Implement Cacher for watch in apiserver

2025-07-23 11:50:44 +00:00 · 2015-07-28 08:26:53 +02:00 · 2015-07-28 08:26:53 +02:00 · e424da7d0d
commit e424da7d0d
parent 8dcbebae5e
5 changed files with 703 additions and 18 deletions
--- a/pkg/client/cache/reflector.go
+++ b/pkg/client/cache/reflector.go
@ -170,30 +170,27 @@ func (r *Reflector) resyncChan() (<-chan time.Time, func() bool) {
 	return t.C, t.Stop
 }

-func (r *Reflector) ListAndWatch(stopCh <-chan struct{}) {
+// Returns error if ListAndWatch didn't even tried to initialize watch.
+func (r *Reflector) ListAndWatch(stopCh <-chan struct{}) error {
 	var resourceVersion string
 	resyncCh, cleanup := r.resyncChan()
 	defer cleanup()

 	list, err := r.listerWatcher.List()
 	if err != nil {
-		util.HandleError(fmt.Errorf("%s: Failed to list %v: %v", r.name, r.expectedType, err))
-		return
+		return fmt.Errorf("%s: Failed to list %v: %v", r.name, r.expectedType, err)
 	}
 	meta, err := meta.Accessor(list)
 	if err != nil {
-		util.HandleError(fmt.Errorf("%s: Unable to understand list result %#v", r.name, list))
-		return
+		return fmt.Errorf("%s: Unable to understand list result %#v", r.name, list)
 	}
 	resourceVersion = meta.ResourceVersion()
 	items, err := runtime.ExtractList(list)
 	if err != nil {
-		util.HandleError(fmt.Errorf("%s: Unable to understand list result %#v (%v)", r.name, list, err))
-		return
+		return fmt.Errorf("%s: Unable to understand list result %#v (%v)", r.name, list, err)
 	}
 	if err := r.syncWith(items, resourceVersion); err != nil {
-		util.HandleError(fmt.Errorf("%s: Unable to sync list result: %v", r.name, err))
-		return
+		return fmt.Errorf("%s: Unable to sync list result: %v", r.name, err)
 	}
 	r.setLastSyncResourceVersion(resourceVersion)

@ -220,13 +217,13 @@ func (r *Reflector) ListAndWatch(stopCh <-chan struct{}) {
 					}
 				}
 			}
-			return
+			return nil
 		}
 		if err := r.watchHandler(w, &resourceVersion, resyncCh, stopCh); err != nil {
 			if err != errorResyncRequested && err != errorStopRequested {
 				glog.Warningf("%s: watch of %v ended with: %v", r.name, r.expectedType, err)
 			}
-			return
+			return nil
 		}
 	}
 }
@ -277,6 +274,7 @@ loop:
 				util.HandleError(fmt.Errorf("%s: unable to understand watch event %#v", r.name, event))
 				continue
 			}
+			newResourceVersion := meta.ResourceVersion()
 			switch event.Type {
 			case watch.Added:
 				r.store.Add(event.Object)
@ -290,8 +288,8 @@ loop:
 			default:
 				util.HandleError(fmt.Errorf("%s: unable to understand watch event %#v", r.name, event))
 			}
-			*resourceVersion = meta.ResourceVersion()
-			r.setLastSyncResourceVersion(*resourceVersion)
+			*resourceVersion = newResourceVersion
+			r.setLastSyncResourceVersion(newResourceVersion)
 			eventCount++
 		}
 	}
--- a/pkg/client/cache/watch_cache.go
+++ b/pkg/client/cache/watch_cache.go
@ -123,13 +123,20 @@ func objectToVersionedRuntimeObject(obj interface{}) (runtime.Object, uint64, er
 	if err != nil {
 		return nil, 0, err
 	}
-	resourceVersion, err := strconv.ParseUint(meta.ResourceVersion(), 10, 64)
+	resourceVersion, err := parseResourceVersion(meta.ResourceVersion())
 	if err != nil {
 		return nil, 0, err
 	}
 	return object, resourceVersion, nil
 }

+func parseResourceVersion(resourceVersion string) (uint64, error) {
+	if resourceVersion == "" {
