Per-user-per-device sync streams (#1068)

* Per-user-per-device sync streams

* Tweaks

* Tweaks

* Pass full device into CompleteSync

* Set user IDs and device IDs properly in tests

* Add new test, fix TestNewEventAndWasPreviouslyJoinedToRoom

* nolint a function that is not used yet

* Add test for waking up single device

* Hopefully unstick test

* Try to ensure that TestCorrectStreamWakeup doesn't block forever

* Update tests

7 files changed, 159 insertions, 68 deletions

diff --git a/syncapi/storage/interface.go b/syncapi/storage/interface.go
index 3e9ff053..7e1a40fd 100644
--- a/syncapi/storage/interface.go
+++ b/syncapi/storage/interface.go
@@ -58,7 +58,7 @@ type Database interface {
 	// ID.
 	IncrementalSync(ctx context.Context, device authtypes.Device, fromPos, toPos types.StreamingToken, numRecentEventsPerRoom int, wantFullState bool) (*types.Response, error)
 	// CompleteSync returns a complete /sync API response for the given user.
-	CompleteSync(ctx context.Context, userID string, numRecentEventsPerRoom int) (*types.Response, error)
+	CompleteSync(ctx context.Context, device authtypes.Device, numRecentEventsPerRoom int) (*types.Response, error)
 	// GetAccountDataInRange returns all account data for a given user inserted or
 	// updated between two given positions
 	// Returns a map following the format data[roomID] = []dataTypes
diff --git a/syncapi/storage/shared/syncserver.go b/syncapi/storage/shared/syncserver.go
index 145a3dbf..888f85e0 100644
--- a/syncapi/storage/shared/syncserver.go
+++ b/syncapi/storage/shared/syncserver.go
@@ -666,10 +666,10 @@ func (d *Database) getResponseWithPDUsForCompleteSync(
 }
 
 func (d *Database) CompleteSync(
-	ctx context.Context, userID string, numRecentEventsPerRoom int,
+	ctx context.Context, device authtypes.Device, numRecentEventsPerRoom int,
 ) (*types.Response, error) {
 	res, toPos, joinedRoomIDs, err := d.getResponseWithPDUsForCompleteSync(
-		ctx, userID, numRecentEventsPerRoom,
+		ctx, device.UserID, numRecentEventsPerRoom,
 	)
 	if err != nil {
 		return nil, err
diff --git a/syncapi/storage/storage_test.go b/syncapi/storage/storage_test.go
index 6b045852..bb8554f4 100644
--- a/syncapi/storage/storage_test.go
+++ b/syncapi/storage/storage_test.go
@@ -181,7 +181,7 @@ func TestSyncResponse(t *testing.T) {
 			Name: "CompleteSync limited",
 			DoSync: func() (*types.Response, error) {
 				// limit set to 5
-				return db.CompleteSync(ctx, testUserIDA, 5)
+				return db.CompleteSync(ctx, testUserDeviceA, 5)
 			},
 			// want the last 5 events
 			WantTimeline: events[len(events)-5:],
@@ -193,7 +193,7 @@ func TestSyncResponse(t *testing.T) {
 		{
 			Name: "CompleteSync",
 			DoSync: func() (*types.Response, error) {
-				return db.CompleteSync(ctx, testUserIDA, len(events)+1)
+				return db.CompleteSync(ctx, testUserDeviceA, len(events)+1)
 			},
 			WantTimeline: events,
 			// We want no state at all as that field in /sync is the delta between the token (beginning of time)
diff --git a/syncapi/sync/notifier.go b/syncapi/sync/notifier.go
index b3ed5cd0..9b410a0c 100644
--- a/syncapi/sync/notifier.go
+++ b/syncapi/sync/notifier.go
@@ -37,8 +37,8 @@ type Notifier struct {
 	streamLock *sync.Mutex
 	// The latest sync position
 	currPos types.StreamingToken
-	// A map of user_id => UserStream which can be used to wake a given user's /sync request.
-	userStreams map[string]*UserStream
+	// A map of user_id => device_id => UserStream which can be used to wake a given user's /sync request.
+	userDeviceStreams map[string]map[string]*UserDeviceStream
 	// The last time we cleaned out stale entries from the userStreams map
 	lastCleanUpTime time.Time
 }
@@ -50,7 +50,7 @@ func NewNotifier(pos types.StreamingToken) *Notifier {
 	return &Notifier{
 		currPos:             pos,
 		roomIDToJoinedUsers: make(map[string]userIDSet),
-		userStreams:         make(map[string]*UserStream),
+		userDeviceStreams:   make(map[string]map[string]*UserDeviceStream),
 		streamLock:          &sync.Mutex{},
 		lastCleanUpTime:     time.Now(),
 	}
@@ -123,7 +123,7 @@ func (n *Notifier) OnNewEvent(
 // GetListener returns a UserStreamListener that can be used to wait for
 // updates for a user. Must be closed.
 // notify for anything before sincePos
-func (n *Notifier) GetListener(req syncRequest) UserStreamListener {
+func (n *Notifier) GetListener(req syncRequest) UserDeviceStreamListener {
 	// Do what synapse does: https://github.com/matrix-org/synapse/blob/v0.20.0/synapse/notifier.py#L298
 	// - Bucket request into a lookup map keyed off a list of joined room IDs and separately a user ID
 	// - Incoming events wake requests for a matching room ID
@@ -137,7 +137,7 @@ func (n *Notifier) GetListener(req syncRequest) UserStreamListener {
 
