watch_test.go

/*
Copyright 2014 The Kubernetes Authors.

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 apiserver

import (
	"encoding/json"
	"fmt"
	"io"
	"io/ioutil"
	"math/rand"
	"net/http"
	"net/http/httptest"
	"net/url"
	"reflect"
	"sync"
	"testing"
	"time"

	"golang.org/x/net/websocket"
	"k8s.io/kubernetes/pkg/api"
	"k8s.io/kubernetes/pkg/api/rest"
	apitesting "k8s.io/kubernetes/pkg/api/testing"
	metav1 "k8s.io/kubernetes/pkg/apis/meta/v1"
	apiservertesting "k8s.io/kubernetes/pkg/apiserver/testing"
	"k8s.io/kubernetes/pkg/fields"
	"k8s.io/kubernetes/pkg/labels"
	"k8s.io/kubernetes/pkg/runtime"
	"k8s.io/kubernetes/pkg/runtime/serializer/streaming"
	"k8s.io/kubernetes/pkg/util/diff"
	"k8s.io/kubernetes/pkg/util/wait"
	"k8s.io/kubernetes/pkg/watch"
	"k8s.io/kubernetes/pkg/watch/versioned"
)

// watchJSON defines the expected JSON wire equivalent of watch.Event
type watchJSON struct {
	Type   watch.EventType `json:"type,omitempty"`
	Object json.RawMessage `json:"object,omitempty"`
}

// roundTripOrDie round trips an object to get defaults set.
func roundTripOrDie(codec runtime.Codec, object runtime.Object) runtime.Object {
	data, err := runtime.Encode(codec, object)
	if err != nil {
		panic(err)
	}
	obj, err := runtime.Decode(codec, data)
	if err != nil {
		panic(err)
	}
	return obj
}

var watchTestTable = []struct {
	t   watch.EventType
	obj runtime.Object
}{
	{watch.Added, &apiservertesting.Simple{ObjectMeta: api.ObjectMeta{Name: "foo"}}},
	{watch.Modified, &apiservertesting.Simple{ObjectMeta: api.ObjectMeta{Name: "bar"}}},
	{watch.Deleted, &apiservertesting.Simple{ObjectMeta: api.ObjectMeta{Name: "bar"}}},
}

var podWatchTestTable = []struct {
	t   watch.EventType
	obj runtime.Object
}{
	{watch.Added, roundTripOrDie(codec, &api.Pod{ObjectMeta: api.ObjectMeta{Name: "foo"}})},
	{watch.Modified, roundTripOrDie(codec, &api.Pod{ObjectMeta: api.ObjectMeta{Name: "bar"}})},
	{watch.Deleted, roundTripOrDie(codec, &api.Pod{ObjectMeta: api.ObjectMeta{Name: "bar"}})},
}

func TestWatchWebsocket(t *testing.T) {
	simpleStorage := &SimpleRESTStorage{}
	_ = rest.Watcher(simpleStorage) // Give compile error if this doesn't work.
	handler := handle(map[string]rest.Storage{"simples": simpleStorage})
	server := httptest.NewServer(handler)
	defer server.Close()

	dest, _ := url.Parse(server.URL)
	dest.Scheme = "ws" // Required by websocket, though the server never sees it.
	dest.Path = "/" + prefix + "/" + testGroupVersion.Group + "/" + testGroupVersion.Version + "/watch/simples"
	dest.RawQuery = ""

	ws, err := websocket.Dial(dest.String(), "", "http://localhost")
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}

	try := func(action watch.EventType, object runtime.Object) {
		// Send
		simpleStorage.fakeWatch.Action(action, object)
		// Test receive
		var got watchJSON
		err := websocket.JSON.Receive(ws, &got)
		if err != nil {
			t.Fatalf("Unexpected error: %v", err)
		}
		if got.Type != action {
			t.Errorf("Unexpected type: %v", got.Type)
		}
		gotObj, err := runtime.Decode(codec, got.Object)
		if err != nil {
			t.Fatalf("Decode error: %v\n%v", err, got)
		}
		if _, err := api.GetReference(gotObj); err != nil {
			t.Errorf("Unable to construct reference: %v", err)
		}
		if e, a := object, gotObj; !reflect.DeepEqual(e, a) {
			t.Errorf("Expected %#v, got %#v", e, a)
		}
	}

	for _, item := range watchTestTable {
		try(item.t, item.obj)
	}
	simpleStorage.fakeWatch.Stop()