+		return 0, nil
+	}
+	return strconv.ParseUint(resourceVersion, 10, 64)
+}
+
 func (w *WatchCache) processEvent(event watch.Event, resourceVersion uint64, updateFunc func(runtime.Object) error) error {
 	w.Lock()
 	defer w.Unlock()
@ -186,7 +193,7 @@ func (w *WatchCache) Replace(objs []interface{}) error {
 }

 func (w *WatchCache) ReplaceWithVersion(objs []interface{}, resourceVersion string) error {
-	version, err := strconv.ParseUint(resourceVersion, 10, 64)
+	version, err := parseResourceVersion(resourceVersion)
 	if err != nil {
 		return err
 	}
@ -227,15 +234,15 @@ func (w *WatchCache) GetAllEventsSince(resourceVersion uint64) ([]watch.Event, e
 	if size > 0 {
 		oldest = w.cache[w.startIndex%w.capacity].resourceVersion
 	}
+	if resourceVersion < oldest {
+		return nil, fmt.Errorf("too old resource version: %d (%d)", resourceVersion, oldest)
+	}

 	// Binary seatch the smallest index at which resourceVersion is not smaller than
 	// the given one.
 	f := func(i int) bool {
 		return w.cache[(w.startIndex+i)%w.capacity].resourceVersion >= resourceVersion
 	}
-	if size > 0 && resourceVersion < oldest {
-		return nil, fmt.Errorf("too old resource version: %d (%d)", resourceVersion, oldest)
-	}
 	first := sort.Search(size, f)
 	result := make([]watch.Event, size-first)
 	for i := 0; i < size-first; i++ {
--- a/pkg/storage/cacher.go
+++ b/pkg/storage/cacher.go
@ -0,0 +1,334 @@
+/*
+Copyright 2015 The Kubernetes Authors All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package storage
+
+import (
+	"fmt"
+	"reflect"
+	"strconv"
+	"strings"
+	"sync"
+
+	"k8s.io/kubernetes/pkg/client/cache"
+	"k8s.io/kubernetes/pkg/conversion"
+	"k8s.io/kubernetes/pkg/runtime"
+	"k8s.io/kubernetes/pkg/util"
+	"k8s.io/kubernetes/pkg/watch"
+
+	"github.com/golang/glog"
+)
+
+// CacherConfig contains the configuration for a given Cache.
+type CacherConfig struct {
+	// Maximum size of the history cached in memory.
+	CacheCapacity int
+
+	// An underlying storage.Interface.
+	Storage Interface
+
+	// An underlying storage.Versioner.
+	Versioner Versioner
+
+	// The Cache will be caching objects of a given Type and assumes that they
+	// are all stored under ResourcePrefix directory in the underlying database.
+	Type           interface{}
+	ResourcePrefix string
+
+	// KeyFunc is used to get a key in the underyling storage for a given object.
+	KeyFunc func(runtime.Object) (string, error)
+
+	// NewList is a function that creates new empty object storing a list of
+	// objects of type Type.
+	NewListFunc func() runtime.Object
+
+	// Cacher will be stopped when the StopChannel will be closed.
+	StopChannel <-chan struct{}
+}
+
+// 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.
+type Cacher struct {
+	sync.RWMutex
+
+	// Whether Cacher is initialized.
+	initialized sync.WaitGroup
+	initOnce    sync.Once
+
+	// "sliding window" of recent changes of objects and the current state.
+	watchCache *cache.WatchCache
+	reflector  *cache.Reflector
+
+	// Registered watchers.
+	watcherIdx int
+	watchers   map[int]*cacheWatcher
+
+	// 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)
+}
+
+// Create a new Cacher responsible from service WATCH and LIST requests from its
+// internal cache and updating its cache in the background based on the given
+// configuration.
