[WIP] ✨ Add MachinePool Machines implementation

[mboersma]

What this PR does / why we need it:

Implements the MachinePool Machines proposal in CAPI and for the Docker provider. This should be considered a POC and is intended to help illuminate the proposal and any shortcomings or issues it may have.

Which issue(s) this PR fixes:

Fixes #4063

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[k8s-ci-robot]

@mboersma: PR needs rebase.

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[k8s-ci-robot]

@mboersma: 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-e2e-informing-ipv6-main	d64fec0	link	false	/test pull-cluster-api-e2e-informing-ipv6-main
pull-cluster-api-build-main	d64fec0	link	true	/test pull-cluster-api-build-main
pull-cluster-api-test-main	d64fec0	link	true	/test pull-cluster-api-test-main
pull-cluster-api-apidiff-main	d64fec0	link	false	/test pull-cluster-api-apidiff-main
pull-cluster-api-e2e-informing-main	d64fec0	link	false	/test pull-cluster-api-e2e-informing-main
pull-cluster-api-verify-main	d64fec0	link	true	/test pull-cluster-api-verify-main
pull-cluster-api-e2e-main	d64fec0	link	true	/test pull-cluster-api-e2e-main
pull-cluster-api-test-mink8s-main	d64fec0	link	true	/test pull-cluster-api-test-mink8s-main

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.

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[k8s-triage-robot]

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/lifecycle stale

[killianmuldoon]

/remove-lifecycle stale

[OmkarDeshpande7]

Hi, @mboersma @Jont828 thanks for your efforts on this PR, much awaited changes indeed.
Just curious about the estimated timeline here. Thank you in advance.

[mboersma]

Hi @OmkarDeshpande7, sorry for my late reponse (I was on vacation).

This PR will be closed soon in favor of a new one that follows the finalized proposal. I've been reimplementing this in a different way, reusing the existing DockerMachine resources instead of creating a parallel DockerMachinePoolMachine resource.

I'm getting there but it's been slow, apologies for the wait. I'll tag you in the new PR when it's out there. I was going to wait until then to close this, but if it's causing confusion feel free to close it now, it's just a reference POC for a previous version of the proposal.

[k8s-triage-robot]

The Kubernetes project currently lacks enough contributors to adequately respond to all issues and PRs.

This bot triages issues and PRs according to the following rules:

• After 90d of inactivity, lifecycle/stale is applied
• After 30d of inactivity since lifecycle/stale was applied, lifecycle/rotten is applied
• After 30d of inactivity since lifecycle/rotten was applied, the issue is closed

You can:

• Mark this issue or PR as fresh with /remove-lifecycle stale
• Mark this issue or PR as rotten with /lifecycle rotten
• Close this issue or PR with /close
• Offer to help out with Issue Triage

Please send feedback to sig-contributor-experience at kubernetes/community.

/lifecycle stale

[anmolsachan]

Hey @mboersma, Thank you for working on this as this is a really important and big change. A lot of things depend on it like kubernetes/autoscaler#4676.

Was there a replacement PR for this?
Also, do you have any timelines for this and the autoscalar support work? I and my team will be happy to help out on this if you need any help here.

[OmkarDeshpande7]

/remove-lifecycle stale

[dtzar]

@mboersma - Can you please post a link to anything which references the "favor of a new one that follows the finalized proposal."?

[Jont828]

@dtzar AFAIK, this is the latest version of the machinepool machines proposal that I'm going off of.

[mboersma]

Closing in favor of #7938.