fix(ftx): use timer.ticker()

pkg/exchange/ftx/stream.go

@@ -129,7 +129,7 @@ func (s *Stream) Subscribe(channel types.Channel, symbol string, option types.Su
 		// FTX does not support kline channel, do polling
 		go s.subscribeKLine(symbol, option)
 	} else {
-		panic("only support book channel now")
+		panic("only support book/kline channel now")
 	}
 }
 
@@ -153,35 +153,39 @@ func (s *Stream) subscribeKLine(symbol string, option types.SubscribeOptions) {
 		return
 	}
 
+	ticker := time.NewTicker(interval.Duration())
+	defer ticker.Stop()
+
 	for {
-		if !s.isConnected {
-			time.Sleep(time.Second * 2)
-			continue
+		select {
+		case <-s.ctx.Done():
+			if err := s.ctx.Err(); err != nil {
+				logger.WithError(err).Errorf("subscribeKLine goroutine is terminated")
+			}
+		case <-ticker.C:
+			klines := getLastKLine(s.exchange, s.ctx, symbol, interval)
+			if len(klines) >= 0 {
+				// handle mutiple klines, get the latest one
+				s.klineMessage <- klines[len(klines)-1]
+			}
 		}
-
-		// get the last kline
-		since := time.Now().Add(time.Duration(-1*(interval.Minutes())) * time.Minute)
-		kline, err := s.exchange.QueryKLines(s.ctx, symbol, interval, types.KLineQueryOptions{
-			StartTime: &since,
-		})
-		if err != nil {
-			logger.WithError(err).Errorf("failed to get kline data")
-			time.Sleep(time.Second * 5)
-			continue
-		}
-		if len(kline) <= 0 {
-			time.Sleep(time.Second * 5)
-			continue
-		}
-
-		s.klineMessage <- kline[0]
-
-		intervalSec := int64(interval.Minutes() * 60)
-		nextReq := intervalSec - time.Now().Unix()%intervalSec + 1
-		time.Sleep(time.Second * time.Duration(nextReq))
 	}
 }
 
+func getLastKLine(e *Exchange, ctx context.Context, symbol string, interval types.Interval) []types.KLine {
+	// set since to more 30s ago to avoid getting no kline candle
+	since := time.Now().Add(time.Duration(-1*(interval.Minutes()*60+30)) * time.Second)
+	klines, err := e.QueryKLines(ctx, symbol, interval, types.KLineQueryOptions{
+		StartTime: &since,
+	})
+	if err != nil {
+		logger.WithError(err).Errorf("failed to get kline data")
+		return klines
+	}
+
+	return klines
+}
+
 func (s *Stream) Close() error {
 	s.subscriptions = nil
 	if s.ws != nil {