介绍

所有trigger继承自BaseTrigger，IntervalTrigger是其中最为典型的一种。

主要方法 get_next_fire_time，

if 前一次点火时间:
            下一次点火时间 = 前一次点火时间 + 间隔
        elif 开始日期（第一次点火时间） > now:
            下一次点火时间 = 开始日期
        else:
            延误N次点火
            下一次点火时间 = 第N+1次点火时间
点火时间抖动

源代码

from math import ceil

from tzlocal import get_localzone

from apscheduler.triggers.base import BaseTrigger
from apscheduler.util import convert_to_datetime, timedelta_seconds, datetime_repr, astimezone


class IntervalTrigger(BaseTrigger):
    """
    Triggers on specified intervals, starting on ``start_date`` if specified, ``datetime.now()`` +
    interval otherwise.

    :param int weeks: number of weeks to wait
    :param int days: number of days to wait
    :param int hours: number of hours to wait
    :param int minutes: number of minutes to wait
    :param int seconds: number of seconds to wait
    :param datetime|str start_date: starting point for the interval calculation
    :param datetime|str end_date: latest possible date/time to trigger on
    :param datetime.tzinfo|str timezone: time zone to use for the date/time calculations
    :param int|None jitter: advance or delay the job execution by ``jitter`` seconds at most.
    """

    __slots__ = 'timezone', 'start_date', 'end_date', 'interval', 'interval_length', 'jitter'

    def __init__(self, weeks=0, days=0, hours=0, minutes=0, seconds=0, start_date=None,
                 end_date=None, timezone=None, jitter=None):
        self.interval = timedelta(weeks=weeks, days=days, hours=hours, minutes=minutes,
                                  seconds=seconds)   # 间隔时间
        self.interval_length = timedelta_seconds(self.interval)  # 间隔秒
        if self.interval_length == 0:
            self.interval = timedelta(seconds=1)
            self.interval_length = 1

        if timezone:
            self.timezone = astimezone(timezone)
        elif isinstance(start_date, datetime) and start_date.tzinfo:
            self.timezone = start_date.tzinfo
        elif isinstance(end_date, datetime) and end_date.tzinfo:
            self.timezone = end_date.tzinfo
        else:
            self.timezone = get_localzone()

        start_date = start_date or (datetime.now(self.timezone) + self.interval)
        self.start_date = convert_to_datetime(start_date, self.timezone, 'start_date')
        self.end_date = convert_to_datetime(end_date, self.timezone, 'end_date')

        self.jitter = jitter

    def get_next_fire_time(self, previous_fire_time, now):
        if previous_fire_time:
            next_fire_time = previous_fire_time + self.interval
        elif self.start_date > now:
            next_fire_time = self.start_date
        else:
            # 延误
            # 延误时间 D = T0- Ts, 延误次数 N = [D/I], 准备第N+1次点火T1 = Ts + I * N
            timediff_seconds = timedelta_seconds(now - self.start_date)
            next_interval_num = int(ceil(timediff_seconds / self.interval_length))
            next_fire_time = self.start_date + self.interval * next_interval_num

        if self.jitter is not None:
            # 点火时间抖动
            next_fire_time = self._apply_jitter(next_fire_time, self.jitter, now)

        if not self.end_date or next_fire_time <= self.end_date:
            return self.timezone.normalize(next_fire_time)

    def __getstate__(self):
        return {
            'version': 2,
            'timezone': self.timezone,
            'start_date': self.start_date,
            'end_date': self.end_date,
            'interval': self.interval,
            'jitter': self.jitter,
        }

    def __setstate__(self, state):
        # This is for compatibility with APScheduler 3.0.x
        if isinstance(state, tuple):
            state = state[1]

        if 'version' in state and state['version']> 2:
            raise ValueError(
                'Got serialized data for version %s of %s, but only versions up to 2 can be '
                'handled' % (state['version'], self.__class__.__name__))

        self.timezone = state['timezone']
        self.start_date = state['start_date']
        self.end_date = state['end_date']
        self.interval = state['interval']
        self.interval_length = timedelta_seconds(self.interval)
        self.jitter = state.get('jitter')

    def __str__(self):
        return 'interval[%s]' % str(self.interval)

    def __repr__(self):
        options = ['interval=%r' % self.interval, 'start_date=%r' % datetime_repr(self.start_date)]
        if self.end_date:
            options.append("end_date=%r" % datetime_repr(self.end_date))
        if self.jitter:
            options.append('jitter=%s' % self.jitter)

        return "<%s (%s, timezone='%s')>" % (
            self.__class__.__name__, ', '.join(options), self.timezone)