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Fix: Use Patch instead of Update to add/remove finalizers #1801

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@Baarsgaard Baarsgaard commented Dec 18, 2024

Managed to solve the perpetual drift noted in #1776 that is rooted in us applying finalizers and updating unintended fields on CRs.

I first attempted to use JSONPatch, but I could not for the life of me get the libraries to comply, despite handcrafting a working patches with kubectl.
MergePatch worked immediately.

Currently, the implementation is hardcoded to only support arrays of one finalizer. More work can be done to make this support multiple if the need ever arises.

@Baarsgaard Baarsgaard marked this pull request as ready for review December 18, 2024 11:45
@Baarsgaard Baarsgaard force-pushed the fix_finalizer_cfg_drift branch from 172cf54 to 1fa382c Compare December 20, 2024 23:49
@Baarsgaard Baarsgaard changed the title Refactor(Internal): Use Patch instead of Update to set/remove finalizers Fix: Use Patch instead of Update to add/remove finalizers Dec 20, 2024
// Remove finalizer through a MergePatch
// Avoids updating the entire object and only changes the finalizers
func removeFinalizer(ctx context.Context, cl client.Client, cr client.Object) error {
patch := []byte(`{"metadata":{"finalizers":null}}`)
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@weisdd weisdd Dec 21, 2024

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Although it's nice that you can fix the drift with these changes, I would disagree with the way how patches are formed. - Kubernetes objects may have multiple finalizers, whereas, in this PR, there is an assumption that there will always be a single finalizer (owned by the grafana-operator). - Some users might have their own finalizers (think of custom operators).

Since controllerutil has two functions that safely add (AddFinalizer) / remove (RemoveFinalizer ) a particular finalizer, you can, for instance, have them modify finalizers in a CR object and then prepare a patch by copying value from metadata.finalizers.

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@Baarsgaard Baarsgaard Dec 21, 2024

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Sure, I'll try and whip up a solution that safely patches the finalizers.

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