Merge pull request #35029 from wojtek-t/avoid_computing_keys_multiple_times

Automatic merge from submit-queue

Avoid computing keys multiple times in Cacher

This should significantly reduce both cpu-usage and number of allocations in Cacher.

This is a proper follow-up from #30998

@deads2k @liggitt

pkg/storage/cacher.go

@@ -125,6 +125,8 @@ func (i *indexedWatchers) terminateAll(objectType reflect.Type) {
 	}
 }
 
+type filterObjectFunc func(string, runtime.Object) bool
+
 // Cacher is responsible for serving WATCH and LIST requests for a given
 // resource from its internal cache and updating its cache in the background
 // based on the underlying storage contents.
@@ -161,9 +163,6 @@ type Cacher struct {
 	// Versioner is used to handle resource versions.
 	versioner Versioner
 
-	// keyFunc is used to get a key in the underyling storage for a given object.
-	keyFunc func(runtime.Object) (string, error)
-
 	// triggerFunc is used for optimizing amount of watchers that needs to process
 	// an incoming event.
 	triggerFunc TriggerPublisherFunc
@@ -183,7 +182,7 @@ type Cacher struct {
 // internal cache and updating its cache in the background based on the given
 // configuration.
 func NewCacherFromConfig(config CacherConfig) *Cacher {
-	watchCache := newWatchCache(config.CacheCapacity)
+	watchCache := newWatchCache(config.CacheCapacity, config.KeyFunc)
 	listerWatcher := newCacherListerWatcher(config.Storage, config.ResourcePrefix, config.NewListFunc)
 
 	// Give this error when it is constructed rather than when you get the
@@ -201,7 +200,6 @@ func NewCacherFromConfig(config CacherConfig) *Cacher {
 		watchCache:  watchCache,
 		reflector:   cache.NewReflector(listerWatcher, config.Type, watchCache, 0),
 		versioner:   config.Versioner,
-		keyFunc:     config.KeyFunc,
 		triggerFunc: config.TriggerPublisherFunc,
 		watcherIdx:  0,
 		watchers: indexedWatchers{
@@ -328,7 +326,7 @@ func (c *Cacher) Watch(ctx context.Context, key string, resourceVersion string,
 	c.Lock()
 	defer c.Unlock()
 	forget := forgetWatcher(c, c.watcherIdx, triggerValue, triggerSupported)
-	watcher := newCacheWatcher(watchRV, chanSize, initEvents, filterFunction(key, c.keyFunc, pred), forget)
+	watcher := newCacheWatcher(watchRV, chanSize, initEvents, filterFunction(key, pred), forget)
 
 	c.watchers.addWatcher(watcher, c.watcherIdx, triggerValue, triggerSupported)
 	c.watcherIdx++
@@ -382,7 +380,7 @@ func (c *Cacher) List(ctx context.Context, key string, resourceVersion string, p
 	if err != nil || listVal.Kind() != reflect.Slice {
 		return fmt.Errorf("need a pointer to slice, got %v", listVal.Kind())
 	}
-	filter := filterFunction(key, c.keyFunc, pred)
+	filter := filterFunction(key, pred)
 
 	objs, readResourceVersion, err := c.watchCache.WaitUntilFreshAndList(listRV, trace)
 	if err != nil {
@@ -390,12 +388,12 @@ func (c *Cacher) List(ctx context.Context, key string, resourceVersion string, p
 	}
 	trace.Step(fmt.Sprintf("Listed %d items from cache", len(objs)))
 	for _, obj := range objs {
-		object, ok := obj.(runtime.Object)
+		elem, ok := obj.(*storeElement)
 		if !ok {
-			return fmt.Errorf("non runtime.Object returned from storage: %v", obj)
+			return fmt.Errorf("non *storeElement returned from storage: %v", obj)
 		}
-		if filter(object) {
+		if filter(elem.Key, elem.Object) {
-			listVal.Set(reflect.Append(listVal, reflect.ValueOf(object).Elem()))
+			listVal.Set(reflect.Append(listVal, reflect.ValueOf(elem.Object).Elem()))
 		}
 	}
 	trace.Step(fmt.Sprintf("Filtered %d items", listVal.Len()))
@@ -524,14 +522,9 @@ func forgetWatcher(c *Cacher, index int, triggerValue string, triggerSupported b
 	}
 }
 
