From 30e3b52b1e7f02b8a159acefa99627b6ad1104c7 Mon Sep 17 00:00:00 2001
From: Matthias <xmatthias@outlook.com>
Date: Sat, 19 Jan 2019 20:02:37 +0100
Subject: [PATCH 1/3] catch errors found in #1491

---
 freqtrade/exchange/__init__.py | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/freqtrade/exchange/__init__.py b/freqtrade/exchange/__init__.py
index 90a33a226..b8d32306e 100644
--- a/freqtrade/exchange/__init__.py
+++ b/freqtrade/exchange/__init__.py
@@ -556,12 +556,17 @@ class Exchange(object):
         tickers = await asyncio.gather(*input_coroutines, return_exceptions=True)
 
         # handle caching
-        for pair, ticks in tickers:
+        for res in tickers:
+            if isinstance(res, Exception):
+                logger.warning("Async code raised an exception: %s", res.__class__.__name__)
+                continue
+            pair = res[0]
+            ticks = res[1]
             # keeping last candle time as last refreshed time of the pair
             if ticks:
                 self._pairs_last_refresh_time[pair] = ticks[-1][0] // 1000
-            # keeping parsed dataframe in cache
-            self._klines[pair] = parse_ticker_dataframe(ticks, tick_interval, fill_missing=True)
+                # keeping parsed dataframe in cache
+                self._klines[pair] = parse_ticker_dataframe(ticks, tick_interval, fill_missing=True)
         return tickers
 
     @retrier_async
@@ -578,9 +583,12 @@ class Exchange(object):
             # Ex: Bittrex returns a list of tickers ASC (oldest first, newest last)
             # when GDAX returns a list of tickers DESC (newest first, oldest last)
             # Only sort if necessary to save computing time
-            if data and data[0][0] > data[-1][0]:
-                data = sorted(data, key=lambda x: x[0])
-
+            try:
+                if data and data[0][0] > data[-1][0]:
+                    data = sorted(data, key=lambda x: x[0])
+            except IndexError:
+                logger.exception("Error loading %s. Result was %s.", pair, data)
+                return pair, None
             logger.debug("done fetching %s ...", pair)
             return pair, data
 

From 4e760e1a5e52e213be77931ed4f9586f5de7cdb1 Mon Sep 17 00:00:00 2001
From: Matthias <xmatthias@outlook.com>
Date: Sat, 19 Jan 2019 20:03:04 +0100
Subject: [PATCH 2/3] Test for errors found in 1491

fixes #1491
---
 freqtrade/tests/exchange/test_exchange.py | 24 +++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/freqtrade/tests/exchange/test_exchange.py b/freqtrade/tests/exchange/test_exchange.py
index 29154bc39..26808e78a 100644
--- a/freqtrade/tests/exchange/test_exchange.py
+++ b/freqtrade/tests/exchange/test_exchange.py
@@ -923,6 +923,30 @@ async def test_async_get_candles_history(default_conf, mocker):
     assert exchange._async_get_candle_history.call_count == 2
 
 
+@pytest.mark.asyncio
+async def test_async_get_candles_history_inv_result(default_conf, mocker, caplog):
+
+    async def mock_get_candle_hist(pair, *args, **kwargs):
+        if pair == 'ETH/BTC':
+            return [[]]
+        else:
+            raise TypeError()
+
+    exchange = get_patched_exchange(mocker, default_conf)
+
+    # Monkey-patch async function with empty result
+    exchange._api_async.fetch_ohlcv = MagicMock(side_effect=mock_get_candle_hist)
+
+    pairs = ['ETH/BTC', 'XRP/BTC']
+    res = await exchange.async_get_candles_history(pairs, "5m")
+    assert type(res) is list
+    assert len(res) == 2
+    assert type(res[0]) is tuple
+    assert type(res[1]) is TypeError
+    assert log_has("Error loading ETH/BTC. Result was [[]].", caplog.record_tuples)
+    assert log_has("Async code raised an exception: TypeError", caplog.record_tuples)
+
+
 def test_get_order_book(default_conf, mocker, order_book_l2):
     default_conf['exchange']['name'] = 'binance'
     api_mock = MagicMock()

From b48430f9221c33407dc6c35d890ba916a0876a8a Mon Sep 17 00:00:00 2001
From: Matthias <xmatthias@outlook.com>
Date: Sat, 19 Jan 2019 20:21:33 +0100
Subject: [PATCH 3/3] Return list not None

---
 freqtrade/exchange/__init__.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/freqtrade/exchange/__init__.py b/freqtrade/exchange/__init__.py
index b8d32306e..e0e4d7723 100644
--- a/freqtrade/exchange/__init__.py
+++ b/freqtrade/exchange/__init__.py
@@ -588,7 +588,7 @@ class Exchange(object):
                     data = sorted(data, key=lambda x: x[0])
             except IndexError:
                 logger.exception("Error loading %s. Result was %s.", pair, data)
-                return pair, None
+                return pair, []
             logger.debug("done fetching %s ...", pair)
             return pair, data