	var got watchJSON
	err = websocket.JSON.Receive(ws, &got)
	if err == nil {
		t.Errorf("Unexpected non-error")
	}
}

func TestWatchWebsocketClientClose(t *testing.T) {
	simpleStorage := &SimpleRESTStorage{}
	_ = rest.Watcher(simpleStorage) // Give compile error if this doesn't work.
	handler := handle(map[string]rest.Storage{"simples": simpleStorage})
	server := httptest.NewServer(handler)
	defer server.Close()

	dest, _ := url.Parse(server.URL)
	dest.Scheme = "ws" // Required by websocket, though the server never sees it.
	dest.Path = "/" + prefix + "/" + testGroupVersion.Group + "/" + testGroupVersion.Version + "/watch/simples"
	dest.RawQuery = ""

	ws, err := websocket.Dial(dest.String(), "", "http://localhost")
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}

	try := func(action watch.EventType, object runtime.Object) {
		// Send
		simpleStorage.fakeWatch.Action(action, object)
		// Test receive
		var got watchJSON
		err := websocket.JSON.Receive(ws, &got)
		if err != nil {
			t.Fatalf("Unexpected error: %v", err)
		}
		if got.Type != action {
			t.Errorf("Unexpected type: %v", got.Type)
		}
		gotObj, err := runtime.Decode(codec, got.Object)
		if err != nil {
			t.Fatalf("Decode error: %v\n%v", err, got)
		}
		if _, err := api.GetReference(gotObj); err != nil {
			t.Errorf("Unable to construct reference: %v", err)
		}
		if e, a := object, gotObj; !reflect.DeepEqual(e, a) {
			t.Errorf("Expected %#v, got %#v", e, a)
		}
	}

	// Send/receive should work
	for _, item := range watchTestTable {
		try(item.t, item.obj)
	}

	// Sending normal data should be ignored
	websocket.JSON.Send(ws, map[string]interface{}{"test": "data"})

	// Send/receive should still work
	for _, item := range watchTestTable {
		try(item.t, item.obj)
	}

	// Client requests a close
	ws.Close()

	select {
	case data, ok := <-simpleStorage.fakeWatch.ResultChan():
		if ok {
			t.Errorf("expected a closed result channel, but got watch result %#v", data)
		}
	case <-time.After(5 * time.Second):
		t.Errorf("watcher did not close when client closed")
	}

	var got watchJSON
	err = websocket.JSON.Receive(ws, &got)
	if err == nil {
		t.Errorf("Unexpected non-error")
	}
}

func TestWatchRead(t *testing.T) {
	simpleStorage := &SimpleRESTStorage{}
	_ = rest.Watcher(simpleStorage) // Give compile error if this doesn't work.
	handler := handle(map[string]rest.Storage{"simples": simpleStorage})
	server := httptest.NewServer(handler)
	defer server.Close()

	dest, _ := url.Parse(server.URL)
	dest.Path = "/" + prefix + "/" + testGroupVersion.Group + "/" + testGroupVersion.Version + "/simples"
	dest.RawQuery = "watch=1"

	connectHTTP := func(accept string) (io.ReadCloser, string) {
		client := http.Client{}
		request, err := http.NewRequest("GET", dest.String(), nil)
		if err != nil {
			t.Fatalf("unexpected error: %v", err)
		}
		request.Header.Add("Accept", accept)

		response, err := client.Do(request)
		if err != nil {
			t.Fatalf("unexpected error: %v", err)
		}

		if response.StatusCode != http.StatusOK {
			b, _ := ioutil.ReadAll(response.Body)
			t.Fatalf("Unexpected response for accept: %q: %#v\n%s", accept, response, string(b))
		}
		return response.Body, response.Header.Get("Content-Type")
	}

	connectWebSocket := func(accept string) (io.ReadCloser, string) {
		dest := *dest
		dest.Scheme = "ws" // Required by websocket, though the server never sees it.
		config, err := websocket.NewConfig(dest.String(), "http://localhost")
		if err != nil {
			t.Fatalf("unexpected error: %v", err)
		}
		config.Header.Add("Accept", accept)
		ws, err := websocket.DialConfig(config)
		if err != nil {
			t.Fatalf("unexpected error: %v", err)
		}
		return ws, "__default__"
	}