 	n.removeEmptyUserStreams()
 
-	return n.fetchUserStream(req.device.UserID, true).GetListener(req.ctx)
+	return n.fetchUserDeviceStream(req.device.UserID, req.device.ID, true).GetListener(req.ctx)
 }
 
 // Load the membership states required to notify users correctly.
@@ -173,29 +173,71 @@ func (n *Notifier) setUsersJoinedToRooms(roomIDToUserIDs map[string][]string) {
 	}
 }
 
+// wakeupUsers will wake up the sync strems for all of the devices for all of the
+// specified user IDs.
 func (n *Notifier) wakeupUsers(userIDs []string, newPos types.StreamingToken) {
 	for _, userID := range userIDs {
-		stream := n.fetchUserStream(userID, false)
-		if stream != nil {
+		for _, stream := range n.fetchUserStreams(userID) {
+			if stream == nil {
+				continue
+			}
 			stream.Broadcast(newPos) // wake up all goroutines Wait()ing on this stream
 		}
 	}
 }
 
-// fetchUserStream retrieves a stream unique to the given user. If makeIfNotExists is true,
-// a stream will be made for this user if one doesn't exist and it will be returned. This
+// wakeupUserDevice will wake up the sync stream for a specific user device. Other
+// device streams will be left alone.
+// nolint:unused
+func (n *Notifier) wakeupUserDevice(userDevices map[string]string, newPos types.StreamingToken) {
+	for userID, deviceID := range userDevices {
+		if stream := n.fetchUserDeviceStream(userID, deviceID, false); stream != nil {
+			stream.Broadcast(newPos) // wake up all goroutines Wait()ing on this stream
+		}
+	}
+}
+
+// fetchUserDeviceStream retrieves a stream unique to the given device. If makeIfNotExists is true,
+// a stream will be made for this device if one doesn't exist and it will be returned. This
 // function does not wait for data to be available on the stream.
 // NB: Callers should have locked the mutex before calling this function.
-func (n *Notifier) fetchUserStream(userID string, makeIfNotExists bool) *UserStream {
-	stream, ok := n.userStreams[userID]
-	if !ok && makeIfNotExists {
+func (n *Notifier) fetchUserDeviceStream(userID, deviceID string, makeIfNotExists bool) *UserDeviceStream {
+	_, ok := n.userDeviceStreams[userID]
+	if !ok {
+		if !makeIfNotExists {
+			return nil
+		}
+		n.userDeviceStreams[userID] = map[string]*UserDeviceStream{}
+	}
+	stream, ok := n.userDeviceStreams[userID][deviceID]
+	if !ok {
+		if !makeIfNotExists {
+			return nil
+		}
 		// TODO: Unbounded growth of streams (1 per user)
-		stream = NewUserStream(userID, n.currPos)
-		n.userStreams[userID] = stream
+		if stream = NewUserDeviceStream(userID, deviceID, n.currPos); stream != nil {
+			n.userDeviceStreams[userID][deviceID] = stream
+		}
 	}
 	return stream
 }
 
