Unnecessary updates to statefulset, etc. issued by notebook-controller when nothing is actually changed

[jiridanek]

• What is the proper way to compare resource object? kubernetes-sigs/kubebuilder#592

This describes several approaches how to do comparisons. Our problem is that we use

kubeflow/components/common/reconcilehelper/util.go

Lines 128 to 130 in 5b2857f

	if !reflect.DeepEqual(to.Spec.Template.Spec, from.Spec.Template.Spec) {
	requireUpdate = true
	}

and that's the dumbest option of them all. They have multiple other alternatives which can be explored. We probably should not do this on our fork, if this is ever touched it should be in upstream kubeflow.

edit2: kubeflow is aware,

• Notebooks 2.0 // Controller // Replace reflect.DeepEqual with equality.Semantic.DeepEqual kubeflow/notebooks#69

It's not really a problem, I hope, but it makes it harder doing upgrade test, because resources change version even if content is exactly the same.

edit: or do they, actually?

[jiridanek]

Alternatives discussed in the link are

• client.Create dry run, if err := r.Client.Update(ctx, object, client.DryRunAll); err != nil { // client package is "sigs.k8s.io/controller-runtime/pkg/client"
• apiequality.Semantic.DeepEqual, see https://godoc.org/k8s.io/apimachinery/pkg/api/equality
• ...