Log reason for backgroud service stop

Log `msg` argument to simplify debugging.

Signed-off-by: Elzbieta Kotulska <elzbieta.kotulska@frequenz.com>

Author: ela-kotulska-frequenz

src/frequenz/sdk/actor/_actor.py

@@ -153,5 +153,8 @@ def cancel(self, msg: str | None = None) -> None:
         Args:
             msg: The message to be passed to the tasks being cancelled.
         """
+        if msg is not None:
+            _logger.info("Actor %s cancelled, reason: %s", self, msg)
+
         self._is_cancelled = True
         return super().cancel(msg)

src/frequenz/sdk/actor/_background_service.py

@@ -6,9 +6,12 @@
 import abc
 import asyncio
 import collections.abc
+import logging
 from types import TracebackType
 from typing import Any, Self
 
+_logger = logging.getLogger(__name__)
+
 
 class BackgroundService(abc.ABC):
     """A background service that can be started and stopped.
@@ -167,6 +170,10 @@ def cancel(self, msg: str | None = None) -> None:
         Args:
             msg: The message to be passed to the tasks being cancelled.
         """
+        _logger.debug(
+            "Service %s cancelled%s", self, f": {msg}" if msg is not None else ""
+        )
+
         for task in self._tasks:
             task.cancel(msg)