	testCases := []struct {
		Accept              string
		ExpectedContentType string
		MediaType           string
	}{
		{
			Accept:              "application/json",
			ExpectedContentType: "application/json",
			MediaType:           "application/json",
		},
		{
			Accept:              "application/json;stream=watch",
			ExpectedContentType: "application/json", // legacy behavior
			MediaType:           "application/json",
		},
		// TODO: yaml stream serialization requires that RawExtension.MarshalJSON
		// be able to understand nested encoding (since yaml calls json.Marshal
		// rather than yaml.Marshal, which results in the raw bytes being in yaml).
		// Same problem as thirdparty object.
		/*{
			Accept:              "application/yaml",
			ExpectedContentType: "application/yaml;stream=watch",
			MediaType:           "application/yaml",
		},*/
		{
			Accept:              "application/vnd.kubernetes.protobuf",
			ExpectedContentType: "application/vnd.kubernetes.protobuf;stream=watch",
			MediaType:           "application/vnd.kubernetes.protobuf",
		},
		{
			Accept:              "application/vnd.kubernetes.protobuf;stream=watch",
			ExpectedContentType: "application/vnd.kubernetes.protobuf;stream=watch",
			MediaType:           "application/vnd.kubernetes.protobuf",
		},
	}
	protocols := []struct {
		name        string
		selfFraming bool
		fn          func(string) (io.ReadCloser, string)
	}{
		{name: "http", fn: connectHTTP},
		{name: "websocket", selfFraming: true, fn: connectWebSocket},
	}

	for _, protocol := range protocols {
		for _, test := range testCases {
			info, ok := runtime.SerializerInfoForMediaType(api.Codecs.SupportedMediaTypes(), test.MediaType)
			if !ok || info.StreamSerializer == nil {
				t.Fatal(info)
			}
			streamSerializer := info.StreamSerializer

			r, contentType := protocol.fn(test.Accept)
			defer r.Close()

			if contentType != "__default__" && contentType != test.ExpectedContentType {
				t.Errorf("Unexpected content type: %#v", contentType)
			}
			objectCodec := api.Codecs.DecoderToVersion(info.Serializer, testInternalGroupVersion)

			var fr io.ReadCloser = r
			if !protocol.selfFraming {
				fr = streamSerializer.Framer.NewFrameReader(r)
			}
			d := streaming.NewDecoder(fr, streamSerializer.Serializer)

			var w *watch.FakeWatcher
			for w == nil {
				w = simpleStorage.Watcher()
				time.Sleep(time.Millisecond)
			}

			for i, item := range podWatchTestTable {
				action, object := item.t, item.obj
				name := fmt.Sprintf("%s-%s-%d", protocol.name, test.MediaType, i)

				// Send
				w.Action(action, object)
				// Test receive
				var got versioned.Event
				_, _, err := d.Decode(nil, &got)
				if err != nil {
					t.Fatalf("%s: Unexpected error: %v", name, err)
				}
				if got.Type != string(action) {
					t.Errorf("%s: Unexpected type: %v", name, got.Type)
				}

				gotObj, err := runtime.Decode(objectCodec, got.Object.Raw)
				if err != nil {
					t.Fatalf("%s: Decode error: %v", name, err)
				}
				if _, err := api.GetReference(gotObj); err != nil {
					t.Errorf("%s: Unable to construct reference: %v", name, err)
				}
				if e, a := object, gotObj; !api.Semantic.DeepEqual(e, a) {
					t.Errorf("%s: different: %s", name, diff.ObjectDiff(e, a))
				}
			}
			w.Stop()

			var got versioned.Event
			_, _, err := d.Decode(nil, &got)
			if err == nil {
				t.Errorf("Unexpected non-error")
			}

			r.Close()
		}
	}
}

func TestWatchHTTPAccept(t *testing.T) {
	simpleStorage := &SimpleRESTStorage{}
	handler := handle(map[string]rest.Storage{"simples": simpleStorage})
	server := httptest.NewServer(handler)
	defer server.Close()
	client := http.Client{}

	dest, _ := url.Parse(server.URL)
	dest.Path = "/" + prefix + "/" + testGroupVersion.Group + "/" + testGroupVersion.Version + "/watch/simples"
	dest.RawQuery = ""

	request, err := http.NewRequest("GET", dest.String(), nil)
	if err != nil {
		t.Errorf("unexpected error: %v", err)
	}

	request.Header.Set("Accept", "application/XYZ")
	response, err := client.Do(request)
	if err != nil {
		t.Errorf("unexpected error: %v", err)
	}

