🐛 Watch external objects for machine before deleting

[g-gaston]

What this PR does / why we need it:
This fixes a race condition in the machine controller when the controller is restarted after a machine has been marked for deletion but before the infra machine or bootstrap config are deleted. In that case, the controller doesn't have watches on those external objects, so the reconciliation is not triggered once they are deleted. This means that Machines stay in Deleting state for the resync period, the default is 10 minutes.

/area machine

[sbueringer]

Very nice! Just one finding

[sbueringer]

/assign @fabriziopandini @chrischdi

[sbueringer]

Thx!

/lgtm

/assign @fabriziopandini @vincepri @chrischdi

I think we should backport

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: cd62ed545b544f666be181291293817ebbcb8126

[chrischdi]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: chrischdi

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [chrischdi]

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

[g-gaston]

/cherry-pick release-1.6

[k8s-infra-cherrypick-robot]

@g-gaston: #10041 failed to apply on top of branch "release-1.6":

Applying: Watch external objects for machine before deleting
Using index info to reconstruct a base tree...
M	internal/controllers/machine/machine_controller.go
M	internal/controllers/machine/machine_controller_phases.go
M	internal/controllers/machine/machine_controller_test.go
Falling back to patching base and 3-way merge...
Auto-merging internal/controllers/machine/machine_controller_test.go
Auto-merging internal/controllers/machine/machine_controller_phases.go
CONFLICT (content): Merge conflict in internal/controllers/machine/machine_controller_phases.go
Auto-merging internal/controllers/machine/machine_controller.go
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
Patch failed at 0001 Watch external objects for machine before deleting
When you have resolved this problem, run "git am --continue".
If you prefer to skip this patch, run "git am --skip" instead.
To restore the original branch and stop patching, run "git am --abort".

In response to this:

/cherry-pick release-1.6

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.