Add configuration point to SharedInformer to transform objects before storing

staging/src/k8s.io/client-go/tools/cache/controller.go

@@ -17,6 +17,7 @@ limitations under the License.
 package cache
 
 import (
+	"errors"
 	"sync"
 	"time"
 
@@ -406,6 +407,49 @@ func NewTransformingIndexerInformer(
 	return clientState, newInformer(lw, objType, resyncPeriod, h, clientState, transformer)
 }
 
+// Multiplexes updates in the form of a list of Deltas into a Store, and informs
+// a given handler of events OnUpdate, OnAdd, OnDelete
+func processDeltas(
+	// Object which receives event notifications from the given deltas
+	handler ResourceEventHandler,
+	clientState Store,
+	transformer TransformFunc,
+	deltas Deltas,
+) error {
+	// from oldest to newest
+	for _, d := range deltas {
+		obj := d.Object
+		if transformer != nil {
+			var err error
+			obj, err = transformer(obj)
+			if err != nil {
+				return err
+			}
+		}
+
+		switch d.Type {
+		case Sync, Replaced, Added, Updated:
+			if old, exists, err := clientState.Get(obj); err == nil && exists {
+				if err := clientState.Update(obj); err != nil {
+					return err
+				}
+				handler.OnUpdate(old, obj)
+			} else {
+				if err := clientState.Add(obj); err != nil {
+					return err
+				}
+				handler.OnAdd(obj)
+			}
+		case Deleted:
+			if err := clientState.Delete(obj); err != nil {
+				return err
+			}
+			handler.OnDelete(obj)
+		}
+	}
+	return nil
+}
+
 // newInformer returns a controller for populating the store while also
 // providing event notifications.
 //
@@ -444,38 +488,10 @@ func newInformer(
 		RetryOnError:     false,
 
 		Process: func(obj interface{}) error {
-			// from oldest to newest
-			for _, d := range obj.(Deltas) {
-				obj := d.Object
-				if transformer != nil {
-					var err error
-					obj, err = transformer(obj)
-					if err != nil {
-						return err
-					}
-				}
-
-				switch d.Type {
-				case Sync, Replaced, Added, Updated:
-					if old, exists, err := clientState.Get(obj); err == nil && exists {
-						if err := clientState.Update(obj); err != nil {
-							return err
-						}
-						h.OnUpdate(old, obj)
-					} else {
-						if err := clientState.Add(obj); err != nil {
-							return err
-						}
-						h.OnAdd(obj)
-					}
-				case Deleted:
-					if err := clientState.Delete(obj); err != nil {
-						return err
-					}
-					h.OnDelete(obj)
-				}
+			if deltas, ok := obj.(Deltas); ok {
+				return processDeltas(h, clientState, transformer, deltas)
 			}
-			return nil
+			return errors.New("object given as Process argument is not Deltas")
 		},
 	}
 	return New(cfg)

staging/src/k8s.io/client-go/tools/cache/shared_informer.go

@@ -17,6 +17,7 @@ limitations under the License.
 package cache
 
 import (
+	"errors"
 	"fmt"
 	"sync"
 	"time"
@@ -180,6 +181,20 @@ type SharedInformer interface {
 	// The handler should return quickly - any expensive processing should be
 	// offloaded.
 	SetWatchErrorHandler(handler WatchErrorHandler) error
+
+	// The TransformFunc is called for each object which is about to be stored.
+	//
+	// This function is intended for you to take the opportunity to
+	// remove, transform, or normalize fields. One use case is to strip unused
+	// metadata fields out of objects to save on RAM cost.
+	//
+	// Must be set before starting the informer.
+	//
+	// Note: Since the object given to the handler may be already shared with
+	//	other goroutines, it is advisable to copy the object being
+	//  transform before mutating it at all and returning the copy to prevent
+	//	data races.
+	SetTransform(handler TransformFunc) error
 }
 
 // SharedIndexInformer provides add and get Indexers ability based on SharedInformer.
@@ -318,6 +333,8 @@ type sharedIndexInformer struct {
 
 	// Called whenever the ListAndWatch drops the connection with an error.
 	watchErrorHandler WatchErrorHandler
+
+	transform TransformFunc
 }
 
 // dummyController hides the fact that a SharedInformer is different from a dedicated one
@@ -365,6 +382,18 @@ func (s *sharedIndexInformer) SetWatchErrorHandler(handler WatchErrorHandler) er
 	return nil
 }
 
+func (s *sharedIndexInformer) SetTransform(handler TransformFunc) error {
+	s.startedLock.Lock()
+	defer s.startedLock.Unlock()
+
+	if s.started {
+		return fmt.Errorf("informer has already started")
+	}
+
+	s.transform = handler
+	return nil
+}
+
 func (s *sharedIndexInformer) Run(stopCh <-chan struct{}) {
 	defer utilruntime.HandleCrash()
 
@@ -538,45 +567,47 @@ func (s *sharedIndexInformer) HandleDeltas(obj interface{}) error {
 	s.blockDeltas.Lock()
 	defer s.blockDeltas.Unlock()
 
