Handle RV in Get calls to storage interface.

pkg/registry/core/service/allocator/etcd/etcd.go

@@ -174,7 +174,7 @@ func (e *Etcd) tryUpdate(fn func() error) error {
 // etcd. If the key does not exist, the object will have an empty ResourceVersion.
 func (e *Etcd) Get() (*api.RangeAllocation, error) {
 	existing := &api.RangeAllocation{}
-	if err := e.storage.Get(context.TODO(), e.baseKey, existing, true); err != nil {
+	if err := e.storage.Get(context.TODO(), e.baseKey, "", existing, true); err != nil {
 		return nil, storeerr.InterpretGetError(err, e.resource, "")
 	}
 	return existing, nil

pkg/registry/core/service/allocator/etcd/etcd_test.go

@@ -80,7 +80,7 @@ func TestStore(t *testing.T) {
 	other := allocator.NewAllocationMap(100, "rangeSpecValue")
 
 	allocation := &api.RangeAllocation{}
-	if err := storage.storage.Get(context.TODO(), key(), allocation, false); err != nil {
+	if err := storage.storage.Get(context.TODO(), key(), "", allocation, false); err != nil {
 		t.Fatal(err)
 	}
 	if allocation.Range != "rangeSpecValue" {

pkg/registry/generic/registry/store.go

@@ -262,7 +262,7 @@ func (e *Store) Create(ctx api.Context, obj runtime.Object) (runtime.Object, err
 		if !kubeerr.IsAlreadyExists(err) {
 			return nil, err
 		}
-		if errGet := e.Storage.Get(ctx, key, out, false); errGet != nil {
+		if errGet := e.Storage.Get(ctx, key, "", out, false); errGet != nil {
 			return nil, err
 		}
 		accessor, errGetAcc := meta.Accessor(out)
@@ -483,7 +483,8 @@ func (e *Store) Get(ctx api.Context, name string) (runtime.Object, error) {
 	if err != nil {
 		return nil, err
 	}
-	if err := e.Storage.Get(ctx, key, obj, false); err != nil {
+	// TODO: Once we pass GetOptions to this method, pass the ResourceVersion from it.
+	if err := e.Storage.Get(ctx, key, "", obj, false); err != nil {
 		return nil, storeerr.InterpretGetError(err, e.QualifiedResource, name)
 	}
 	if e.Decorator != nil {
@@ -695,7 +696,7 @@ func (e *Store) Delete(ctx api.Context, name string, options *api.DeleteOptions)
 	}
 
 	obj := e.NewFunc()
-	if err := e.Storage.Get(ctx, key, obj, false); err != nil {
+	if err := e.Storage.Get(ctx, key, "", obj, false); err != nil {
 		return nil, storeerr.InterpretDeleteError(err, e.QualifiedResource, name)
 	}
 	// support older consumers of delete by treating "nil" as delete immediately

pkg/storage/cacher.go

@@ -345,8 +345,48 @@ func (c *Cacher) WatchList(ctx context.Context, key string, resourceVersion stri
 }
 
 // Implements storage.Interface.
-func (c *Cacher) Get(ctx context.Context, key string, objPtr runtime.Object, ignoreNotFound bool) error {
-	return c.storage.Get(ctx, key, objPtr, ignoreNotFound)
+func (c *Cacher) Get(ctx context.Context, key string, resourceVersion string, objPtr runtime.Object, ignoreNotFound bool) error {
+	if resourceVersion == "" {
+		// If resourceVersion is not specified, serve it from underlying
+		// storage (for backward compatibility).
+		return c.storage.Get(ctx, key, resourceVersion, objPtr, ignoreNotFound)
+	}
+
+	// If resourceVersion is specified, serve it from cache.
+	// It's guaranteed that the returned value is at least that
+	// fresh as the given resourceVersion.
+	getRV, err := ParseListResourceVersion(resourceVersion)
+	if err != nil {
+		return err
+	}
+
+	// Do not create a trace - it's not for free and there are tons
+	// of Get requests. We can add it if it will be really needed.
+	c.ready.wait()
+
+	objVal, err := conversion.EnforcePtr(objPtr)
+	if err != nil {
+		return err
+	}
+
+	obj, exists, readResourceVersion, err := c.watchCache.WaitUntilFreshAndGet(getRV, key, nil)
+	if err != nil {
+		return fmt.Errorf("failed to wait for fresh get: %v", err)
+	}
+
+	if exists {
+		elem, ok := obj.(*storeElement)
+		if !ok {
+			return fmt.Errorf("non *storeElement returned from storage: %v", obj)
+		}
+		objVal.Set(reflect.ValueOf(elem.Object).Elem())
+	} else {
+		objVal.Set(reflect.Zero(objVal.Type()))
+		if !ignoreNotFound {
+			return NewKeyNotFoundError(key, int64(readResourceVersion))
+		}
+	}
+	return nil
 }
 
