python - 如何使用 Django 模型动态创建 cron 作业？
问题描述
我需要为模型中的每个对象创建一个 cron 作业。我研究了 celery 和 crontab，但这些库直接从代码中使用静态 crons。任何有助于为模型中的每个对象动态创建任务的库？
解决方案
我在这里找到了一些模型驱动的示例代码（Django 模型 cron 作业）
更改条目时会同步 crontab，并提供相关的环境变量、函数名和参数。您可能希望将其存储为名为“调度程序”的应用程序以匹配导入。
# FILE: models.py
#!/usr/bin/env python
# -*- coding: UTF-8 -*-
"""
Title: Scheduler models
Author: Will Hardy (http://willhardy.com.au)
Date: December 2007
Test suite: manage.py test scheduler
$Revision: $
Description: Integrates Python and the native crontab.
A more beginner-friendly interface is offered, and entries are stored in a database.
The database is used to update the local crontab.
"""
__all__ = ('Task', 'update_crontab')
import os
import tempfile
from django.db import models
from datetime import datetime, timedelta
import calendar
from django.utils.translation import ugettext as _
TIME_SCALES = (
("hour", _("hour")),
("day", _("day")),
("week", _("week")),
("month", _("month")),
("year", _("year")),
)
class Task(models.Model):
"""
Add a task to be entered into this user's crontab.
When the time comes, a simple python function is called with a single text
argument. This interface is not intended to be comprehensive, rather, it is
intended to be pointed to a python function that is specially prepared to
carry out the intended function and only needs to be told when.
name: A name is good for the user to remember this, but is not necessary.
active: Allows the task to be temporarily switched off.
start: A date and time when this task should be run.
stop: A date and time after which repetitions should not take place.
time_scale: The type of repetition that will take place.
period: How often the repetitions will take place. (zero is for no repetitions)
times_run: How many times this has already been executed
function: The full path to the python function to be executed (with periods).
argument: A single string argument to be given to the function.
expert: Allows direct manipulation of the crontab entry (only the time/date part please!)
"""
name = models.CharField(_("name"), max_length=200, default="", blank=True)
active = models.BooleanField(_("active"), default=True)
start = models.DateTimeField(_("start"), default=datetime.now(), null=True, blank=True)
stop = models.DateTimeField(_("stop"), null=True, blank=True)
time_scale = models.CharField(max_length=5, choices=TIME_SCALES, null=True, blank=True)
period = models.PositiveSmallIntegerField(default=0, null=True)
times_run = models.PositiveSmallIntegerField(default=0, editable=False)
function = models.CharField(max_length=200)
arguments = models.CharField(max_length=200, default="", blank=True)
#expert = models.CharField(max_length=100, default="", blank=True)
class Meta:
verbose_name = _("task")
verbose_name_plural = _("tasks")
class Admin:
list_display = ('__unicode__', 'start', 'time_scale', 'times_run')
def __unicode__(self):
" A useful textual description of this task. "
if self.name:
return self.name
elif self.arguments:
# TODO: A better automatic description i.e. "Automatic task every tuesday."
return u"%s %s" % (self.get_function_name(), self.arguments)
else:
return u"Task %d" % self.id
def save(self):
""" Updates the crontab when a task is saved.
"""
super(Task, self).save()
update_crontab()
def get_module_path(self):
""" Get the module path, without the function name.
>>> start = datetime(2007, 12, 1, 6, 23)
>>> task = Task(function="path.to.test", start=start)
>>> task.get_module_path()
'path.to'
>>> task.function = "test"
>>> task.get_module_path()
''
>>> task.function = ""
>>> task.get_module_path()
''
"""
return ".".join(self.function.split(".")[:-1])
def get_function_name(self):
""" Get the function name, without the module path.
>>> start = datetime(2007, 12, 1, 6, 23)
>>> task = Task(function="path.to.test", start=start)
>>> task.get_function_name()
'test'
>>> task.function = "test"
>>> task.get_function_name()
'test'
>>> task.function = ""
>>> task.get_function_name()
''
"""
return self.function.split(".")[-1]
def get_crontab_entry(self):
""" Gets the entire contrab line, including time specification and command.
