Use ScaleHandler for all scalable resources

pkg/registry/core/replicationcontroller/storage/storage.go

@@ -27,6 +27,7 @@ import (
 	"k8s.io/apimachinery/pkg/labels"
 	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apimachinery/pkg/runtime/schema"
+	"k8s.io/apiserver/pkg/endpoints/handlers/fieldmanager"
 	"k8s.io/apiserver/pkg/registry/generic"
 	genericregistry "k8s.io/apiserver/pkg/registry/generic/registry"
 	"k8s.io/apiserver/pkg/registry/rest"
@@ -49,6 +50,11 @@ type ControllerStorage struct {
 	Scale      *ScaleREST
 }
 
+// maps a group version to the replicas path in a deployment object
+var replicasPathInReplicationController = fieldmanager.ResourcePathMappings{
+	schema.GroupVersion{Group: "", Version: "v1"}.String(): fieldpath.MakePathOrDie("spec", "replicas"),
+}
+
 func NewStorage(optsGetter generic.RESTOptionsGetter) (ControllerStorage, error) {
 	controllerREST, statusREST, err := NewREST(optsGetter)
 	if err != nil {
@@ -239,8 +245,19 @@ func (i *scaleUpdatedObjectInfo) UpdatedObject(ctx context.Context, oldObj runti
 		return nil, errors.NewNotFound(api.Resource("replicationcontrollers/scale"), i.name)
 	}
 
+	managedFieldsHandler := fieldmanager.NewScaleHandler(
+		replicationcontroller.ManagedFields,
+		schema.GroupVersion{Group: "", Version: "v1"},
+		replicasPathInReplicationController,
+	)
+
 	// replicationcontroller -> old scale
 	oldScale := scaleFromRC(replicationcontroller)
+	scaleManagedFields, err := managedFieldsHandler.ToSubresource()
+	if err != nil {
+		return nil, err
+	}
+	oldScale.ManagedFields = scaleManagedFields
 
 	// old scale -> new scale
 	newScaleObj, err := i.reqObjInfo.UpdatedObject(ctx, oldScale)
@@ -272,5 +289,12 @@ func (i *scaleUpdatedObjectInfo) UpdatedObject(ctx context.Context, oldObj runti
 	// move replicas/resourceVersion fields to object and return
 	replicationcontroller.Spec.Replicas = scale.Spec.Replicas
 	replicationcontroller.ResourceVersion = scale.ResourceVersion
+
+	updatedEntries, err := managedFieldsHandler.ToParent(scale.ManagedFields)
+	if err != nil {
+		return nil, err
+	}
+	replicationcontroller.ManagedFields = updatedEntries
+
 	return replicationcontroller, nil
 }