	// TODO: once this is fixed, this test will change
	if response.StatusCode != http.StatusNotAcceptable {
		t.Errorf("Unexpected response %#v", response)
	}
}

func TestWatchParamParsing(t *testing.T) {
	simpleStorage := &SimpleRESTStorage{}
	handler := handle(map[string]rest.Storage{
		"simples":     simpleStorage,
		"simpleroots": simpleStorage,
	})
	server := httptest.NewServer(handler)
	defer server.Close()

	dest, _ := url.Parse(server.URL)

	rootPath := "/" + prefix + "/" + testGroupVersion.Group + "/" + testGroupVersion.Version + "/watch/simples"
	namespacedPath := "/" + prefix + "/" + testGroupVersion.Group + "/" + testGroupVersion.Version + "/watch/namespaces/other/simpleroots"

	table := []struct {
		path            string
		rawQuery        string
		resourceVersion string
		labelSelector   string
		fieldSelector   string
		namespace       string
	}{
		{
			path:            rootPath,
			rawQuery:        "resourceVersion=1234",
			resourceVersion: "1234",
			labelSelector:   "",
			fieldSelector:   "",
			namespace:       api.NamespaceAll,
		}, {
			path:            rootPath,
			rawQuery:        "resourceVersion=314159&fieldSelector=Host%3D&labelSelector=name%3Dfoo",
			resourceVersion: "314159",
			labelSelector:   "name=foo",
			fieldSelector:   "Host=",
			namespace:       api.NamespaceAll,
		}, {
			path:            rootPath,
			rawQuery:        "fieldSelector=id%3dfoo&resourceVersion=1492",
			resourceVersion: "1492",
			labelSelector:   "",
			fieldSelector:   "id=foo",
			namespace:       api.NamespaceAll,
		}, {
			path:            rootPath,
			rawQuery:        "",
			resourceVersion: "",
			labelSelector:   "",
			fieldSelector:   "",
			namespace:       api.NamespaceAll,
		},
		{
			path:            namespacedPath,
			rawQuery:        "resourceVersion=1234",
			resourceVersion: "1234",
			labelSelector:   "",
			fieldSelector:   "",
			namespace:       "other",
		}, {
			path:            namespacedPath,
			rawQuery:        "resourceVersion=314159&fieldSelector=Host%3D&labelSelector=name%3Dfoo",
			resourceVersion: "314159",
			labelSelector:   "name=foo",
			fieldSelector:   "Host=",
			namespace:       "other",
		}, {
			path:            namespacedPath,
			rawQuery:        "fieldSelector=id%3dfoo&resourceVersion=1492",
			resourceVersion: "1492",
			labelSelector:   "",
			fieldSelector:   "id=foo",
			namespace:       "other",
		}, {
			path:            namespacedPath,
			rawQuery:        "",
			resourceVersion: "",
			labelSelector:   "",
			fieldSelector:   "",
			namespace:       "other",
		},
	}

	for _, item := range table {
		simpleStorage.requestedLabelSelector = labels.Everything()
		simpleStorage.requestedFieldSelector = fields.Everything()
		simpleStorage.requestedResourceVersion = "5" // Prove this is set in all cases
		simpleStorage.requestedResourceNamespace = ""
		dest.Path = item.path
		dest.RawQuery = item.rawQuery
		resp, err := http.Get(dest.String())
		if err != nil {
			t.Errorf("%v: unexpected error: %v", item.rawQuery, err)
			continue
		}
		resp.Body.Close()
		if e, a := item.namespace, simpleStorage.requestedResourceNamespace; e != a {
			t.Errorf("%v: expected %v, got %v", item.rawQuery, e, a)
		}
		if e, a := item.resourceVersion, simpleStorage.requestedResourceVersion; e != a {
			t.Errorf("%v: expected %v, got %v", item.rawQuery, e, a)
		}
		if e, a := item.labelSelector, simpleStorage.requestedLabelSelector.String(); e != a {
			t.Errorf("%v: expected %v, got %v", item.rawQuery, e, a)
		}
		if e, a := item.fieldSelector, simpleStorage.requestedFieldSelector.String(); e != a {
			t.Errorf("%v: expected %v, got %v", item.rawQuery, e, a)
		}
	}
}

func TestWatchProtocolSelection(t *testing.T) {
	simpleStorage := &SimpleRESTStorage{}
	handler := handle(map[string]rest.Storage{"simples": simpleStorage})
	server := httptest.NewServer(handler)
	defer server.Close()
	defer server.CloseClientConnections()
	client := http.Client{}

