using unbuffered channels everywhere now. Only change required was to initialize prometeus and the websessions before the matchmaker. This is because at startup the matchmaker wants to write a notification when it starts up but then prometheus and the websessions would not be there to read them.

Alternative solution would be to run all initialization code in go routines to make it independent of initialization order but having a defined initialization order is much cleaner.

cmd/converge/converge.go

@@ -58,6 +58,13 @@ func printHelp(msg string) {
 }
 
 func main() {
+	// for debugging hangs relating to using unbuffered channels
+	//go func() {
+	//	buf := make([]byte, 1000000)
+	//	n := runtime.Stack(buf, true)
+	//	time.Sleep(10 * time.Second)
+	//	log.Println("LOG: \n" + string(buf[:n]))
+	//}()
 
 	downloaddir := "."
 	staticdir := "../static"
@@ -96,8 +103,14 @@ func main() {
 	}
 
 	notifications := NewStateNotifier()
-	admin := matchmaker.NewMatchMaker(notifications)
 	websessions := matchmaker.NewWebSessions(notifications.webNotificationChannel)
+	// monitoring
+	mux := http.NewServeMux()
+	setupPrometheus(mux, notifications.prometheusNotificationChannel)
+	go func() {
+		log.Fatal(http.ListenAndServe(":8001", mux))
+	}()
+	admin := matchmaker.NewMatchMaker(notifications)
 
 	// For agents connecting
 	registrationService := websocketutil.WebSocketService{
@@ -167,13 +180,6 @@ func main() {
 
 	http.HandleFunc("/", catchAllHandler(contextpath))
 
-	// monitoring
-	mux := http.NewServeMux()
-	setupPrometheus(mux, notifications.prometheusNotificationChannel)
-	go func() {
-		log.Fatal(http.ListenAndServe(":8001", mux))
-	}()
-
 	// Start HTTP server
 	fmt.Println("Rendez-vous server listening on :8000")
 	log.Fatal(http.ListenAndServe(":8000", nil))

cmd/converge/notifier.go

@@ -9,8 +9,8 @@ type StateNotifier struct {
 
 func NewStateNotifier() *StateNotifier {
 	return &StateNotifier{
-		webNotificationChannel:        make(chan *models.State, 10),
+		webNotificationChannel:        make(chan *models.State),
-		prometheusNotificationChannel: make(chan *models.State, 10),
+		prometheusNotificationChannel: make(chan *models.State),
 	}
 }
 

cmd/converge/prometheus.go

@@ -191,7 +191,7 @@ func setupPrometheus(mux *http.ServeMux, notifications chan *models.State) {
 	mux.Handle("/metrics", promhttp.Handler())
 }
 
-var prometheusChannel = make(chan func(), 10)
+var prometheusChannel = make(chan func())
 
 // serialize notifidcations and periodi updates of the duration.
 

cmd/fsnotifytest/monitor.go

@@ -54,5 +54,5 @@ func main() {
 	}
 
 	// Block main goroutine forever
-	<-make(chan struct{}, 10)
+	<-make(chan struct{})
 }

pkg/agent/session/session.go

@@ -69,7 +69,7 @@ var helpMessageTemplate string
 var helpMessage = formatHelpMessage()
 
 // Events channel for asynchronous events.
-var events = make(chan func(), 10)
+var events = make(chan func())
 
 // External interface, asynchronous, apart from the initialization.
 

pkg/comms/gobchannel.go

@@ -64,8 +64,8 @@ func ReceiveAsync[T any](channel GOBChannel, result chan T, errors chan<- error)
 }
 
 func SendWithTimeout[T any](channel GOBChannel, obj T) error {
-	done := make(chan bool, 10)
+	done := make(chan bool)
-	errors := make(chan error, 10)
+	errors := make(chan error)
 
 	SendAsync(channel, obj, done, errors)
 	select {
@@ -79,8 +79,8 @@ func SendWithTimeout[T any](channel GOBChannel, obj T) error {
 }
 
 func ReceiveWithTimeout[T any](channel GOBChannel) (T, error) {
-	result := make(chan T, 10)
+	result := make(chan T)
-	errors := make(chan error, 10)
+	errors := make(chan error)
 
 	ReceiveAsync(channel, result, errors)
 	select {

pkg/server/matchmaker/websessions.go

@@ -73,7 +73,7 @@ func (sessions *WebSessions) NewSession(wsConnection net.Conn, ctx context.Conte
 	sessions.mutex.Lock()
 	defer sessions.mutex.Unlock()
 	session := &WebSession{
-		notifications: make(chan *models.State, 10),
+		notifications: make(chan *models.State),
 		conn:          wsConnection,
 		ctx:           ctx,
 	}