Incrementing EndpointSlice generation when labels change

[robscott]

What type of PR is this?

/kind cleanup

What this PR does / why we need it:

EndpointSlice labels can be quite meaningful. They are used to indicate the controller they are managed by and the Service they are associated with. Changing these labels can have significant effects on how the EndpointSlice is consumed so incrementing generation seems appropriate.

Special notes for your reviewer:

This is especially relevant to #99345 where we updated the EndpointSlice controller to track EndpointSlice generations. This change to strategy was suggested by @wojtek-t in #99345 (comment).

Does this PR introduce a user-facing change?

EndpointSlice generation is now incremented when labels change.

/sig network
/triage accepted
/priority important-soon
/cc @wojtek-t @aojea
/assign @liggitt

[wojtek-t]

I was actually suggesting going even step further and adding:

else {
  ogNewMeta.Generation = og.OldMeta.Generation
}

But I would like to hear Jordan`s opinion (if that doesn't violate some conventions, backward compatibility, etc.)

[liggitt]

rest.BeforeUpdate already resets generation to the current value before calling strategy.PrepareForUpdate:

kubernetes/staging/src/k8s.io/apiserver/pkg/registry/rest/update.go

Lines 105 to 113 in c8fe1d9

	objectMeta.SetGeneration(oldMeta.GetGeneration())
	// Ensure managedFields state is removed unless ServerSideApply is enabled
	if !utilfeature.DefaultFeatureGate.Enabled(features.ServerSideApply) {
	oldMeta.SetManagedFields(nil)
	objectMeta.SetManagedFields(nil)
	}
	strategy.PrepareForUpdate(ctx, obj, old)

[wojtek-t]

Good point - I missed that thanks.

[liggitt]

there's precedent from deployments for considering specific fields outside spec in computing generation:

kubernetes/pkg/registry/apps/deployment/strategy.go

Lines 106 to 109 in c8fe1d9

	if !apiequality.Semantic.DeepEqual(newDeployment.Spec, oldDeployment.Spec) ||
	!apiequality.Semantic.DeepEqual(newDeployment.Annotations, oldDeployment.Annotations) {
	newDeployment.Generation = oldDeployment.Generation + 1
	}

this seems reasonable to me, but will defer final ack to @thockin who has more context on the endpointslice API bits

/unassign
/assign @thockin

[thockin]

Thanks!

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: robscott, thockin

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[wojtek-t]

For posterity - LGTM too.