+// fetchUserStreams retrieves all streams for the given user. If makeIfNotExists is true,
+// a stream will be made for this user if one doesn't exist and it will be returned. This
+// function does not wait for data to be available on the stream.
+// NB: Callers should have locked the mutex before calling this function.
+func (n *Notifier) fetchUserStreams(userID string) []*UserDeviceStream {
+	user, ok := n.userDeviceStreams[userID]
+	if !ok {
+		return []*UserDeviceStream{}
+	}
+	streams := []*UserDeviceStream{}
+	for _, stream := range user {
+		streams = append(streams, stream)
+	}
+	return streams
+}
+
 // Not thread-safe: must be called on the OnNewEvent goroutine only
 func (n *Notifier) addJoinedUser(roomID, userID string) {
 	if _, ok := n.roomIDToJoinedUsers[roomID]; !ok {
@@ -236,9 +278,14 @@ func (n *Notifier) removeEmptyUserStreams() {
 	n.lastCleanUpTime = now
 
 	deleteBefore := now.Add(-5 * time.Minute)
-	for key, value := range n.userStreams {
-		if value.TimeOfLastNonEmpty().Before(deleteBefore) {
-			delete(n.userStreams, key)
+	for user, byUser := range n.userDeviceStreams {
+		for device, stream := range byUser {
+			if stream.TimeOfLastNonEmpty().Before(deleteBefore) {
+				delete(n.userDeviceStreams[user], device)
+			}
+			if len(n.userDeviceStreams[user]) == 0 {
+				delete(n.userDeviceStreams, user)
+			}
 		}
 	}
 }
diff --git a/syncapi/sync/notifier_test.go b/syncapi/sync/notifier_test.go
index 7d979fcc..14ddef20 100644
--- a/syncapi/sync/notifier_test.go
+++ b/syncapi/sync/notifier_test.go
@@ -41,9 +41,11 @@ var (
 )
 
 var (
-	roomID = "!test:localhost"
-	alice  = "@alice:localhost"
-	bob    = "@bob:localhost"
+	roomID   = "!test:localhost"
+	alice    = "@alice:localhost"
+	aliceDev = "alicedevice"
+	bob      = "@bob:localhost"
+	bobDev   = "bobdev"
 )
 
 func init() {
@@ -107,7 +109,7 @@ func mustEqualPositions(t *testing.T, got, want types.StreamingToken) {
 // Test that the current position is returned if a request is already behind.
 func TestImmediateNotification(t *testing.T) {
 	n := NewNotifier(syncPositionBefore)
-	pos, err := waitForEvents(n, newTestSyncRequest(alice, syncPositionVeryOld))
+	pos, err := waitForEvents(n, newTestSyncRequest(alice, aliceDev, syncPositionVeryOld))
 	if err != nil {
 		t.Fatalf("TestImmediateNotification error: %s", err)
 	}
@@ -124,7 +126,7 @@ func TestNewEventAndJoinedToRoom(t *testing.T) {
 	var wg sync.WaitGroup
 	wg.Add(1)
 	go func() {
-		pos, err := waitForEvents(n, newTestSyncRequest(bob, syncPositionBefore))
+		pos, err := waitForEvents(n, newTestSyncRequest(bob, bobDev, syncPositionBefore))
 		if err != nil {
 			t.Errorf("TestNewEventAndJoinedToRoom error: %w", err)
 		}
@@ -132,7 +134,7 @@ func TestNewEventAndJoinedToRoom(t *testing.T) {
 		wg.Done()
 	}()
 