-	// from oldest to newest
-	for _, d := range obj.(Deltas) {
-		switch d.Type {
-		case Sync, Replaced, Added, Updated:
-			s.cacheMutationDetector.AddObject(d.Object)
-			if old, exists, err := s.indexer.Get(d.Object); err == nil && exists {
-				if err := s.indexer.Update(d.Object); err != nil {
-					return err
-				}
+	if deltas, ok := obj.(Deltas); ok {
+		return processDeltas(s, s.indexer, s.transform, deltas)
+	}
+	return errors.New("object given as Process argument is not Deltas")
+}
 
-				isSync := false
-				switch {
-				case d.Type == Sync:
-					// Sync events are only propagated to listeners that requested resync
-					isSync = true
-				case d.Type == Replaced:
-					if accessor, err := meta.Accessor(d.Object); err == nil {
-						if oldAccessor, err := meta.Accessor(old); err == nil {
-							// Replaced events that didn't change resourceVersion are treated as resync events
-							// and only propagated to listeners that requested resync
-							isSync = accessor.GetResourceVersion() == oldAccessor.GetResourceVersion()
-						}
-					}
-				}
-				s.processor.distribute(updateNotification{oldObj: old, newObj: d.Object}, isSync)
-			} else {
-				if err := s.indexer.Add(d.Object); err != nil {
-					return err
-				}
-				s.processor.distribute(addNotification{newObj: d.Object}, false)
-			}
-		case Deleted:
-			if err := s.indexer.Delete(d.Object); err != nil {
-				return err
-			}
-			s.processor.distribute(deleteNotification{oldObj: d.Object}, false)
+// Conforms to ResourceEventHandler
+func (s *sharedIndexInformer) OnAdd(obj interface{}) {
+	// Invocation of this function is locked under s.blockDeltas, so it is
+	// save to distribute the notification
+	s.cacheMutationDetector.AddObject(obj)
+	s.processor.distribute(addNotification{newObj: obj}, false)
+}
+
+// Conforms to ResourceEventHandler
+func (s *sharedIndexInformer) OnUpdate(old, new interface{}) {
+	isSync := false
+
+	// If is a Sync event, isSync should be true
+	// If is a Replaced event, isSync is true if resource version is unchanged.
+	// If RV is unchanged: this is a Sync/Replaced event, so isSync is true
+
+	if accessor, err := meta.Accessor(new); err == nil {
+		if oldAccessor, err := meta.Accessor(old); err == nil {
+			// Events that didn't change resourceVersion are treated as resync events
+			// and only propagated to listeners that requested resync
+			isSync = accessor.GetResourceVersion() == oldAccessor.GetResourceVersion()
 		}
 	}
-	return nil
+
+	// Invocation of this function is locked under s.blockDeltas, so it is
+	// save to distribute the notification
+	s.cacheMutationDetector.AddObject(new)
+	s.processor.distribute(updateNotification{oldObj: old, newObj: new}, isSync)
+}
+
+// Conforms to ResourceEventHandler
+func (s *sharedIndexInformer) OnDelete(old interface{}) {
+	// Invocation of this function is locked under s.blockDeltas, so it is
+	// save to distribute the notification
+	s.processor.distribute(deleteNotification{oldObj: old}, false)
 }
 
 // sharedProcessor has a collection of processorListener and can

staging/src/k8s.io/client-go/tools/cache/shared_informer_test.go

@@ -23,7 +23,7 @@ import (
 	"testing"
 	"time"
 
-	"k8s.io/api/core/v1"
+	v1 "k8s.io/api/core/v1"
 	"k8s.io/apimachinery/pkg/api/meta"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/util/sets"
@@ -357,3 +357,36 @@ func TestSharedInformerErrorHandling(t *testing.T) {
 	}
 	close(stop)
 }
+
+func TestSharedInformerTransformer(t *testing.T) {
+	// source simulates an apiserver object endpoint.
+	source := fcache.NewFakeControllerSource()
+
+	source.Add(&v1.Pod{ObjectMeta: metav1.ObjectMeta{Name: "pod1", UID: "pod1", ResourceVersion: "1"}})
+	source.Add(&v1.Pod{ObjectMeta: metav1.ObjectMeta{Name: "pod2", UID: "pod2", ResourceVersion: "2"}})
+
+	informer := NewSharedInformer(source, &v1.Pod{}, 1*time.Second).(*sharedIndexInformer)
+	informer.SetTransform(func(obj interface{}) (interface{}, error) {
+		if pod, ok := obj.(*v1.Pod); ok {
+			name := pod.GetName()
+
+			if upper := strings.ToUpper(name); upper != name {
+				copied := pod.DeepCopyObject().(*v1.Pod)
+				copied.SetName(upper)
+				return copied, nil
+			}
+		}
+		return obj, nil
+	})
+
+	listenerTransformer := newTestListener("listenerTransformer", 0, "POD1", "POD2")
+	informer.AddEventHandler(listenerTransformer)
+
+	stop := make(chan struct{})
+	go informer.Run(stop)
+	defer close(stop)
+
+	if !listenerTransformer.ok() {
+		t.Errorf("%s: expected %v, got %v", listenerTransformer.name, listenerTransformer.expectedItemNames, listenerTransformer.receivedItemNames)
+	}
+}