+func NewCacher(config CacherConfig) *Cacher {
+	watchCache := cache.NewWatchCache(config.CacheCapacity)
+	listerWatcher := newCacherListerWatcher(config.Storage, config.ResourcePrefix, config.NewListFunc)
+
+	cacher := &Cacher{
+		initialized: sync.WaitGroup{},
+		watchCache:  watchCache,
+		reflector:   cache.NewReflector(listerWatcher, config.Type, watchCache, 0),
+		watcherIdx:  0,
+		watchers:    make(map[int]*cacheWatcher),
+		versioner:   config.Versioner,
+		keyFunc:     config.KeyFunc,
+	}
+	cacher.initialized.Add(1)
+	// See startCaching method for why explanation on it.
+	watchCache.SetOnReplace(func() {
+		cacher.initOnce.Do(func() { cacher.initialized.Done() })
+		cacher.Unlock()
+	})
+	watchCache.SetOnEvent(cacher.processEvent)
+
+	stopCh := config.StopChannel
+	go util.Until(func() { cacher.startCaching(stopCh) }, 0, stopCh)
+	cacher.initialized.Wait()
+	return cacher
+}
+
+func (c *Cacher) startCaching(stopChannel <-chan struct{}) {
+	c.Lock()
+	c.terminateAllWatchers()
+	// We explicitly do NOT Unlock() in this method.
+	// This is because we do not want to allow any WATCH/LIST methods before
+	// the cache is initialized. Once the underlying cache is propagated,
+	// onReplace handler will be called, which will do the Unlock() as
+	// configured in NewCacher().
+	// Note: the same bahavior is also triggered every time we fall out of
+	// backen storage (e.g. etcd's) watch event window.
+	// Note that since onReplace may be not called due to errors, we explicitly
+	// need to retry it on errors under lock.
+	for {
+		err := c.reflector.ListAndWatch(stopChannel)
+		if err == nil {
+			break
+		}
+	}
+}
+
+// Implements Watch (signature from storage.Interface).
+func (c *Cacher) Watch(key string, resourceVersion uint64, filter FilterFunc) (watch.Interface, error) {
+	c.Lock()
+	defer c.Unlock()
+
+	initEvents, err := c.watchCache.GetAllEventsSince(resourceVersion)
+	if err != nil {
+		return nil, err
+	}
+	watcher := newCacheWatcher(initEvents, filterFunction(key, c.keyFunc, filter), forgetWatcher(c, c.watcherIdx))
+	c.watchers[c.watcherIdx] = watcher
+	c.watcherIdx++
+	return watcher, nil
+}
+
+// Implements WatchList (signature from storage.Interface).
+func (c *Cacher) WatchList(key string, resourceVersion uint64, filter FilterFunc) (watch.Interface, error) {
+	return c.Watch(key, resourceVersion, filter)
+}
+
+// Implements List (signature from storage.Interface).
+func (c *Cacher) List(key string, listObj runtime.Object) error {
+	listPtr, err := runtime.GetItemsPtr(listObj)
+	if err != nil {
+		return err
+	}
+	listVal, err := conversion.EnforcePtr(listPtr)
+	if err != nil || listVal.Kind() != reflect.Slice {
+		return fmt.Errorf("need a pointer to slice, got %v", listVal.Kind())
+	}
+	filter := filterFunction(key, c.keyFunc, Everything)
+
+	objs, resourceVersion := c.watchCache.ListWithVersion()
+	for _, obj := range objs {
+		object, ok := obj.(runtime.Object)
+		if !ok {
+			return fmt.Errorf("non runtime.Object returned from storage: %v", obj)
+		}
+		if filter(object) {
+			listVal.Set(reflect.Append(listVal, reflect.ValueOf(object).Elem()))
+		}
+	}
+	if c.versioner != nil {
+		if err := c.versioner.UpdateList(listObj, resourceVersion); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (c *Cacher) processEvent(event watch.Event) {
+	c.Lock()
+	defer c.Unlock()
+	for _, watcher := range c.watchers {
+		watcher.add(event)
+	}
+}
+
+func (c *Cacher) terminateAllWatchers() {
+	for key, watcher := range c.watchers {
+		delete(c.watchers, key)
+		watcher.stop()
+	}
+}
+
+func forgetWatcher(c *Cacher, index int) func() {
+	return func() {
+		c.Lock()
+		defer c.Unlock()
+		// It's possible that the watcher is already not in the map (e.g. in case of
+		// simulaneous Stop() and terminateAllWatchers(), but it doesn't break anything.
