Fallback to threaded resolver in case AsyncResolver fails (#5882)

In case the c-ares based AsyncResolver fails to initialize, let's
fallback to the threaded resolver. This would have helped for aiodns
3.3.0 issue when clients were unable to allocate more inotify watches.

This is fixed in aiodns 3.4.0, but we should still fallback to the
threaded resolver as a precautionary measure.

Author: agners

supervisor/coresys.py

@@ -13,6 +13,7 @@
 from typing import TYPE_CHECKING, Any, Self, TypeVar
 
 import aiohttp
+from pycares import AresError
 
 from .config import CoreConfig
 from .const import (
@@ -121,13 +122,17 @@ async def init_websession(self) -> None:
         if self._websession:
             await self._websession.close()
 
-        resolver = aiohttp.AsyncResolver()
+        try:
+            resolver = aiohttp.AsyncResolver(loop=self.loop)
+            # pylint: disable=protected-access
+            _LOGGER.debug(
+                "Initializing ClientSession with AsyncResolver. Using nameservers %s",
+                resolver._resolver.nameservers,
+            )
+        except AresError as err:
+            _LOGGER.exception("Unable to initialize async DNS resolver: %s", err)
+            resolver = aiohttp.ThreadedResolver(loop=self.loop)
 
-        # pylint: disable=protected-access
-        _LOGGER.debug(
-            "Initializing ClientSession with AsyncResolver. Using nameservers %s",
-            resolver._resolver.nameservers,
-        )
         connector = aiohttp.TCPConnector(loop=self.loop, resolver=resolver)
 
         session = aiohttp.ClientSession(