⚠️ Set MachinePool feature flag default to true + Beta

[mboersma]

What this PR does / why we need it:

Sets the default for EXP_MACHINE_POOL to true, so MachinePools are an "always on" feature (unless the user disables it).

This seems like the first step en route to moving MachinePools to beta status based on discussion at last week's community meeting, but please let me know if there are other prerequisites or details I've missed.

Which issue(s) this PR fixes:

Refs #9005

/area machinepool

[mboersma]

For some reason this change is preventing the "When following the Cluster API quick-start with ClusterClass" spec from deleting its cluster; it times out in AfterEach. I can reproduce this locally and I'll try to figure it out.

[sbueringer]

For some reason this change is preventing the "When following the Cluster API quick-start with ClusterClass" spec from deleting its cluster; it times out in AfterEach. I can reproduce this locally and I'll try to figure it out.

Sounds really strange. I think the feature flag was already enabled in all e2e tests (https://github.com/kubernetes-sigs/cluster-api/blob/main/test/e2e/config/docker.yaml#L263)

[fabriziopandini]

Modified the PR type so this change pops up in the release notes

[jackfrancis]

Any updates here?

[mboersma]

No updates, I was out for a week and have had other tasks. I'll dig into this again today.

It looks like a latent bug somewhere in the DockerMP controller, when ClusterClass is also enabled. I made one attempt to fix the code but it wasn't sufficient. We thought the feature flag was on in all the tests, but perhaps not.

[mboersma]

I'm clearly grasping at straws here, since I can't reproduce this locally (it always passes and cleanup doesn't error out).

One thing I noticed is this at the end of every containerd.log:

Mar 12 19:01:56.278779 q��������uick-start-ur0y9c-md-0-rqn8x-vlkx6-57shl containerd[128]: time="2024-03-12T19:01:56.278678475Z" level=error msg="failed to reload cni configuration after receiving fs change event(WRITE         \"/etc/cni/net.d/10-kindnet.conflist.temp\")" error="cni config load failed: no network config found in /etc/cni/net.d: cni plugin not initialized: failed to load cni config"
Mar 12 19:01:56.279274 quick-start-ur0y9c-md-0-rqn8x-vlkx6-57shl containerd[128]: time="2024-03-12T19:01:56.278842167Z" level=error msg="failed to reload cni configuration after receiving fs change event(WRITE         \"/etc/cni/net.d/10-kindnet.conflist.temp\")" error="cni config load failed: no network config found in /etc/cni/net.d: cni plugin not initialized: failed to load cni config"
Mar 12 19:01:56.279274 quick-start-ur0y9c-md-0-rqn8x-vlkx6-57shl containerd[128]: time="2024-03-12T19:01:56.278941917Z" level=error msg="failed to reload cni configuration after receiving fs change event(WRITE         \"/etc/cni/net.d/10-kindnet.conflist.temp\")" error="cni config load failed: no network config found in /etc/cni/net.d: cni plugin not initialized: failed to load cni config"

Edit: never mind, that seems to be true for passing PRs as well.

[sbueringer]

I'll take a closer look when I get around to it

[sbueringer]

I have no clue, but wondering if it should be changed to Beta

(but has nothing to do with the CI failure of course)

[neolit123]

+1 in core k8s features are defaulted to true in beta.

[mboersma]

Can we just change it to Beta here then?

The graduation criteria for MachinePools in its proposal are still "TBD," and MachinePool Machines have landed and seem stable, so I think this makes sense; I'll go ahead and do so and squash. But please let me know if there is anything else we should consider.

[sbueringer]

Sounds good to me. After a few years it's fair to call it beta :)

[sbueringer]

@mboersma Pushed a commit to also enable MachinePools in CAPD per default. But I don't think this causes the issue.

Based on the logs I can see that MachinePools is enabled in CAPD anyway (because we enable the feature gate via docker.yaml).

This should also mean that changing the manager.yaml's shouldn't be relevant

[mboersma]

Pushed a commit to also enable MachinePools in CAPD per default.

Thanks! I'm surprised I missed this... But I agree, it's probably not related.

My guess is that there's some race condition-type bug in deleting a Docker MachinePool this happens to trigger. Locally, I've run e2e many times but only seen a couple of these failures.

But clearly changing the MachinePool feature flag to true also changed some behavior, although we assumed it was already true everywhere.

[neolit123]

are we anticipating any users to complain "we don't want MP on by default" and if yes what would be their story?

[mboersma]

are we anticipating any users to complain "we don't want MP on by default" and if yes what would be their story?

I'm sure someone will object, and I understand from the point of view of "keep it simple." I don't think there's much cost to turning it on, especially if your clusters don't contain MachinePools. Changing the default here shouldn't be a breaking change (this PR notwithstanding 😛).

In terms of this change, they can still set EXP_MACHINE_POOL to false. That's annoying, but we went through the same evolution with ClusterResourceSet.

[sbueringer]

Last one from my side, otherwise lgtm: #10141 (comment)
Feel free to squash

I think it's fine to enable per default and also to eventually get rid of the feature flag in later releases.

I think if folks have a problem with an additional controller being enabled per default they can implement a webhook blocking creations of MachinePools (or of course while we still have the feature flag disable it)

[mboersma]

/retitle ⚠️ Set MachinePool feature flag default to true + Beta

[nawazkh]

/lgtm

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: 09879fd4885b2042d5eb6a2ed29ca2a9dff325d2

[sbueringer]

Last one

[sbueringer]

cc @mboersma ^^

[sbueringer]

Thx!

/lgtm

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: 6b7170d400000b57e047c959fc2e85c64f3704bb

[fabriziopandini]

/lgtm
/approve

@mboersma thanks for taking care of this!
When we will start thinking about GA, we should figure out how to move the code out of the exp folder, but that's not necessary for this step

[k8s-ci-robot]

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