+		delete(c.watchers, index)
+	}
+}
+
+func filterFunction(key string, keyFunc func(runtime.Object) (string, error), filter FilterFunc) FilterFunc {
+	return func(obj runtime.Object) bool {
+		objKey, err := keyFunc(obj)
+		if err != nil {
+			glog.Errorf("Invalid object for filter: %v", obj)
+			return false
+		}
+		if !strings.HasPrefix(objKey, key) {
+			return false
+		}
+		return filter(obj)
+	}
+}
+
+// Returns resource version to which the underlying cache is synced.
+func (c *Cacher) LastSyncResourceVersion() (uint64, error) {
+	c.RLock()
+	defer c.RUnlock()
+
+	resourceVersion := c.reflector.LastSyncResourceVersion()
+	if resourceVersion == "" {
+		return 0, nil
+	}
+	return strconv.ParseUint(resourceVersion, 10, 64)
+}
+
+// cacherListerWatcher opaques storage.Interface to expose cache.ListerWatcher.
+type cacherListerWatcher struct {
+	storage        Interface
+	resourcePrefix string
+	newListFunc    func() runtime.Object
+}
+
+func newCacherListerWatcher(storage Interface, resourcePrefix string, newListFunc func() runtime.Object) cache.ListerWatcher {
+	return &cacherListerWatcher{
+		storage:        storage,
+		resourcePrefix: resourcePrefix,
+		newListFunc:    newListFunc,
+	}
+}
+
+// Implements cache.ListerWatcher interface.
+func (lw *cacherListerWatcher) List() (runtime.Object, error) {
+	list := lw.newListFunc()
+	if err := lw.storage.List(lw.resourcePrefix, list); err != nil {
+		return nil, err
+	}
+	return list, nil
+}
+
+// Implements cache.ListerWatcher interface.
+func (lw *cacherListerWatcher) Watch(resourceVersion string) (watch.Interface, error) {
+	version, err := ParseWatchResourceVersion(resourceVersion, lw.resourcePrefix)
+	if err != nil {
+		return nil, err
+	}
+	return lw.storage.WatchList(lw.resourcePrefix, version, Everything)
+}
+
+// cacherWatch implements watch.Interface
+type cacheWatcher struct {
+	sync.Mutex
+	input   chan watch.Event
+	result  chan watch.Event
+	filter  FilterFunc
+	stopped bool
+	forget  func()
+}
+
+func newCacheWatcher(initEvents []watch.Event, filter FilterFunc, forget func()) *cacheWatcher {
+	watcher := &cacheWatcher{
+		input:   make(chan watch.Event, 10),
+		result:  make(chan watch.Event, 10),
+		filter:  filter,
+		stopped: false,
+		forget:  forget,
+	}
+	go watcher.process(initEvents)
+	return watcher
+}
+
+// Implements watch.Interface.
+func (c *cacheWatcher) ResultChan() <-chan watch.Event {
+	return c.result
+}
+
+// Implements watch.Interface.
