Merge pull request kubernetes#48269 from FengyunPan/add-gc-metric

Automatic merge from submit-queue (batch tested with PRs 48518, 48525, 48269)

Update comment for garbagecollector

Update comment for garbagecollector, update not exist func.

**Release note**:
```release-note
NONE
```

Author: Kubernetes Submit Queue

pkg/controller/garbagecollector/garbagecollector_test.go

@@ -272,7 +272,7 @@ func TestProcessEvent(t *testing.T) {
 	var testScenarios = []struct {
 		name string
 		// a series of events that will be supplied to the
-		// GraphBuilder.eventQueue.
+		// GraphBuilder.graphChanges.
 		events []event
 	}{
 		{

pkg/controller/garbagecollector/graph.go

@@ -34,8 +34,8 @@ func (s objectReference) String() string {
 	return fmt.Sprintf("[%s/%s, namespace: %s, name: %s, uid: %s]", s.APIVersion, s.Kind, s.Namespace, s.Name, s.UID)
 }
 
-// The single-threaded GraphBuilder.processEvent() is the sole writer of the
-// nodes. The multi-threaded GarbageCollector.processItem() reads the nodes.
+// The single-threaded GraphBuilder.processGraphChanges() is the sole writer of the
+// nodes. The multi-threaded GarbageCollector.attemptToDeleteItem() reads the nodes.
 // WARNING: node has different locks on different fields. setters and getters
 // use the respective locks, so the return values of the getters can be
 // inconsistent.
@@ -46,7 +46,7 @@ type node struct {
 	// dependents are the nodes that have node.identity as a
 	// metadata.ownerReference.
 	dependents map[*node]struct{}
-	// this is set by processEvent() if the object has non-nil DeletionTimestamp
+	// this is set by processGraphChanges() if the object has non-nil DeletionTimestamp
 	// and has the FinalizerDeleteDependents.
 	deletingDependents     bool
 	deletingDependentsLock sync.RWMutex

pkg/controller/garbagecollector/graph_builder.go

@@ -259,7 +259,7 @@ func (gb *GraphBuilder) enqueueChanges(e *event) {
 // addDependentToOwners adds n to owners' dependents list. If the owner does not
 // exist in the gb.uidToNode yet, a "virtual" node will be created to represent
 // the owner. The "virtual" node will be enqueued to the attemptToDelete, so that
-// processItem() will verify if the owner exists according to the API server.
+// attemptToDeleteItem() will verify if the owner exists according to the API server.
 func (gb *GraphBuilder) addDependentToOwners(n *node, owners []metav1.OwnerReference) {
 	for _, owner := range owners {
 		ownerNode, ok := gb.uidToNode.Read(owner.UID)