	dest, _ := url.Parse(server.URL)
	dest.Path = "/" + prefix + "/" + testGroupVersion.Group + "/" + testGroupVersion.Version + "/watch/simples"
	dest.RawQuery = ""

	table := []struct {
		isWebsocket bool
		connHeader  string
	}{
		{true, "Upgrade"},
		{true, "keep-alive, Upgrade"},
		{true, "upgrade"},
		{false, "keep-alive"},
	}

	for _, item := range table {
		request, err := http.NewRequest("GET", dest.String(), nil)
		if err != nil {
			t.Errorf("unexpected error: %v", err)
		}
		request.Header.Set("Connection", item.connHeader)
		request.Header.Set("Upgrade", "websocket")

		response, err := client.Do(request)
		if err != nil {
			t.Errorf("unexpected error: %v", err)
		}

		// The requests recognized as websocket requests based on connection
		// and upgrade headers will not also have the necessary Sec-Websocket-*
		// headers so it is expected to throw a 400
		if item.isWebsocket && response.StatusCode != http.StatusBadRequest {
			t.Errorf("Unexpected response %#v", response)
		}

		if !item.isWebsocket && response.StatusCode != http.StatusOK {
			t.Errorf("Unexpected response %#v", response)
		}
	}

}

type fakeTimeoutFactory struct {
	timeoutCh chan time.Time
	done      chan struct{}
}

func (t *fakeTimeoutFactory) TimeoutCh() (<-chan time.Time, func() bool) {
	return t.timeoutCh, func() bool {
		defer close(t.done)
		return true
	}
}

func TestWatchHTTPTimeout(t *testing.T) {
	watcher := watch.NewFake()
	timeoutCh := make(chan time.Time)
	done := make(chan struct{})

	info, ok := runtime.SerializerInfoForMediaType(api.Codecs.SupportedMediaTypes(), runtime.ContentTypeJSON)
	if !ok || info.StreamSerializer == nil {
		t.Fatal(info)
	}
	serializer := info.StreamSerializer

	// Setup a new watchserver
	watchServer := &WatchServer{
		watching: watcher,

		mediaType:       "testcase/json",
		framer:          serializer.Framer,
		encoder:         newCodec,
		embeddedEncoder: newCodec,

		fixup: func(obj runtime.Object) {},
		t:     &fakeTimeoutFactory{timeoutCh, done},
	}

	s := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
		watchServer.ServeHTTP(w, req)
	}))
	defer s.Close()

	// Setup a client
	dest, _ := url.Parse(s.URL)
	dest.Path = "/" + prefix + "/" + newGroupVersion.Group + "/" + newGroupVersion.Version + "/simple"
	dest.RawQuery = "watch=true"

	req, _ := http.NewRequest("GET", dest.String(), nil)
	client := http.Client{}
	resp, err := client.Do(req)
	watcher.Add(&apiservertesting.Simple{TypeMeta: metav1.TypeMeta{APIVersion: newGroupVersion.String()}})

	// Make sure we can actually watch an endpoint
	decoder := json.NewDecoder(resp.Body)
	var got watchJSON
	err = decoder.Decode(&got)
	if err != nil {
		t.Fatalf("Unexpected error: %v", err)
	}

	// Timeout and check for leaks
	close(timeoutCh)
	select {
	case <-done:
		if !watcher.Stopped {
			t.Errorf("Leaked watch on timeout")
		}
	case <-time.After(wait.ForeverTestTimeout):
		t.Errorf("Failed to stop watcher after %s of timeout signal", wait.ForeverTestTimeout.String())
	}

	// Make sure we can't receive any more events through the timeout watch
	err = decoder.Decode(&got)
	if err != io.EOF {
		t.Errorf("Unexpected non-error")
	}
}

const benchmarkSeed = 100

func benchmarkItems() []api.Pod {
	apiObjectFuzzer := apitesting.FuzzerFor(nil, api.SchemeGroupVersion, rand.NewSource(benchmarkSeed))
	items := make([]api.Pod, 3)
	for i := range items {
		apiObjectFuzzer.Fuzz(&items[i])
		items[i].Spec.InitContainers, items[i].Status.InitContainerStatuses = nil, nil
	}
	return items
}

