storage: support watch on ranges

etcdserver/api/v3rpc/watch.go

@@ -16,7 +16,6 @@ package v3rpc
 
 import (
 	"io"
-	"reflect"
 
 	"github.com/coreos/etcd/etcdserver"
 	pb "github.com/coreos/etcd/etcdserver/etcdserverpb"
@@ -100,9 +99,10 @@ func (sws *serverWatchStream) recvLoop() error {
 			}
 
 			creq := uv.CreateRequest
-			toWatch := creq.Key
+			if len(creq.RangeEnd) == 1 && creq.RangeEnd[0] == 0 {
-			isPrefix := len(creq.RangeEnd) != 0
+				// support  >= key queries
-			badPrefix := isPrefix && !reflect.DeepEqual(getPrefix(toWatch), creq.RangeEnd)
+				creq.RangeEnd = []byte{}
+			}
 
 			rev := creq.StartRevision
 			wsrev := sws.watchStream.Rev()
@@ -112,16 +112,15 @@ func (sws *serverWatchStream) recvLoop() error {
 				rev = wsrev + 1
 			}
 			// do not allow future watch revision
-			// do not allow range that is not a prefix
 			id := storage.WatchID(-1)
-			if !futureRev && !badPrefix {
+			if !futureRev {
-				id = sws.watchStream.Watch(toWatch, isPrefix, rev)
+				id = sws.watchStream.Watch(creq.Key, creq.RangeEnd, rev)
 			}
 			sws.ctrlStream <- &pb.WatchResponse{
 				Header:   sws.newResponseHeader(wsrev),
 				WatchId:  int64(id),
 				Created:  true,
-				Canceled: futureRev || badPrefix,
+				Canceled: futureRev,
 			}
 		case *pb.WatchRequest_CancelRequest:
 			if uv.CancelRequest != nil {
@@ -237,21 +236,3 @@ func (sws *serverWatchStream) newResponseHeader(rev int64) *pb.ResponseHeader {
 		RaftTerm:  sws.raftTimer.Term(),
 	}
 }
-
-// TODO: remove getPrefix when storage supports full range watchers
-
-func getPrefix(key []byte) []byte {
-	end := make([]byte, len(key))
-	copy(end, key)
-	for i := len(end) - 1; i >= 0; i-- {
-		if end[i] < 0xff {
-			end[i] = end[i] + 1
-			end = end[:i+1]
-			return end
-		}
-	}
-	// next prefix does not exist (e.g., 0xffff);
-	// default to WithFromKey policy
-	end = []byte{0}
-	return end
-}

storage/kv_test.go

@@ -722,13 +722,10 @@ func TestWatchableKVWatch(t *testing.T) {
 	w := s.NewWatchStream()
 	defer w.Close()
 
-	wid := w.Watch([]byte("foo"), true, 0)
+	wid := w.Watch([]byte("foo"), []byte("fop"), 0)
 