-	stream := lockedFetchUserStream(n, bob)
+	stream := lockedFetchUserStream(n, bob, bobDev)
 	waitForBlocking(stream, 1)
 
 	n.OnNewEvent(&randomMessageEvent, "", nil, syncPositionAfter)
@@ -140,6 +142,43 @@ func TestNewEventAndJoinedToRoom(t *testing.T) {
 	wg.Wait()
 }
 
+func TestCorrectStream(t *testing.T) {
+	n := NewNotifier(syncPositionBefore)
+	stream := lockedFetchUserStream(n, bob, bobDev)
+	if stream.UserID != bob {
+		t.Fatalf("expected user %q, got %q", bob, stream.UserID)
+	}
+	if stream.DeviceID != bobDev {
+		t.Fatalf("expected device %q, got %q", bobDev, stream.DeviceID)
+	}
+}
+
+func TestCorrectStreamWakeup(t *testing.T) {
+	n := NewNotifier(syncPositionBefore)
+	awoken := make(chan string)
+
+	streamone := lockedFetchUserStream(n, alice, "one")
+	streamtwo := lockedFetchUserStream(n, alice, "two")
+
+	go func() {
+		select {
+		case <-streamone.signalChannel:
+			awoken <- "one"
+		case <-streamtwo.signalChannel:
+			awoken <- "two"
+		}
+	}()
+
+	time.Sleep(1 * time.Second)
+
+	wake := "two"
+	n.wakeupUserDevice(map[string]string{alice: wake}, syncPositionAfter)
+
+	if result := <-awoken; result != wake {
+		t.Fatalf("expected to wake %q, got %q", wake, result)
+	}
+}
+
 // Test that an invite unblocks the request
 func TestNewInviteEventForUser(t *testing.T) {
 	n := NewNotifier(syncPositionBefore)
@@ -150,7 +189,7 @@ func TestNewInviteEventForUser(t *testing.T) {
 	var wg sync.WaitGroup
 	wg.Add(1)
 	go func() {
-		pos, err := waitForEvents(n, newTestSyncRequest(bob, syncPositionBefore))
+		pos, err := waitForEvents(n, newTestSyncRequest(bob, bobDev, syncPositionBefore))
 		if err != nil {
 			t.Errorf("TestNewInviteEventForUser error: %w", err)
 		}
@@ -158,7 +197,7 @@ func TestNewInviteEventForUser(t *testing.T) {
 		wg.Done()
 	}()
 
-	stream := lockedFetchUserStream(n, bob)
+	stream := lockedFetchUserStream(n, bob, bobDev)
 	waitForBlocking(stream, 1)
 
 	n.OnNewEvent(&aliceInviteBobEvent, "", nil, syncPositionAfter)
@@ -176,7 +215,7 @@ func TestEDUWakeup(t *testing.T) {
 	var wg sync.WaitGroup
 	wg.Add(1)
 	go func() {
-		pos, err := waitForEvents(n, newTestSyncRequest(bob, syncPositionAfter))
+		pos, err := waitForEvents(n, newTestSyncRequest(bob, bobDev, syncPositionAfter))
 		if err != nil {
 			t.Errorf("TestNewInviteEventForUser error: %w", err)
 		}
@@ -184,7 +223,7 @@ func TestEDUWakeup(t *testing.T) {
 		wg.Done()
 	}()
 
-	stream := lockedFetchUserStream(n, bob)
+	stream := lockedFetchUserStream(n, bob, bobDev)
 	waitForBlocking(stream, 1)
 
 	n.OnNewEvent(&aliceInviteBobEvent, "", nil, syncPositionNewEDU)
@@ -202,7 +241,7 @@ func TestMultipleRequestWakeup(t *testing.T) {
 	var wg sync.WaitGroup
 	wg.Add(3)
 	poll := func() {
-		pos, err := waitForEvents(n, newTestSyncRequest(bob, syncPositionBefore))
+		pos, err := waitForEvents(n, newTestSyncRequest(bob, bobDev, syncPositionBefore))
 		if err != nil {
 			t.Errorf("TestMultipleRequestWakeup error: %w", err)
 		}
@@ -213,7 +252,7 @@ func TestMultipleRequestWakeup(t *testing.T) {
 	go poll()
 	go poll()
 
