exchanges: Add UpdateTickers method and reserve UpdateTicker for single ticker symbol update requests (if supported) (#764)

* exchanges: add an UpdateTickers method to the main exchange interface

This method will fetch all currency pair tickers of a given asset type
and update them internally, does nothing for now.

* exchanges: refactor UpdateTicker on all exchanges

Keep the exact previous behaviour but implement the UpdateTickers
method and refactor UpdateTicker by using it where applicable.

* sync_manager: update all tickers when batching is enabled

* binance: UpdateTicker to fetch single ticker symbol

* ftx: UpdateTicker to fetch single ticker symbol

exchanges/btse/btse_test.go

@@ -256,6 +256,20 @@ func TestUpdateTicker(t *testing.T) {
 	}
 }
 
+func TestUpdateTickers(t *testing.T) {
+	t.Parallel()
+
+	err := b.UpdateTickers(asset.Spot)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = b.UpdateTickers(asset.Futures)
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
 func TestGetServerTime(t *testing.T) {
 	t.Parallel()
 	_, err := b.GetServerTime()

exchanges/btse/btse_wrapper.go

@@ -284,17 +284,17 @@ func (b *BTSE) UpdateTradablePairs(forceUpdate bool) error {
 	return nil
 }
 
-// UpdateTicker updates and returns the ticker for a currency pair
-func (b *BTSE) UpdateTicker(p currency.Pair, assetType asset.Item) (*ticker.Price, error) {
-	tickers, err := b.GetMarketSummary("", assetType == asset.Spot)
+// UpdateTickers updates the ticker for all currency pairs of a given asset type
+func (b *BTSE) UpdateTickers(a asset.Item) error {
+	tickers, err := b.GetMarketSummary("", a == asset.Spot)
 	if err != nil {
-		return nil, err
+		return err
 	}
 	for x := range tickers {
 		var pair currency.Pair
 		pair, err = currency.NewPairFromString(tickers[x].Symbol)
 		if err != nil {
-			return nil, err
+			return err
 		}
 
 		err = ticker.ProcessTicker(&ticker.Price{
@@ -306,13 +306,22 @@ func (b *BTSE) UpdateTicker(p currency.Pair, assetType asset.Item) (*ticker.Pric
 			Volume:       tickers[x].Volume,
 			High:         tickers[x].High24Hr,
 			ExchangeName: b.Name,
-			AssetType:    assetType})
+			AssetType:    a})
 		if err != nil {
-			return nil, err
+			return err
 		}
 	}
 
-	return ticker.GetTicker(b.Name, p, assetType)
+	return nil
+}
+
+// UpdateTicker updates and returns the ticker for a currency pair
+func (b *BTSE) UpdateTicker(p currency.Pair, a asset.Item) (*ticker.Price, error) {
+	err := b.UpdateTickers(a)
+	if err != nil {
+		return nil, err
+	}
+	return ticker.GetTicker(b.Name, p, a)
 }
 
 // FetchTicker returns the ticker for a currency pair