+func (c *cacheWatcher) Stop() {
+	c.forget()
+	c.stop()
+}
+
+func (c *cacheWatcher) stop() {
+	c.Lock()
+	defer c.Unlock()
+	if !c.stopped {
+		c.stopped = true
+		close(c.input)
+	}
+}
+
+func (c *cacheWatcher) add(event watch.Event) {
+	c.input <- event
+}
+
+func (c *cacheWatcher) process(initEvents []watch.Event) {
+	for _, event := range initEvents {
+		if c.filter(event.Object) {
+			c.result <- event
+		}
+	}
+	defer close(c.result)
+	defer c.Stop()
+	for {
+		event, ok := <-c.input
+		if !ok {
+			return
+		}
+		if c.filter(event.Object) {
+			c.result <- event
+		}
+	}
+}
--- a/pkg/storage/cacher_test.go
+++ b/pkg/storage/cacher_test.go
@ -0,0 +1,337 @@
+/*
+Copyright 2015 The Kubernetes Authors All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package storage_test
+
+import (
+	"fmt"
+	"reflect"
+	"testing"
+	"time"
+
+	"github.com/coreos/go-etcd/etcd"
+
+	"k8s.io/kubernetes/pkg/api"
+	"k8s.io/kubernetes/pkg/api/testapi"
+	"k8s.io/kubernetes/pkg/runtime"
+	"k8s.io/kubernetes/pkg/storage"
+	etcdstorage "k8s.io/kubernetes/pkg/storage/etcd"
+	"k8s.io/kubernetes/pkg/tools"
+	"k8s.io/kubernetes/pkg/tools/etcdtest"
+	"k8s.io/kubernetes/pkg/util"
+	"k8s.io/kubernetes/pkg/util/wait"
+	"k8s.io/kubernetes/pkg/watch"
+)
+
+func newTestCacher(client tools.EtcdClient) *storage.Cacher {
+	prefix := "pods"
+	config := storage.CacherConfig{
+		CacheCapacity:  10,
+		Versioner:      etcdstorage.APIObjectVersioner{},
+		Storage:        etcdstorage.NewEtcdStorage(client, testapi.Codec(), etcdtest.PathPrefix()),
+		Type:           &api.Pod{},
+		ResourcePrefix: prefix,
+		KeyFunc:        func(obj runtime.Object) (string, error) { return storage.NamespaceKeyFunc(prefix, obj) },
+		NewListFunc:    func() runtime.Object { return &api.PodList{} },
+		StopChannel:    util.NeverStop,
+	}
+	return storage.NewCacher(config)
+}
+
+func makeTestPod(name string) *api.Pod {
+	return &api.Pod{
+		ObjectMeta: api.ObjectMeta{Namespace: "ns", Name: name},
+		Spec: api.PodSpec{
+			DNSPolicy:     api.DNSClusterFirst,
+			RestartPolicy: api.RestartPolicyAlways,
+		},
+	}
+}
+
+func waitForUpToDateCache(cacher *storage.Cacher, resourceVersion uint64) error {
+	ready := func() (bool, error) {
+		result, err := cacher.LastSyncResourceVersion()
+		if err != nil {
+			return false, err
+		}
+		return result == resourceVersion, nil
+	}
+	return wait.Poll(10*time.Millisecond, 100*time.Millisecond, ready)
+}
+
+func TestList(t *testing.T) {
+	fakeClient := tools.NewFakeEtcdClient(t)
+	prefixedKey := etcdtest.AddPrefix("pods")
+	fakeClient.ExpectNotFoundGet(prefixedKey)
+	cacher := newTestCacher(fakeClient)
+	fakeClient.WaitForWatchCompletion()
+
+	podFoo := makeTestPod("foo")
+	podBar := makeTestPod("bar")
+	podBaz := makeTestPod("baz")
+
+	podFooPrime := makeTestPod("foo")
+	podFooPrime.Spec.NodeName = "fakeNode"
+
+	testCases := []*etcd.Response{
+		{
+			Action: "create",
+			Node: &etcd.Node{
+				Value:         string(runtime.EncodeOrDie(testapi.Codec(), podFoo)),
+				CreatedIndex:  1,
+				ModifiedIndex: 1,
+			},
+		},
+		{
+			Action: "create",
+			Node: &etcd.Node{
+				Value:         string(runtime.EncodeOrDie(testapi.Codec(), podBar)),
+				CreatedIndex:  2,
+				ModifiedIndex: 2,
+			},
+		},
+		{
+			Action: "create",
+			Node: &etcd.Node{
+				Value:         string(runtime.EncodeOrDie(testapi.Codec(), podBaz)),
+				CreatedIndex:  3,
+				ModifiedIndex: 3,
+			},
+		},
+		{
+			Action: "set",
+			Node: &etcd.Node{
+				Value:         string(runtime.EncodeOrDie(testapi.Codec(), podFooPrime)),
+				CreatedIndex:  1,
+				ModifiedIndex: 4,
+			},
+			PrevNode: &etcd.Node{
+				Value:         string(runtime.EncodeOrDie(testapi.Codec(), podFoo)),
+				CreatedIndex:  1,
+				ModifiedIndex: 1,
+			},
+		},
+		{
+			Action: "delete",
+			Node: &etcd.Node{
+				CreatedIndex:  1,
+				ModifiedIndex: 5,
+			},
+			PrevNode: &etcd.Node{
+				Value:         string(runtime.EncodeOrDie(testapi.Codec(), podBar)),
+				CreatedIndex:  1,
+				ModifiedIndex: 1,
+			},
+		},
+	}
+
+	// Propagate some data to etcd.
