Enable listing from memory

pkg/client/cache/reflector.go

@@ -227,7 +227,10 @@ func (r *Reflector) ListAndWatch(stopCh <-chan struct{}) error {
 	resyncCh, cleanup := r.resyncChan()
 	defer cleanup()
 
-	options := unversioned.ListOptions{}
+	// Explicitly set "0" as resource version - it's fine for the List()
+	// to be served from cache and potentially be delayed relative to
+	// etcd contents. Reflector framework will catch up via Watch() eventually.
+	options := unversioned.ListOptions{ResourceVersion: "0"}
 	list, err := r.listerWatcher.List(options)
 	if err != nil {
 		return fmt.Errorf("%s: Failed to list %v: %v", r.name, r.expectedType, err)

pkg/storage/cacher.go

@@ -48,11 +48,6 @@ type CacherConfig struct {
 	// An underlying storage.Versioner.
 	Versioner Versioner
 
-	// Whether to serve Lists from in-memory cache.
-	//
-	// NOTE: DO NOT SET TO TRUE IN PRODUCTION CODE!
-	ListFromCache bool
-
 	// 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{}
@@ -107,11 +102,6 @@ type Cacher struct {
 
 	// keyFunc is used to get a key in the underyling storage for a given object.
 	keyFunc func(runtime.Object) (string, error)
-
-	// Whether to serve Lists from in-memory cache.
-	//
-	// NOTE: DO NOT SET TO TRUE IN PRODUCTION CODE!
-	ListFromCache bool
 }
 
 // Create a new Cacher responsible from service WATCH and LIST requests from its
@@ -153,15 +143,14 @@ func NewCacherFromConfig(config CacherConfig) *Cacher {
 	listerWatcher := newCacherListerWatcher(config.Storage, config.ResourcePrefix, config.NewListFunc)
 
 	cacher := &Cacher{
-		usable:        sync.RWMutex{},
-		storage:       config.Storage,
-		watchCache:    watchCache,
-		reflector:     cache.NewReflector(listerWatcher, config.Type, watchCache, 0),
-		watcherIdx:    0,
-		watchers:      make(map[int]*cacheWatcher),
-		versioner:     config.Versioner,
-		keyFunc:       config.KeyFunc,
-		ListFromCache: config.ListFromCache,
+		usable:     sync.RWMutex{},
+		storage:    config.Storage,
+		watchCache: watchCache,
+		reflector:  cache.NewReflector(listerWatcher, config.Type, watchCache, 0),
+		watcherIdx: 0,
+		watchers:   make(map[int]*cacheWatcher),
+		versioner:  config.Versioner,
+		keyFunc:    config.KeyFunc,
 	}
 	cacher.usable.Lock()
 	// See startCaching method for why explanation on it.
@@ -270,10 +259,16 @@ func (c *Cacher) GetToList(ctx context.Context, key string, filter FilterFunc, l
 
 // Implements storage.Interface.
 func (c *Cacher) List(ctx context.Context, key string, resourceVersion string, filter FilterFunc, listObj runtime.Object) error {
-	if !c.ListFromCache {
+	if resourceVersion == "" {
+		// If resourceVersion is not specified, serve it from underlying
+		// storage (for backward compatibility).
 		return c.storage.List(ctx, key, resourceVersion, filter, listObj)
 	}
 
+	// If resourceVersion is specified, serve it from cache.
+	// It's guaranteed that the returned value is at least that
+	// fresh as the given resourceVersion.
+
 	listRV, err := ParseListResourceVersion(resourceVersion)
 	if err != nil {
 		return err

pkg/storage/cacher_test.go

@@ -52,7 +52,6 @@ func newTestCacher(s storage.Interface) *storage.Cacher {
 		CacheCapacity:  10,
 		Storage:        s,
 		Versioner:      etcdstorage.APIObjectVersioner{},
-		ListFromCache:  true,
 		Type:           &api.Pod{},
 		ResourcePrefix: prefix,
 		KeyFunc:        func(obj runtime.Object) (string, error) { return storage.NamespaceKeyFunc(prefix, obj) },

test/e2e/load.go

@@ -214,7 +214,10 @@ func scaleRC(wg *sync.WaitGroup, config *RCConfig) {
 	expectNoError(ScaleRC(config.Client, config.Namespace, config.Name, newSize, true),
 		fmt.Sprintf("scaling rc %s for the first time", config.Name))
 	selector := labels.SelectorFromSet(labels.Set(map[string]string{"name": config.Name}))
-	options := unversioned.ListOptions{LabelSelector: unversioned.LabelSelector{selector}}
+	options := unversioned.ListOptions{
+		LabelSelector:   unversioned.LabelSelector{selector},
+		ResourceVersion: "0",
+	}
 	_, err := config.Client.Pods(config.Namespace).List(options)
 	expectNoError(err, fmt.Sprintf("listing pods from rc %v", config.Name))
 }