-	stream := lockedFetchUserStream(n, bob)
+	stream := lockedFetchUserStream(n, bob, bobDev)
 	waitForBlocking(stream, 3)
 
 	n.OnNewEvent(&randomMessageEvent, "", nil, syncPositionAfter)
@@ -240,24 +279,24 @@ func TestNewEventAndWasPreviouslyJoinedToRoom(t *testing.T) {
 	// Make bob leave the room
 	leaveWG.Add(1)
 	go func() {
-		pos, err := waitForEvents(n, newTestSyncRequest(bob, syncPositionBefore))
+		pos, err := waitForEvents(n, newTestSyncRequest(bob, bobDev, syncPositionBefore))
 		if err != nil {
 			t.Errorf("TestNewEventAndWasPreviouslyJoinedToRoom error: %w", err)
 		}
 		mustEqualPositions(t, pos, syncPositionAfter)
 		leaveWG.Done()
 	}()
-	bobStream := lockedFetchUserStream(n, bob)
+	bobStream := lockedFetchUserStream(n, bob, bobDev)
 	waitForBlocking(bobStream, 1)
 	n.OnNewEvent(&bobLeaveEvent, "", nil, syncPositionAfter)
 	leaveWG.Wait()
 
 	// send an event into the room. Make sure alice gets it. Bob should not.
 	var aliceWG sync.WaitGroup
-	aliceStream := lockedFetchUserStream(n, alice)
+	aliceStream := lockedFetchUserStream(n, alice, aliceDev)
 	aliceWG.Add(1)
 	go func() {
-		pos, err := waitForEvents(n, newTestSyncRequest(alice, syncPositionAfter))
+		pos, err := waitForEvents(n, newTestSyncRequest(alice, aliceDev, syncPositionAfter))
 		if err != nil {
 			t.Errorf("TestNewEventAndWasPreviouslyJoinedToRoom error: %w", err)
 		}
@@ -267,7 +306,7 @@ func TestNewEventAndWasPreviouslyJoinedToRoom(t *testing.T) {
 
 	go func() {
 		// this should timeout with an error (but the main goroutine won't wait for the timeout explicitly)
-		_, err := waitForEvents(n, newTestSyncRequest(bob, syncPositionAfter))
+		_, err := waitForEvents(n, newTestSyncRequest(bob, bobDev, syncPositionAfter))
 		if err == nil {
 			t.Errorf("TestNewEventAndWasPreviouslyJoinedToRoom expect error but got nil")
 		}
@@ -300,7 +339,7 @@ func waitForEvents(n *Notifier, req syncRequest) (types.StreamingToken, error) {
 }
 
 // Wait until something is Wait()ing on the user stream.
-func waitForBlocking(s *UserStream, numBlocking uint) {
+func waitForBlocking(s *UserDeviceStream, numBlocking uint) {
 	for numBlocking != s.NumWaiting() {
 		// This is horrible but I don't want to add a signalling mechanism JUST for testing.
 		time.Sleep(1 * time.Microsecond)
@@ -309,16 +348,19 @@ func waitForBlocking(s *UserStream, numBlocking uint) {
 
 // lockedFetchUserStream invokes Notifier.fetchUserStream, respecting Notifier.streamLock.
 // A new stream is made if it doesn't exist already.
-func lockedFetchUserStream(n *Notifier, userID string) *UserStream {
+func lockedFetchUserStream(n *Notifier, userID, deviceID string) *UserDeviceStream {
 	n.streamLock.Lock()
 	defer n.streamLock.Unlock()
 
-	return n.fetchUserStream(userID, true)
+	return n.fetchUserDeviceStream(userID, deviceID, true)
 }
 
