[英]How to dynamically create cron jobs with Django model?
I need to create a cron job for each object in a model.我需要为模型中的每个对象创建一个 cron 作业。 I researched about celery and crontab, but these libraries use a static crons directly from code.
我研究了 celery 和 crontab,但这些库直接从代码中使用静态 crons。 Any library that help to dynamically create a tasks to each object in a model?
任何有助于为模型中的每个对象动态创建任务的库?
from django.db.models import signals
from django.db import transaction
from django.dispatch import receiver
from .tasks import <some celery task>
@receiver(signals.post_save, sender=User)
def run_task_on_user_save(sender, instance, created, **kwargs):
if created:
transaction.on_commit(
lambda: <some celery task>
)
You can use django signals to run a task on every new User save.您可以使用django 信号在每个新用户保存时运行任务。
or或者
You could use django celery beat to run periodic tasks and have the task loop through all your objects to preform the logic you need.您可以使用django celery beat运行周期性任务,并让任务循环遍历所有对象以执行所需的逻辑。
I found some sample code that is model-driven here (Django model cron jobs)我在这里找到了一些模型驱动的示例代码(Django 模型 cron 作业)
The crontab is synchronised when an entry is changed, and relevant environment variables, function name and arguments are provided.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。 You might want to store this as an app called "scheduler" to match the imports.
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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