-func filterFunction(key string, keyFunc func(runtime.Object) (string, error), p SelectionPredicate) FilterFunc {
+func filterFunction(key string, p SelectionPredicate) filterObjectFunc {
 	f := SimpleFilter(p)
-	filterFunc := func(obj runtime.Object) bool {
+	filterFunc := func(objKey string, obj runtime.Object) bool {
-		objKey, err := keyFunc(obj)
-		if err != nil {
-			glog.Errorf("invalid object for filter. Obj: %v. Err: %v", obj, err)
-			return false
-		}
 		if !hasPathPrefix(objKey, key) {
 			return false
 		}
@@ -626,12 +619,12 @@ type cacheWatcher struct {
 	sync.Mutex
 	input   chan watchCacheEvent
 	result  chan watch.Event
-	filter  FilterFunc
+	filter  filterObjectFunc
 	stopped bool
 	forget  func(bool)
 }
 
-func newCacheWatcher(resourceVersion uint64, chanSize int, initEvents []watchCacheEvent, filter FilterFunc, forget func(bool)) *cacheWatcher {
+func newCacheWatcher(resourceVersion uint64, chanSize int, initEvents []watchCacheEvent, filter filterObjectFunc, forget func(bool)) *cacheWatcher {
 	watcher := &cacheWatcher{
 		input:   make(chan watchCacheEvent, chanSize),
 		result:  make(chan watch.Event, chanSize),
@@ -707,11 +700,12 @@ func (c *cacheWatcher) add(event *watchCacheEvent) {
 	}
 }
 
-func (c *cacheWatcher) sendWatchCacheEvent(event watchCacheEvent) {
+// NOTE: sendWatchCacheEvent is assumed to not modify <event> !!!
-	curObjPasses := event.Type != watch.Deleted && c.filter(event.Object)
+func (c *cacheWatcher) sendWatchCacheEvent(event *watchCacheEvent) {
+	curObjPasses := event.Type != watch.Deleted && c.filter(event.Key, event.Object)
 	oldObjPasses := false
 	if event.PrevObject != nil {
-		oldObjPasses = c.filter(event.PrevObject)
+		oldObjPasses = c.filter(event.Key, event.PrevObject)
 	}
 	if !curObjPasses && !oldObjPasses {
 		// Watcher is not interested in that object.
@@ -752,7 +746,7 @@ func (c *cacheWatcher) process(initEvents []watchCacheEvent, resourceVersion uin
 	const initProcessThreshold = 500 * time.Millisecond
 	startTime := time.Now()
 	for _, event := range initEvents {
-		c.sendWatchCacheEvent(event)
+		c.sendWatchCacheEvent(&event)
 	}
 	processingTime := time.Since(startTime)
 	if processingTime > initProcessThreshold {
@@ -772,7 +766,7 @@ func (c *cacheWatcher) process(initEvents []watchCacheEvent, resourceVersion uin
 		}
 		// only send events newer than resourceVersion
 		if event.ResourceVersion > resourceVersion {
-			c.sendWatchCacheEvent(event)
+			c.sendWatchCacheEvent(&event)
 		}
 	}
 }

pkg/storage/watch_cache.go

@@ -46,9 +46,27 @@ type watchCacheEvent struct {
 	Type            watch.EventType
 	Object          runtime.Object
 	PrevObject      runtime.Object
+	Key             string
 	ResourceVersion uint64
 }
 
