fluent: fix panic on failing TLS connect

fluent/fluent.go

@@ -458,31 +458,40 @@ func (f *Fluent) close() {
 // connect establishes a new connection using the specified transport. Caller should
 // take care of locking muconn first.
 func (f *Fluent) connect(ctx context.Context) (err error) {
+	var conn net.Conn
+
 	switch f.Config.FluentNetwork {
 	case "tcp":
-		f.conn, err = f.dialer.DialContext(ctx,
+		conn, err = f.dialer.DialContext(ctx,
 			f.Config.FluentNetwork,
 			f.Config.FluentHost+":"+strconv.Itoa(f.Config.FluentPort))
 	case "tls":
 		tlsConfig := &tls.Config{InsecureSkipVerify: f.Config.TlsInsecureSkipVerify}
-		f.conn, err = tls.DialWithDialer(
+		var tlsConn *tls.Conn
+		tlsConn, err = tls.DialWithDialer(
 			&net.Dialer{Timeout: f.Config.Timeout},
 			"tcp",
 			f.Config.FluentHost+":"+strconv.Itoa(f.Config.FluentPort), tlsConfig,
 		)
+		if err == nil {
+			conn = tlsConn
+		}
 	case "unix":
-		f.conn, err = f.dialer.DialContext(ctx,
+		conn, err = f.dialer.DialContext(ctx,
 			f.Config.FluentNetwork,
 			f.Config.FluentSocketPath)
 	default:
 		err = NewErrUnknownNetwork(f.Config.FluentNetwork)
 	}
 
-	if err == nil {
-		f.latestReconnectTime = time.Now()
+	if err != nil {
+		return err
 	}
 
-	return err
+	f.conn = conn
+	f.latestReconnectTime = time.Now()
+
+	return nil
 }
 
 var errIsClosing = errors.New("fluent logger is closing")

fluent/fluent_test.go

@@ -683,6 +683,34 @@ func TestNoPanicOnAsyncMultipleClose(t *testing.T) {
 	f.Close()
 }
 
+func TestNoPanicOnFailingTLSConnect(t *testing.T) {
+	l, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("Unexpected error: %v", err)
+	}
+	port := l.Addr().(*net.TCPAddr).Port
+	l.Close()
+
+	f, _ := New(Config{
+		FluentNetwork: "tls",
+		FluentHost:    "127.0.0.1",
+		FluentPort:    port,
+		Timeout:       50 * time.Millisecond,
+		RetryWait:     1,
+		MaxRetry:      1,
+	})
+	if f == nil {
+		t.Fatal("Expected a logger instance")
+	}
+	defer f.Close()
+
+	for i := 0; i < 2; i++ {
+		if err := f.Post("tag", map[string]string{"log": "msg"}); err == nil {
+			t.Error("Expected an error posting to an unreachable TLS endpoint")
+		}
+	}
+}
+
 func TestCloseOnFailingAsyncReconnect(t *testing.T) {
 	testcases := map[string]Config{
 		"with RequestAck": {