-	s.Put([]byte("foo"), []byte("bar"), 1)
+	wev := []storagepb.Event{
-	select {
+		{Type: storagepb.PUT,
-	case resp := <-w.Chan():
-		wev := storagepb.Event{
-			Type: storagepb.PUT,
 			Kv: &storagepb.KeyValue{
 				Key:            []byte("foo"),
 				Value:          []byte("bar"),
@@ -737,23 +734,8 @@ func TestWatchableKVWatch(t *testing.T) {
 				Version:        1,
 				Lease:          1,
 			},
-		}
+		},
-		if resp.WatchID != wid {
+		{
-			t.Errorf("resp.WatchID got = %d, want = %d", resp.WatchID, wid)
-		}
-		ev := resp.Events[0]
-		if !reflect.DeepEqual(ev, wev) {
-			t.Errorf("watched event = %+v, want %+v", ev, wev)
-		}
-	case <-time.After(5 * time.Second):
-		// CPU might be too slow, and the routine is not able to switch around
-		testutil.FatalStack(t, "failed to watch the event")
-	}
-
-	s.Put([]byte("foo1"), []byte("bar1"), 2)
-	select {
-	case resp := <-w.Chan():
-		wev := storagepb.Event{
 			Type: storagepb.PUT,
 			Kv: &storagepb.KeyValue{
 				Key:            []byte("foo1"),
@@ -763,49 +745,8 @@ func TestWatchableKVWatch(t *testing.T) {
 				Version:        1,
 				Lease:          2,
 			},
-		}
-		if resp.WatchID != wid {
-			t.Errorf("resp.WatchID got = %d, want = %d", resp.WatchID, wid)
-		}
-		ev := resp.Events[0]
-		if !reflect.DeepEqual(ev, wev) {
-			t.Errorf("watched event = %+v, want %+v", ev, wev)
-		}
-	case <-time.After(5 * time.Second):
-		testutil.FatalStack(t, "failed to watch the event")
-	}
-
-	w = s.NewWatchStream()
-	wid = w.Watch([]byte("foo1"), false, 1)
-
-	select {
-	case resp := <-w.Chan():
-		wev := storagepb.Event{
-			Type: storagepb.PUT,
-			Kv: &storagepb.KeyValue{
-				Key:            []byte("foo1"),
-				Value:          []byte("bar1"),
-				CreateRevision: 3,
-				ModRevision:    3,
-				Version:        1,
-				Lease:          2,
 		},
-		}
+		{
-		if resp.WatchID != wid {
-			t.Errorf("resp.WatchID got = %d, want = %d", resp.WatchID, wid)
-		}
-		ev := resp.Events[0]
-		if !reflect.DeepEqual(ev, wev) {
-			t.Errorf("watched event = %+v, want %+v", ev, wev)
-		}
-	case <-time.After(5 * time.Second):
-		testutil.FatalStack(t, "failed to watch the event")
-	}
-
-	s.Put([]byte("foo1"), []byte("bar11"), 3)
-	select {
-	case resp := <-w.Chan():
-		wev := storagepb.Event{
 			Type: storagepb.PUT,
 			Kv: &storagepb.KeyValue{
 				Key:            []byte("foo1"),
@@ -815,13 +756,63 @@ func TestWatchableKVWatch(t *testing.T) {
 				Version:        2,
 				Lease:          3,
 			},
+		},
 	}
+
+	s.Put([]byte("foo"), []byte("bar"), 1)
+	select {
+	case resp := <-w.Chan():
 		if resp.WatchID != wid {
 			t.Errorf("resp.WatchID got = %d, want = %d", resp.WatchID, wid)
 		}
 		ev := resp.Events[0]
-		if !reflect.DeepEqual(ev, wev) {
+		if !reflect.DeepEqual(ev, wev[0]) {
-			t.Errorf("watched event = %+v, want %+v", ev, wev)
+			t.Errorf("watched event = %+v, want %+v", ev, wev[0])
+		}
+	case <-time.After(5 * time.Second):
+		// CPU might be too slow, and the routine is not able to switch around
+		testutil.FatalStack(t, "failed to watch the event")
+	}
+
+	s.Put([]byte("foo1"), []byte("bar1"), 2)
+	select {
+	case resp := <-w.Chan():
+		if resp.WatchID != wid {
+			t.Errorf("resp.WatchID got = %d, want = %d", resp.WatchID, wid)
+		}
+		ev := resp.Events[0]
+		if !reflect.DeepEqual(ev, wev[1]) {
+			t.Errorf("watched event = %+v, want %+v", ev, wev[1])
+		}
+	case <-time.After(5 * time.Second):
+		testutil.FatalStack(t, "failed to watch the event")
+	}
+
+	w = s.NewWatchStream()
+	wid = w.Watch([]byte("foo1"), []byte("foo2"), 3)
+
+	select {
+	case resp := <-w.Chan():
+		if resp.WatchID != wid {
+			t.Errorf("resp.WatchID got = %d, want = %d", resp.WatchID, wid)
+		}
+		ev := resp.Events[0]
+		if !reflect.DeepEqual(ev, wev[1]) {
+			t.Errorf("watched event = %+v, want %+v", ev, wev[1])
+		}
+	case <-time.After(5 * time.Second):
+		testutil.FatalStack(t, "failed to watch the event")
+	}
+
+	s.Put([]byte("foo1"), []byte("bar11"), 3)
+	select {
+	case resp := <-w.Chan():
+		if resp.WatchID != wid {
+			t.Errorf("resp.WatchID got = %d, want = %d", resp.WatchID, wid)
+		}
+		ev := resp.Events[0]
+		if !reflect.DeepEqual(ev, wev[2]) {
+			t.Errorf("watched event = %+v, want %+v", ev, wev[2])
 		}
 	case <-time.After(5 * time.Second):
 		testutil.FatalStack(t, "failed to watch the event")

storage/watchable_store.go

@@ -16,8 +16,6 @@ package storage
 
 import (
 	"log"
-	"math"
-	"strings"
 	"sync"
 	"time"
 
@@ -34,103 +32,8 @@ const (
 	chanBufLen = 1024
 )
 
-var (
-	// watchBatchMaxRevs is the maximum distinct revisions that
-	// may be sent to an unsynced watcher at a time. Declared as
-	// var instead of const for testing purposes.
-	watchBatchMaxRevs = 1000
-)
-
-type eventBatch struct {
-	// evs is a batch of revision-ordered events
-	evs []storagepb.Event
-	// revs is the minimum unique revisions observed for this batch
-	revs int
-	// moreRev is first revision with more events following this batch
-	moreRev int64
-}
-
-type (
-	watcherSetByKey map[string]watcherSet
-	watcherSet      map[*watcher]struct{}
-	watcherBatch    map[*watcher]*eventBatch
-)
-
-func (eb *eventBatch) add(ev storagepb.Event) {
-	if eb.revs > watchBatchMaxRevs {
-		// maxed out batch size
-		return
-	}
-
-	if len(eb.evs) == 0 {
-		// base case
-		eb.revs = 1
-		eb.evs = append(eb.evs, ev)
-		return
-	}
-
-	// revision accounting
-	ebRev := eb.evs[len(eb.evs)-1].Kv.ModRevision
-	evRev := ev.Kv.ModRevision
-	if evRev > ebRev {
-		eb.revs++
-		if eb.revs > watchBatchMaxRevs {
-			eb.moreRev = evRev
-			return
-		}
-	}
-
-	eb.evs = append(eb.evs, ev)
-}
-
-func (wb watcherBatch) add(w *watcher, ev storagepb.Event) {
-	eb := wb[w]
-	if eb == nil {
-		eb = &eventBatch{}
-		wb[w] = eb
-	}
-	eb.add(ev)
-}
-
-func (w watcherSet) add(wa *watcher) {
-	if _, ok := w[wa]; ok {
-		panic("add watcher twice!")
-	}
-	w[wa] = struct{}{}
-}
-
-func (w watcherSetByKey) add(wa *watcher) {
-	set := w[string(wa.key)]
-	if set == nil {
-		set = make(watcherSet)
-		w[string(wa.key)] = set
-	}
-	set.add(wa)
-}
-
-func (w watcherSetByKey) getSetByKey(key string) (watcherSet, bool) {
-	set, ok := w[key]
-	return set, ok
-}
-
-func (w watcherSetByKey) delete(wa *watcher) bool {
-	k := string(wa.key)
-	if v, ok := w[k]; ok {
-		if _, ok := v[wa]; ok {
-			delete(v, wa)
-			// if there is nothing in the set,
-			// remove the set
-			if len(v) == 0 {
-				delete(w, k)
-			}
-			return true
-		}
-	}
-	return false
-}
-
 type watchable interface {
-	watch(key []byte, prefix bool, startRev int64, id WatchID, ch chan<- WatchResponse) (*watcher, cancelFunc)
+	watch(key, end []byte, startRev int64, id WatchID, ch chan<- WatchResponse) (*watcher, cancelFunc)
 	rev() int64
 }
 
