From b0e52e8c876032b648e82dea8d551eb1334de3c7 Mon Sep 17 00:00:00 2001
From: Elzbieta Kotulska <elzbieta.kotulska@frequenz.com>
Date: Thu, 21 Nov 2024 11:38:28 +0100
Subject: [PATCH] Change FileWatcher to stop printing watchfiles debug log

The underlying Rust code performs periodic checks to see
if it should stop watching. These checks raise TimeoutError,
which by default would log misleading debug messages.
Setting yield_on_timeout=True makes it yield an empty
set instead of printing debug logs.
We handle these empty sets in the `ready()` method by
continuing to wait.
---
 src/frequenz/channels/file_watcher.py | 17 ++++++++++++-----
 tests/test_file_watcher.py            |  1 +
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/src/frequenz/channels/file_watcher.py b/src/frequenz/channels/file_watcher.py
index a4dc3074..ce10fb01 100644
--- a/src/frequenz/channels/file_watcher.py
+++ b/src/frequenz/channels/file_watcher.py
@@ -159,6 +159,11 @@ def __init__(
             watch_filter=self._filter_events,
             force_polling=force_polling,
             poll_delay_ms=int(polling_interval.total_seconds() * 1_000),
+            # The underlying Rust code performs periodic checks to see if it should stop watching.
+            # These checks raise TimeoutError, which by default would log misleading debug messages.
+            # Setting yield_on_timeout=True makes it yield an empty set instead of printing debug
+            # logs. We handle these empty sets in the `ready()` method by continuing to wait.
+            yield_on_timeout=True,
         )
         self._awatch_stopped_exc: Exception | None = None
         self._changes: set[FileChange] = set()
@@ -204,11 +209,13 @@ async def ready(self) -> bool:
         if self._awatch_stopped_exc is not None:
             return False
 
-        try:
-            self._changes = await anext(self._awatch)
-        except StopAsyncIteration as err:
-            self._awatch_stopped_exc = err
-            return False
+        # awatch will yield an empty set if rust notify timeout is reached.
+        while len(self._changes) == 0:
+            try:
+                self._changes = await anext(self._awatch)
+            except StopAsyncIteration as err:
+                self._awatch_stopped_exc = err
+                return False
 
         return True
 
diff --git a/tests/test_file_watcher.py b/tests/test_file_watcher.py
index 720de807..0e11207a 100644
--- a/tests/test_file_watcher.py
+++ b/tests/test_file_watcher.py
@@ -102,6 +102,7 @@ async def test_file_watcher_filter_events(
                 watch_filter=filter_events,
                 force_polling=True,
                 poll_delay_ms=1_000,
+                yield_on_timeout=True,
             )
         ]
         for event_type in EventType: