Merge pull request #44058 from caesarxuchao/background-cascading

Automatic merge from submit-queue (batch tested with PRs 44058, 48085, 48077, 48076, 47823)

Make background garbage collection cascading

Fix #44046, fix #47843 where user reported that the garbage collector didn't delete pods when a deployment was deleted with PropagationPolicy=Background.

The cause is that when propagating background garbage collection request, the garbage collector deletes dependents with DeleteOptions.PropagationPolicy=nil, which means the default GC policy of a resource (defined by its REST strategy) and the existing GC-related finalizers will decide how the delete request is propagated further. Unfortunately, the default GC policy for RS is orphaning, so the pods are behind when a deployment is deleted.

This PR changes the garbage collector to delete dependents with DeleteOptions.PropagationPolicy=Background when the owner is deleted in background. This means the dependent's existing GC finalizers will be overridden, making orphaning less flexible (see this made-up [case](https://github.com/kubernetes/kubeadm/issues/149#issuecomment-278942012)). I think sacrificing the flexibility of orphaning is worthwhile, because making the behavior of background garbage collection matching users' expectation is more important.

cc @lavalamp @kargakis @krmayankk @enisoc 

```release-note
The garbage collector now cascades deletion properly when deleting an object with propagationPolicy="background". This resolves issue [#44046](https://github.com/kubernetes/kubernetes/issues/44046), so that when a deployment is deleted with propagationPolicy="background", the garbage collector ensures dependent pods are deleted as well.
```

pkg/controller/controller_ref_manager.go

@@ -341,9 +341,8 @@ func (m *ReplicaSetControllerRefManager) ClaimReplicaSets(sets []*extensions.Rep
 	return claimed, utilerrors.NewAggregate(errlist)
 }
 
-// AdoptReplicaSet sends a patch to take control of the ReplicaSet and also
-// sets the finalizers to foregroundDeletion. It returns the error if
-// the patching fails.
+// AdoptReplicaSet sends a patch to take control of the ReplicaSet. It returns
+// the error if the patching fails.
 func (m *ReplicaSetControllerRefManager) AdoptReplicaSet(rs *extensions.ReplicaSet) error {
 	if err := m.canAdopt(); err != nil {
 		return fmt.Errorf("can't adopt ReplicaSet %v/%v (%v): %v", rs.Namespace, rs.Name, rs.UID, err)
@@ -351,14 +350,7 @@ func (m *ReplicaSetControllerRefManager) AdoptReplicaSet(rs *extensions.ReplicaS
 	// Note that ValidateOwnerReferences() will reject this patch if another
 	// OwnerReference exists with controller=true.
 	addControllerPatch := fmt.Sprintf(
-		`{
-			"metadata":
-			{	
-				"ownerReferences": [{"apiVersion":"%s","kind":"%s","name":"%s","uid":"%s","controller":true,"blockOwnerDeletion":true}],
-				"uid":"%s",
-				"finalizers": ["foregroundDeletion"]
-			}
-		}`,
+		`{"metadata":{"ownerReferences":[{"apiVersion":"%s","kind":"%s","name":"%s","uid":"%s","controller":true,"blockOwnerDeletion":true}],"uid":"%s"}}`,
 		m.controllerKind.GroupVersion(), m.controllerKind.Kind,
 		m.controller.GetName(), m.controller.GetUID(), rs.UID)
 	return m.rsControl.PatchReplicaSet(rs.Namespace, rs.Name, []byte(addControllerPatch))

pkg/controller/deployment/sync.go

@@ -300,7 +300,6 @@ func (dc *DeploymentController) getNewReplicaSet(d *extensions.Deployment, rsLis
 			Name:            d.Name + "-" + podTemplateSpecHash,
 			Namespace:       d.Namespace,
 			OwnerReferences: []metav1.OwnerReference{*newControllerRef(d)},
-			Finalizers:      []string{metav1.FinalizerDeleteDependents},
 		},
 		Spec: extensions.ReplicaSetSpec{
 			Replicas:        new(int32),

pkg/controller/garbagecollector/garbagecollector.go

@@ -364,7 +364,7 @@ func (gc *GarbageCollector) attemptToDeleteItem(item *node) error {
 				break
 			}
 		}
-		glog.V(2).Infof("at least one owner of object %s has FinalizerDeletingDependents, and the object itself has dependents, so it is going to be deleted with Foreground", item.identity)
+		glog.V(2).Infof("at least one owner of object %s has FinalizerDeletingDependents, and the object itself has dependents, so it is going to be deleted in Foreground", item.identity)
 		// the deletion event will be observed by the graphBuilder, so the item
 		// will be processed again in processDeletingDependentsItem. If it
 		// doesn't have dependents, the function will remove the
@@ -375,9 +375,21 @@ func (gc *GarbageCollector) attemptToDeleteItem(item *node) error {
 	default:
 		// item doesn't have any solid owner, so it needs to be garbage
 		// collected. Also, none of item's owners is waiting for the deletion of
-		// the dependents, so GC deletes item with Default.
-		glog.V(2).Infof("delete object %s with Default", item.identity)
-		return gc.deleteObject(item.identity, nil)
+		// the dependents, so set propagationPolicy based on existing finalizers.
+		var policy metav1.DeletionPropagation
+		switch {
+		case hasOrphanFinalizer(latest):
+			// if an existing orphan finalizer is already on the object, honor it.
+			policy = metav1.DeletePropagationOrphan
+		case hasDeleteDependentsFinalizer(latest):
+			// if an existing foreground finalizer is already on the object, honor it.
+			policy = metav1.DeletePropagationForeground
+		default:
+			// otherwise, default to background.
+			policy = metav1.DeletePropagationBackground
+		}
+		glog.V(2).Infof("delete object %s with propagation policy %s", item.identity, policy)
+		return gc.deleteObject(item.identity, &policy)
 	}
 }