@@ -140,11 +43,11 @@ type watchableStore struct {
 	*store
 
 	// contains all unsynced watchers that needs to sync with events that have happened
-	unsynced watcherSetByKey
+	unsynced watcherGroup
 
 	// contains all synced watchers that are in sync with the progress of the store.
 	// The key of the map is the key that the watcher watches on.
-	synced watcherSetByKey
+	synced watcherGroup
 
 	stopc chan struct{}
 	wg    sync.WaitGroup
@@ -157,8 +60,8 @@ type cancelFunc func()
 func newWatchableStore(b backend.Backend, le lease.Lessor) *watchableStore {
 	s := &watchableStore{
 		store:    NewStore(b, le),
-		unsynced: make(watcherSetByKey),
+		unsynced: newWatcherGroup(),
-		synced:   make(watcherSetByKey),
+		synced:   newWatcherGroup(),
 		stopc:    make(chan struct{}),
 	}
 	if s.le != nil {
@@ -268,13 +171,13 @@ func (s *watchableStore) NewWatchStream() WatchStream {
 	}
 }
 
-func (s *watchableStore) watch(key []byte, prefix bool, startRev int64, id WatchID, ch chan<- WatchResponse) (*watcher, cancelFunc) {
+func (s *watchableStore) watch(key, end []byte, startRev int64, id WatchID, ch chan<- WatchResponse) (*watcher, cancelFunc) {
 	s.mu.Lock()
 	defer s.mu.Unlock()
 
 	wa := &watcher{
 		key: key,
-		prefix: prefix,
+		end: end,
 		cur: startRev,
 		id:  id,
 		ch:  ch,
@@ -342,15 +245,16 @@ func (s *watchableStore) syncWatchers() {
 	s.store.mu.Lock()
 	defer s.store.mu.Unlock()
 
-	if len(s.unsynced) == 0 {
+	if s.unsynced.size() == 0 {
 		return
 	}
 
 	// in order to find key-value pairs from unsynced watchers, we need to
 	// find min revision index, and these revisions can be used to
 	// query the backend store of key-value pairs
-	prefixes, minRev := s.scanUnsync()
 	curRev := s.store.currentRev.main
+	compactionRev := s.store.compactMainRev
+	minRev := s.unsynced.scanMinRev(curRev, compactionRev)
 	minBytes, maxBytes := newRevBytes(), newRevBytes()
 	revToBytes(revision{main: minRev}, minBytes)
 	revToBytes(revision{main: curRev + 1}, maxBytes)
@@ -360,10 +264,10 @@ func (s *watchableStore) syncWatchers() {
 	tx := s.store.b.BatchTx()
 	tx.Lock()
 	revs, vs := tx.UnsafeRange(keyBucketName, minBytes, maxBytes, 0)
-	evs := kvsToEvents(revs, vs, s.unsynced, prefixes)
+	evs := kvsToEvents(&s.unsynced, revs, vs)
 	tx.Unlock()
 
-	for w, eb := range newWatcherBatch(s.unsynced, evs) {
+	for w, eb := range newWatcherBatch(&s.unsynced, evs) {
 		select {
 		// s.store.Rev also uses Lock, so just return directly
 		case w.ch <- WatchResponse{WatchID: w.id, Events: eb.evs, Revision: s.store.currentRev.main}:
@@ -383,56 +287,18 @@ func (s *watchableStore) syncWatchers() {
 		s.unsynced.delete(w)
 	}
 
-	slowWatcherGauge.Set(float64(len(s.unsynced)))
+	slowWatcherGauge.Set(float64(s.unsynced.size()))
-}
-
-func (s *watchableStore) scanUnsync() (prefixes map[string]struct{}, minRev int64) {
-	curRev := s.store.currentRev.main
-	compactionRev := s.store.compactMainRev
-
-	prefixes = make(map[string]struct{})
-	minRev = int64(math.MaxInt64)
-	for _, set := range s.unsynced {
-		for w := range set {
-			k := string(w.key)
-
-			if w.cur > curRev {
-				panic("watcher current revision should not exceed current revision")
-			}
-
-			if w.cur < compactionRev {
-				select {
-				case w.ch <- WatchResponse{WatchID: w.id, CompactRevision: compactionRev}:
-					s.unsynced.delete(w)
-				default:
-					// retry next time
-				}
-				continue
-			}
-
-			if minRev > w.cur {
-				minRev = w.cur
-			}
-
-			if w.prefix {
-				prefixes[k] = struct{}{}
-			}
-		}
-	}
-
-	return prefixes, minRev
 }
 
