Store previous value in WatchCache for filtering

pkg/client/cache/watch_cache.go

@@ -27,12 +27,27 @@ import (
 	"k8s.io/kubernetes/pkg/watch"
 )
 
+// TODO(wojtek-t): All structure in this file should be private to
+// pkg/storage package. We should remove the reference to WatchCache
+// from Reflector (by changing the Replace method signature in Store
+// interface to take resource version too) and move it under pkg/storage.
+
+// WatchCacheEvent is a single "watch event" that is send to users of
+// WatchCache. Additionally to a typical "watch.Event" it contains
+// the previous value of the object to enable proper filtering in the
+// upper layers.
+type WatchCacheEvent struct {
+	Type       watch.EventType
+	Object     runtime.Object
+	PrevObject runtime.Object
+}
+
 // watchCacheElement is a single "watch event" stored in a cache.
 // It contains the resource version of the object and the object
 // itself.
 type watchCacheElement struct {
 	resourceVersion uint64
-	event           watch.Event
+	watchCacheEvent WatchCacheEvent
 }
 
 // WatchCache implements a Store interface.
@@ -66,8 +81,9 @@ type WatchCache struct {
 	// This handler is run at the end of every successful Replace() method.
 	onReplace func()
 
-	// This handler is run at the end of every Add/Update/Delete method.
-	onEvent func(watch.Event)
+	// This handler is run at the end of every Add/Update/Delete method
+	// and additionally gets the previous value of the object.
+	onEvent func(WatchCacheEvent)
 }
 
 func NewWatchCache(capacity int) *WatchCache {
@@ -140,16 +156,27 @@ func parseResourceVersion(resourceVersion string) (uint64, error) {
 func (w *WatchCache) processEvent(event watch.Event, resourceVersion uint64, updateFunc func(runtime.Object) error) error {
 	w.Lock()
 	defer w.Unlock()
-	if w.onEvent != nil {
-		w.onEvent(event)
+	previous, exists, err := w.store.Get(event.Object)
+	if err != nil {
+		return err
 	}
-	w.updateCache(resourceVersion, event)
+	var prevObject runtime.Object
+	if exists {
+		prevObject = previous.(runtime.Object)
+	} else {
+		prevObject = nil
+	}
+	watchCacheEvent := WatchCacheEvent{event.Type, event.Object, prevObject}
+	if w.onEvent != nil {
+		w.onEvent(watchCacheEvent)
+	}
+	w.updateCache(resourceVersion, watchCacheEvent)
 	w.resourceVersion = resourceVersion
 	return updateFunc(event.Object)
 }
 
 // Assumes that lock is already held for write.
-func (w *WatchCache) updateCache(resourceVersion uint64, event watch.Event) {
+func (w *WatchCache) updateCache(resourceVersion uint64, event WatchCacheEvent) {
 	if w.endIndex == w.startIndex+w.capacity {
 		// Cache is full - remove the oldest element.
 		w.startIndex++
@@ -219,13 +246,13 @@ func (w *WatchCache) SetOnReplace(onReplace func()) {
 	w.onReplace = onReplace
 }
 
-func (w *WatchCache) SetOnEvent(onEvent func(watch.Event)) {
+func (w *WatchCache) SetOnEvent(onEvent func(WatchCacheEvent)) {
 	w.Lock()
 	defer w.Unlock()
 	w.onEvent = onEvent
 }
 
-func (w *WatchCache) GetAllEventsSince(resourceVersion uint64) ([]watch.Event, error) {
+func (w *WatchCache) GetAllEventsSince(resourceVersion uint64) ([]WatchCacheEvent, error) {
 	w.RLock()
 	defer w.RUnlock()
 
