Automated cherry pick of #821: keep desired replicas annotation up to date even if no (#822)

* keep desired replicas annotation up to date even if no scaling happens

* Update pkg/controller/deployment_sync_test.go

Co-authored-by: Himanshu Sharma <79965161+himanshu-kun@users.noreply.github.com>

---------

Co-authored-by: Himanshu Sharma <79965161+himanshu-kun@users.noreply.github.com>

Author: rishabh-11

pkg/controller/deployment_sync.go

@@ -404,7 +404,10 @@ func (dc *controller) scale(ctx context.Context, deployment *v1alpha1.MachineDep
 	// deployment. If there is no active machine set, then we should scale up the newest machine set.
 	if activeOrLatest := FindActiveOrLatest(newIS, oldISs); activeOrLatest != nil {
 		if (activeOrLatest.Spec.Replicas) == (deployment.Spec.Replicas) {
-			return nil
+			// to deal with the case where the DesiredReplicas annotation is outdated (issue - https://github.com/gardener/machine-controller-manager/issues/815)
+			klog.V(3).Infof("DesiredReplicas annotation possibly outdated for the machineSet %s, updating if needed...", activeOrLatest.Name)
+			_, _, err := dc.scaleMachineSet(ctx, activeOrLatest, deployment.Spec.Replicas, deployment, "no-op")
+			return err
 		}
 		klog.V(3).Infof("Scaling latest/theOnlyActive machineSet %s", activeOrLatest.Name)
 		_, _, err := dc.scaleMachineSetAndRecordEvent(ctx, activeOrLatest, deployment.Spec.Replicas, deployment)

pkg/controller/deployment_sync_test.go

@@ -455,8 +455,9 @@ var _ = Describe("deployment_sync", func() {
 					controlObjects = append(controlObjects, data.setup.oldISs[i])
 				}
 
-				controlObjects = append(controlObjects, data.setup.newIS)
-
+				if data.setup.newIS != nil {
+					controlObjects = append(controlObjects, data.setup.newIS)
+				}
 				c, trackers := createController(stop, testNamespace, controlObjects, nil, nil)
 				defer trackers.Stop()
 				waitForCacheSync(stop, c)
@@ -840,6 +841,21 @@ var _ = Describe("deployment_sync", func() {
 					err: false,
 				},
 			}),
+			Entry("if no scaling needed but DesiredReplicas Annotation for the only active machineSet is outdated, it should be updated with the correct value", &data{
+				setup: setup{
+					machineDeployment: newMachineDeployment(mDeploymentSpecTemplate, 1, 500, 2, 0, nil, nil, nil, nil),
+					oldISs: []*machinev1.MachineSet{
+						newMachineSet(mSetSpecTemplate, nameMachineSet1, 1, 500, nil, nil, map[string]string{DesiredReplicasAnnotation: "2", MaxReplicasAnnotation: "3"}, nil),
+					},
+					newIS: nil,
+				},
+				expect: expect{
+					err: false,
+					machineSets: []*machinev1.MachineSet{
+						newMachineSet(mSetSpecTemplate, nameMachineSet1, 1, 500, nil, nil, map[string]string{DesiredReplicasAnnotation: "1", MaxReplicasAnnotation: "3"}, nil),
+					},
+				},
+			}),
 		)
 	})
 })