 // kvsToEvents gets all events for the watchers from all key-value pairs
-func kvsToEvents(revs, vals [][]byte, wsk watcherSetByKey, pfxs map[string]struct{}) (evs []storagepb.Event) {
+func kvsToEvents(wg *watcherGroup, revs, vals [][]byte) (evs []storagepb.Event) {
 	for i, v := range vals {
 		var kv storagepb.KeyValue
 		if err := kv.Unmarshal(v); err != nil {
 			log.Panicf("storage: cannot unmarshal event: %v", err)
 		}
 
-		k := string(kv.Key)
+		if !wg.contains(string(kv.Key)) {
-		if _, ok := wsk.getSetByKey(k); !ok && !matchPrefix(k, pfxs) {
 			continue
 		}
 
@@ -450,13 +316,7 @@ func kvsToEvents(revs, vals [][]byte, wsk watcherSetByKey, pfxs map[string]struc
 // notify notifies the fact that given event at the given rev just happened to
 // watchers that watch on the key of the event.
 func (s *watchableStore) notify(rev int64, evs []storagepb.Event) {
-	we := newWatcherBatch(s.synced, evs)
+	for w, eb := range newWatcherBatch(&s.synced, evs) {
-	for _, wm := range s.synced {
-		for w := range wm {
-			eb, ok := we[w]
-			if !ok {
-				continue
-			}
 		if eb.revs != 1 {
 			panic("unexpected multiple revisions in notification")
 		}
@@ -467,11 +327,10 @@ func (s *watchableStore) notify(rev int64, evs []storagepb.Event) {
 			// move slow watcher to unsynced
 			w.cur = rev
 			s.unsynced.add(w)
-				delete(wm, w)
+			s.synced.delete(w)
 			slowWatcherGauge.Inc()
 		}
 	}
-	}
 }
 
 func (s *watchableStore) rev() int64 { return s.store.Rev() }
@@ -479,9 +338,9 @@ func (s *watchableStore) rev() int64 { return s.store.Rev() }
 type watcher struct {
 	// the watcher key
 	key []byte
-	// prefix indicates if watcher is on a key or a prefix.
+	// end indicates the end of the range to watch.
-	// If prefix is true, the watcher is on a prefix.
+	// If end is set, the watcher is on a range.
-	prefix bool
+	end []byte
 	// cur is the current watcher revision.
 	// If cur is behind the current revision of the KV,
 	// watcher is unsynced and needs to catch up.
@@ -492,42 +351,3 @@ type watcher struct {
 	// The chan might be shared with other watchers.
 	ch chan<- WatchResponse
 }
-
-// newWatcherBatch maps watchers to their matched events. It enables quick
-// events look up by watcher.
-func newWatcherBatch(sm watcherSetByKey, evs []storagepb.Event) watcherBatch {
-	wb := make(watcherBatch)
-	for _, ev := range evs {
-		key := string(ev.Kv.Key)
-
-		// check all prefixes of the key to notify all corresponded watchers
-		for i := 0; i <= len(key); i++ {
-			for w := range sm[key[:i]] {
-				// don't double notify
-				if ev.Kv.ModRevision < w.cur {
-					continue
-				}
-
-				// the watcher needs to be notified when either it watches prefix or
-				// the key is exactly matched.
-				if !w.prefix && i != len(ev.Kv.Key) {
-					continue
-				}
-				wb.add(w, ev)
-			}
-		}
-	}
-
-	return wb
-}
-
-// matchPrefix returns true if key has any matching prefix
-// from prefixes map.
-func matchPrefix(key string, prefixes map[string]struct{}) bool {
-	for p := range prefixes {
-		if strings.HasPrefix(key, p) {
-			return true
-		}
-	}
-	return false
-}

storage/watchable_store_bench_test.go

@@ -40,11 +40,11 @@ func BenchmarkWatchableStoreUnsyncedCancel(b *testing.B) {
 	// in unsynced for this benchmark.
 	ws := &watchableStore{
 		store:    s,
-		unsynced: make(watcherSetByKey),
+		unsynced: newWatcherGroup(),
 
 		// to make the test not crash from assigning to nil map.
 		// 'synced' doesn't get populated in this test.
-		synced: make(watcherSetByKey),
+		synced: newWatcherGroup(),
 	}
 
 	defer func() {
@@ -69,7 +69,7 @@ func BenchmarkWatchableStoreUnsyncedCancel(b *testing.B) {
 	watchIDs := make([]WatchID, watcherN)
 	for i := 0; i < watcherN; i++ {
 		// non-0 value to keep watchers in unsynced
-		watchIDs[i] = w.Watch(testKey, true, 1)
+		watchIDs[i] = w.Watch(testKey, nil, 1)
 	}
 
 	// random-cancel N watchers to make it not biased towards
@@ -109,7 +109,7 @@ func BenchmarkWatchableStoreSyncedCancel(b *testing.B) {
 	watchIDs := make([]WatchID, watcherN)
 	for i := 0; i < watcherN; i++ {
 		// 0 for startRev to keep watchers in synced
-		watchIDs[i] = w.Watch(testKey, true, 0)
+		watchIDs[i] = w.Watch(testKey, nil, 0)
 	}
 
