Add K8s Docker runtime support deprecation release note

[bmelbourne]

What this PR does / why we need it:
As Kubernetes will deprecate Docker runtime support from version 1.20 and will be removed in a future release (currently planned for the 1.22 release in late 2021), notify users that the default container runtime will be set to containerd from kOps 1.20.

https://github.com/kubernetes/kubernetes/tree/master/CHANGELOG/CHANGELOG-1.20.md#deprecation

Which issue(s) this PR fixes
#10356

Special notes for your reviewer:
PR #10370 raised to set default container runtime to containerd in kOps 1.20.

[k8s-ci-robot]

Hi @bmelbourne. Thanks for your PR.

I'm waiting for a kubernetes member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[bmelbourne]

/assign @geojaz

[olemarkus]

Any reason not to do this as part of #10370 ?

Also, I think we should follow the k8s deprecation here. Meaning that kOps will still use docker as default prior to k8s 1.20.

[bmelbourne]

Any reason not to do this as part of #10370 ?

Also, I think we should follow the k8s deprecation here. Meaning that kOps will still use docker as default prior to k8s 1.20.

That's essentially the purpose of this deprecation release note (once merged in KOps 1.19)...we'll be notifying users that containerd will become the default container runtime from kOps 1.20 (as covered in #10370).

[olemarkus]

Ah, it is for the 1.19 notes.

/cc @hakman

[geojaz]

@bmelbourne Thanks! This lgtm, but I think it could use just a quick iteration.

I think we should call out that kOps won't do anything (automatically) to existing clusters running on Docker. And as long you're iterating, I would prefer the note to be something like:
As of kOps 1.20, new clusters will default to use containerd instead of Docker. Existing clusters can define their upgrade path manually. This change in default behavior is in line with the upstream deprecation of Docker in K8s 1.20.

I like this because it calls out the action item clearly at the beginning and leaves the explanation and further details for those who are interested. Also, this way, we're not trying to predict the future and possibly having to fix later :)

[k8s-ci-robot]

@bmelbourne: Cannot trigger testing until a trusted user reviews the PR and leaves an /ok-to-test message.

In response to this:

/retest

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[moshevayner]

/ok-to-test

[moshevayner]

/retest

[moshevayner]

Hey @bmelbourne
It looks like the CI/verify test is still failing, complains that it needs you to run make apimachinery.
My guess is that since your branch is 27 days old, it might've been forked off one with failing tests? 🤷🏼‍♂️
Either way, I could suggest that you try and pull master into your branch and see if it helps, or alternatively run make apimachinery, even though I'm not sure why would a release notes change cause that to fail.

[rifelpet]

The failing test is due to https://github.com/kubernetes/kops/issues I'd like to address that once and for all rather than punting this to next year. I'm hoping we can get that fixed soon so I wouldn't worry about the failing test for now

[geojaz]

/label retest-not-required-docs-only

[k8s-ci-robot]

@geojaz: The label(s) /label retest-not-required-docs-only cannot be applied. These labels are supported: api-review, community/discussion, community/maintenance, community/question, cuj/build-train-deploy, cuj/multi-user, platform/aws, platform/azure, platform/gcp, platform/minikube, platform/other, tide/merge-method-merge, tide/merge-method-rebase, tide/merge-method-squash

In response to this:

/label retest-not-required-docs-only

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[geojaz]

/retest

[geojaz]

@bmelbourne I think the other stuff is ready now so we can do one last rebase and make apimachinery :)

[olemarkus]

/lgtm

[hakman]

/hold pending decision in today's Office Hours call

[hakman]

Considering that most periodic tests are passing using containerd, we decided in yesterday's Office Hours to go ahead with the deprecation as described here. Thanks @bmelbourne, I will look at the other PR that changes the default later this week.
/hold cancel
/lgtm
/approve

[geojaz]

/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: bmelbourne, geojaz, hakman

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