Merge pull request #1712 from freqtrade/log/tofile

Allow logging to file

freqtrade/arguments.py

@@ -71,6 +71,13 @@ class Arguments(object):
             dest='loglevel',
             default=0,
         )
+        self.parser.add_argument(
+            '--logfile',
+            help='Log to the file specified',
+            dest='logfile',
+            type=str,
+            metavar='FILE'
+        )
         self.parser.add_argument(
             '--version',
             action='version',

freqtrade/configuration.py

@@ -4,16 +4,18 @@ This module contains the configuration class
 import json
 import logging
 import os
+import sys
 from argparse import Namespace
-from typing import Any, Dict, Optional
+from logging.handlers import RotatingFileHandler
+from typing import Any, Dict, List, Optional
 
 import ccxt
 from jsonschema import Draft4Validator, validate
 from jsonschema.exceptions import ValidationError, best_match
 
 from freqtrade import OperationalException, constants
-from freqtrade.state import RunMode
 from freqtrade.misc import deep_merge_dicts
+from freqtrade.state import RunMode
 
 logger = logging.getLogger(__name__)
 
@@ -116,9 +118,22 @@ class Configuration(object):
             config.update({'verbosity': self.args.loglevel})
         else:
             config.update({'verbosity': 0})
+
+        # Log to stdout, not stderr
+        log_handlers: List[logging.Handler] = [logging.StreamHandler(sys.stdout)]
+        if 'logfile' in self.args and self.args.logfile:
+            config.update({'logfile': self.args.logfile})
+
+        # Allow setting this as either configuration or argument
+        if 'logfile' in config:
+            log_handlers.append(RotatingFileHandler(config['logfile'],
+                                                    maxBytes=1024 * 1024,  # 1Mb
+                                                    backupCount=10))
+
         logging.basicConfig(
             level=logging.INFO if config['verbosity'] < 1 else logging.DEBUG,
             format='%(asctime)s - %(name)s - %(levelname)s - %(message)s',
+            handlers=log_handlers
         )
         set_loggers(config['verbosity'])
         logger.info('Verbosity set to %s', config['verbosity'])

freqtrade/tests/test_configuration.py

@@ -5,6 +5,7 @@ import logging
 from argparse import Namespace
 from copy import deepcopy
 from unittest.mock import MagicMock
+from pathlib import Path
 
 import pytest
 from jsonschema import Draft4Validator, ValidationError, validate
@@ -547,6 +548,23 @@ def test_set_loggers() -> None:
     assert logging.getLogger('telegram').level is logging.INFO
 
 
+def test_set_logfile(default_conf, mocker):
+    mocker.patch('freqtrade.configuration.open',
+                 mocker.mock_open(read_data=json.dumps(default_conf)))
+
+    arglist = [
+        '--logfile', 'test_file.log',
+    ]
+    args = Arguments(arglist, '').get_parsed_arg()
+    configuration = Configuration(args)
+    validated_conf = configuration.load_config()
+
+    assert validated_conf['logfile'] == "test_file.log"
+    f = Path("test_file.log")
+    assert f.is_file()
+    f.unlink()
+
+
 def test_load_config_warn_forcebuy(default_conf, mocker, caplog) -> None:
     default_conf['forcebuy_enable'] = True
     mocker.patch('freqtrade.configuration.open', mocker.mock_open(