 	// randomly cancel watchers to make it not biased towards

storage/watchable_store_test.go

@@ -40,11 +40,11 @@ func TestWatch(t *testing.T) {
 	s.Put(testKey, testValue, lease.NoLease)
 
 	w := s.NewWatchStream()
-	w.Watch(testKey, true, 0)
+	w.Watch(testKey, nil, 0)
 
-	if _, ok := s.synced[string(testKey)]; !ok {
+	if !s.synced.contains(string(testKey)) {
 		// the key must have had an entry in synced
-		t.Errorf("existence = %v, want true", ok)
+		t.Errorf("existence = false, want true")
 	}
 }
 
@@ -61,15 +61,15 @@ func TestNewWatcherCancel(t *testing.T) {
 	s.Put(testKey, testValue, lease.NoLease)
 
 	w := s.NewWatchStream()
-	wt := w.Watch(testKey, true, 0)
+	wt := w.Watch(testKey, nil, 0)
 
 	if err := w.Cancel(wt); err != nil {
 		t.Error(err)
 	}
 
-	if _, ok := s.synced[string(testKey)]; ok {
+	if s.synced.contains(string(testKey)) {
 		// the key shoud have been deleted
-		t.Errorf("existence = %v, want false", ok)
+		t.Errorf("existence = true, want false")
 	}
 }
 
@@ -83,11 +83,11 @@ func TestCancelUnsynced(t *testing.T) {
 	// in unsynced to test if syncWatchers works as expected.
 	s := &watchableStore{
 		store:    NewStore(b, &lease.FakeLessor{}),
-		unsynced: make(watcherSetByKey),
+		unsynced: newWatcherGroup(),
 
 		// to make the test not crash from assigning to nil map.
 		// 'synced' doesn't get populated in this test.
-		synced: make(watcherSetByKey),
+		synced: newWatcherGroup(),
 	}
 
 	defer func() {
@@ -112,7 +112,7 @@ func TestCancelUnsynced(t *testing.T) {
 	watchIDs := make([]WatchID, watcherN)
 	for i := 0; i < watcherN; i++ {
 		// use 1 to keep watchers in unsynced
-		watchIDs[i] = w.Watch(testKey, true, 1)
+		watchIDs[i] = w.Watch(testKey, nil, 1)
 	}
 
 	for _, idx := range watchIDs {
@@ -125,8 +125,8 @@ func TestCancelUnsynced(t *testing.T) {
 	//
 	// unsynced should be empty
 	// because cancel removes watcher from unsynced
-	if len(s.unsynced) != 0 {
+	if size := s.unsynced.size(); size != 0 {
-		t.Errorf("unsynced size = %d, want 0", len(s.unsynced))
+		t.Errorf("unsynced size = %d, want 0", size)
 	}
 }
 
@@ -138,8 +138,8 @@ func TestSyncWatchers(t *testing.T) {
 
 	s := &watchableStore{
 		store:    NewStore(b, &lease.FakeLessor{}),
-		unsynced: make(watcherSetByKey),
+		unsynced: newWatcherGroup(),
-		synced:   make(watcherSetByKey),
+		synced:   newWatcherGroup(),
 	}
 
 	defer func() {
@@ -158,13 +158,13 @@ func TestSyncWatchers(t *testing.T) {
 
 	for i := 0; i < watcherN; i++ {
 		// specify rev as 1 to keep watchers in unsynced
-		w.Watch(testKey, true, 1)
+		w.Watch(testKey, nil, 1)
 	}
 
 	// Before running s.syncWatchers() synced should be empty because we manually
 	// populate unsynced only
-	sws, _ := s.synced.getSetByKey(string(testKey))
+	sws := s.synced.watcherSetByKey(string(testKey))
-	uws, _ := s.unsynced.getSetByKey(string(testKey))
+	uws := s.unsynced.watcherSetByKey(string(testKey))
 
 	if len(sws) != 0 {
 		t.Fatalf("synced[string(testKey)] size = %d, want 0", len(sws))
@@ -177,8 +177,8 @@ func TestSyncWatchers(t *testing.T) {
 	// this should move all unsynced watchers to synced ones
 	s.syncWatchers()
 
-	sws, _ = s.synced.getSetByKey(string(testKey))
+	sws = s.synced.watcherSetByKey(string(testKey))
-	uws, _ = s.unsynced.getSetByKey(string(testKey))
+	uws = s.unsynced.watcherSetByKey(string(testKey))
 
 	// After running s.syncWatchers(), synced should not be empty because syncwatchers
 	// populates synced in this test case
@@ -240,7 +240,7 @@ func TestWatchCompacted(t *testing.T) {
 	}
 
 	w := s.NewWatchStream()
-	wt := w.Watch(testKey, true, compactRev-1)
+	wt := w.Watch(testKey, nil, compactRev-1)
 
 	select {
 	case resp := <-w.Chan():
@@ -275,7 +275,7 @@ func TestWatchBatchUnsynced(t *testing.T) {
 	}
 
 	w := s.NewWatchStream()
-	w.Watch(v, false, 1)
+	w.Watch(v, nil, 1)
 	for i := 0; i < batches; i++ {
 		if resp := <-w.Chan(); len(resp.Events) != watchBatchMaxRevs {
 			t.Fatalf("len(events) = %d, want %d", len(resp.Events), watchBatchMaxRevs)
@@ -284,8 +284,8 @@ func TestWatchBatchUnsynced(t *testing.T) {
 
 	s.store.mu.Lock()
 	defer s.store.mu.Unlock()
-	if len(s.synced) != 1 {
+	if size := s.synced.size(); size != 1 {
-		t.Errorf("synced size = %d, want 1", len(s.synced))
+		t.Errorf("synced size = %d, want 1", size)
 	}
 }
 
