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# -*- coding: utf-8 -*-
Schedules define the intervals at which periodic tasks
should run.
:copyright: (c) 2009 - 2012 by Ask Solem.
:license: BSD, see LICENSE for more details.
from __future__ import absolute_import
import re
from datetime import datetime, timedelta
from dateutil.relativedelta import relativedelta
from . import current_app
from .utils import is_iterable
from .utils.timeutils import (timedelta_seconds, weekday, maybe_timedelta,
remaining, humanize_seconds)
from .datastructures import AttributeDict
class ParseException(Exception):
"""Raised by crontab_parser when the input can't be parsed."""
class schedule(object):
relative = False
def __init__(self, run_every=None, relative=False, nowfun=None):
self.run_every = maybe_timedelta(run_every)
self.relative = relative
self.nowfun = nowfun
def now(self):
return (self.nowfun or
def remaining_estimate(self, last_run_at):
"""Returns when the periodic task should run next as a timedelta."""
return remaining(last_run_at, self.run_every, relative=self.relative,
def is_due(self, last_run_at):
"""Returns tuple of two items `(is_due, next_time_to_run)`,
where next time to run is in seconds.
* `(True, 20)`, means the task should be run now, and the next
time to run is in 20 seconds.
* `(False, 12)`, means the task should be run in 12 seconds.
You can override this to decide the interval at runtime,
but keep in mind the value of :setting:`CELERYBEAT_MAX_LOOP_INTERVAL`,
which decides the maximum number of seconds celerybeat can sleep
between re-checking the periodic task intervals. So if you
dynamically change the next run at value, and the max interval is
set to 5 minutes, it will take 5 minutes for the change to take
effect, so you may consider lowering the value of
:setting:`CELERYBEAT_MAX_LOOP_INTERVAL` if responsiveness is of
importance to you.
.. admonition:: Scheduler max interval variance
The default max loop interval may vary for different schedulers.
For the default scheduler the value is 5 minutes, but for e.g.
the django-celery database scheduler the value is 5 seconds.
rem_delta = self.remaining_estimate(last_run_at)
rem = timedelta_seconds(rem_delta)
if rem == 0:
return True, self.seconds
return False, rem
def __repr__(self):
return "<freq: %s>" % self.human_seconds
def __eq__(self, other):
if isinstance(other, schedule):
return self.run_every == other.run_every
return self.run_every == other
def seconds(self):
return timedelta_seconds(self.run_every)
def human_seconds(self):
return humanize_seconds(self.seconds)
class crontab_parser(object):
"""Parser for crontab expressions. Any expression of the form 'groups'
(see BNF grammar below) is accepted and expanded to a set of numbers.
These numbers represent the units of time that the crontab needs to
run on::
digit :: '0'..'9'
dow :: 'a'..'z'
number :: digit+ | dow+
steps :: number
range :: number ( '-' number ) ?
numspec :: '*' | range
expr :: numspec ( '/' steps ) ?
groups :: expr ( ',' expr ) *
The parser is a general purpose one, useful for parsing hours, minutes and
day_of_week expressions. Example usage::
>>> minutes = crontab_parser(60).parse("*/15")
[0, 15, 30, 45]
>>> hours = crontab_parser(24).parse("*/4")
[0, 4, 8, 12, 16, 20]
>>> day_of_week = crontab_parser(7).parse("*")
[0, 1, 2, 3, 4, 5, 6]
It can also parse day_of_month and month_of_year expressions if initialized
with an minimum of 1. Example usage::
>>> days_of_month = crontab_parser(31, 1).parse("*/3")
[1, 4, 7, 10, 13, 16, 19, 22, 25, 28, 31]
>>> months_of_year = crontab_parser(12, 1).parse("*/2")
[1, 3, 5, 7, 9, 11]
>>> months_of_year = crontab_parser(12, 1).parse("2-12/2")
[2, 4, 6, 8, 10, 12]
The maximum possible expanded value returned is found by the formula::
max_ + min_ - 1
ParseException = ParseException
_range = r'(\w+?)-(\w+)'
_steps = r'/(\w+)?'
