Use atomic writes for the storage file (#1014)

Co-authored-by: Stefan Agner <stefan@agner.ch>

Author: marcelveldt

matter_server/server/storage.py

@@ -5,8 +5,11 @@
 import asyncio
 import logging
 from pathlib import Path
+import shutil
 from typing import TYPE_CHECKING, Any, cast
 
+from atomicwrites import atomic_write
+
 from ..common.helpers.json import JSON_DECODE_EXCEPTIONS, json_dumps, json_loads
 
 if TYPE_CHECKING:
@@ -152,11 +155,14 @@ async def async_save(self) -> None:
 
         def do_save() -> None:
             # make backup before we write a new file
-            if self.filename.is_file():
-                self.filename.replace(self.filename_backup)
+            self.filename_backup.unlink(True)
+            shutil.copy(self.filename, self.filename_backup)
 
-            with open(self.filename, "w", encoding="utf-8") as _file:
+            # use atomomic write to avoid corrupting the file
+            # if power is cut during write, we don't write a corrupted file
+            with atomic_write(self.filename, encoding="utf-8", overwrite=True) as _file:
                 _file.write(json_dumps(self._data))
+
             LOGGER.debug("Saved data to persistent storage")
 
         async with self._save_lock:

pyproject.toml

@@ -35,6 +35,7 @@ server = [
   "aiohttp==3.11.11",
   "aiorun==2024.8.1",
   "async-timeout==5.0.1",
+  "atomicwrites==1.4.1",
   "coloredlogs==15.0.1",
   "cryptography==44.0.0",
   "orjson==3.10.12",