@@ -311,14 +311,14 @@ func TestNewMapwatcherToEventMap(t *testing.T) {
 	}
 
 	tests := []struct {
-		sync watcherSetByKey
+		sync []*watcher
 		evs  []storagepb.Event
 
 		wwe map[*watcher][]storagepb.Event
 	}{
 		// no watcher in sync, some events should return empty wwe
 		{
-			watcherSetByKey{},
+			nil,
 			evs,
 			map[*watcher][]storagepb.Event{},
 		},
@@ -326,9 +326,7 @@ func TestNewMapwatcherToEventMap(t *testing.T) {
 		// one watcher in sync, one event that does not match the key of that
 		// watcher should return empty wwe
 		{
-			watcherSetByKey{
+			[]*watcher{ws[2]},
-				string(k2): {ws[2]: struct{}{}},
-			},
 			evs[:1],
 			map[*watcher][]storagepb.Event{},
 		},
@@ -336,9 +334,7 @@ func TestNewMapwatcherToEventMap(t *testing.T) {
 		// one watcher in sync, one event that matches the key of that
 		// watcher should return wwe with that matching watcher
 		{
-			watcherSetByKey{
+			[]*watcher{ws[1]},
-				string(k1): {ws[1]: struct{}{}},
-			},
 			evs[1:2],
 			map[*watcher][]storagepb.Event{
 				ws[1]: evs[1:2],
@@ -349,10 +345,7 @@ func TestNewMapwatcherToEventMap(t *testing.T) {
 		// that matches the key of only one of the watcher should return wwe
 		// with the matching watcher
 		{
-			watcherSetByKey{
+			[]*watcher{ws[0], ws[2]},
-				string(k0): {ws[0]: struct{}{}},
-				string(k2): {ws[2]: struct{}{}},
-			},
 			evs[2:],
 			map[*watcher][]storagepb.Event{
 				ws[2]: evs[2:],
@@ -362,10 +355,7 @@ func TestNewMapwatcherToEventMap(t *testing.T) {
 		// two watchers in sync that watches the same key, two events that
 		// match the keys should return wwe with those two watchers
 		{
-			watcherSetByKey{
+			[]*watcher{ws[0], ws[1]},
-				string(k0): {ws[0]: struct{}{}},
-				string(k1): {ws[1]: struct{}{}},
-			},
 			evs[:2],
 			map[*watcher][]storagepb.Event{
 				ws[0]: evs[:1],
@@ -375,7 +365,12 @@ func TestNewMapwatcherToEventMap(t *testing.T) {
 	}
 
 	for i, tt := range tests {
-		gwe := newWatcherBatch(tt.sync, tt.evs)
+		wg := newWatcherGroup()
+		for _, w := range tt.sync {
+			wg.add(w)
+		}
+
+		gwe := newWatcherBatch(&wg, tt.evs)
 		if len(gwe) != len(tt.wwe) {
 			t.Errorf("#%d: len(gwe) got = %d, want = %d", i, len(gwe), len(tt.wwe))
 		}

storage/watcher.go

@@ -29,16 +29,15 @@ type WatchID int64
 
 type WatchStream interface {
 	// Watch creates a watcher. The watcher watches the events happening or
-	// happened on the given key or key prefix from the given startRev.
+	// happened on the given key or range [key, end) from the given startRev.
 	//
 	// The whole event history can be watched unless compacted.
-	// If `prefix` is true, watch observes all events whose key prefix could be the given `key`.
 	// If `startRev` <=0, watch observes events after currentRev.
 	//
 	// The returned `id` is the ID of this watcher. It appears as WatchID
 	// in events that are sent to the created watcher through stream channel.
 	//
-	Watch(key []byte, prefix bool, startRev int64) WatchID
+	Watch(key, end []byte, startRev int64) WatchID
 
 	// Chan returns a chan. All watch response will be sent to the returned chan.
 	Chan() <-chan WatchResponse
@@ -87,7 +86,7 @@ type watchStream struct {
 
 // Watch creates a new watcher in the stream and returns its WatchID.
 // TODO: return error if ws is closed?
-func (ws *watchStream) Watch(key []byte, prefix bool, startRev int64) WatchID {
+func (ws *watchStream) Watch(key, end []byte, startRev int64) WatchID {
 	ws.mu.Lock()
 	defer ws.mu.Unlock()
 	if ws.closed {
@@ -97,7 +96,7 @@ func (ws *watchStream) Watch(key []byte, prefix bool, startRev int64) WatchID {
 	id := ws.nextID
 	ws.nextID++
 
