ws: Add LastAcknowledgedBeat

This commit adds ws.Handler.LastAcknowledgedBeat to allow ws.Gateway to
monitor whether or not the server is still reachable.

It fixes #324.

gateway/gateway.go

@@ -417,6 +417,14 @@ func (g *gatewayImpl) SendHeartbeat(ctx context.Context) {
 	}
 }
 
+// LastAcknowledgedBeat returns the last acknowledged beat.
+func (g *gatewayImpl) LastAcknowledgedBeat() time.Time {
+	g.beatMutex.Lock()
+	defer g.beatMutex.Unlock()
+
+	return g.echoBeat
+}
+
 // Close closes the state.
 func (g *gatewayImpl) Close() error {
 	g.retryTimer.Stop()

utils/ws/gateway.go

@@ -11,6 +11,10 @@ import (
 	"github.com/pkg/errors"
 )
 
+// ErrHeartbeatTimeout is returned if the server fails to acknowledge our heart
+// beat in time.
+var ErrHeartbeatTimeout = errors.New("server timed out replying to heartbeat")
+
 // ConnectionError is given to the user if the gateway fails to connect to the
 // gateway for any reason, including during an initial connection or a
 // reconnection. To check for this error, use the errors.As function.
@@ -97,6 +101,7 @@ type Gateway struct {
 
 	reconnect chan struct{}
 	heart     lazytime.Ticker
+	heartRate time.Duration
 	srcOp     <-chan Op // from WS
 	outer     outerState
 	lastError error
@@ -125,6 +130,9 @@ type Handler interface {
 	// SendHeartbeat is called by the gateway event loop everytime a heartbeat
 	// needs to be sent over.
 	SendHeartbeat(context.Context)
+	// LastAcknowledgedBeat returns the last time that the server acknowledged
+	// our heart beat.
+	LastAcknowledgedBeat() time.Time
 	// Close closes the handler.
 	Close() error
 }
@@ -263,6 +271,7 @@ func (g *Gateway) QueueReconnect() {
 // ResetHeartbeat resets the heartbeat to be the given duration.
 func (g *Gateway) ResetHeartbeat(d time.Duration) {
 	g.heart.Reset(d)
+	g.heartRate = d
 }
 
 // SendError sends the given error wrapped in a BackgroundErrorEvent into the
@@ -327,7 +336,12 @@ func (g *Gateway) spin(ctx context.Context, h Handler) {
 			g.lastError = nil
 
 		case <-g.heart.C:
-			h.SendHeartbeat(ctx)
+			if h.LastAcknowledgedBeat().Add(2 * g.heartRate).Before(time.Now()) {
+				g.SendError(ErrHeartbeatTimeout)
+				g.QueueReconnect()
+			} else {
+				h.SendHeartbeat(ctx)
+			}
 
 		case <-g.reconnect:
 			// Close the previous connection if it's not already. Ignore the

voice/voicegateway/gateway.go

@@ -45,8 +45,9 @@ type Gateway struct {
 	gateway *ws.Gateway
 	state   State // constant
 
-	mutex sync.RWMutex
-	ready *ReadyEvent
+	mutex   sync.RWMutex
+	beatAck time.Time
+	ready   *ReadyEvent
 }
 
 // DefaultGatewayOpts contains the default options to be used for connecting to
@@ -187,6 +188,10 @@ func (g *gatewayImpl) OnOp(ctx context.Context, op ws.Op) bool {
 				g.gateway.QueueReconnect()
 			}
 		}
+	case *HeartbeatAckEvent:
+		g.mutex.Lock()
+		g.beatAck = time.Now()
+		g.mutex.Unlock()
 	case *ReadyEvent:
 		g.mutex.Lock()
 		g.ready = data
@@ -204,6 +209,13 @@ func (g *gatewayImpl) SendHeartbeat(ctx context.Context) {
 	}
 }
 
+func (g *gatewayImpl) LastAcknowledgedBeat() time.Time {
+	g.mutex.RLock()
+	defer g.mutex.RUnlock()
+
+	return g.beatAck
+}
+
 func (g *gatewayImpl) Close() error {
 	return nil
 }