+// Computing a key of an object is generally non-trivial (it performs
+// e.g. validation underneath). To avoid computing it multiple times
+// (to serve the event in different List/Watch requests), in the
+// underlying store we are keeping pair (key, object).
+type storeElement struct {
+	Key    string
+	Object runtime.Object
+}
+
+func storeElementKey(obj interface{}) (string, error) {
+	elem, ok := obj.(*storeElement)
+	if !ok {
+		return "", fmt.Errorf("not a storeElement: %v", obj)
+	}
+	return elem.Key, nil
+}
+
 // watchCacheElement is a single "watch event" stored in a cache.
 // It contains the resource version of the object and the object
 // itself.
@@ -72,6 +90,9 @@ type watchCache struct {
 	// Maximum size of history window.
 	capacity int
 
+	// keyFunc is used to get a key in the underlying storage for a given object.
+	keyFunc func(runtime.Object) (string, error)
+
 	// cache is used a cyclic buffer - its first element (with the smallest
 	// resourceVersion) is defined by startIndex, its last element is defined
 	// by endIndex (if cache is full it will be startIndex + capacity).
@@ -100,13 +121,14 @@ type watchCache struct {
 	clock clock.Clock
 }
 
-func newWatchCache(capacity int) *watchCache {
+func newWatchCache(capacity int, keyFunc func(runtime.Object) (string, error)) *watchCache {
 	wc := &watchCache{
 		capacity:        capacity,
+		keyFunc:         keyFunc,
 		cache:           make([]watchCacheElement, capacity),
 		startIndex:      0,
 		endIndex:        0,
-		store:           cache.NewStore(cache.MetaNamespaceKeyFunc),
+		store:           cache.NewStore(storeElementKey),
 		resourceVersion: 0,
 		clock:           clock.RealClock{},
 	}
@@ -114,6 +136,7 @@ func newWatchCache(capacity int) *watchCache {
 	return wc
 }
 
+// Add takes runtime.Object as an argument.
 func (w *watchCache) Add(obj interface{}) error {
 	object, resourceVersion, err := objectToVersionedRuntimeObject(obj)
 	if err != nil {
@@ -121,10 +144,11 @@ func (w *watchCache) Add(obj interface{}) error {
 	}
 	event := watch.Event{Type: watch.Added, Object: object}
 
-	f := func(obj runtime.Object) error { return w.store.Add(obj) }
+	f := func(elem *storeElement) error { return w.store.Add(elem) }
 	return w.processEvent(event, resourceVersion, f)
 }
 
+// Update takes runtime.Object as an argument.
 func (w *watchCache) Update(obj interface{}) error {
 	object, resourceVersion, err := objectToVersionedRuntimeObject(obj)
 	if err != nil {
@@ -132,10 +156,11 @@ func (w *watchCache) Update(obj interface{}) error {
 	}
 	event := watch.Event{Type: watch.Modified, Object: object}
 
-	f := func(obj runtime.Object) error { return w.store.Update(obj) }
+	f := func(elem *storeElement) error { return w.store.Update(elem) }
 	return w.processEvent(event, resourceVersion, f)
 }
 
+// Delete takes runtime.Object as an argument.
 func (w *watchCache) Delete(obj interface{}) error {
 	object, resourceVersion, err := objectToVersionedRuntimeObject(obj)
 	if err != nil {
@@ -143,7 +168,7 @@ func (w *watchCache) Delete(obj interface{}) error {
 	}
 	event := watch.Event{Type: watch.Deleted, Object: object}
 
-	f := func(obj runtime.Object) error { return w.store.Delete(obj) }
+	f := func(elem *storeElement) error { return w.store.Delete(elem) }
 	return w.processEvent(event, resourceVersion, f)
 }
 
@@ -170,43 +195,57 @@ func parseResourceVersion(resourceVersion string) (uint64, error) {
 	return strconv.ParseUint(resourceVersion, 10, 64)
 }
 