-	_, c := ws.watchable.watch(key, prefix, startRev, id, ws.ch)
+	_, c := ws.watchable.watch(key, end, startRev, id, ws.ch)
 
 	ws.cancels[id] = c
 	return id

storage/watcher_bench_test.go

@@ -33,6 +33,6 @@ func BenchmarkKVWatcherMemoryUsage(b *testing.B) {
 	b.ReportAllocs()
 	b.StartTimer()
 	for i := 0; i < b.N; i++ {
-		w.Watch([]byte(fmt.Sprint("foo", i)), false, 0)
+		w.Watch([]byte(fmt.Sprint("foo", i)), nil, 0)
 	}
 }

storage/watcher_group.go

@@ -0,0 +1,269 @@
+// Copyright 2016 CoreOS, Inc.
+//
+// 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 (
+	"math"
+
+	"github.com/coreos/etcd/pkg/adt"
+	"github.com/coreos/etcd/storage/storagepb"
+)
+
+var (
+	// watchBatchMaxRevs is the maximum distinct revisions that
+	// may be sent to an unsynced watcher at a time. Declared as
+	// var instead of const for testing purposes.
+	watchBatchMaxRevs = 1000
+)
+
+type eventBatch struct {
+	// evs is a batch of revision-ordered events
+	evs []storagepb.Event
+	// revs is the minimum unique revisions observed for this batch
+	revs int
+	// moreRev is first revision with more events following this batch
+	moreRev int64
+}
+
+func (eb *eventBatch) add(ev storagepb.Event) {
+	if eb.revs > watchBatchMaxRevs {
+		// maxed out batch size
+		return
+	}
+
+	if len(eb.evs) == 0 {
+		// base case
+		eb.revs = 1
+		eb.evs = append(eb.evs, ev)
+		return
+	}
+
+	// revision accounting
+	ebRev := eb.evs[len(eb.evs)-1].Kv.ModRevision
+	evRev := ev.Kv.ModRevision
+	if evRev > ebRev {
+		eb.revs++
+		if eb.revs > watchBatchMaxRevs {
+			eb.moreRev = evRev
+			return
+		}
+	}
+
+	eb.evs = append(eb.evs, ev)
+}
+
+type watcherBatch map[*watcher]*eventBatch
+
+func (wb watcherBatch) add(w *watcher, ev storagepb.Event) {
+	eb := wb[w]
+	if eb == nil {
+		eb = &eventBatch{}
+		wb[w] = eb
+	}
+	eb.add(ev)
+}
+
+// newWatcherBatch maps watchers to their matched events. It enables quick
+// events look up by watcher.
+func newWatcherBatch(wg *watcherGroup, evs []storagepb.Event) watcherBatch {
+	wb := make(watcherBatch)
+	for _, ev := range evs {
+		for w := range wg.watcherSetByKey(string(ev.Kv.Key)) {
+			if ev.Kv.ModRevision >= w.cur {
+				// don't double notify
+				wb.add(w, ev)
+			}
+		}
+	}
+	return wb
+}
+
+type watcherSet map[*watcher]struct{}
+
+func (w watcherSet) add(wa *watcher) {
+	if _, ok := w[wa]; ok {
+		panic("add watcher twice!")
+	}
+	w[wa] = struct{}{}
+}
+
+func (w watcherSet) union(ws watcherSet) {
+	for wa := range ws {
+		w.add(wa)
+	}
+}
+
+func (w watcherSet) delete(wa *watcher) {
+	if _, ok := w[wa]; !ok {
+		panic("removing missing watcher!")
+	}
+	delete(w, wa)
+}
+
+type watcherSetByKey map[string]watcherSet
+
+func (w watcherSetByKey) add(wa *watcher) {
+	set := w[string(wa.key)]
+	if set == nil {
+		set = make(watcherSet)
+		w[string(wa.key)] = set
+	}
+	set.add(wa)
+}
+
+func (w watcherSetByKey) delete(wa *watcher) bool {
+	k := string(wa.key)
+	if v, ok := w[k]; ok {
+		if _, ok := v[wa]; ok {
+			delete(v, wa)
+			if len(v) == 0 {
+				// remove the set; nothing left
+				delete(w, k)
+			}
+			return true
+		}
+	}
+	return false
+}
+
+type interval struct {
+	begin string
+	end   string
+}
+
+type watcherSetByInterval map[interval]watcherSet
+
+// watcherGroup is a collection of watchers organized by their ranges
+type watcherGroup struct {
+	// keyWatchers has the watchers that watch on a single key
+	keyWatchers watcherSetByKey
+	// ranges has the watchers that watch a range; it is sorted by interval
+	ranges adt.IntervalTree
+	// watchers is the set of all watchers
+	watchers watcherSet
+}
+
+func newWatcherGroup() watcherGroup {
+	return watcherGroup{
+		keyWatchers: make(watcherSetByKey),
+		watchers:    make(watcherSet),
+	}
+}
+
+// add puts a watcher in the group.
+func (wg *watcherGroup) add(wa *watcher) {
+	wg.watchers.add(wa)
+	if wa.end == nil {
+		wg.keyWatchers.add(wa)
+		return
+	}
+
+	// interval already registered?
+	ivl := adt.NewStringAffineInterval(string(wa.key), string(wa.end))
+	if iv := wg.ranges.Find(ivl); iv != nil {
+		iv.Val.(watcherSet).add(wa)
+		return
+	}
+
+	// not registered, put in interval tree
+	ws := make(watcherSet)
+	ws.add(wa)
+	wg.ranges.Insert(ivl, ws)
+}
+
+// contains is whether the given key has a watcher in the group.
+func (wg *watcherGroup) contains(key string) bool {
+	_, ok := wg.keyWatchers[key]
+	return ok || wg.ranges.Contains(adt.NewStringAffinePoint(key))
+}
+
+// size gives the number of unique watchers in the group.
+func (wg *watcherGroup) size() int { return len(wg.watchers) }
+
+// delete removes a watcher from the group.
+func (wg *watcherGroup) delete(wa *watcher) bool {
+	if _, ok := wg.watchers[wa]; !ok {
+		return false
+	}
+	wg.watchers.delete(wa)
+	if wa.end == nil {
+		wg.keyWatchers.delete(wa)
+		return true
+	}
+
+	ivl := adt.NewStringAffineInterval(string(wa.key), string(wa.end))
+	iv := wg.ranges.Find(ivl)
+	if iv == nil {
+		return false
+	}
+
+	ws := iv.Val.(watcherSet)
+	delete(ws, wa)
+	if len(ws) == 0 {
+		// remove interval missing watchers
+		if ok := wg.ranges.Delete(ivl); !ok {
+			panic("could not remove watcher from interval tree")
+		}
+	}
+
+	return true
+}
+
+func (wg *watcherGroup) scanMinRev(curRev int64, compactRev int64) int64 {
+	minRev := int64(math.MaxInt64)
+	for w := range wg.watchers {
+		if w.cur > curRev {
+			panic("watcher current revision should not exceed current revision")
+		}
+		if w.cur < compactRev {
+			select {
+			case w.ch <- WatchResponse{WatchID: w.id, CompactRevision: compactRev}:
+				wg.delete(w)
+			default:
+				// retry next time
+			}
+			continue
+		}
+		if minRev > w.cur {
+			minRev = w.cur
+		}
+	}
+	return minRev
+}
+
+// watcherSetByKey gets the set of watchers that recieve events on the given key.
+func (wg *watcherGroup) watcherSetByKey(key string) watcherSet {
+	wkeys := wg.keyWatchers[key]
+	wranges := wg.ranges.Stab(adt.NewStringAffinePoint(key))
+
+	// zero-copy cases
+	switch {
+	case len(wranges) == 0:
+		// no need to merge ranges or copy; reuse single-key set
+		return wkeys
+	case len(wranges) == 0 && len(wkeys) == 0:
+		return nil
+	case len(wranges) == 1 && len(wkeys) == 0:
+		return wranges[0].Val.(watcherSet)
+	}
+
+	// copy case
+	ret := make(watcherSet)
+	ret.union(wg.keyWatchers[key])
+	for _, item := range wranges {
+		ret.union(item.Val.(watcherSet))
+	}
+	return ret
+}

