✨ Add scale subresource logic to fake client #2855

TheSpiritXIII · 2024-06-17T14:56:59Z

Adds basic GET/UPDATE support to the scale sub-resource according to the docs: https://pkg.go.dev/sigs.k8s.io/controller-runtime/pkg/client#SubResourceClientConstructor

k8s-ci-robot · 2024-06-17T14:57:08Z

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troy0820 · 2024-06-17T16:01:42Z

pkg/client/fake/client.go

+func applyScale(obj client.Object, scale *autoscalingv1.Scale) error {
+	switch obj := obj.(type) {
+	case *appsv1.Deployment:
+		obj.Spec.Replicas = &scale.Spec.Replicas
+	case *appsv1.ReplicaSet:
+		obj.Spec.Replicas = &scale.Spec.Replicas
+	case *corev1.ReplicationController:
+		obj.Spec.Replicas = &scale.Spec.Replicas
+	case *appsv1.StatefulSet:
+		obj.Spec.Replicas = &scale.Spec.Replicas
+	default:
+		// TODO: CRDs https://kubernetes.io/docs/tasks/extend-kubernetes/custom-resources/custom-resource-definitions/#scale-subresource
+		return fmt.Errorf("unable to extract scale from type %T", obj)
+	}
+	return nil
+}


Wouldn't this not allow people who make CRs who wish to use the sub resource scale be limited to only allow the types in the case statement available?

Correct. This would be more work: we'd have to look-up the custom resource definition to get the scale replica field path. I propose we leave this for a future PR, since it also means writing more unit tests and I'm not sure I have bandwidth.

troy0820 · 2024-06-17T16:03:55Z

pkg/client/fake/client.go

+	switch sw.subResource {
+	case "scale":
+		scale, isScale := subResource.(*autoscalingv1.Scale)
+		if !isScale {
+			return apierrors.NewBadRequest(fmt.Sprintf("got invalid type %t, expected Scale", subResource))
+		}
+		if err := sw.client.Get(ctx, client.ObjectKeyFromObject(obj), obj); err != nil {
+			return err
+		}
+		scaleOut, err := extractScale(obj)
+		if err != nil {
+			return err
+		}
+		*scale = scaleOut
+		return nil
+	default:
+		return fmt.Errorf("fakeSubResourceClient does not support get for %s", sw.subResource)
+	}


Having to use the subresource client to then use the actual client seems like we wouldn't need the sub resource client to do the GET. The value of the scale is indicative on the spec and the subresource client has to get that value from the actual client where it's derived.

This is implemented on the server-side as far as I know. I cannot just lookup on the client because the fake client doesn't know how to extract this information. It's something of a meta-resource.

Fair and not criticizing the implementation but asking because you need to deal with this the way you are dealing with it.

alvaroaleman

Thanks a lot for looking into this, really appreciated! Few comments, we need to make really sure we behave the same way as the KAS does everywhere, because as soon as we release this, some ppl will start depending on whatever behavior it exhibits which might cause tests to incorrectly pass if this doesn't exactly match the kube apiserver behavior.

pkg/client/fake/client.go

alvaroaleman · 2024-06-18T14:48:24Z

pkg/client/fake/client.go

+		}
+		scale, isScale := updateOptions.SubResourceBody.(*autoscalingv1.Scale)
+		if !isScale {
+			return apierrors.NewBadRequest(fmt.Sprintf("got invalid type %t, expected Scale", updateOptions.SubResourceBody))


Is this the behavior of the KAS, to first complain with a bad request about the request body before checking if the main resource even exists? Please look it up and add a reference link to the relevant code in the KAS as comment.

I was unable to find it; am I looking at the right place? https://github.com/search?q=repo%3Akubernetes%2Fapiserver+scale+-path%3Atest&type=code

Nonetheless, I was able to reproduce it with client.Client.Get and your intuition is correct: it looks up the object first! Great catch.

I think the upstream code is here: https://github.com/kubernetes/kubernetes/blob/fb6bbc9781d11a87688c398778525c4e1dcb0f08/pkg/registry/apps/deployment/storage/storage.go#L320

Not exactly a quick read though it seems.

alvaroaleman · 2024-06-18T14:49:15Z

pkg/client/fake/client.go

+
+func extractScale(obj client.Object) (autoscalingv1.Scale, error) {
+	switch obj := obj.(type) {
+	case *appsv1.Deployment:


Is go smart enough to allow expression this in a single switch case:

Suggested change

case *appsv1.Deployment:

case *appsv1.Deployment, *appsv1.ReplicaSet:

No, sadly :/

pkg/client/fake/client.go

alvaroaleman · 2024-06-24T03:37:30Z

Will try to give this a proper review this week, sorry for the delay.
/ok-to-test

TheSpiritXIII · 2024-07-01T17:48:55Z

/retest

k8s-ci-robot added the cncf-cla: yes Indicates the PR's author has signed the CNCF CLA. label Jun 17, 2024

k8s-ci-robot added the needs-ok-to-test Indicates a PR that requires an org member to verify it is safe to test. label Jun 17, 2024

k8s-ci-robot requested review from alvaroaleman and FillZpp June 17, 2024 14:57

k8s-ci-robot added the size/L Denotes a PR that changes 100-499 lines, ignoring generated files. label Jun 17, 2024

troy0820 reviewed Jun 17, 2024

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alvaroaleman reviewed Jun 18, 2024

View reviewed changes

TheSpiritXIII force-pushed the fake-scale-subresource branch from 9d4522d to 1dc0cb5 Compare June 18, 2024 19:24

TheSpiritXIII requested a review from alvaroaleman June 18, 2024 20:49

k8s-ci-robot added ok-to-test Indicates a non-member PR verified by an org member that is safe to test. and removed needs-ok-to-test Indicates a PR that requires an org member to verify it is safe to test. labels Jun 24, 2024

Add scale subresource logic to fake client

65442bb

TheSpiritXIII force-pushed the fake-scale-subresource branch from 1dc0cb5 to 65442bb Compare July 1, 2024 17:44

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✨ Add scale subresource logic to fake client #2855

✨ Add scale subresource logic to fake client #2855

TheSpiritXIII commented Jun 17, 2024

k8s-ci-robot commented Jun 17, 2024

k8s-ci-robot commented Jun 17, 2024

k8s-ci-robot commented Jun 17, 2024

troy0820 Jun 17, 2024

TheSpiritXIII Jun 18, 2024

troy0820 Jun 17, 2024

TheSpiritXIII Jun 18, 2024

troy0820 Jun 18, 2024

alvaroaleman left a comment

alvaroaleman Jun 18, 2024 •

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TheSpiritXIII Jun 18, 2024

alvaroaleman Jun 24, 2024

alvaroaleman Jun 18, 2024

TheSpiritXIII Jun 18, 2024

alvaroaleman commented Jun 24, 2024

TheSpiritXIII commented Jul 1, 2024

	case *appsv1.Deployment:
	case appsv1.Deployment, appsv1.ReplicaSet:

✨ Add scale subresource logic to fake client #2855

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✨ Add scale subresource logic to fake client #2855

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TheSpiritXIII commented Jun 17, 2024

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alvaroaleman Jun 18, 2024 •

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