-func (w *watchCache) processEvent(event watch.Event, resourceVersion uint64, updateFunc func(runtime.Object) error) error {
+func (w *watchCache) processEvent(event watch.Event, resourceVersion uint64, updateFunc func(*storeElement) error) error {
+	key, err := w.keyFunc(event.Object)
+	if err != nil {
+		return fmt.Errorf("couldn't compute key: %v", err)
+	}
+	elem := &storeElement{Key: key, Object: event.Object}
+
 	w.Lock()
 	defer w.Unlock()
-	previous, exists, err := w.store.Get(event.Object)
+	previous, exists, err := w.store.Get(elem)
 	if err != nil {
 		return err
 	}
 	var prevObject runtime.Object
 	if exists {
-		prevObject = previous.(runtime.Object)
+		prevObject = previous.(*storeElement).Object
+	}
+	watchCacheEvent := watchCacheEvent{
+		Type:            event.Type,
+		Object:          event.Object,
+		PrevObject:      prevObject,
+		Key:             key,
+		ResourceVersion: resourceVersion,
 	}
-	watchCacheEvent := watchCacheEvent{event.Type, event.Object, prevObject, resourceVersion}
 	if w.onEvent != nil {
 		w.onEvent(watchCacheEvent)
 	}
-	w.updateCache(resourceVersion, watchCacheEvent)
+	w.updateCache(resourceVersion, &watchCacheEvent)
 	w.resourceVersion = resourceVersion
 	w.cond.Broadcast()
-	return updateFunc(event.Object)
+	return updateFunc(elem)
 }
 
 // Assumes that lock is already held for write.
-func (w *watchCache) updateCache(resourceVersion uint64, event watchCacheEvent) {
+func (w *watchCache) updateCache(resourceVersion uint64, event *watchCacheEvent) {
 	if w.endIndex == w.startIndex+w.capacity {
 		// Cache is full - remove the oldest element.
 		w.startIndex++
 	}
-	w.cache[w.endIndex%w.capacity] = watchCacheElement{resourceVersion, event}
+	w.cache[w.endIndex%w.capacity] = watchCacheElement{resourceVersion, *event}
 	w.endIndex++
 }
 
+// List returns list of pointers to <storeElement> objects.
 func (w *watchCache) List() []interface{} {
 	w.RLock()
 	defer w.RUnlock()
 	return w.store.List()
 }
 
+// WaitUntilFreshAndList returns list of pointers to <storeElement> objects.
 func (w *watchCache) WaitUntilFreshAndList(resourceVersion uint64, trace *util.Trace) ([]interface{}, uint64, error) {
 	startTime := w.clock.Now()
 	go func() {
@@ -244,30 +283,56 @@ func (w *watchCache) ListKeys() []string {
 	return w.store.ListKeys()
 }
 
+// Get takes runtime.Object as a parameter. However, it returns
+// pointer to <storeElement>.
 func (w *watchCache) Get(obj interface{}) (interface{}, bool, error) {
+	object, ok := obj.(runtime.Object)
+	if !ok {
+		return nil, false, fmt.Errorf("obj does not implement runtime.Object interface: %v", obj)
+	}
+	key, err := w.keyFunc(object)
+	if err != nil {
+		return nil, false, fmt.Errorf("couldn't compute key: %v", err)
+	}
+
 	w.RLock()
 	defer w.RUnlock()
-	return w.store.Get(obj)
+	return w.store.Get(&storeElement{Key: key, Object: object})
 }
 
+// GetByKey returns pointer to <storeElement>.
 func (w *watchCache) GetByKey(key string) (interface{}, bool, error) {
 	w.RLock()
 	defer w.RUnlock()
 	return w.store.GetByKey(key)
 }
 
+// Replace takes slice of runtime.Object as a paramater.
 func (w *watchCache) Replace(objs []interface{}, resourceVersion string) error {
 	version, err := parseResourceVersion(resourceVersion)
 	if err != nil {
 		return err
 	}
 
