ashb commented on a change in pull request #13930:
URL: https://github.com/apache/airflow/pull/13930#discussion_r567835695
##########
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:
+ _schedule_interval = cron_presets.get(self.schedule_interval) #
type: Optional[ScheduleInterval]
+ elif self.schedule_interval == '@once':
+ _schedule_interval = None
+ else:
+ _schedule_interval = self.schedule_interval
+ return _schedule_interval
+
+ def is_fixed_time_schedule(self):
+ """
+ Figures out if the DAG schedule has a fixed time (e.g. 3 AM).
+
+ :return: True if the schedule has a fixed time, False if not.
+ """
+ now = datetime.now()
+ cron = croniter(self.normalized_schedule_interval(), now)
+
+ start = cron.get_next(datetime)
+ cron_next = cron.get_next(datetime)
+
+ if cron_next.minute == start.minute and cron_next.hour == start.hour:
+ return True
+
+ return False
+
+ def date_range(
+ self,
+ start_date: datetime,
+ num: Optional[int] = None,
+ end_date: Optional[datetime] = timezone.utcnow(),
+ ) -> List[datetime]:
+ if num is not None:
+ end_date = None
+ return utils_date_range(
+ start_date=start_date, end_date=end_date, num=num,
delta=self.normalized_schedule_interval()
+ )
+
+ def following_schedule(self, dttm):
+ """
+ Calculates the following schedule for this dag in UTC.
+
+ :param dttm: utc datetime
+ :return: utc datetime
+ """
+ if isinstance(self.normalized_schedule_interval(), str):
+ # we don't want to rely on the transitions created by
+ # croniter as they are not always correct
+ dttm = pendulum.instance(dttm)
+ naive = timezone.make_naive(dttm, self.timezone)
+ cron = croniter(self.normalized_schedule_interval(), naive)
+
+ # We assume that DST transitions happen on the minute/hour
Review comment:
Not a new assumption -- this is just moving the existing code around.
So far, yes, this is a reasonable assumption though, yes
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