>>> start = datetime(2007, 12, 1, 6, 23)
>>> task = Task(function="test", start=start)
>>> task.get_crontab_entry() is None
True
>>> task.id = 5
>>> len(task.get_crontab_entry().split())
9
"""
crontab_time = self.get_crontab_time()
crontab_command = self.get_crontab_command()
crontab_argument = self.get_crontab_argument()
if crontab_time and crontab_command and crontab_argument:
return ' '.join([crontab_time, crontab_command, crontab_argument])
def get_crontab_argument(self):
""" Forms the argument to be used for the crontab command.
>>> start = datetime(2007, 12, 1, 6, 23)
>>> task = Task(function="test", start=start)
>>> task.get_crontab_argument() is None
True
>>> task.id = 5
>>> task.get_crontab_argument()
'task_005'
"""
if self.id:
return 'task_%03d' % self.id
def get_crontab_command(self):
""" Forms the command to be used for the crontab command.
>>> start = datetime(2007, 12, 1, 6, 23)
>>> task = Task(function="test", start=start)
>>> task.get_crontab_command().rstrip("c").endswith("py") or task.get_crontab_command()
True
TODO: Prevent issues with spaces in filename
"""
path = get_command_path()
return "%s %s" % ("/usr/bin/env python", path)
def get_crontab_time(self):
""" Get the time part of a crontab line for this task.
This is a space separated list of 5 entries:
"2 * * * *"
Multiple values are also possible, if self.period is set:
"2,32 * * * *"
>>> the_time = datetime(2007, 12, 1, 6, 23) # Sat 1 Dec 2007, 6:23am
>>> task = Task(function="test", start=the_time)
>>> task.period = 1
>>> task.time_scale = "hour"
>>> task.get_crontab_time()
'23 * * * *'
>>> task.time_scale = "day"
>>> task.get_crontab_time()
'23 6 * * *'
>>> task.time_scale = "week"
>>> task.get_crontab_time()
'23 6 * * 6'
>>> task.time_scale = "month"
>>> task.get_crontab_time()
'23 6 1 * *'
>>> task.period = 2
>>> task.time_scale = "day"
>>> task.get_crontab_time()
'23 6,18 * * *'
>>> task.time_scale = "year"
>>> task.get_crontab_time()
'23 6 1 6,12 *'
>>> task.period = 6
>>> task.time_scale = "month"
>>> task.get_crontab_time()
'23 6 1,6,11,16,21,26 * *'
>>> task.period = 0
>>> task.get_crontab_time()
'23 6 1 12 *'
>>> task.period = 5
>>> task.time_scale = None
>>> task.get_crontab_time()
'23 6 1 12 *'
"""
def with_repeats(start, max):
""" Get a sequence of repeated values in CSV form.
e.g. with_repeats(14, 31) with a period of 3 will give: "4,14,24"
"""
values = get_stepped_sequence(start, max, self.period)
# Convert to string and join using commas
return ",".join([ str(v) for v in values ])
# Synchronise our period and timescale if repetition is turned off
if self.period == 0:
self.time_scale = None
if self.time_scale is None:
self.period = 0
# Default all values to stars
minute = hour = day = month = weekday = "*"
if self.time_scale == "hour":
minute = with_repeats(self.start.minute, 60)
elif self.time_scale == "day":
minute = str(self.start.minute)
hour = with_repeats(self.start.hour, 24)
elif self.time_scale == "week":
minute = str(self.start.minute)
hour = str(self.start.hour)
weekday = with_repeats((self.start.weekday() + 1) % 7, 7)
elif self.time_scale == "month":
minute = str(self.start.minute)
hour = str(self.start.hour)
day = with_repeats(self.start.day, 31)
else: # catch both "year" and None
minute = str(self.start.minute)
hour = str(self.start.hour)
day = str(self.start.day)
month = with_repeats(self.start.month, 12)
return " ".join([minute, hour, day, month, weekday])
def next_occurrence(self, reference=None):
""" The time and date of the next occurace to take place.
