utils: Add support for a QueueLogger

Logging to a file has the potential to block a the main thread, a QueueLogger resolves this by forwarding logging request to a secondary thread.

Signed-off-by:  Eric Callahan <arksine.code@gmail.com>

moonraker/moonraker.py

@@ -12,12 +12,13 @@ import socket
 import logging
 import json
 import confighelper
+import utils
 from tornado import gen, iostream
 from tornado.ioloop import IOLoop, PeriodicCallback
 from tornado.util import TimeoutError
 from tornado.locks import Event
 from app import MoonrakerApp
-from utils import ServerError, MoonrakerLoggingHandler
+from utils import ServerError
 
 INIT_MS = 1000
 
@@ -450,14 +451,7 @@ def main():
     # Setup Logging
     log_file = os.path.normpath(os.path.expanduser(cmd_line_args.logfile))
     cmd_line_args.logfile = log_file
-    root_logger = logging.getLogger()
-    file_hdlr = MoonrakerLoggingHandler(
-        log_file, when='midnight', backupCount=2)
-    root_logger.addHandler(file_hdlr)
-    root_logger.setLevel(logging.INFO)
-    formatter = logging.Formatter(
-        '%(asctime)s [%(filename)s:%(funcName)s()] - %(message)s')
-    file_hdlr.setFormatter(formatter)
+    utils.setup_logging(log_file)
 
     if sys.version_info < (3, 7):
         msg = f"Moonraker requires Python 3.7 or above.  " \

moonraker/utils.py

@@ -4,14 +4,29 @@
 #
 # This file may be distributed under the terms of the GNU GPLv3 license
 import logging
+import logging.handlers
 import os
 import subprocess
+import asyncio
+from queue import SimpleQueue as Queue
 
 class ServerError(Exception):
     def __init__(self, message, status_code=400):
         Exception.__init__(self, message)
         self.status_code = status_code
 
+# Coroutine friendly QueueHandler courtesy of Martjin Pieters:
+# https://www.zopatista.com/python/2019/05/11/asyncio-logging/
+class LocalQueueHandler(logging.handlers.QueueHandler):
+    def emit(self, record: logging.LogRecord) -> None:
+        # Removed the call to self.prepare(), handle task cancellation
+        try:
+            self.enqueue(record)
+        except asyncio.CancelledError:
+            raise
+        except Exception:
+            self.handleError(record)
+
 class MoonrakerLoggingHandler(logging.handlers.TimedRotatingFileHandler):
     def __init__(self, filename, **kwargs):
         super(MoonrakerLoggingHandler, self).__init__(filename, **kwargs)
@@ -51,3 +66,17 @@ def get_software_version():
         logging.exception("Error runing git describe")
 
     return "?"
+
+def setup_logging(log_file):
+    root_logger = logging.getLogger()
+    queue = Queue()
+    queue_handler = LocalQueueHandler(queue)
+    root_logger.addHandler(queue_handler)
+    root_logger.setLevel(logging.INFO)
+    file_hdlr = MoonrakerLoggingHandler(
+        log_file, when='midnight', backupCount=2)
+    formatter = logging.Formatter(
+        '%(asctime)s [%(filename)s:%(funcName)s()] - %(message)s')
+    file_hdlr.setFormatter(formatter)
+    listener = logging.handlers.QueueListener(queue, file_hdlr)
+    listener.start()