moonraker: gracefully handle invalid log paths

Don't exit the server if the log path is invalid.  Instead start
logging to stdout and add a warning for the user to
resolve.

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

moonraker/moonraker.py

@@ -122,6 +122,10 @@ class Server:
         self.register_upload_handler = app.register_upload_handler
         self.register_api_transport = app.register_api_transport
 
+        log_warn: Optional[str] = args.get('log_warning')
+        if log_warn is not None:
+            self.add_warning(log_warn)
+
         self.register_endpoint(
             "/server/info", ['GET'], self._handle_info_request)
         self.register_endpoint(
@@ -854,7 +858,8 @@ def main() -> None:
         app_args['log_file'] = os.path.normpath(
             os.path.expanduser(cmd_line_args.logfile))
     app_args['software_version'] = version
-    ql, file_logger = utils.setup_logging(app_args)
+    ql, file_logger, warning = utils.setup_logging(app_args)
+    app_args['log_warning'] = warning
 
     if sys.version_info < (3, 7):
         msg = f"Moonraker requires Python 3.7 or above.  " \

moonraker/utils.py

@@ -138,7 +138,8 @@ def get_software_version() -> str:
 
 def setup_logging(app_args: Dict[str, Any]
                   ) -> Tuple[logging.handlers.QueueListener,
-                             Optional[MoonrakerLoggingHandler]]:
+                             Optional[MoonrakerLoggingHandler],
+                             Optional[str]]:
     root_logger = logging.getLogger()
     queue: Queue = Queue()
     queue_handler = LocalQueueHandler(queue)
@@ -150,20 +151,30 @@ def setup_logging(app_args: Dict[str, Any]
     stdout_hdlr.setFormatter(stdout_fmt)
     for name, val in app_args.items():
         logging.info(f"{name}: {val}")
-    file_hdlr = None
-    if app_args.get('log_file', ""):
-        file_hdlr = MoonrakerLoggingHandler(
-            app_args, 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, stdout_hdlr)
-    else:
+    warning: Optional[str] = None
+    file_hdlr: Optional[MoonrakerLoggingHandler] = None
+    listener: Optional[logging.handlers.QueueListener] = None
+    log_file: str = app_args.get('log_file', "")
+    if log_file:
+        try:
+            file_hdlr = MoonrakerLoggingHandler(
+                app_args, 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, stdout_hdlr)
+        except Exception:
+            log_file = os.path.normpath(log_file)
+            dir_name = os.path.dirname(log_file)
+            warning = f"Unable to create log file at '{log_file}'. " \
+                      f"Make sure that the folder '{dir_name}' exists " \
+                      f"and Moonraker has Read/Write access to the folder. "
+    if listener is None:
         listener = logging.handlers.QueueListener(
             queue, stdout_hdlr)
     listener.start()
-    return listener, file_hdlr
+    return listener, file_hdlr, warning
 
 def hash_directory(dir_path: str,
                    ignore_exts: List[str],