[eventsub] Replace keepalive timer

as `time.Timer` wasn't really suited for how it was used

Signed-off-by: Knut Ahlers <knut@ahlers.me>

pkg/twitch/eventsubWebsocketClient.go

@@ -166,7 +166,8 @@ func (e *EventSubSocketClient) Run() error {
 		errC             = make(chan error, 1)
 		keepaliveTimeout = socketInitialTimeout
 		msgC             = make(chan eventSubSocketMessage, 1)
-		socketTimeout    = time.NewTimer(keepaliveTimeout)
+		timeoutC         = make(chan struct{}, 1)
+		socketTimeout    = newKeepaliveTracker(timeoutC, keepaliveTimeout)
 	)
 
 	if err := e.connect(e.socketDest, msgC, errC, "client init"); err != nil {
@@ -187,9 +188,14 @@ func (e *EventSubSocketClient) Run() error {
 				return err
 			}
 
-		case <-socketTimeout.C:
+		case <-timeoutC:
 			// No message received, deeming connection dead
-			socketTimeout.Reset(socketInitialTimeout)
+			e.logger.WithFields(logrus.Fields{
+				"expired":    socketTimeout.ExpiresAt(),
+				"last_event": socketTimeout.LastRenew(),
+			}).Warn("eventsub socket missed keepalive")
+
+			socketTimeout = newKeepaliveTracker(timeoutC, socketInitialTimeout)
 			if err := e.connect(e.socketDest, msgC, errC, "socket timeout"); err != nil {
 				errC <- errors.Wrap(err, "re-connecting after timeout")
 				continue
@@ -198,7 +204,7 @@ func (e *EventSubSocketClient) Run() error {
 		case msg := <-msgC:
 			// The keepalive timer is reset with each notification or
 			// keepalive message.
-			socketTimeout.Reset(keepaliveTimeout)
+			socketTimeout.Renew(keepaliveTimeout)
 
 			switch msg.Metadata.MessageType {
 			case eventsubSocketMessageTypeKeepalive:

pkg/twitch/keepalive.go

@@ -0,0 +1,39 @@
+package twitch
+
+import "time"
+
+const keepaliveTrackerCheckInterval = 100 * time.Millisecond
+
+type (
+	keepaliveTracker struct {
+		c       chan<- struct{}
+		expires time.Time
+		renewed time.Time
+	}
+)
+
+func newKeepaliveTracker(timeout chan<- struct{}, d time.Duration) *keepaliveTracker {
+	t := &keepaliveTracker{
+		c:       timeout,
+		expires: time.Now().Add(d),
+	}
+
+	go t.run()
+
+	return t
+}
+
+func (t keepaliveTracker) ExpiresAt() time.Time { return t.expires }
+func (t keepaliveTracker) LastRenew() time.Time { return t.renewed }
+
+func (t *keepaliveTracker) Renew(d time.Duration) {
+	t.expires = time.Now().Add(d)
+	t.renewed = time.Now()
+}
+
+func (t *keepaliveTracker) run() {
+	for t.expires.After(time.Now()) {
+		time.Sleep(keepaliveTrackerCheckInterval)
+	}
+	t.c <- struct{}{}
+}