check if we have a successful connection so we do not need to connect…

… to other servers

relay/client/picker.go

@@ -45,19 +45,25 @@ func (sp *ServerPicker) PickServer(parentCtx context.Context) (*Client, error) {
 	concurrentLimiter := make(chan struct{}, maxConcurrentServers)
 
 	log.Debugf("pick server from list: %v", sp.ServerURLs.Load().([]string))
+	go sp.processConnResults(connResultChan, successChan)
 	for _, url := range sp.ServerURLs.Load().([]string) {
-		// todo check if we have a successful connection so we do not need to connect to other servers
-		concurrentLimiter <- struct{}{}
-		go func(url string) {
-			defer func() {
-				<-concurrentLimiter
-			}()
-			sp.startConnection(parentCtx, connResultChan, url)
-		}(url)
+		select {
+		case concurrentLimiter <- struct{}{}:
+			go func(url string) {
+				defer func() {
+					<-concurrentLimiter
+				}()
+				sp.startConnection(parentCtx, connResultChan, url)
+			}(url)
+		case cr, ok := <-successChan:
+			if !ok {
+				return nil, errors.New("failed to connect to any relay server: all attempts failed")
+			}
+			log.Infof("chosen home Relay server: %s with latency %s", cr.Url, cr.Latency)
+			return cr.RelayClient, nil
+		}
 	}
 
-	go sp.processConnResults(connResultChan, successChan)
-
 	select {
 	case cr, ok := <-successChan:
 		if !ok {
@@ -106,18 +112,8 @@ func (sp *ServerPicker) processConnResults(resultChan chan connResult, successCh
 		}
 		log.Infof("connected to Relay server: %s with latency %s", cr.Url, cr.Latency)
 
-		// Already connected to a lower latency server
-		if hasSuccess && cr.Latency > bestLatencyResult.Latency {
-			log.Infof("closing unnecessary Relay connection to: %s", cr.Url)
-			if err := cr.RelayClient.Close(); err != nil {
-				log.Errorf("failed to close connection to %s: %v", cr.Url, err)
-			}
-			continue
-		} else if hasSuccess { // Connected to a higher latency server in bestLatencyResult, disconnect from it
-			log.Infof("closing unnecessary Relay connection to: %s", bestLatencyResult.Url)
-			if err := bestLatencyResult.RelayClient.Close(); err != nil {
-				log.Errorf("failed to close connection to %s: %v", bestLatencyResult.Url, err)
-			}
+		if hasSuccess {
+			cr = lowestLatency(cr, bestLatencyResult)
 		}
 
 		// First successful connection, start a timer to return the result
@@ -138,3 +134,17 @@ func (sp *ServerPicker) processConnResults(resultChan chan connResult, successCh
 	}
 	close(successChan)
 }
+
+func lowestLatency(a, b connResult) connResult {
+	if a.Latency > b.Latency {
+		if err := b.RelayClient.Close(); err != nil {
+			log.Errorf("failed to close connection to %s: %v", b.Url, err)
+		}
+		return a
+	}
+
+	if err := a.RelayClient.Close(); err != nil {
+		log.Errorf("failed to close connection to %s: %v", a.Url, err)
+	}
+	return b
+}