ashb commented on a change in pull request #13930:
URL: https://github.com/apache/airflow/pull/13930#discussion_r567834660
##########
File path: airflow/models/dag.py
##########
@@ -109,6 +110,312 @@ def get_last_dagrun(dag_id, session,
include_externally_triggered=False):
return query.first()
+class AbstractTimetable(LoggingMixin):
+ """Abstract class for Timetable."""
+
+ @abstractmethod
+ def normalized_schedule_interval(self) -> Optional[ScheduleInterval]:
+ raise NotImplementedError()
+
+ @abstractmethod
+ def is_fixed_time_schedule(self):
+ raise NotImplementedError()
+
+ @abstractmethod
+ def date_range(
+ self,
+ start_date: datetime,
+ num: Optional[int] = None,
+ end_date: Optional[datetime] = timezone.utcnow(),
+ ) -> List[datetime]:
+ raise NotImplementedError()
+
+ @abstractmethod
+ def following_schedule(self, dttm):
+ raise NotImplementedError()
+
+ @abstractmethod
+ def previous_schedule(self, dttm):
+ raise NotImplementedError()
+
+ @abstractmethod
+ def next_dagrun_info(
+ self,
+ date_last_automated_dagrun: Optional[pendulum.DateTime],
+ tasks,
+ ) -> Tuple[Optional[pendulum.DateTime], Optional[pendulum.DateTime]]:
+ raise NotImplementedError()
+
+ @abstractmethod
+ def get_run_dates(self, start_date, end_date=None):
+ raise NotImplementedError()
+
+
+class CronTimetable(AbstractTimetable):
+ """Timetable implementation for Cron."""
+
+ def __init__(
+ self,
+ schedule_interval=None,
+ timezone=None,
+ catchup=None,
+ start_date=None,
+ end_date=None,
+ ):
+ self.schedule_interval = schedule_interval
+ self.timezone = timezone
+ self.catchup = catchup
+ self.start_date = start_date
+ self.end_date = end_date
+
+ def normalized_schedule_interval(self) -> Optional[ScheduleInterval]:
+ """
+ Returns Normalized Schedule Interval. This is used internally by the
Scheduler to
+ schedule DAGs.
+
+ 1. Converts Cron Preset to a Cron Expression (e.g ``@monthly`` to ``0
0 1 * *``)
+ 2. If Schedule Interval is "@once" return "None"
+ 3. If not (1) or (2) returns schedule_interval
+ """
+ if isinstance(self.schedule_interval, str) and self.schedule_interval
in cron_presets:
Review comment:
Backport what?
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