Which issue(s) this PR fixes:

Special notes for your reviewer:

Enhancement issue: kubernetes/enhancements#2000

Does this PR introduce a user-facing change?

Kubelet Graceful Node Shutdown feature is now beta. 

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

- [KEP]: https://github.com/kubernetes/enhancements/blob/master/keps/sig-node/2000-graceful-node-shutdown/README.md

[bobbypage]

/triage accepted
/sig node
/cc @SergeyKanzhelev @mrunalp @wzshiming

[bobbypage]

/hold

[SergeyKanzhelev]

/priority important-soon
/triage accepted
/lgtm

[pacoxu]

/retest
a kubectl timeout

[wzshiming]

/lgtm

[bobbypage]

/assign @thockin

for api review (there's a few small changes)

/assign @derekwaynecarr

for approvals

[derekwaynecarr]

thanks for following up from slack

/approve
/lgtm

[thockin]

I only looked at the apis part Seems OK

[thockin]

We're adding a new +featureGate=GracefulNodeShutdown tag - if you put it here, later tooling will use it automatically.

[bobbypage]

thanks, I can add that.

Should the featureGate=GracefulNodeShutdown tag be added here or in https://github.com/kubernetes/kubernetes/blob/master/staging/src/k8s.io/kubelet/config/v1beta1/types.go (where I see there's already existing tags like +optional)?

[thockin]

How is metav1.Duration{Duration: 0} different from zeroDuration ? They seem identical to me?

[bobbypage]

It should be the same, I just added it to be explicit that we actually want to the default value here (since all the existing kubelet config time duration fields compared against zeroDuration here and set the appropriate default).

So I think it can be dropped, but was thinking would be better to be explicit about the default. Let me know what you think.

[thockin]

The versioned files or both.

…

On Fri, Mar 5, 2021 at 3:01 PM David Porter ***@***.***> wrote: ***@***.**** commented on this pull request. ------------------------------ In pkg/kubelet/apis/config/types.go <#99735 (comment)> : > @@ -379,10 +379,10 @@ type KubeletConfiguration struct { // EnableSystemLogHandler enables /logs handler. EnableSystemLogHandler bool // ShutdownGracePeriod specifies the total duration that the node should delay the shutdown and total grace period for pod termination during a node shutdown. - // Defaults to 30 seconds, requires GracefulNodeShutdown feature gate to be enabled. + // Defaults to 0 seconds. thanks, I can add that. Should the featureGate=GracefulNodeShutdown tag be added here or in https://github.com/kubernetes/kubernetes/blob/master/staging/src/k8s.io/kubelet/config/v1beta1/types.go (where there's I see there's already existing tags like +optional)? — You are receiving this because you were assigned. Reply to this email directly, view it on GitHub <#99735 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABKWAVDJ6KWCQWDG7FL2EBDTCFPC5ANCNFSM4YSC7VCQ> .

[thockin]

It's just a smell to see `if x == 0 { x = 0 }` - like something went wrong and forgot to get updated. I'll approve - fix it or not at your leisure. /approve

…

On Fri, Mar 5, 2021 at 3:04 PM David Porter ***@***.***> wrote: ***@***.**** commented on this pull request. ------------------------------ In pkg/kubelet/apis/config/v1beta1/defaults.go <#99735 (comment)> : > @@ -252,4 +252,10 @@ func SetDefaults_KubeletConfiguration(obj *kubeletconfigv1beta1.KubeletConfigura if obj.EnableDebugFlagsHandler == nil { obj.EnableDebugFlagsHandler = utilpointer.BoolPtr(true) } + if obj.ShutdownGracePeriod == zeroDuration { + obj.ShutdownGracePeriod = metav1.Duration{Duration: 0} It should be the same, I just added it to be explicit that we actually want to the default value here (since all the existing kubelet config time duration fields compared against zeroDuration here and set the appropriate default). So I think it can be dropped, but was thinking would be better to be explicit about the default. — You are receiving this because you were assigned. Reply to this email directly, view it on GitHub <#99735 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABKWAVC6HATGZDDCL3GFTLLTCFPQNANCNFSM4YSC7VCQ> .

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: bobbypage, derekwaynecarr, mrunalp, thockin, wzshiming

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:

• pkg/features/OWNERS [derekwaynecarr,thockin]
• pkg/kubelet/OWNERS [derekwaynecarr,mrunalp,thockin]
• pkg/kubelet/apis/config/OWNERS [thockin]
• staging/src/k8s.io/kubelet/config/OWNERS [thockin]

Approvers can indicate their approval by writing /approve in a comment
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[bobbypage]

Updated PR by adding +featureGate=GracefulNodeShutdown tag and removal of the explicit time duration defaulting

[thockin]

/lgtm

[bobbypage]

thanks all!

/unhold

[fejta-bot]

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