Disconnect dispatcher at cleanup

Author: Marenz

RELEASE_NOTES.md

@@ -14,4 +14,4 @@
 
 ## Bug Fixes
 
-<!-- Here goes notable bug fixes that are worth a special mention or explanation -->
+- Fixed an issue in the `Dispatcher` class where the client connection was not properly disconnected during cleanup, potentially causing unclosed socket errors.

src/frequenz/dispatch/_dispatcher.py

@@ -9,6 +9,7 @@
 import logging
 from asyncio import Event
 from datetime import timedelta
+from types import TracebackType
 from typing import Awaitable, Callable, Self
 
 from frequenz.channels import Receiver
@@ -361,6 +362,25 @@ async def __aenter__(self) -> Self:
         await self.wait_for_initialization()
         return self
 
+    @override
+    async def __aexit__(
+        self,
+        exc_type: type[BaseException] | None,
+        exc_value: BaseException | None,
+        traceback: TracebackType | None,
+    ) -> None:
+        """Exit an async context.
+
+        Stop this background service and disconnect the client.
+
+        Args:
+            exc_type: The exception type.
+            exc_value: The exception value.
+            traceback: The traceback object.
+        """
+        await super().__aexit__(exc_type, exc_value, traceback)
+        await self._client.disconnect()
+
     def new_lifecycle_events_receiver(
         self, dispatch_type: str
     ) -> Receiver[DispatchEvent]: