[GitHub] [airflow] bluek1te commented on issue #27399: CronTriggerTimetable lost one task occasionally

["bluek1te (via GitHub)" <gi...@apache.org>]

bluek1te commented on issue #27399:
URL: https://github.com/apache/airflow/issues/27399#issuecomment-1448436386

   Hello friends. Thinking about @Gollum999's explanation of the problem case, I ended up being able to fix the missed run issue by doing this:
   
   ```diff
   diff --git a/airflow/timetables/trigger.py b/airflow/timetables/trigger.py
   index 86ab58cc4d..67dd239f89 100644
   --- a/airflow/timetables/trigger.py
   +++ b/airflow/timetables/trigger.py
   @@ -93,7 +93,8 @@ class CronTriggerTimetable(CronMixin, Timetable):
                if restriction.earliest is not None and current_time < restriction.earliest:
                    next_start_time = self._align_to_next(restriction.earliest)
                else:
   -                next_start_time = self._align_to_next(current_time)
   +                prev_start_time = self._align_to_prev(current_time)
   +                next_start_time = self._align_to_next(prev_start_time)
            if restriction.latest is not None and restriction.latest < next_start_time:
                return None
            return DagRunInfo.interval(next_start_time - self._interval, next_start_time)
   ```
   Instead of aligning next with the current time and running into the race condition with the scheduler, it might be better if we align next to the previously scheduled time.
   I would like to open this up to a formal PR if y'all think this is sufficient. Thoughts?


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