-func newTestSyncRequest(userID string, since types.StreamingToken) syncRequest {
+func newTestSyncRequest(userID, deviceID string, since types.StreamingToken) syncRequest {
 	return syncRequest{
-		device:        authtypes.Device{UserID: userID},
+		device: authtypes.Device{
+			UserID: userID,
+			ID:     deviceID,
+		},
 		timeout:       1 * time.Minute,
 		since:         &since,
 		wantFullState: false,
diff --git a/syncapi/sync/requestpool.go b/syncapi/sync/requestpool.go
index 82ce283b..bd29b333 100644
--- a/syncapi/sync/requestpool.go
+++ b/syncapi/sync/requestpool.go
@@ -47,7 +47,6 @@ func (rp *RequestPool) OnIncomingSyncRequest(req *http.Request, device *authtype
 	var syncData *types.Response
 
 	// Extract values from request
-	userID := device.UserID
 	syncReq, err := newSyncRequest(req, *device)
 	if err != nil {
 		return util.JSONResponse{
@@ -56,10 +55,11 @@ func (rp *RequestPool) OnIncomingSyncRequest(req *http.Request, device *authtype
 		}
 	}
 	logger := util.GetLogger(req.Context()).WithFields(log.Fields{
-		"userID":  userID,
-		"since":   syncReq.since,
-		"timeout": syncReq.timeout,
-		"limit":   syncReq.limit,
+		"userID":   device.UserID,
+		"deviceID": device.ID,
+		"since":    syncReq.since,
+		"timeout":  syncReq.timeout,
+		"limit":    syncReq.limit,
 	})
 
 	currPos := rp.notifier.CurrentPosition()
@@ -136,7 +136,7 @@ func (rp *RequestPool) OnIncomingSyncRequest(req *http.Request, device *authtype
 func (rp *RequestPool) currentSyncForUser(req syncRequest, latestPos types.StreamingToken) (res *types.Response, err error) {
 	// TODO: handle ignored users
 	if req.since == nil {
-		res, err = rp.db.CompleteSync(req.ctx, req.device.UserID, req.limit)
+		res, err = rp.db.CompleteSync(req.ctx, req.device, req.limit)
 	} else {
 		res, err = rp.db.IncrementalSync(req.ctx, req.device, *req.since, latestPos, req.limit, req.wantFullState)
 	}
diff --git a/syncapi/sync/userstream.go b/syncapi/sync/userstream.go
index b2eafa3d..ff9a4d00 100644
--- a/syncapi/sync/userstream.go
+++ b/syncapi/sync/userstream.go
@@ -23,12 +23,13 @@ import (
 	"github.com/matrix-org/dendrite/syncapi/types"
 )
 
-// UserStream represents a communication mechanism between the /sync request goroutine
+// UserDeviceStream represents a communication mechanism between the /sync request goroutine
 // and the underlying sync server goroutines.
 // Goroutines can get a UserStreamListener to wait for updates, and can Broadcast()
 // updates.
-type UserStream struct {
-	UserID string
+type UserDeviceStream struct {
+	UserID   string
+	DeviceID string
 	// The lock that protects changes to this struct
 	lock sync.Mutex
 	// Closed when there is an update.
@@ -41,18 +42,19 @@ type UserStream struct {
 	numWaiting uint
 }
 
-// UserStreamListener allows a sync request to wait for updates for a user.
-type UserStreamListener struct {
-	userStream *UserStream
+// UserDeviceStreamListener allows a sync request to wait for updates for a user.
+type UserDeviceStreamListener struct {
+	userStream *UserDeviceStream
 
