Source code for airflow.timetables._cron

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from __future__ import annotations

import datetime
from functools import cached_property
from typing import Any

from cron_descriptor import CasingTypeEnum, ExpressionDescriptor, FormatException, MissingFieldException
from croniter import CroniterBadCronError, CroniterBadDateError, croniter
from pendulum import DateTime
from pendulum.tz.timezone import Timezone

from airflow.exceptions import AirflowTimetableInvalid
from airflow.utils.dates import cron_presets
from airflow.utils.timezone import convert_to_utc, make_aware, make_naive


def _is_schedule_fixed(expression: str) -> bool:
    """Figures out if the schedule has a fixed time (e.g. 3 AM every day).

    :return: True if the schedule has a fixed time, False if not.

    Detection is done by "peeking" the next two cron trigger time; if the
    two times have the same minute and hour value, the schedule is fixed,
    and we *don't* need to perform the DST fix.

    This assumes DST happens on whole minute changes (e.g. 12:59 -> 12:00).
    """
    cron = croniter(expression)
    next_a = cron.get_next(datetime.datetime)
    next_b = cron.get_next(datetime.datetime)
    return next_b.minute == next_a.minute and next_b.hour == next_a.hour


[docs]class CronMixin: """Mixin to provide interface to work with croniter.""" def __init__(self, cron: str, timezone: str | Timezone) -> None: self._expression = cron_presets.get(cron, cron) if isinstance(timezone, str): timezone = Timezone(timezone) self._timezone = timezone descriptor = ExpressionDescriptor( expression=self._expression, casing_type=CasingTypeEnum.Sentence, use_24hour_time_format=True ) try: # checking for more than 5 parameters in Cron and avoiding evaluation for now, # as Croniter has inconsistent evaluation with other libraries if len(croniter(self._expression).expanded) > 5: raise FormatException() interval_description: str = descriptor.get_description() except (CroniterBadCronError, FormatException, MissingFieldException): interval_description = "" self.description: str = interval_description
[docs] def __eq__(self, other: Any) -> bool: """Both expression and timezone should match. This is only for testing purposes and should not be relied on otherwise. """ if not isinstance(other, type(self)): return NotImplemented return self._expression == other._expression and self._timezone == other._timezone
@property
[docs] def summary(self) -> str: return self._expression
[docs] def validate(self) -> None: try: croniter(self._expression) except (CroniterBadCronError, CroniterBadDateError) as e: raise AirflowTimetableInvalid(str(e))
@cached_property def _should_fix_dst(self) -> bool: # This is lazy so instantiating a schedule does not immediately raise # an exception. Validity is checked with validate() during DAG-bagging. return not _is_schedule_fixed(self._expression) def _get_next(self, current: DateTime) -> DateTime: """Get the first schedule after specified time, with DST fixed.""" naive = make_naive(current, self._timezone) cron = croniter(self._expression, start_time=naive) scheduled = cron.get_next(datetime.datetime) if not self._should_fix_dst: return convert_to_utc(make_aware(scheduled, self._timezone)) delta = scheduled - naive return convert_to_utc(current.in_timezone(self._timezone) + delta) def _get_prev(self, current: DateTime) -> DateTime: """Get the first schedule before specified time, with DST fixed.""" naive = make_naive(current, self._timezone) cron = croniter(self._expression, start_time=naive) scheduled = cron.get_prev(datetime.datetime) if not self._should_fix_dst: return convert_to_utc(make_aware(scheduled, self._timezone)) delta = naive - scheduled return convert_to_utc(current.in_timezone(self._timezone) - delta) def _align_to_next(self, current: DateTime) -> DateTime: """Get the next scheduled time. This is ``current + interval``, unless ``current`` falls right on the interval boundary, when ``current`` is returned. """ next_time = self._get_next(current) if self._get_prev(next_time) != current: return next_time return current def _align_to_prev(self, current: DateTime) -> DateTime: """Get the prev scheduled time. This is ``current - interval``, unless ``current`` falls right on the interval boundary, when ``current`` is returned. """ prev_time = self._get_prev(current) if self._get_next(prev_time) != current: return prev_time return current

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