Exit from processConnResults after all tries (#2621)

* Exit from processConnResults after all tries

If all server is unavailable then the server picker never return
because we never close the result channel.
Count the number of the results and exit when we reached the
expected size

relay/client/picker.go

@@ -35,12 +35,15 @@ func (sp *ServerPicker) PickServer(parentCtx context.Context, urls []string) (*C
 
 	connResultChan := make(chan connResult, totalServers)
 	successChan := make(chan connResult, 1)
-
 	concurrentLimiter := make(chan struct{}, maxConcurrentServers)
+
 	for _, url := range urls {
+		// 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 }()
+			defer func() {
+				<-concurrentLimiter
+			}()
 			sp.startConnection(parentCtx, connResultChan, url)
 		}(url)
 	}
@@ -72,7 +75,8 @@ func (sp *ServerPicker) startConnection(ctx context.Context, resultChan chan con
 
 func (sp *ServerPicker) processConnResults(resultChan chan connResult, successChan chan connResult) {
 	var hasSuccess bool
-	for cr := range resultChan {
+	for numOfResults := 0; numOfResults < cap(resultChan); numOfResults++ {
+		cr := <-resultChan
 		if cr.Err != nil {
 			log.Debugf("failed to connect to Relay server: %s: %v", cr.Url, cr.Err)
 			continue

relay/client/picker_test.go

@@ -0,0 +1,31 @@
+package client
+
+import (
+	"context"
+	"errors"
+	"testing"
+	"time"
+)
+
+func TestServerPicker_UnavailableServers(t *testing.T) {
+	sp := ServerPicker{
+		TokenStore: nil,
+		PeerID:     "test",
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
+	defer cancel()
+
+	go func() {
+		_, err := sp.PickServer(ctx, []string{"rel://dummy1", "rel://dummy2"})
+		if err == nil {
+			t.Error(err)
+		}
+		cancel()
+	}()
+
+	<-ctx.Done()
+	if errors.Is(ctx.Err(), context.DeadlineExceeded) {
+		t.Errorf("PickServer() took too long to complete")
+	}
+}