 	// Whether the stream has been closed
 	hasClosed bool
 }
 
-// NewUserStream creates a new user stream
-func NewUserStream(userID string, currPos types.StreamingToken) *UserStream {
-	return &UserStream{
+// NewUserDeviceStream creates a new user stream
+func NewUserDeviceStream(userID, deviceID string, currPos types.StreamingToken) *UserDeviceStream {
+	return &UserDeviceStream{
 		UserID:            userID,
+		DeviceID:          deviceID,
 		timeOfLastChannel: time.Now(),
 		pos:               currPos,
 		signalChannel:     make(chan struct{}),
@@ -62,18 +64,18 @@ func NewUserStream(userID string, currPos types.StreamingToken) *UserStream {
 // GetListener returns UserStreamListener that a sync request can use to wait
 // for new updates with.
 // UserStreamListener must be closed
-func (s *UserStream) GetListener(ctx context.Context) UserStreamListener {
+func (s *UserDeviceStream) GetListener(ctx context.Context) UserDeviceStreamListener {
 	s.lock.Lock()
 	defer s.lock.Unlock()
 
 	s.numWaiting++ // We decrement when UserStreamListener is closed
 
-	listener := UserStreamListener{
+	listener := UserDeviceStreamListener{
 		userStream: s,
 	}
 
 	// Lets be a bit paranoid here and check that Close() is being called
-	runtime.SetFinalizer(&listener, func(l *UserStreamListener) {
+	runtime.SetFinalizer(&listener, func(l *UserDeviceStreamListener) {
 		if !l.hasClosed {
 			l.Close()
 		}
@@ -83,7 +85,7 @@ func (s *UserStream) GetListener(ctx context.Context) UserStreamListener {
 }
 
 // Broadcast a new sync position for this user.
-func (s *UserStream) Broadcast(pos types.StreamingToken) {
+func (s *UserDeviceStream) Broadcast(pos types.StreamingToken) {
 	s.lock.Lock()
 	defer s.lock.Unlock()
 
@@ -96,7 +98,7 @@ func (s *UserStream) Broadcast(pos types.StreamingToken) {
 
 // NumWaiting returns the number of goroutines waiting for waiting for updates.
 // Used for metrics and testing.
-func (s *UserStream) NumWaiting() uint {
+func (s *UserDeviceStream) NumWaiting() uint {
 	s.lock.Lock()
 	defer s.lock.Unlock()
 	return s.numWaiting
@@ -105,7 +107,7 @@ func (s *UserStream) NumWaiting() uint {
 // TimeOfLastNonEmpty returns the last time that the number of waiting listeners
 // was non-empty, may be time.Now() if number of waiting listeners is currently
 // non-empty.
-func (s *UserStream) TimeOfLastNonEmpty() time.Time {
+func (s *UserDeviceStream) TimeOfLastNonEmpty() time.Time {
 	s.lock.Lock()
 	defer s.lock.Unlock()
 
@@ -118,7 +120,7 @@ func (s *UserStream) TimeOfLastNonEmpty() time.Time {
 
 // GetSyncPosition returns last sync position which the UserStream was
 // notified about
-func (s *UserStreamListener) GetSyncPosition() types.StreamingToken {
+func (s *UserDeviceStreamListener) GetSyncPosition() types.StreamingToken {
 	s.userStream.lock.Lock()
 	defer s.userStream.lock.Unlock()
 
@@ -130,7 +132,7 @@ func (s *UserStreamListener) GetSyncPosition() types.StreamingToken {
 // sincePos specifies from which point we want to be notified about. If there
 // has already been an update after sincePos we'll return a closed channel
 // immediately.
-func (s *UserStreamListener) GetNotifyChannel(sincePos types.StreamingToken) <-chan struct{} {
+func (s *UserDeviceStreamListener) GetNotifyChannel(sincePos types.StreamingToken) <-chan struct{} {
 	s.userStream.lock.Lock()
 	defer s.userStream.lock.Unlock()
 
@@ -147,7 +149,7 @@ func (s *UserStreamListener) GetNotifyChannel(sincePos types.StreamingToken) <-c
 }
 
 // Close cleans up resources used
-func (s *UserStreamListener) Close() {
+func (s *UserDeviceStreamListener) Close() {
 	s.userStream.lock.Lock()
 	defer s.userStream.lock.Unlock()