Fix memory leak in the timer

RELEASE_NOTES.md

@@ -1,19 +1,17 @@
 # Frequenz channels Release Notes
 
+## Summary
+
+<!-- Here goes a general summary of what this release is about -->
+
 ## Upgrading
 
-- `FileWatcher`: The file polling mechanism is now forced by default. This provides reliable and consistent file monitoring on network file systems (e.g., CIFS). However, it may have a performance impact on local file systems or when monitoring a large number of files.
-  - To disable file polling, set the `force_polling` parameter to `False`.
-  - The `polling_interval` parameter defines the interval for polling changes. This is relevant only when polling is enabled and defaults to 1 second.
+<!-- Here goes notes on how to upgrade from previous versions, including deprecations and what they should be replaced with -->
 
 ## New Features
 
-- `Timer.reset()` now supports setting the interval and will restart the timer with the new interval.
+<!-- Here goes the main new features and examples or instructions on how to use them -->
 
 ## Bug Fixes
 
-- `FileWatcher`:
-  - Fixed `ready()` method to return False when an error occurs. Before this fix, `select()` (and other code using `ready()`) never detected the `FileWatcher` was stopped and the `select()` loop was continuously waking up to inform the receiver was ready.
-  - Reports file events correctly on network file systems like CIFS.
-
-- `Timer.stop()` and `Timer.reset()` now immediately stop the timer if it is running. Before this fix, the timer would continue to run until the next interval.
+- Fixed a memory leak in the timer.

src/frequenz/channels/timer.py

@@ -682,14 +682,20 @@ async def ready(self) -> bool:  # noqa: DOC502
         # could be reset while we are sleeping, in which case we need to recalculate
         # the time to the next tick and try again.
         while time_to_next_tick > 0:
-            await next(
-                asyncio.as_completed(
-                    [
-                        asyncio.sleep(time_to_next_tick / 1_000_000),
-                        self._reset_event.wait(),
-                    ]
-                )
+            _, pending = await asyncio.wait(
+                [
+                    asyncio.create_task(asyncio.sleep(time_to_next_tick / 1_000_000)),
+                    asyncio.create_task(self._reset_event.wait()),
+                ],
+                return_when=asyncio.FIRST_COMPLETED,
             )
+            for task in pending:
+                task.cancel()
+                try:
+                    await task
+                except asyncio.CancelledError:
+                    pass
+
             self._reset_event.clear()
             now = self._now()
             time_to_next_tick = self._next_tick_time - now