Add PatchService method in service/helper.

addressed review comments

staging/src/k8s.io/cloud-provider/service/helpers/helper.go

@@ -17,10 +17,14 @@ limitations under the License.
 package helpers
 
 import (
+	"encoding/json"
 	"fmt"
 	"strings"
 
 	v1 "k8s.io/api/core/v1"
+	"k8s.io/apimachinery/pkg/types"
+	"k8s.io/apimachinery/pkg/util/strategicpatch"
+	corev1 "k8s.io/client-go/kubernetes/typed/core/v1"
 	utilnet "k8s.io/utils/net"
 )
 
@@ -121,6 +125,40 @@ func LoadBalancerStatusEqual(l, r *v1.LoadBalancerStatus) bool {
 	return ingressSliceEqual(l.Ingress, r.Ingress)
 }
 
+// PatchService patches the given service's Status or ObjectMeta based on the original and
+// updated ones. Change to spec will be ignored.
+func PatchService(c corev1.CoreV1Interface, oldSvc, newSvc *v1.Service) (*v1.Service, error) {
+	// Reset spec to make sure only patch for Status or ObjectMeta.
+	newSvc.Spec = oldSvc.Spec
+
+	patchBytes, err := getPatchBytes(oldSvc, newSvc)
+	if err != nil {
+		return nil, err
+	}
+
+	return c.Services(oldSvc.Namespace).Patch(oldSvc.Name, types.StrategicMergePatchType, patchBytes, "status")
+
+}
+
+func getPatchBytes(oldSvc, newSvc *v1.Service) ([]byte, error) {
+	oldData, err := json.Marshal(oldSvc)
+	if err != nil {
+		return nil, fmt.Errorf("failed to Marshal oldData for svc %s/%s: %v", oldSvc.Namespace, oldSvc.Name, err)
+	}
+
+	newData, err := json.Marshal(newSvc)
+	if err != nil {
+		return nil, fmt.Errorf("failed to Marshal newData for svc %s/%s: %v", newSvc.Namespace, newSvc.Name, err)
+	}
+
+	patchBytes, err := strategicpatch.CreateTwoWayMergePatch(oldData, newData, v1.Service{})
+	if err != nil {
+		return nil, fmt.Errorf("failed to CreateTwoWayMergePatch for svc %s/%s: %v", oldSvc.Namespace, oldSvc.Name, err)
+	}
+	return patchBytes, nil
+
+}
+
 func ingressSliceEqual(lhs, rhs []v1.LoadBalancerIngress) bool {
 	if len(lhs) != len(rhs) {
 		return false

staging/src/k8s.io/cloud-provider/service/helpers/helper_test.go

@@ -17,11 +17,13 @@ limitations under the License.
 package helpers
 
 import (
+	"reflect"
 	"strings"
 	"testing"
 
 	v1 "k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/client-go/kubernetes/fake"
 	utilnet "k8s.io/utils/net"
 )
 
@@ -269,3 +271,78 @@ func TestHasLBFinalizer(t *testing.T) {
 		})
 	}
 }
+
+func TestPatchService(t *testing.T) {
+	svcOrigin := &v1.Service{
+		ObjectMeta: metav1.ObjectMeta{
+			Name:        "test-patch",
+			Annotations: map[string]string{},
+		},
+		Spec: v1.ServiceSpec{
+			ClusterIP: "10.0.0.1",
+		},
+	}
+	fakeCs := fake.NewSimpleClientset(svcOrigin)
+
+	// Issue a separate update and verify patch doesn't fail after this.
+	svcToUpdate := svcOrigin.DeepCopy()
+	addAnnotations(svcToUpdate)
+	if _, err := fakeCs.CoreV1().Services(svcOrigin.Namespace).Update(svcToUpdate); err != nil {
+		t.Fatalf("Failed to update service: %v", err)
+	}
+
+	// Attempt to patch based the original service.
+	svcToPatch := svcOrigin.DeepCopy()
+	svcToPatch.Finalizers = []string{"foo"}
+	svcToPatch.Spec.ClusterIP = "10.0.0.2"
+	svcToPatch.Status = v1.ServiceStatus{
+		LoadBalancer: v1.LoadBalancerStatus{
+			Ingress: []v1.LoadBalancerIngress{
+				{IP: "8.8.8.8"},
+			},
+		},
+	}
+	svcPatched, err := PatchService(fakeCs.CoreV1(), svcOrigin, svcToPatch)
+	if err != nil {
+		t.Fatalf("Failed to patch service: %v", err)
+	}
+
+	// Service returned by patch will contain latest content (e.g from
+	// the separate update).
+	addAnnotations(svcToPatch)
+	if !reflect.DeepEqual(svcPatched, svcToPatch) {
+		t.Errorf("PatchStatus() = %+v, want %+v", svcPatched, svcToPatch)
+	}
+	// Explicitly validate if spec is unchanged from origin.
+	if !reflect.DeepEqual(svcPatched.Spec, svcOrigin.Spec) {
+		t.Errorf("Got spec = %+v, want %+v", svcPatched.Spec, svcOrigin.Spec)
+	}
+}
+
+func Test_getPatchBytes(t *testing.T) {
+	origin := &v1.Service{
+		ObjectMeta: metav1.ObjectMeta{
+			Name:       "test-patch-bytes",
+			Finalizers: []string{"foo"},
+		},
+	}
+	updated := &v1.Service{
+		ObjectMeta: metav1.ObjectMeta{
+			Name:       "test-patch-bytes",
+			Finalizers: []string{"foo", "bar"},
+		},
+	}
+
+	b, err := getPatchBytes(origin, updated)
+	if err != nil {
+		t.Fatal(err)
+	}
+	expected := `{"metadata":{"$setElementOrder/finalizers":["foo","bar"],"finalizers":["bar"]}}`
+	if string(b) != expected {
+		t.Errorf("getPatchBytes(%+v, %+v) = %s ; want %s", origin, updated, string(b), expected)
+	}
+}
+
+func addAnnotations(svc *v1.Service) {
+	svc.Annotations["foo"] = "bar"
+}