_star = r'\*'
def __init__(self, max_=60, min_=0):
self.max_ = max_
self.min_ = min_
self.pats = (
(re.compile(self._range + self._steps), self._range_steps),
(re.compile(self._range), self._expand_range),
(re.compile(self._star + self._steps), self._star_steps),
(re.compile('^' + self._star + '$'), self._expand_star))
def parse(self, spec):
acc = set()
for part in spec.split(','):
if not part:
raise self.ParseException("empty part")
acc |= set(self._parse_part(part))
return acc
def _parse_part(self, part):
for regex, handler in self.pats:
m = regex.match(part)
if m:
return handler(m.groups())
return self._expand_range((part, ))
def _expand_range(self, toks):
fr = self._expand_number(toks[0])
if len(toks) > 1:
to = self._expand_number(toks[1])
return range(fr, min(to + 1, self.max_ + 1))
return [fr]
def _range_steps(self, toks):
if len(toks) != 3 or not toks[2]:
raise self.ParseException("empty filter")
return self._expand_range(toks[:2])[::int(toks[2])]
def _star_steps(self, toks):
if not toks or not toks[0]:
raise self.ParseException("empty filter")
return self._expand_star()[::int(toks[0])]
def _expand_star(self, *args):
return range(self.min_, self.max_ + self.min_)
def _expand_number(self, s):
if isinstance(s, basestring) and s[0] == '-':
raise self.ParseException("negative numbers not supported")
i = int(s)
except ValueError:
i = weekday(s)
except KeyError:
raise ValueError("Invalid weekday literal '%s'." % s)
if i < self.min_:
raise ValueError("Invalid beginning range - %s < %s." %
(i, self.min_))
return i
class crontab(schedule):
"""A crontab can be used as the `run_every` value of a
:class:`PeriodicTask` to add cron-like scheduling.
Like a :manpage:`cron` job, you can specify units of time of when
you would like the task to execute. It is a reasonably complete
implementation of cron's features, so it should provide a fair
degree of scheduling needs.
You can specify a minute, an hour, a day of the week, a day of the
month, and/or a month in the year in any of the following formats:
.. attribute:: minute
- A (list of) integers from 0-59 that represent the minutes of
an hour of when execution should occur; or
- A string representing a crontab pattern. This may get pretty
advanced, like `minute="*/15"` (for every quarter) or
.. attribute:: hour
- A (list of) integers from 0-23 that represent the hours of
a day of when execution should occur; or
- A string representing a crontab pattern. This may get pretty
advanced, like `hour="*/3"` (for every three hours) or
`hour="0,8-17/2"` (at midnight, and every two hours during
office hours).
.. attribute:: day_of_week
- A (list of) integers from 0-6, where Sunday = 0 and Saturday =
6, that represent the days of a week that execution should
- A string representing a crontab pattern. This may get pretty
advanced, like `day_of_week="mon-fri"` (for weekdays only).
(Beware that `day_of_week="*/2"` does not literally mean
"every two days", but "every day that is divisible by two"!)
.. attribute:: day_of_month
- A (list of) integers from 1-31 that represents the days of the
month that execution should occur.
- A string representing a crontab pattern. This may get pretty
advanced, such as `day_of_month="2-30/3"` (for every even
numbered day) or `day_of_month="1-7,15-21"` (for the first and
third weeks of the month).
.. attribute:: month_of_year
- A (list of) integers from 1-12 that represents the months of
the year during which execution can occur.
- A string representing a crontab pattern. This may get pretty
advanced, such as `month_of_year="*/3"` (for the first month
of every quarter) or `month_of_year="2-12/2"` (for every even
numbered month).
It is important to realize that any day on which execution should
occur must be represented by entries in all three of the day and
month attributes. For example, if `day_of_week` is 0 and `day_of_month`
is every seventh day, only months that begin on Sunday and are also
in the `month_of_year` attribute will have execution events. Or,
`day_of_week` is 1 and `day_of_month` is "1-7,15-21" means every
first and third monday of every month present in `month_of_year`.
def _expand_cronspec(cronspec, max_, min_=0):
"""Takes the given cronspec argument in one of the forms::
int (like 7)
basestring (like '3-5,*/15', '*', or 'monday')
set (like set([0,15,30,45]))
list (like [8-17])
And convert it to an (expanded) set representing all time unit
values on which the crontab triggers. Only in case of the base
type being 'basestring', parsing occurs. (It is fast and
happens only once for each crontab instance, so there is no
significant performance overhead involved.)
For the other base types, merely Python type conversions happen.
The argument `max_` is needed to determine the expansion of '*'
and ranges.
The argument `min_` is needed to determine the expansion of '*'
and ranges for 1-based cronspecs, such as day of month or month
of year. The default is sufficient for minute, hour, and day of
if isinstance(cronspec, int):
result = set([cronspec])
elif isinstance(cronspec, basestring):
result = crontab_parser(max_, min_).parse(cronspec)
elif isinstance(cronspec, set):
result = cronspec
elif is_iterable(cronspec):
result = set(cronspec)
raise TypeError(
"Argument cronspec needs to be of any of the "
"following types: int, basestring, or an iterable type. "
"'%s' was given." % type(cronspec))
# assure the result does not preceed the min or exceed the max
for number in result:
if number >= max_ + min_ or number < min_:
raise ValueError(
"Invalid crontab pattern. Valid "
"range is %d-%d. '%d' was found." %
(min_, max_ - 1 + min_, number))
return result
def _delta_to_next(self, last_run_at, next_hour, next_minute):
Takes a datetime of last run, next minute and hour, and
returns a relativedelta for the next scheduled day and time.