>>> reference = datetime(2007, 12, 12, 17, 51) # Wed 12 Dec 2007, 5:51pm
>>> start = datetime(2007, 11, 3, 6, 23) # Sat 3 Nov 2007, 6:23am
>>> task = Task(function="test", start=start)
>>> task.period = 2
>>> task.time_scale = "hour"
>>> task.next_occurrence(reference=reference)
datetime.datetime(2007, 12, 12, 17, 53)
>>> task.time_scale = "day"
>>> task.next_occurrence(reference=reference)
datetime.datetime(2007, 12, 12, 18, 23)
>>> task.time_scale = "week"
>>> task.period = 1
>>> task.next_occurrence(reference=reference)
datetime.datetime(2007, 12, 15, 6, 23)
>>> task.time_scale = "month"
>>> task.next_occurrence(reference=reference)
datetime.datetime(2008, 1, 3, 6, 23)
"""
#def get_next_step(start, ref, max):
#" A convenience function that provides the next step "
#steps = get_stepped_sequence(start, max, self.period)
#steps = [ (i > ref and i) or i+max for i in steps ]
#value = min(steps)
#return value
if not reference:
reference = datetime.now()
attempt = None
period_delta = None
if self.start > reference:
return self.start
minute, hour, day, month, year = reference.minute, reference.hour, reference.day, reference.month, reference.year
# For each possible time scale, work out a naive start time and a period delta.
# If the start time is behind the reference time, increment until we have a time in the future.
if self.time_scale == "hour":
period_delta = timedelta(minutes=60/self.period)
minute = self.start.minute
if self.time_scale == "day":
period_delta = timedelta(hours=24/self.period)
minute = self.start.minute
hour = self.start.hour
if self.time_scale == "week":
period_delta = timedelta(hours=7*24/self.period)
minute = self.start.minute
hour = self.start.hour
# Move backwards in time to the correct day of the week
day_correction = self.start.weekday() - reference.weekday()
if day_correction > 0:
day_correction - 7
correction_delta = timedelta(days=day_correction)
attempt = datetime(year, month, day, hour, minute) + correction_delta
if self.time_scale == "month":
minute = self.start.minute
hour = self.start.hour
day = self.start.day
# Days in current month needs to be accurate, to avoid landing on
# another day of the month
days_in_month = reference.month in (1,3,5,7,8,10,12) and 31 or \
reference.month in (4,6,9,11) and 30 or \
calendar.isleap(reference.year) and 29 or 28
period_delta = timedelta(days=days_in_month/self.period)
if self.time_scale == "year":
days_in_year = calendar.isleap(reference.year) and reference.month <= 2 and 366 or \
calendar.isleap(reference.year+1) and reference.month > 2 and 366 or 365
period_delta = timedelta(days=days_in_year/self.period)
minute = self.start.minute
hour = self.start.hour
day = self.start.day
month = self.start.month
# If nothing was matched either, given up
if not period_delta:
return self.start > reference and self.start or None
# If not done already, make an attempt
if not attempt:
attempt = datetime(year, month, day, hour, minute)
# Keep incrementing the attempt until it is in the future
while attempt < reference:
attempt += period_delta
return attempt
def upcoming(self, reference=None):
""" If the task has started or is due to start in the next 24 hours.
>>> reference_01 = datetime(2007, 11, 11, 17, 51)
>>> reference_02 = datetime(2007, 11, 12, 17, 51)
>>> start = datetime(2007, 11, 13, 6, 23)
>>> task = Task(function="test", start=start)
>>> task.upcoming(reference=reference_01)
False
>>> task.upcoming(reference=reference_02)
True
>>> task.upcoming()
True
"""
if not reference:
reference = datetime.now()
return self.start - reference < timedelta(hours=24)
def imminent(self, reference=None):
""" If this task needs to be executed very soon
(and thus should be done immediately).
>>> reference_01 = datetime(2007, 11, 11, 17, 51)
>>> reference_02 = datetime(2007, 11, 12, 17, 51)
>>> start = datetime(2007, 11, 12, 17, 52)
>>> task = Task(function="test", start=start)
>>> task.imminent(reference=reference_01)
False
>>> task.imminent(reference=reference_02)
True
>>> task.imminent()
False
"""
if not reference:
reference = datetime.now()
next = self.next_occurrence(reference=reference)
if next:
return next - reference < timedelta(minutes=5)
return False
def get_stepped_sequence(start, max, period):
""" Get a stepped sequence, wrapping around a max value.
period is the number of values involved.