 // Implements storage.Interface.
@@ -384,7 +424,7 @@ func (c *Cacher) GetToList(ctx context.Context, key string, resourceVersion stri
 
 	obj, exists, readResourceVersion, err := c.watchCache.WaitUntilFreshAndGet(listRV, key, trace)
 	if err != nil {
-		return fmt.Errorf("failed to wait for fresh list: %v", err)
+		return fmt.Errorf("failed to wait for fresh get: %v", err)
 	}
 	trace.Step("Got from cache")
 

pkg/storage/cacher_test.go

@@ -90,12 +90,43 @@ func updatePod(t *testing.T, s storage.Interface, obj, old *api.Pod) *api.Pod {
 	}
 	obj.ResourceVersion = ""
 	result := &api.Pod{}
-	if err := s.Get(context.TODO(), key, result, false); err != nil {
+	if err := s.Get(context.TODO(), key, "", result, false); err != nil {
 		t.Errorf("unexpected error: %v", err)
 	}
 	return result
 }
 
+func TestGet(t *testing.T) {
+	server, etcdStorage := newEtcdTestStorage(t, testapi.Default.Codec(), etcdtest.PathPrefix())
+	defer server.Terminate(t)
+	cacher := newTestCacher(etcdStorage, 10)
+	defer cacher.Stop()
+
+	podFoo := makeTestPod("foo")
+	fooCreated := updatePod(t, etcdStorage, podFoo, nil)
+
+	// We pass the ResourceVersion from the above Create() operation.
+	result := &api.Pod{}
+	if err := cacher.Get(context.TODO(), "pods/ns/foo", fooCreated.ResourceVersion, result, true); err != nil {
+		t.Errorf("Unexpected error: %v", err)
+	}
+	if e, a := *fooCreated, *result; !reflect.DeepEqual(e, a) {
+		t.Errorf("Expected: %#v, got: %#v", e, a)
+	}
+
+	if err := cacher.Get(context.TODO(), "pods/ns/bar", fooCreated.ResourceVersion, result, true); err != nil {
+		t.Errorf("Unexpected error: %v", err)
+	}
+	emptyPod := api.Pod{}
+	if e, a := emptyPod, *result; !reflect.DeepEqual(e, a) {
+		t.Errorf("Expected: %#v, got: %#v", e, a)
+	}
+
+	if err := cacher.Get(context.TODO(), "pods/ns/bar", fooCreated.ResourceVersion, result, false); !storage.IsNotFound(err) {
+		t.Errorf("Unexpected error: %v", err)
+	}
+}
+
 func TestList(t *testing.T) {
 	server, etcdStorage := newEtcdTestStorage(t, testapi.Default.Codec(), etcdtest.PathPrefix())
 	defer server.Terminate(t)

pkg/storage/etcd/etcd_helper.go

@@ -232,7 +232,7 @@ func (h *etcdHelper) WatchList(ctx context.Context, key string, resourceVersion
 }
 
 // Implements storage.Interface.
-func (h *etcdHelper) Get(ctx context.Context, key string, objPtr runtime.Object, ignoreNotFound bool) error {
+func (h *etcdHelper) Get(ctx context.Context, key string, resourceVersion string, objPtr runtime.Object, ignoreNotFound bool) error {
 	if ctx == nil {
 		glog.Errorf("Context is nil")
 	}

pkg/storage/etcd/etcd_helper_test.go

@@ -240,7 +240,7 @@ func TestGet(t *testing.T) {
 		t.Errorf("Unexpected error %#v", err)
 	}
 	expect = got
-	if err := helper.Get(context.TODO(), key, &got, false); err != nil {
+	if err := helper.Get(context.TODO(), key, "", &got, false); err != nil {
 		t.Errorf("Unexpected error %#v", err)
 	}
 	if !reflect.DeepEqual(got, expect) {
@@ -256,7 +256,7 @@ func TestGetNotFoundErr(t *testing.T) {
 	helper := newEtcdHelper(server.Client, testapi.Default.Codec(), key)
 
 	var got api.Pod
-	err := helper.Get(context.TODO(), boguskey, &got, false)
+	err := helper.Get(context.TODO(), boguskey, "", &got, false)
 	if !storage.IsNotFound(err) {
 		t.Errorf("Unexpected reponse on key=%v, err=%v", key, err)
 	}
@@ -276,7 +276,7 @@ func TestCreate(t *testing.T) {
 	if err != nil {
 		t.Errorf("Unexpected error %#v", err)
 	}
-	err = helper.Get(context.TODO(), "/some/key", returnedObj, false)
+	err = helper.Get(context.TODO(), "/some/key", "", returnedObj, false)
 	if err != nil {
 		t.Errorf("Unexpected error %#v", err)
 	}
@@ -332,7 +332,7 @@ func TestGuaranteedUpdate(t *testing.T) {
 	}
 