+	toReplace := make([]interface{}, 0, len(objs))
+	for _, obj := range objs {
+		object, ok := obj.(runtime.Object)
+		if !ok {
+			return fmt.Errorf("didn't get runtime.Object for replace: %#v", obj)
+		}
+		key, err := w.keyFunc(object)
+		if err != nil {
+			return fmt.Errorf("couldn't compute key: %v", err)
+		}
+		toReplace = append(toReplace, &storeElement{Key: key, Object: object})
+	}
+
 	w.Lock()
 	defer w.Unlock()
 
 	w.startIndex = 0
 	w.endIndex = 0
-	if err := w.store.Replace(objs, resourceVersion); err != nil {
+	if err := w.store.Replace(toReplace, resourceVersion); err != nil {
 		return err
 	}
 	w.resourceVersion = version
@@ -306,7 +371,16 @@ func (w *watchCache) GetAllEventsSinceThreadUnsafe(resourceVersion uint64) ([]wa
 		allItems := w.store.List()
 		result := make([]watchCacheEvent, len(allItems))
 		for i, item := range allItems {
-			result[i] = watchCacheEvent{Type: watch.Added, Object: item.(runtime.Object)}
+			elem, ok := item.(*storeElement)
+			if !ok {
+				return nil, fmt.Errorf("not a storeElement: %v", elem)
+			}
+			result[i] = watchCacheEvent{
+				Type:            watch.Added,
+				Object:          elem.Object,
+				Key:             elem.Key,
+				ResourceVersion: w.resourceVersion,
+			}
 		}
 		return result, nil
 	}

pkg/storage/watch_cache_test.go

@@ -44,7 +44,10 @@ func makeTestPod(name string, resourceVersion uint64) *api.Pod {
 
 // newTestWatchCache just adds a fake clock.
 func newTestWatchCache(capacity int) *watchCache {
-	wc := newWatchCache(capacity)
+	keyFunc := func(obj runtime.Object) (string, error) {
+		return NamespaceKeyFunc("prefix", obj)
+	}
+	wc := newWatchCache(capacity, keyFunc)
 	wc.clock = clock.NewFakeClock(time.Now())
 	return wc
 }
@@ -60,7 +63,7 @@ func TestWatchCacheBasic(t *testing.T) {
 	if item, ok, _ := store.Get(pod1); !ok {
 		t.Errorf("didn't find pod")
 	} else {
-		if !api.Semantic.DeepEqual(pod1, item) {
+		if !api.Semantic.DeepEqual(&storeElement{Key: "prefix/ns/pod", Object: pod1}, item) {
 			t.Errorf("expected %v, got %v", pod1, item)
 		}
 	}
@@ -71,7 +74,7 @@ func TestWatchCacheBasic(t *testing.T) {
 	if item, ok, _ := store.Get(pod2); !ok {
 		t.Errorf("didn't find pod")
 	} else {
-		if !api.Semantic.DeepEqual(pod2, item) {
+		if !api.Semantic.DeepEqual(&storeElement{Key: "prefix/ns/pod", Object: pod2}, item) {
 			t.Errorf("expected %v, got %v", pod1, item)
 		}
 	}
@@ -90,7 +93,7 @@ func TestWatchCacheBasic(t *testing.T) {
 	{
 		podNames := sets.String{}
 		for _, item := range store.List() {
-			podNames.Insert(item.(*api.Pod).ObjectMeta.Name)
+			podNames.Insert(item.(*storeElement).Object.(*api.Pod).ObjectMeta.Name)
 		}
 		if !podNames.HasAll("pod1", "pod2", "pod3") {
 			t.Errorf("missing pods, found %v", podNames)
@@ -108,7 +111,7 @@ func TestWatchCacheBasic(t *testing.T) {
 	{
 		podNames := sets.String{}
 		for _, item := range store.List() {
-			podNames.Insert(item.(*api.Pod).ObjectMeta.Name)
+			podNames.Insert(item.(*storeElement).Object.(*api.Pod).ObjectMeta.Name)
 		}
 		if !podNames.HasAll("pod4", "pod5") {
 			t.Errorf("missing pods, found %v", podNames)