Clean up deep copy needed for UpdateStatefulSet

Change-Id: Id732358183d682d1a945cfee56f83bcaac0d7c31

pkg/controller/statefulset/stateful_set.go

@@ -472,8 +472,7 @@ func (ssc *StatefulSetController) syncStatefulSet(ctx context.Context, set *apps
 	klog.V(4).Infof("Syncing StatefulSet %v/%v with %d pods", set.Namespace, set.Name, len(pods))
 	var status *apps.StatefulSetStatus
 	var err error
-	// TODO: investigate where we mutate the set during the update as it is not obvious.
-	status, err = ssc.control.UpdateStatefulSet(ctx, set.DeepCopy(), pods)
+	status, err = ssc.control.UpdateStatefulSet(ctx, set, pods)
 	if err != nil {
 		return err
 	}

pkg/controller/statefulset/stateful_set_control.go

@@ -75,6 +75,8 @@ type defaultStatefulSetControl struct {
 // in no particular order. Clients using the burst strategy should be careful to ensure they
 // understand the consistency implications of having unpredictable numbers of pods available.
 func (ssc *defaultStatefulSetControl) UpdateStatefulSet(ctx context.Context, set *apps.StatefulSet, pods []*v1.Pod) (*apps.StatefulSetStatus, error) {
+	set = set.DeepCopy() // set is modified when a new revision is created in performUpdate. Make a copy now to avoid mutation errors.
+
 	// list all revisions and sort them
 	revisions, err := ssc.ListRevisions(set)
 	if err != nil {

pkg/controller/statefulset/stateful_set_control_test.go

@@ -2326,7 +2326,6 @@ func scaleUpStatefulSetControl(set *apps.StatefulSet,
 		if err := invariants(set, om); err != nil {
 			return err
 		}
-		//fmt.Printf("Ravig pod conditions %v %v", set.Status.ReadyReplicas, *set.Spec.Replicas)
 	}
 	return invariants(set, om)
 }