Make unbounded channels explicit.

We used to have unbounded channels embedded within rtpconn
and webClient.  Make the structure explicit and testable.

rtpconn/rtpconn.go

@@ -23,6 +23,7 @@ import (
 	"github.com/jech/galene/packetcache"
 	"github.com/jech/galene/packetmap"
 	"github.com/jech/galene/rtptime"
+	"github.com/jech/galene/unbounded"
 )
 
 type bitrate struct {
@@ -403,7 +404,7 @@ type rtpUpTrack struct {
 	jitter   *jitter.Estimator
 	cname    atomic.Value
 
-	actionCh   chan struct{}
+	actions    *unbounded.Channel[trackAction]
 	readerDone chan struct{}
 
 	mu            sync.Mutex
@@ -412,7 +413,6 @@ type rtpUpTrack struct {
 	srRTPTime     uint32
 	local         []conn.DownTrack
 	bufferedNACKs []uint16
-	actions       []trackAction
 }
 
 const (
@@ -427,17 +427,7 @@ type trackAction struct {
 }
 
 func (up *rtpUpTrack) action(action int, track conn.DownTrack) {
-	up.mu.Lock()
-	empty := len(up.actions) == 0
-	up.actions = append(up.actions, trackAction{action, track})
-	up.mu.Unlock()
-
-	if empty {
-		select {
-		case up.actionCh <- struct{}{}:
-		default:
-		}
-	}
+	up.actions.Put(trackAction{action, track})
 }
 
 func (up *rtpUpTrack) AddLocal(local conn.DownTrack) error {
@@ -682,7 +672,7 @@ func newUpConn(c group.Client, id string, label string, offer string) (*rtpUpCon
 			cache:      packetcache.New(minPacketCache(remote)),
 			rate:       estimator.New(time.Second),
 			jitter:     jitter.New(remote.Codec().ClockRate),
-			actionCh:   make(chan struct{}, 1),
+			actions:    unbounded.New[trackAction](),
 			readerDone: make(chan struct{}),
 		}
 
@@ -923,7 +913,7 @@ func maxUpBitrate(t *rtpUpTrack) uint64 {
 	// assume that lower spatial layers take up 1/5 of
 	// the throughput
 	if maxsid > 0 {
-		maxrate = sadd(maxrate, maxrate / 4)
+		maxrate = sadd(maxrate, maxrate/4)
 	}
 	// assume that each layer takes two times less
 	// throughput than the higher one.  Then we've
@@ -1003,7 +993,7 @@ func sendUpRTCP(up *rtpUpConnection) error {
 		}
 		ssrcs = append(ssrcs, uint32(t.track.SSRC()))
 		if t.Kind() == webrtc.RTPCodecTypeAudio {
-			rate = sadd(rate, 100 * 1024)
+			rate = sadd(rate, 100*1024)
 		} else if t.Label() == "l" {
 			rate = sadd(rate, group.LowBitrate)
 		} else {

rtpconn/rtpreader.go

@@ -31,11 +31,8 @@ func readLoop(track *rtpUpTrack) {
 	for {
 
 		select {
-		case <-track.actionCh:
-			track.mu.Lock()
-			actions := track.actions
-			track.actions = nil
-			track.mu.Unlock()
+		case <-track.actions.Ch:
+			actions := track.actions.Get()
 			for _, action := range actions {
 				switch action.action {
 				case trackActionAdd, trackActionDel:

rtpconn/webclient.go

@@ -20,6 +20,7 @@ import (
 	"github.com/jech/galene/group"
 	"github.com/jech/galene/ice"
 	"github.com/jech/galene/token"
+	"github.com/jech/galene/unbounded"
 )
 
 func errorToWSCloseMessage(id string, err error) (*clientMessage, []byte) {
@@ -65,16 +66,11 @@ type webClient struct {
 	done        chan struct{}
 	writeCh     chan interface{}
 	writerDone  chan struct{}
-	actionCh    chan struct{}
+	actions     *unbounded.Channel[any]
 
 	mu   sync.Mutex
 	down map[string]*rtpDownConnection
 	up   map[string]*rtpUpConnection
-
-	// action may be called with the group mutex taken, and therefore
-	// actions needs to use its own mutex.
-	actionMu sync.Mutex
-	actions  []interface{}
 }
 
 func (c *webClient) Group() *group.Group {
@@ -106,9 +102,10 @@ func (c *webClient) SetPermissions(perms []string) {
 }
 
 func (c *webClient) PushClient(group, kind, id string, username string, perms []string, data map[string]interface{}) error {
-	return c.action(pushClientAction{
+	c.action(pushClientAction{
 		group, kind, id, username, perms, data,
 	})
+	return nil
 }
 
 type clientMessage struct {
@@ -733,7 +730,8 @@ func (c *webClient) setRequestedStream(down *rtpDownConnection, requested []stri
 }
 
 func (c *webClient) RequestConns(target group.Client, g *group.Group, id string) error {
-	return c.action(requestConnsAction{g, target, id})
+	c.action(requestConnsAction{g, target, id})
+	return nil
 }
 
 func requestConns(target group.Client, g *group.Group, id string) {
@@ -804,10 +802,7 @@ func requestedTracks(c *webClient, requested []string, tracks []conn.UpTrack) ([
 }
 
 func (c *webClient) PushConn(g *group.Group, id string, up conn.Up, tracks []conn.UpTrack, replace string) error {
-	err := c.action(pushConnAction{g, id, up, tracks, replace})
-	if err != nil {
-		return err
-	}
+	c.action(pushConnAction{g, id, up, tracks, replace})
 	return nil
 }
 