Only called when day_of_month and/or month_of_year cronspec
is specified to further limit scheduled task execution.
from bisect import bisect, bisect_left
datedata = AttributeDict(year=last_run_at.year)
days_of_month = sorted(self.day_of_month)
months_of_year = sorted(self.month_of_year)
def day_out_of_range(year, month, day):
datetime(year=year, month=month, day=day)
except ValueError:
return True
return False
def roll_over():
while 1:
flag = (datedata.dom == len(days_of_month) or
if flag:
datedata.dom = 0
datedata.moy += 1
if datedata.moy == len(months_of_year):
datedata.moy = 0
datedata.year += 1
if last_run_at.month in self.month_of_year:
datedata.dom = bisect(days_of_month,
datedata.moy = bisect_left(months_of_year, last_run_at.month)
datedata.dom = 0
datedata.moy = bisect(months_of_year, last_run_at.month)
while not (datetime(year=datedata.year,
).isoweekday() % 7
) in self.day_of_week:
datedata.dom += 1
return relativedelta(year=datedata.year,
def __init__(self, minute='*', hour='*', day_of_week='*',
day_of_month='*', month_of_year='*', nowfun=None):
self._orig_minute = minute
self._orig_hour = hour
self._orig_day_of_week = day_of_week
self._orig_day_of_month = day_of_month
self._orig_month_of_year = month_of_year
self.hour = self._expand_cronspec(hour, 24)
self.minute = self._expand_cronspec(minute, 60)
self.day_of_week = self._expand_cronspec(day_of_week, 7)
self.day_of_month = self._expand_cronspec(day_of_month, 31, 1)
self.month_of_year = self._expand_cronspec(month_of_year, 12, 1)
self.nowfun = nowfun or
def __repr__(self):
return ("<crontab: %s %s %s %s %s (m/h/d/dM/MY)>" %
(self._orig_minute or "*",
self._orig_hour or "*",
self._orig_day_of_week or "*",
self._orig_day_of_month or "*",
self._orig_month_of_year or "*"))
def __reduce__(self):
return (self.__class__, (self._orig_minute,
self._orig_month_of_year), None)
def remaining_estimate(self, last_run_at):
"""Returns when the periodic task should run next as a timedelta."""
dow_num = last_run_at.isoweekday() % 7 # Sunday is day 0, not day 7
execute_this_date = (last_run_at.month in self.month_of_year and in self.day_of_month and
dow_num in self.day_of_week)
execute_this_hour = (execute_this_date and
last_run_at.hour in self.hour and
last_run_at.minute < max(self.minute))
if execute_this_hour:
next_minute = min(minute for minute in self.minute
if minute > last_run_at.minute)
delta = relativedelta(minute=next_minute,
next_minute = min(self.minute)
execute_today = (execute_this_date and
last_run_at.hour < max(self.hour))
if execute_today:
next_hour = min(hour for hour in self.hour
if hour > last_run_at.hour)
delta = relativedelta(hour=next_hour,
next_hour = min(self.hour)
all_dom_moy = (self._orig_day_of_month == "*" and
self._orig_month_of_year == "*")
if all_dom_moy:
next_day = min([day for day in self.day_of_week
if day > dow_num] or
add_week = next_day == dow_num
delta = relativedelta(weeks=add_week and 1 or 0,
weekday=(next_day - 1) % 7,
delta = self._delta_to_next(last_run_at,
next_hour, next_minute)
return remaining(last_run_at, delta, now=self.nowfun())
def is_due(self, last_run_at):
"""Returns tuple of two items `(is_due, next_time_to_run)`,
where next time to run is in seconds.
See :meth:`celery.schedules.schedule.is_due` for more information.
rem_delta = self.remaining_estimate(last_run_at)
rem = timedelta_seconds(rem_delta)
due = rem == 0
if due:
rem_delta = self.remaining_estimate(last_run_at=self.nowfun())
rem = timedelta_seconds(rem_delta)
return due, rem
def __eq__(self, other):
if isinstance(other, crontab):
return (other.month_of_year == self.month_of_year and
other.day_of_month == self.day_of_month and
other.day_of_week == self.day_of_week and
other.hour == self.hour and
other.minute == self.minute)
return other is self
def maybe_schedule(s, relative=False):
if isinstance(s, int):
s = timedelta(seconds=s)
if isinstance(s, timedelta):
return schedule(s, relative)
return s
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