>>> get_stepped_sequence(3, 56, 4)
[3, 17, 31, 45]
>>> get_stepped_sequence(45, 46, 2)
[22, 45]
>>> get_stepped_sequence(45, 46, 1)
[45]
>>> get_stepped_sequence(45, 46, 0)
[45]
>>> get_stepped_sequence(47, 46, 0)
[]
>>> get_stepped_sequence(5, 11, 12)
[]
"""
# Some exceptional cases
if start > max:
return []
if period > max:
return []
if not period:
return [ start ]
step = max / period
values = []
while len(values) < period:
offset = len(values) * step
value = ((offset + start - 1) % max) + 1
values.append(value)
values.sort()
return values
def get_command_path():
""" Returns the path to the command to be run through cron. """
return '%s/%s' % (os.path.dirname(__file__), 'run_task.py')
def update_crontab():
""" Synchronises the database and the crontab.
Issue: any jobs that are imminent may not be run.
"""
tasks = Task.objects.all()
# Create a series of entries from each of the tasks
lines = [ task.get_crontab_entry() for task in tasks ]
# Add an extra line for maintenance
#lines.append(Task.get_maintenance_entry())
# Join the lines into a single file
crontab = "\n".join(lines)
# Get the preexisting crontab and remove old lines
old_crontab = tempfile.NamedTemporaryFile()
filename = old_crontab.name
os.system('crontab -l > %s' % filename)
# Remove old lines
crontab_lines = []
for line in old_crontab.readlines():
if get_command_path() not in line:
crontab_lines.append(line)
old_crontab.close()
# Append environment lines to the crontab
# Whatever environment is being used to update the crontab
# will be set in the crontab so that the script that is
# eventually run, will run with the same environment variables..
# 1. name of the settings module for django
settings_key = 'DJANGO_SETTINGS_MODULE'
if settings_key in os.environ:
settings_module = os.environ[settings_key]
else:
settings_module = 'settings'
if settings_module.split('.')[-1] == '__init__':
settings_module = ".".join(settings_module.split(".")[:-1] + ['settings'])
environment_line = '%s=%s\n' % (settings_key, settings_module)
if environment_line not in crontab_lines:
crontab_lines.append(environment_line)
# 2. python path
pythonpath_key = 'PYTHONPATH'
environment_line = '%s=%s\n' % (pythonpath_key, os.environ[pythonpath_key])
if pythonpath_key in os.environ and environment_line not in crontab_lines:
crontab_lines.append(environment_line)
# Append new lines
for task in Task.objects.filter(active=True):
entry = task.get_crontab_entry() + '\n'
if entry:
crontab_lines.append(entry)
# Set the new crontab
new_crontab = tempfile.NamedTemporaryFile()
new_crontab.writelines(crontab_lines)
new_filename = new_crontab.name
new_crontab.flush()
os.system('crontab %s' % new_filename)
new_crontab.close()
# FILE: views.py
#!/usr/bin/env python
# -*- coding: UTF-8 -*-
"""
Title: Scheduler views
Author: Will Hardy (http://willhardy.com.au)
Date: December 2007
Test suite: ../models test scheduler
$Revision: $
Description: Intergrates Python and the native crontab.
A more beginner-friendly interface is offered, and entries are stored in a database.
The database is used to update the local crontab.
"""
from scheduler.models import Task
def run_task(task_id):
""" Run the task with the given ID.
>>> task = Task(function="scheduler.tests.test_function")
>>> task.save()
>>> run_task(task.id)
Success!
"""
task = Task.objects.get(id=task_id)
module = __import__(task.get_module_path(), [], [], task.get_function_name())
function = getattr(module, task.get_function_name())
if task.arguments:
args = task.arguments.split(",")
function(*args)
else:
function()
# Do some accounting
task.times_run += 1
task.save()
# FILE: run_task.py
#!/usr/bin/env python
# -*- coding: UTF-8 -*-
"""
Title: Scheduler crontab entry point
Author: Will Hardy (http://willhardy.com.au)
Date: December 2007
$Revision: $
Description: This script is to be called directly.
"""
import os
import sys
from scheduler.models import Task, update_crontab
from scheduler.views import run_task
if __name__ == "__main__":
# If this module is called directly, run the given task
usage = 'USAGE: %s task_id' % sys.argv[0]
if len(sys.argv) == 2:
command = sys.argv[1]
if command == "update":
update_crontab()
exit()
# Try to parse the task id from the command
if command.startswith('task_'):
command = command[5:]
try:
task_id = int(command)
except ValueError:
sys.exit(usage)
# Run the task matching the given task_id
try:
run_task(task_id)
except Task.DoesNotExist:
sys.exit("Task with this ID (%s) does not exist." % task_id)
else:
sys.exit(usage)
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