Speed up backups by increasing buffer size (#4229)

* Speed up backups by increasing buffer size

This is the same change as home-assistant/core#90613
but for supervisor

If the backup takes too long, core will release the lock on the database
and the backup will be no good

https://github.com/home-assistant/core/blob/2fc34e7cced87a8e042919e059d3a07bb760c77f/homeassistant/components/recorder/core.py#L926

cpython uses copyfileobj under the hood for fast copies but the default buffer size is quite low which increases the amount of time in python code when copying the sqlite database. As this is the usually the bulk of the backup, increasing the buffer can help reduce the backup time quite a bit.

Ideally this would all use sendfile under the hood as it would shift nearly all the burden out of userspace but tarfile doesn't currently try that https://github.com/python/cpython/blob/4664a7cf689946f0c9854cadee7c6aa9c276a8cf/Lib/shutil.py#L106

related:
In testing (non encrypted) improvement was at least as good as python/cpython#71386

* add the const

supervisor/backups/backup.py

@@ -44,7 +44,7 @@
 from ..utils import remove_folder
 from ..utils.dt import parse_datetime, utcnow
 from ..utils.json import write_json_file
-from .const import BackupType
+from .const import BUF_SIZE, BackupType
 from .utils import key_to_iv, password_to_key
 from .validate import SCHEMA_BACKUP
 
@@ -330,7 +330,11 @@ async def _addon_save(addon: Addon):
             """Task to store an add-on into backup."""
             tar_name = f"{addon.slug}.tar{'.gz' if self.compressed else ''}"
             addon_file = SecureTarFile(
-                Path(self._tmp.name, tar_name), "w", key=self._key, gzip=self.compressed
+                Path(self._tmp.name, tar_name),
+                "w",
+                key=self._key,
+                gzip=self.compressed,
+                bufsize=BUF_SIZE,
             )
 
             # Take backup
@@ -365,7 +369,11 @@ async def _addon_restore(addon_slug: str):
             """Task to restore an add-on into backup."""
             tar_name = f"{addon_slug}.tar{'.gz' if self.compressed else ''}"
             addon_file = SecureTarFile(
-                Path(self._tmp.name, tar_name), "r", key=self._key, gzip=self.compressed
+                Path(self._tmp.name, tar_name),
+                "r",
+                key=self._key,
+                gzip=self.compressed,
+                bufsize=BUF_SIZE,
             )
 
             # If exists inside backup
@@ -406,7 +414,7 @@ def _folder_save(name: str):
             # Take backup
             _LOGGER.info("Backing up folder %s", name)
             with SecureTarFile(
-                tar_name, "w", key=self._key, gzip=self.compressed
+                tar_name, "w", key=self._key, gzip=self.compressed, bufsize=BUF_SIZE
             ) as tar_file:
                 atomic_contents_add(
                     tar_file,
@@ -453,7 +461,11 @@ def _restore() -> None:
                 try:
                     _LOGGER.info("Restore folder %s", name)
                     with SecureTarFile(
-                        tar_name, "r", key=self._key, gzip=self.compressed
+                        tar_name,
+                        "r",
+                        key=self._key,
+                        gzip=self.compressed,
+                        bufsize=BUF_SIZE,
                     ) as tar_file:
                         tar_file.extractall(path=origin_dir, members=tar_file)
                     _LOGGER.info("Restore folder %s done", name)
@@ -479,7 +491,7 @@ async def store_homeassistant(self):
             self._tmp.name, f"homeassistant.tar{'.gz' if self.compressed else ''}"
         )
         homeassistant_file = SecureTarFile(
-            tar_name, "w", key=self._key, gzip=self.compressed
+            tar_name, "w", key=self._key, gzip=self.compressed, bufsize=BUF_SIZE
         )
 
         await self.sys_homeassistant.backup(homeassistant_file)
@@ -496,7 +508,7 @@ async def restore_homeassistant(self) -> Awaitable[None]:
             self._tmp.name, f"homeassistant.tar{'.gz' if self.compressed else ''}"
         )
         homeassistant_file = SecureTarFile(
-            tar_name, "r", key=self._key, gzip=self.compressed
+            tar_name, "r", key=self._key, gzip=self.compressed, bufsize=BUF_SIZE
         )
 
         await self.sys_homeassistant.restore(homeassistant_file)

supervisor/backups/const.py

@@ -1,6 +1,8 @@
 """Backup consts."""
 from enum import Enum
 
+BUF_SIZE = 2**20 * 4  # 4MB
+
 
 class BackupType(str, Enum):
     """Backup type enum."""