Log reason for service stop

[ela-kotulska-frequenz]

To simplify debugging

[Copilot]

Pull Request Overview

This PR adds logging of cancellation reasons for both the background service and actor components.

• Adds a module-level logger and debug log in _background_service.py
• Adds an info-level log in _actor.py when an actor is cancelled

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/frequenz/sdk/actor/_background_service.py	Imported logging, initialized _logger, and added a debug log call in cancel()
src/frequenz/sdk/actor/_actor.py	Added an info log call in cancel(), but missing logger import/definition

Comments suppressed due to low confidence (3)

src/frequenz/sdk/actor/_background_service.py:174

• This new debug logging for cancellation isn't covered by existing tests. Consider adding unit tests to verify that the cancellation reason is logged correctly.

        _logger.debug("Service %s cancelled, reason: %s", self.name, msg)

src/frequenz/sdk/actor/_actor.py:147

• Add tests to ensure the actor's cancellation reason is logged at info level, matching the new behavior introduced here.

        _logger.info("Actor %s cancelled, reason: %s", self.name, msg)

src/frequenz/sdk/actor/_actor.py:147

• The _logger is used here but not defined or imported. Please add import logging and initialize _logger = logging.getLogger(__name__) at the top of this file.

        _logger.info("Actor %s cancelled, reason: %s", self.name, msg)

[Marenz]

Isn't this calling the super method and then its logged twice?

[ela-kotulska-frequenz]

In Actor has info log.
In Backgroud has debug log.

Having info log in BackgroundService will create lots of unnecessary logs (that we probably don't need).

Do you have different idea?

[Marenz]

Ah, well in this case it seems fine then. Didn't notice the different levels

[shsms]

Cancel sounds like a rare event, and it's useful to know. INFO doesn't trigger any alerts. It wouldn't be too bad if we just had INFO in the background service.

[llucax]

Oh, I didn't see this comment. For me this still sounds like a debug, because I guess it is only useful when debugging, when things are working you should see an INFO for the actor stopping, and that should be enough. That said, I'm OK to merge if there is enough consensus.

[llucax]

I'm not sure if this should be info or debug also, it seems like it might be too fine grained detail for a normal run, as we are already logging when it actually stops, so cancel would only be interesting if there is a bug and the cancel is not resulting in a stop.

[llucax]

Maybe it would be a bit easier to the eyes like this?

Suggested change

	_logger.info("Service %s cancelled, reason: %s", self.name, msg)
	_logger.info("Service %s cancelled%s", self.name, msg, f": {msg}" if msg is not None else "")