Switch GC absentOwnerCache to full reference

Before deleting an object based on absent owners, GC verifies absence of those owners with a live lookup.

The coordinates used to perform that live lookup are the ones specified in the ownerReference of the child.

In order to performantly delete multiple children from the same parent (e.g. 1000 pods from a replicaset),
a 404 response to a lookup is cached in absentOwnerCache.

Previously, the cache was a simple uid set. However, since children can disagree on the coordinates
that should be used to look up a given uid, the cache should record the exact coordinates verified absent.
This is a [apiVersion, kind, namespace, name, uid] tuple.

pkg/controller/garbagecollector/graph_builder.go

@@ -104,7 +104,7 @@ type GraphBuilder struct {
 	attemptToOrphan workqueue.RateLimitingInterface
 	// GraphBuilder and GC share the absentOwnerCache. Objects that are known to
 	// be non-existent are added to the cached.
-	absentOwnerCache *UIDCache
+	absentOwnerCache *ReferenceCache
 	sharedInformers  informerfactory.InformerFactory
 	ignoredResources map[schema.GroupResource]struct{}
 }
@@ -327,8 +327,10 @@ func DefaultIgnoredResources() map[schema.GroupResource]struct{} {
 // enqueueVirtualDeleteEvent is used to add a virtual delete event to be processed for virtual nodes
 // once it is determined they do not have backing objects in storage
 func (gb *GraphBuilder) enqueueVirtualDeleteEvent(ref objectReference) {
+	gv, _ := schema.ParseGroupVersion(ref.APIVersion)
 	gb.graphChanges.Add(&event{
 		eventType: deleteEvent,
+		gvk:       gv.WithKind(ref.Kind),
 		obj: &metaonly.MetadataOnlyObject{
 			TypeMeta:   metav1.TypeMeta{APIVersion: ref.APIVersion, Kind: ref.Kind},
 			ObjectMeta: metav1.ObjectMeta{Namespace: ref.Namespace, UID: ref.UID, Name: ref.Name},
@@ -348,7 +350,7 @@ func (gb *GraphBuilder) addDependentToOwners(n *node, owners []metav1.OwnerRefer
 			// exist in the graph yet.
 			ownerNode = &node{
 				identity: objectReference{
-					OwnerReference: owner,
+					OwnerReference: ownerReferenceCoordinates(owner),
 					Namespace:      n.identity.Namespace,
 				},
 				dependents: make(map[*node]struct{}),
@@ -603,7 +605,15 @@ func (gb *GraphBuilder) processGraphChanges() bool {
 		existingNode.dependentsLock.RLock()
 		defer existingNode.dependentsLock.RUnlock()
 		if len(existingNode.dependents) > 0 {
-			gb.absentOwnerCache.Add(accessor.GetUID())
+			gb.absentOwnerCache.Add(objectReference{
+				OwnerReference: metav1.OwnerReference{
+					APIVersion: event.gvk.GroupVersion().String(),
+					Kind:       event.gvk.Kind,
+					Name:       accessor.GetName(),
+					UID:        accessor.GetUID(),
+				},
+				Namespace: accessor.GetNamespace(),
+			})
 		}
 		for dep := range existingNode.dependents {
 			gb.attemptToDelete.Add(dep)