Stop raising exception when actor is stopped.

BacgroundService raises BaseExceptionGroup.
We can check if it was cancelled by checking
if all exceptions on BaseGroupException are CancelledError.

Signed-off-by: Elzbieta Kotulska <[email protected]>

Author: ela-kotulska-frequenz

RELEASE_NOTES.md

@@ -17,3 +17,5 @@
 ## Bug Fixes
 
 - Fixed bug with formulas raising exception when stopped.
+
+- Fix a bug that raised `CancelledError` when actor was started with `frequenz.sdk.actor.run` and stopped.

src/frequenz/sdk/actor/_run_utils.py

@@ -6,6 +6,7 @@
 
 import asyncio
 import logging
+from typing import Any
 
 from ._actor import Actor
 
@@ -43,7 +44,7 @@ async def run(*actors: Actor) -> None:
         for task in done_tasks:
             # Cancellation needs to be checked first, otherwise the other methods
             # could raise a CancelledError
-            if task.cancelled():
+            if _was_cancelled(task):
                 _logger.info("Actor %s: Cancelled while running.", task.get_name())
             elif exception := task.exception():
                 _logger.error(
@@ -55,3 +56,13 @@ async def run(*actors: Actor) -> None:
                 _logger.info("Actor %s: Finished normally.", task.get_name())
 
     _logger.info("All %s actor(s) finished.", len(actors))
+
+
+def _was_cancelled(task: asyncio.Task[Any]) -> bool:
+    if task.cancelled():
+        return True
+
+    exc = task.exception()
+    return isinstance(exc, BaseExceptionGroup) and all(
+        isinstance(err, asyncio.CancelledError) for err in exc.exceptions
+    )

tests/actor/test_actor.py

@@ -390,6 +390,6 @@ async def cancel_actor() -> None:
         (*RUN_INFO, "Actor EchoActor[EchoActor]: Starting..."),
         (*ACTOR_INFO, "Actor EchoActor[EchoActor]: Started."),
         (*ACTOR_INFO, "Actor EchoActor[EchoActor]: Cancelled."),
-        (*RUN_ERROR, "Actor EchoActor[EchoActor]: Raised an exception while running."),
+        (*RUN_INFO, "Actor EchoActor[EchoActor]: Cancelled while running."),
         (*RUN_INFO, "All 1 actor(s) finished."),
     ]