+	for _, test := range testCases {
+		fakeClient.WatchResponse <- test
+	}
+	if err := waitForUpToDateCache(cacher, 5); err != nil {
+		t.Errorf("watch cache didn't propagated correctly: %v", err)
+	}
+
+	result := &api.PodList{}
+	if err := cacher.List("pods/ns", result); err != nil {
+		t.Errorf("unexpected error: %v", err)
+	}
+	if result.ListMeta.ResourceVersion != "5" {
+		t.Errorf("incorrect resource version: %v", result.ListMeta.ResourceVersion)
+	}
+	if len(result.Items) != 2 {
+		t.Errorf("unexpected list result: %d", len(result.Items))
+	}
+	keys := util.StringSet{}
+	for _, item := range result.Items {
+		keys.Insert(item.ObjectMeta.Name)
+	}
+	if !keys.HasAll("foo", "baz") {
+		t.Errorf("unexpected list result: %#v", result)
+	}
+	for _, item := range result.Items {
+		// unset fields that are set by the infrastructure
+		item.ObjectMeta.ResourceVersion = ""
+		item.ObjectMeta.CreationTimestamp = util.Time{}
+
+		var expected *api.Pod
+		switch item.ObjectMeta.Name {
+		case "foo":
+			expected = podFooPrime
+		case "baz":
+			expected = podBaz
+		default:
+			t.Errorf("unexpected item: %v", item)
+		}
+		if e, a := *expected, item; !reflect.DeepEqual(e, a) {
+			t.Errorf("expected: %#v, got: %#v", e, a)
+		}
+	}
+
+	close(fakeClient.WatchResponse)
+}
+
+func TestWatch(t *testing.T) {
+	fakeClient := tools.NewFakeEtcdClient(t)
+	prefixedKey := etcdtest.AddPrefix("pods")
+	fakeClient.ExpectNotFoundGet(prefixedKey)
+	cacher := newTestCacher(fakeClient)
+	fakeClient.WaitForWatchCompletion()
+
+	podFoo := makeTestPod("foo")
+	podBar := makeTestPod("bar")
+
+	testCases := []struct {
+		object       *api.Pod
+		etcdResponse *etcd.Response
+		event        watch.EventType
+		filtered     bool
+	}{
+		{
+			object: podFoo,
+			etcdResponse: &etcd.Response{
+				Action: "create",
+				Node: &etcd.Node{
+					Value:         string(runtime.EncodeOrDie(testapi.Codec(), podFoo)),
+					CreatedIndex:  1,
+					ModifiedIndex: 1,
+				},
+			},
+			event:    watch.Added,
+			filtered: true,
+		},
+		{
+			object: podBar,
+			etcdResponse: &etcd.Response{
+				Action: "create",
+				Node: &etcd.Node{
+					Value:         string(runtime.EncodeOrDie(testapi.Codec(), podBar)),
+					CreatedIndex:  2,
+					ModifiedIndex: 2,
+				},
+			},
+			event:    watch.Added,
+			filtered: false,
+		},
+		{
+			object: podFoo,
+			etcdResponse: &etcd.Response{
+				Action: "set",
+				Node: &etcd.Node{
+					Value:         string(runtime.EncodeOrDie(testapi.Codec(), podFoo)),
+					CreatedIndex:  1,
+					ModifiedIndex: 3,
+				},
+				PrevNode: &etcd.Node{
+					Value:         string(runtime.EncodeOrDie(testapi.Codec(), podFoo)),
+					CreatedIndex:  1,
+					ModifiedIndex: 1,
+				},
+			},
+			event:    watch.Modified,
+			filtered: true,
+		},
+	}
+
+	// Set up Watch for object "podFoo".
+	watcher, err := cacher.Watch("pods/ns/foo", 1, storage.Everything)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	for _, test := range testCases {
+		fakeClient.WatchResponse <- test.etcdResponse
+		if test.filtered {
+			event := <-watcher.ResultChan()
+			if e, a := test.event, event.Type; e != a {
+				t.Errorf("%v %v", e, a)
+			}
+			// unset fields that are set by the infrastructure
+			obj := event.Object.(*api.Pod)
+			obj.ObjectMeta.ResourceVersion = ""
+			obj.ObjectMeta.CreationTimestamp = util.Time{}
+			if e, a := test.object, obj; !reflect.DeepEqual(e, a) {
+				t.Errorf("expected: %#v, got: %#v", e, a)
+			}
+		}
+	}
+
+	// Check whether we get too-old error.
+	_, err = cacher.Watch("pods/ns/foo", 0, storage.Everything)
+	if err == nil {
+		t.Errorf("expected 'error too old' error")
+	}
+
+	// Now test watch with initial state.
+	initialWatcher, err := cacher.Watch("pods/ns/foo", 1, storage.Everything)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	for _, test := range testCases {
+		if test.filtered {
+			event := <-initialWatcher.ResultChan()
+			if e, a := test.event, event.Type; e != a {
+				t.Errorf("%v %v", e, a)
+			}
+			// unset fields that are set by the infrastructure
+			obj := event.Object.(*api.Pod)
+			obj.ObjectMeta.ResourceVersion = ""
+			obj.ObjectMeta.CreationTimestamp = util.Time{}
+			if e, a := test.object, obj; !reflect.DeepEqual(e, a) {
+				t.Errorf("expected: %#v, got: %#v", e, a)
+			}
+		}
+	}
+
+	close(fakeClient.WatchResponse)
+}
+
+func TestStorageError(t *testing.T) {
+	fakeClient := tools.NewFakeEtcdClient(t)
+	prefixedKey := etcdtest.AddPrefix("pods")
+	fakeClient.ExpectNotFoundGet(prefixedKey)
+	cacher := newTestCacher(fakeClient)
+	fakeClient.WaitForWatchCompletion()
+
+	podFoo := makeTestPod("foo")
+
+	// Set up Watch for object "podFoo".
+	watcher, err := cacher.Watch("pods/ns/foo", 1, storage.Everything)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	fakeClient.WatchResponse <- &etcd.Response{
+		Action: "create",
+		Node: &etcd.Node{
+			Value:         string(runtime.EncodeOrDie(testapi.Codec(), podFoo)),
+			CreatedIndex:  1,
+			ModifiedIndex: 1,
+		},
+	}
+	_ = <-watcher.ResultChan()
+
+	// Injecting error is simulating error from etcd.
+	// This is almost the same what would happen e.g. in case of
+	// "error too old" when reconnecting to etcd watch.
+	fakeClient.WatchInjectError <- fmt.Errorf("fake error")
+
+	_, ok := <-watcher.ResultChan()
+	if ok {
+		t.Errorf("unexpected event")
+	}
+}
--- a/pkg/storage/util.go
+++ b/pkg/storage/util.go
@ -20,6 +20,7 @@ import (
 	"strconv"

 	"k8s.io/kubernetes/pkg/api/errors"
+	"k8s.io/kubernetes/pkg/api/meta"
 	"k8s.io/kubernetes/pkg/runtime"
 	"k8s.io/kubernetes/pkg/util/fielderrors"
 )
@ -49,3 +50,11 @@ func ParseWatchResourceVersion(resourceVersion, kind string) (uint64, error) {
 	}
 	return version + 1, nil
 }
+
+func NamespaceKeyFunc(prefix string, obj runtime.Object) (string, error) {
+	meta, err := meta.Accessor(obj)
+	if err != nil {
+		return "", err
+	}
+	return prefix + "/" + meta.Namespace() + "/" + meta.Name(), nil
+}