 	objCheck := &storagetesting.TestResource{}
-	err = helper.Get(context.TODO(), key, objCheck, false)
+	err = helper.Get(context.TODO(), key, "", objCheck, false)
 	if err != nil {
 		t.Errorf("Unexpected error %#v", err)
 	}
@@ -442,7 +442,7 @@ func TestGuaranteedUpdate_CreateCollision(t *testing.T) {
 	wgDone.Wait()
 
 	stored := &storagetesting.TestResource{}
-	err := helper.Get(context.TODO(), key, stored, false)
+	err := helper.Get(context.TODO(), key, "", stored, false)
 	if err != nil {
 		t.Errorf("Unexpected error %#v", stored)
 	}
@@ -562,7 +562,7 @@ func TestDeleteWithRetry(t *testing.T) {
 	if fake.getCount != expectedRetries {
 		t.Errorf("Expect %d retries, got %d", expectedRetries, fake.getCount)
 	}
-	err = helper.Get(context.TODO(), "/some/key", obj, false)
+	err = helper.Get(context.TODO(), "/some/key", "", obj, false)
 	if !storage.IsNotFound(err) {
 		t.Errorf("Expect an NotFound error, got %v", err)
 	}

pkg/storage/etcd3/store.go

@@ -96,7 +96,7 @@ func (s *store) Versioner() storage.Versioner {
 }
 
 // Get implements storage.Interface.Get.
-func (s *store) Get(ctx context.Context, key string, out runtime.Object, ignoreNotFound bool) error {
+func (s *store) Get(ctx context.Context, key string, resourceVersion string, out runtime.Object, ignoreNotFound bool) error {
 	key = keyWithPrefix(s.pathPrefix, key)
 	getResp, err := s.client.KV.Get(ctx, key, s.getOps...)
 	if err != nil {

pkg/storage/etcd3/store_test.go

@@ -133,7 +133,7 @@ func TestGet(t *testing.T) {
 
 	for i, tt := range tests {
 		out := &api.Pod{}
-		err := store.Get(ctx, tt.key, out, tt.ignoreNotFound)
+		err := store.Get(ctx, tt.key, "", out, tt.ignoreNotFound)
 		if tt.expectNotFoundErr {
 			if err == nil || !storage.IsNotFound(err) {
 				t.Errorf("#%d: expecting not found error, but get: %s", i, err)

pkg/storage/interfaces.go

@@ -124,7 +124,9 @@ type Interface interface {
 	// Get unmarshals json found at key into objPtr. On a not found error, will either
 	// return a zero object of the requested type, or an error, depending on ignoreNotFound.
 	// Treats empty responses and nil response nodes exactly like a not found error.
-	Get(ctx context.Context, key string, objPtr runtime.Object, ignoreNotFound bool) error
+	// The returned contents may be delayed, but it is guaranteed that they will
+	// be have at least 'resourceVersion'.
+	Get(ctx context.Context, key string, resourceVersion string, objPtr runtime.Object, ignoreNotFound bool) error
 
 	// GetToList unmarshals json found at key and opaque it into *List api object
 	// (an object that satisfies the runtime.IsList definition).

test/integration/objectmeta/objectmeta_test.go

@@ -70,7 +70,7 @@ func TestIgnoreClusterName(t *testing.T) {
 	assert.Empty(t, nsNew.ClusterName)
 
 	nsEtcd := v1.Namespace{}
-	err = etcdStorage.Get(ctx, ns.Name, &nsEtcd, false)
+	err = etcdStorage.Get(ctx, ns.Name, "", &nsEtcd, false)
 	assert.Nil(t, err)
 	assert.Equal(t, ns.Name, nsEtcd.Name)
 	assert.Empty(t, nsEtcd.ClusterName)
@@ -81,7 +81,7 @@ func TestIgnoreClusterName(t *testing.T) {
 	assert.Empty(t, nsNew.ClusterName)
 
 	nsEtcd = v1.Namespace{}
-	err = etcdStorage.Get(ctx, ns.Name, &nsEtcd, false)
+	err = etcdStorage.Get(ctx, ns.Name, "", &nsEtcd, false)
 	assert.Nil(t, err)
 	assert.Equal(t, ns.Name, nsEtcd.Name)
 	assert.Empty(t, nsEtcd.ClusterName)