MachineDeployment history should also track in-place propagating changes

[ykakarap]

What would you like to be added (User Story)?

As a user I would like track changes to a MachineDeployment in the MD's history. Currently on changes that cause a rollout are captured in the history (as separate MachineSets). As a user I would like MachineDeployment to also track changes to in-place propagating fields.

Detailed Description

Changes to some of the in-place propagating fields could change the properties of the underlying nodes. Example: changes to MachineDeployment.Spec.Template.Lables could change the labels on the underlying nodes.

Therefore it would be nice to be able to capture these changes in MachineDeployment history so that as a user I can rollback to the previous state, using clusterctl alpha rollout undo if necessary.

Anything else you would like to add?

Additional context:

This will primarily benefit classic clusters. For classy clusters, it is not currently possible to rollback to a previous state using clusterctl as the MachineDeployment is managed by cluster topology.

Label(s) to be applied

/kind feature
One or more /area label. See https://github.com/kubernetes-sigs/cluster-api/labels?q=area for the list of labels.

[fabriziopandini]

/triage accepted
/help

[k8s-ci-robot]

@fabriziopandini:
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In response to this:

/triage accepted
/help

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[sbueringer]

I think we have to really balance if the additional complexity this would introduce in the MD/MS controller is justified by user demand. (Especially given that demand for clusterctl rollout seems to be not that great)

[vincepri]

The above might be a use case that’s better solved by external tools like gitops

[fabriziopandini]

/priority backlog