Add proposal for Node OS image caching

[bennycortese]

What type of PR is this?

/kind feature

What this PR does / why we need it:
This PR adds a proposal for a Node OS image caching feature which would be integrated into CAPZ. We need it because it will help security regulations, speed up horizontal scaling and allow users to have pods running faster on new nodes.

Which issue(s) this PR fixes
Fixes #3607

Special notes for your reviewer:

• cherry-pick candidate

TODOs:

• squashed commits
• includes documentation
• adds unit tests

Release note:

Proposal for Node OS image caching feature

[k8s-ci-robot]

Welcome @bennycortese!

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[k8s-ci-robot]

Hi @bennycortese. Thanks for your PR.

I'm waiting for a kubernetes-sigs 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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[mboersma]

/ok-to-test

[nojnhuh]

This is a great start! I think there are a few finer details we should get into a bit more but the overall approach looks good!

[nojnhuh]

(reminder to squash after approval)
/hold

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: +1.51% 🎉

Comparison is base (3684845) 53.25% compared to head (dd44f25) 54.77%.
Report is 188 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3624      +/-   ##
==========================================
+ Coverage   53.25%   54.77%   +1.51%     
==========================================
  Files         185      187       +2     
  Lines       18432    19098     +666     
==========================================
+ Hits         9816    10460     +644     
+ Misses       8074     8070       -4     
- Partials      542      568      +26     

see 46 files with indirect coverage changes

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[willie-yao]

Thanks for all your great work on this @bennycortese! I think it could be helpful to retitle this PR as "Add proposal for node OS image caching" as it is not implementing the feature yet. This can also be added to the release notes in the PR description.

[k8s-ci-robot]

@bennycortese: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-cluster-api-provider-azure-e2e-aks	f979896	link	true	/test pull-cluster-api-provider-azure-e2e-aks
pull-cluster-api-provider-azure-ci-entrypoint	f979896	link	true	/test pull-cluster-api-provider-azure-ci-entrypoint
pull-cluster-api-provider-azure-conformance	f979896	link	false	/test pull-cluster-api-provider-azure-conformance
pull-cluster-api-provider-azure-e2e	f979896	link	true	/test pull-cluster-api-provider-azure-e2e
pull-cluster-api-provider-azure-windows-containerd-upstream-with-ci-artifacts	f979896	link	false	/test pull-cluster-api-provider-azure-windows-containerd-upstream-with-ci-artifacts
pull-cluster-api-provider-azure-conformance-with-ci-artifacts	f979896	link	false	/test pull-cluster-api-provider-azure-conformance-with-ci-artifacts
pull-cluster-api-provider-azure-capi-e2e	f979896	link	false	/test pull-cluster-api-provider-azure-capi-e2e

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository. I understand the commands that are listed here.

[nojnhuh]

The link checker doesn't seem to like https://azure.microsoft.com links, so you might need to ignore those explicitly like this:

cluster-api-provider-azure/docs/book/src/topics/getting-started.md

Lines 7 to 8 in 8893daa

	<!-- markdown-link-check-disable-next-line -->
	- A [Microsoft Azure account](https://azure.microsoft.com/)

[nojnhuh]

/lgtm
/assign @CecileRobertMichon

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: 4faabdf74fcad5f855c1c77ecfa0119b12b75bf4

[willie-yao]

/lgtm

Great work Benny!

[CecileRobertMichon]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: CecileRobertMichon

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Needs approval from an approver in each of these files:

• OWNERS [CecileRobertMichon]

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

[nojnhuh]

@CecileRobertMichon Do we need to keep the hold on this for consensus? I'd originally put the hold on this as a reminder to squash but that all looks good.

[CecileRobertMichon]

/hold cancel

The only person who is listed as reviewer who hasn't lgtm'ed is @jackfrancis and he is on leave so we're good to merge this