@@ -244,9 +271,9 @@ func (w *WatchCache) GetAllEventsSince(resourceVersion uint64) ([]watch.Event, e
 		return w.cache[(w.startIndex+i)%w.capacity].resourceVersion >= resourceVersion
 	}
 	first := sort.Search(size, f)
-	result := make([]watch.Event, size-first)
+	result := make([]WatchCacheEvent, size-first)
 	for i := 0; i < size-first; i++ {
-		result[i] = w.cache[(w.startIndex+first+i)%w.capacity].event
+		result[i] = w.cache[(w.startIndex+first+i)%w.capacity].watchCacheEvent
 	}
 	return result, nil
 }

pkg/client/cache/watch_cache_test.go

@@ -22,6 +22,7 @@ import (
 
 	"k8s.io/kubernetes/pkg/api"
 	"k8s.io/kubernetes/pkg/util"
+	"k8s.io/kubernetes/pkg/watch"
 )
 
 func makeTestPod(name string, resourceVersion uint64) *api.Pod {
@@ -108,6 +109,34 @@ func TestEvents(t *testing.T) {
 	store := NewWatchCache(5)
 
 	store.Add(makeTestPod("pod", 2))
+
+	// Test for Added event.
+	{
+		_, err := store.GetAllEventsSince(1)
+		if err == nil {
+			t.Errorf("expected error too old")
+		}
+	}
+	{
+		result, err := store.GetAllEventsSince(2)
+		if err != nil {
+			t.Errorf("unexpected error: %v", err)
+		}
+		if len(result) != 1 {
+			t.Fatalf("unexpected events: %v", result)
+		}
+		if result[0].Type != watch.Added {
+			t.Errorf("unexpected event type: %v", result[0].Type)
+		}
+		pod := makeTestPod("pod", uint64(2))
+		if !api.Semantic.DeepEqual(pod, result[0].Object) {
+			t.Errorf("unexpected item: %v, expected: %v", result[0].Object, pod)
+		}
+		if result[0].PrevObject != nil {
+			t.Errorf("unexpected item: %v", result[0].PrevObject)
+		}
+	}
+
 	store.Update(makeTestPod("pod", 3))
 	store.Update(makeTestPod("pod", 4))
 
@@ -127,10 +156,17 @@ func TestEvents(t *testing.T) {
 			t.Fatalf("unexpected events: %v", result)
 		}
 		for i := 0; i < 2; i++ {
+			if result[i].Type != watch.Modified {
+				t.Errorf("unexpected event type: %v", result[i].Type)
+			}
 			pod := makeTestPod("pod", uint64(i+3))
 			if !api.Semantic.DeepEqual(pod, result[i].Object) {
 				t.Errorf("unexpected item: %v, expected: %v", result[i].Object, pod)
 			}
+			prevPod := makeTestPod("pod", uint64(i+2))
+			if !api.Semantic.DeepEqual(prevPod, result[i].PrevObject) {
+				t.Errorf("unexpected item: %v, expected: %v", result[i].PrevObject, prevPod)
+			}
 		}
 	}
 
@@ -160,4 +196,28 @@ func TestEvents(t *testing.T) {
 			}
 		}
 	}
+
+	// Test for delete event.
+	store.Delete(makeTestPod("pod", uint64(9)))
+
+	{
+		result, err := store.GetAllEventsSince(9)
+		if err != nil {
+			t.Errorf("unexpected error: %v", err)
+		}
+		if len(result) != 1 {
+			t.Fatalf("unexpected events: %v", result)
+		}
+		if result[0].Type != watch.Deleted {
+			t.Errorf("unexpected event type: %v", result[0].Type)
+		}
+		pod := makeTestPod("pod", uint64(9))
+		if !api.Semantic.DeepEqual(pod, result[0].Object) {
+			t.Errorf("unexpected item: %v, expected: %v", result[0].Object, pod)
+		}
+		prevPod := makeTestPod("pod", uint64(8))
+		if !api.Semantic.DeepEqual(prevPod, result[0].PrevObject) {
+			t.Errorf("unexpected item: %v, expected: %v", result[0].PrevObject, prevPod)
+		}
+	}
 }