storage/watcher_test.go

@@ -35,7 +35,7 @@ func TestWatcherWatchID(t *testing.T) {
 	idm := make(map[WatchID]struct{})
 
 	for i := 0; i < 10; i++ {
-		id := w.Watch([]byte("foo"), false, 0)
+		id := w.Watch([]byte("foo"), nil, 0)
 		if _, ok := idm[id]; ok {
 			t.Errorf("#%d: id %d exists", i, id)
 		}
@@ -57,7 +57,7 @@ func TestWatcherWatchID(t *testing.T) {
 
 	// unsynced watchers
 	for i := 10; i < 20; i++ {
-		id := w.Watch([]byte("foo2"), false, 1)
+		id := w.Watch([]byte("foo2"), nil, 1)
 		if _, ok := idm[id]; ok {
 			t.Errorf("#%d: id %d exists", i, id)
 		}
@@ -86,12 +86,11 @@ func TestWatcherWatchPrefix(t *testing.T) {
 
 	idm := make(map[WatchID]struct{})
 
-	prefixMatch := true
 	val := []byte("bar")
-	keyWatch, keyPut := []byte("foo"), []byte("foobar")
+	keyWatch, keyEnd, keyPut := []byte("foo"), []byte("fop"), []byte("foobar")
 
 	for i := 0; i < 10; i++ {
-		id := w.Watch(keyWatch, prefixMatch, 0)
+		id := w.Watch(keyWatch, keyEnd, 0)
 		if _, ok := idm[id]; ok {
 			t.Errorf("#%d: unexpected duplicated id %x", i, id)
 		}
@@ -118,12 +117,12 @@ func TestWatcherWatchPrefix(t *testing.T) {
 		}
 	}
 
-	keyWatch1, keyPut1 := []byte("foo1"), []byte("foo1bar")
+	keyWatch1, keyEnd1, keyPut1 := []byte("foo1"), []byte("foo2"), []byte("foo1bar")
 	s.Put(keyPut1, val, lease.NoLease)
 
 	// unsynced watchers
 	for i := 10; i < 15; i++ {
-		id := w.Watch(keyWatch1, prefixMatch, 1)
+		id := w.Watch(keyWatch1, keyEnd1, 1)
 		if _, ok := idm[id]; ok {
 			t.Errorf("#%d: id %d exists", i, id)
 		}
@@ -159,7 +158,7 @@ func TestWatchStreamCancelWatcherByID(t *testing.T) {
 	w := s.NewWatchStream()
 	defer w.Close()
 
-	id := w.Watch([]byte("foo"), false, 0)
+	id := w.Watch([]byte("foo"), nil, 0)
 
 	tests := []struct {
 		cancelID WatchID