fix: prevent accessing config files concurrently

server/app/settings.py

@@ -1,3 +1,4 @@
+import atexit
 import copy
 import os
 import sys
@@ -39,6 +40,21 @@ class Settings:
 		'DSL (.dsl/.dsl.dz)': ['.dsl', '.dz']
 	}
 
+	LOCK_FILE = os.path.join(APP_RESOURCES_ROOT, 'lock')
+
+	@classmethod
+	def _acquire_lock(cls) -> None:
+		if os.path.isfile(cls.LOCK_FILE):
+			logger.error('Another instance of the application is running.')
+			sys.exit(1)
+
+		with open(cls.LOCK_FILE, 'w') as f:
+			f.write('locked')
+
+	@classmethod
+	def _release_lock(cls) -> None:
+		os.remove(cls.LOCK_FILE)
+
 	PREFERENCES_FILE = os.path.join(APP_RESOURCES_ROOT, 'preferences.yaml')
 	# a dict with three fields: listening_address, suggestions_mode, running_mode
 
@@ -167,10 +183,10 @@ def parse_path_with_env_variables(path: str) -> str:
 		"""
 		return os.path.expanduser(os.path.expandvars(path))
 
-	@staticmethod
-	def _save_settings_to_file(settings: list | dict, filename: str) -> None:
-		with open(filename, 'w') as settings_file:
-			yaml.dump(settings, settings_file, Dumper=Dumper)
+	def _save_settings_to_file(self, settings: list | dict, filename: str) -> None:
+		with self._config_files_lock:
+			with open(filename, 'w') as settings_file:
+				yaml.dump(settings, settings_file, Dumper=Dumper)
 
 	@staticmethod
 	def _read_settings_from_file(filename: str) -> list | dict:
@@ -218,6 +234,12 @@ def change_suggestions_mode_from_right_side_to_both_sides(self) -> None:
 			preferences_file.write(preferences)
 
 	def __init__(self) -> None:
+		self._acquire_lock()
+		atexit.register(self._release_lock)
+
+		self._config_files_lock = threading.Lock()
+		self._scan_lock = threading.Lock()
+
 		if not os.path.isfile(self.PREFERENCES_FILE):
 			with open(self.PREFERENCES_FILE, 'w') as preferences_file:
 				preferences_file.write('''listening_address: 127.0.0.1
@@ -319,8 +341,6 @@ def __init__(self) -> None:
 			}
 			self._save_misc_configs()
 
-		self._scan_lock = threading.Lock()
-
 	def dictionary_info_valid(self, dictionary_info: dict) -> bool:
 		filename = dictionary_info['dictionary_filename']
 		filename = self.parse_path_with_env_variables(filename)