@@ -854,9 +849,9 @@ func StartClient(conn *websocket.Conn) (err error) {
 	}
 
 	c := &webClient{
-		id:       m.Id,
-		actionCh: make(chan struct{}, 1),
-		done:     make(chan struct{}),
+		id:      m.Id,
+		actions: unbounded.New[any](),
+		done:    make(chan struct{}),
 	}
 
 	defer close(c.done)
@@ -996,11 +991,8 @@ func clientLoop(c *webClient, ws *websocket.Conn, versionError bool) error {
 			case error:
 				return m
 			}
-		case <-c.actionCh:
-			c.actionMu.Lock()
-			actions := c.actions
-			c.actions = nil
-			c.actionMu.Unlock()
+		case <-c.actions.Ch:
+			actions := c.actions.Get()
 			for _, a := range actions {
 				err := handleAction(c, a)
 				if err != nil {
@@ -1090,7 +1082,7 @@ func pushDownConn(c *webClient, id string, up conn.Up, tracks []conn.UpTrack, re
 	return nil
 }
 
-func handleAction(c *webClient, a interface{}) error {
+func handleAction(c *webClient, a any) error {
 	switch a := a.(type) {
 	case pushConnAction:
 		if c.group == nil || c.group != a.group {
@@ -1353,15 +1345,18 @@ func setPermissions(g *group.Group, id string, perm string) error {
 	default:
 		return group.UserError("unknown permission")
 	}
-	return c.action(permissionsChangedAction{})
+	c.action(permissionsChangedAction{})
+	return nil
 }
 
 func (c *webClient) Kick(id string, user *string, message string) error {
-	return c.action(kickAction{id, user, message})
+	c.action(kickAction{id, user, message})
+	return nil
 }
 
 func (c *webClient) Joined(group, kind string) error {
-	return c.action(joinedAction{group, kind})
+	c.action(joinedAction{group, kind})
+	return nil
 }
 
 func kickClient(g *group.Group, id string, user *string, dest string, message string) error {
@@ -2087,22 +2082,8 @@ func (c *webClient) Warn(oponly bool, message string) error {
 
 var ErrClientDead = errors.New("client is dead")
 
-func (c *webClient) action(a interface{}) error {
-	c.actionMu.Lock()
-	empty := len(c.actions) == 0
-	c.actions = append(c.actions, a)
-	c.actionMu.Unlock()
-
-	if empty {
-		select {
-		case c.actionCh <- struct{}{}:
-			return nil
-		case <-c.done:
-			return ErrClientDead
-		default:
-		}
-	}
-	return nil
+func (c *webClient) action(a interface{}) {
+	c.actions.Put(a)
 }
 
 func (c *webClient) write(m clientMessage) error {

unbounded/unbounded.go

@@ -0,0 +1,47 @@
+package unbounded
+
+import (
+	"sync"
+)
+
+// Type Channel implements an unbounded channel
+type Channel[T any] struct {
+	// Ch triggers whenever the channel becomes non-empty
+	Ch chan struct{}
+
+	mu    sync.Mutex
+	queue []T
+}
+
+// New creates a new unbounded channel
+func New[T any]() *Channel[T] {
+	return &Channel[T]{
+		Ch: make(chan struct{}, 1),
+	}
+}
+
+// Put inserts a new element into ch.
+// If ch was previously empty, it triggers ch.Ch.
+func (ch *Channel[T]) Put(v T) {
+	ch.mu.Lock()
+	empty := len(ch.queue) == 0
+	ch.queue = append(ch.queue, v)
+	ch.mu.Unlock()
+
+	if empty {
+		select {
+		case ch.Ch <- struct{}{}:
+		default:
+		}
+	}
+}
+
+// Get removes all the elements of ch.
+// It is usually called when ch.Ch triggers, but may be called at any time.
+func (ch *Channel[T]) Get() []T {
+	ch.mu.Lock()
+	defer ch.mu.Unlock()
+	queue := ch.queue
+	ch.queue = nil
+	return queue
+}

unbounded/unbounded_test.go

@@ -0,0 +1,52 @@
+package unbounded
+
+import (
+	"testing"
+	"time"
+)
+
+func TestUnbounded(t *testing.T) {
+	ch := New[int]()
+
+	go func() {
+		for i := 0; i < 1000; i++ {
+			ch.Put(i)
+		}
+	}()
+
+	n := 0
+	for n < 1000 {
+		<-ch.Ch
+		vs := ch.Get()
+		for _, v := range vs {
+			if n != v {
+				t.Errorf("Expected %v, got %v", n, v)
+			}
+			n++
+		}
+	}
+
+	go func() {
+		for i := 0; i < 1000; i++ {
+			ch.Put(i)
+			time.Sleep(time.Microsecond)
+		}
+	}()
+
+	n = 0
+	for n < 1000 {
+		<-ch.Ch
+		vs := ch.Get()
+		for _, v := range vs {
+			if n != v {
+				t.Errorf("Expected %v, got %v", n, v)
+			}
+			n++
+		}
+	}
+
+	vs := ch.Get()
+	if len(vs) != 0 {
+		t.Errorf("Channel is not empty (%v)", len(vs))
+	}
+}