// BenchmarkWatchHTTP measures the cost of serving a watch.
func BenchmarkWatchHTTP(b *testing.B) {
	items := benchmarkItems()

	simpleStorage := &SimpleRESTStorage{}
	handler := handle(map[string]rest.Storage{"simples": simpleStorage})
	server := httptest.NewServer(handler)
	defer server.Close()
	client := http.Client{}

	dest, _ := url.Parse(server.URL)
	dest.Path = "/" + prefix + "/" + newGroupVersion.Group + "/" + newGroupVersion.Version + "/watch/simples"
	dest.RawQuery = ""

	request, err := http.NewRequest("GET", dest.String(), nil)
	if err != nil {
		b.Fatalf("unexpected error: %v", err)
	}
	response, err := client.Do(request)
	if err != nil {
		b.Fatalf("unexpected error: %v", err)
	}
	if response.StatusCode != http.StatusOK {
		b.Fatalf("Unexpected response %#v", response)
	}

	wg := sync.WaitGroup{}
	wg.Add(1)
	go func() {
		defer response.Body.Close()
		if _, err := io.Copy(ioutil.Discard, response.Body); err != nil {
			b.Fatal(err)
		}
		wg.Done()
	}()

	actions := []watch.EventType{watch.Added, watch.Modified, watch.Deleted}

	b.ResetTimer()
	for i := 0; i < b.N; i++ {
		simpleStorage.fakeWatch.Action(actions[i%len(actions)], &items[i%len(items)])
	}
	simpleStorage.fakeWatch.Stop()
	wg.Wait()
	b.StopTimer()
}

// BenchmarkWatchWebsocket measures the cost of serving a watch.
func BenchmarkWatchWebsocket(b *testing.B) {
	items := benchmarkItems()

	simpleStorage := &SimpleRESTStorage{}
	handler := handle(map[string]rest.Storage{"simples": simpleStorage})
	server := httptest.NewServer(handler)
	defer server.Close()

	dest, _ := url.Parse(server.URL)
	dest.Scheme = "ws" // Required by websocket, though the server never sees it.
	dest.Path = "/" + prefix + "/" + newGroupVersion.Group + "/" + newGroupVersion.Version + "/watch/simples"
	dest.RawQuery = ""

	ws, err := websocket.Dial(dest.String(), "", "http://localhost")
	if err != nil {
		b.Fatalf("unexpected error: %v", err)
	}

	wg := sync.WaitGroup{}
	wg.Add(1)
	go func() {
		defer ws.Close()
		if _, err := io.Copy(ioutil.Discard, ws); err != nil {
			b.Fatal(err)
		}
		wg.Done()
	}()

	actions := []watch.EventType{watch.Added, watch.Modified, watch.Deleted}

	b.ResetTimer()
	for i := 0; i < b.N; i++ {
		simpleStorage.fakeWatch.Action(actions[i%len(actions)], &items[i%len(items)])
	}
	simpleStorage.fakeWatch.Stop()
	wg.Wait()
	b.StopTimer()
}

// BenchmarkWatchProtobuf measures the cost of serving a watch.
func BenchmarkWatchProtobuf(b *testing.B) {
	items := benchmarkItems()

	simpleStorage := &SimpleRESTStorage{}
	handler := handle(map[string]rest.Storage{"simples": simpleStorage})
	server := httptest.NewServer(handler)
	defer server.Close()
	client := http.Client{}

	dest, _ := url.Parse(server.URL)
	dest.Path = "/" + prefix + "/" + newGroupVersion.Group + "/" + newGroupVersion.Version + "/watch/simples"
	dest.RawQuery = ""

	request, err := http.NewRequest("GET", dest.String(), nil)
	if err != nil {
		b.Fatalf("unexpected error: %v", err)
	}
	request.Header.Set("Accept", "application/vnd.kubernetes.protobuf")
	response, err := client.Do(request)
	if err != nil {
		b.Fatalf("unexpected error: %v", err)
	}
	if response.StatusCode != http.StatusOK {
		body, _ := ioutil.ReadAll(response.Body)
		b.Fatalf("Unexpected response %#v\n%s", response, body)
	}

	wg := sync.WaitGroup{}
	wg.Add(1)
	go func() {
		defer response.Body.Close()
		if _, err := io.Copy(ioutil.Discard, response.Body); err != nil {
			b.Fatal(err)
		}
		wg.Done()
	}()

	actions := []watch.EventType{watch.Added, watch.Modified, watch.Deleted}

	b.ResetTimer()
	for i := 0; i < b.N; i++ {
		simpleStorage.fakeWatch.Action(actions[i%len(actions)], &items[i%len(items)])
	}
	simpleStorage.fakeWatch.Stop()
	wg.Wait()
	b.StopTimer()
}