Kronos makes it really easy to define and schedule tasks with cron
Python Other



Define tasks

Kronos collects tasks from cron modules in your project root and each of your applications:

# app/

import kronos
import random

@kronos.register('0 0 * * *')
def complain():
    complaints = [
        "I forgot to migrate our applications's cron jobs to our new server! Darn!",
        "I'm out of complaints! Damnit!"

    print random.choice(complaints)

Kronos works with Django management commands, too:

# app/management/commands/

from import NoArgsCommand

import kronos

@kronos.register('0 0 * * *')
class Command(NoArgsCommand):
    def handle_noargs(self, **options):
        print('Hello, world!')

If your management command accepts arguments, just pass them in the decorator:

# app/management/commands/

from import BaseCommand

import kronos

@kronos.register('0 0 * * *', args={'-l': 'nb'})
class Command(BaseCommand):

    option_list = BaseCommand.option_list + (
      make_option('-l', '--language',
        dest    = 'language',
        type    = 'string',
        default = 'en')

    def handle(self, *args, **options):
        if options['language'] == 'en':
          print('Hello, world!')

        if options['language'] == 'nb':
          print('Hei, verden!')

Run tasks manually

$ python runtask complain
I forgot to migrate our applications's cron jobs to our new server! Darn!

Keep in mind that if the registered task is a django command you have to run it in the normal way:

$ python task

List all registered tasks

$ python showtasks
* List of tasks registered in Kronos *
>> Kronos tasks
    >> my_task_one
    >> my_task_two
>> Django tasks
    >> my_django_task

Register tasks with cron

$ python installtasks
Installed 1 task.

You can review the crontab with a crontab -l command:

$ crontab -l
0 0 * * * /usr/bin/python /path/to/ runtask complain --settings=myprpoject.settings $KRONOS_BREAD_CRUMB
0 0 * * * /usr/bin/python /path/to/ task --settings=myprpoject.settings $KRONOS_BREAD_CRUMB

Usually this line will work pretty well for you, but there can be some rare cases when it requires modification. You can achieve it with a number of settings variables used by kronos:

Python interpreter to build a crontab line (defaults to the interpreter you used to invoke the management command).
Management command to build a crontab line (defaults to in the current working directory).
Extra path which will be added as a --pythonpath option to the management command.
Extra string added at the end of the command. For dirty thinks like > /dev/null 2>&1
Extra string added at the beginning of the command. For dirty thinks like source /path/to/env &&. If you use the virtualenv, you can add the environment path by echo "KRONOS_PREFIX = 'source `echo $VIRTUAL_ENV`/bin/activate && '" >> myprpoject/

Define these variables in your file if you wish to alter crontab lines.

The env variable $KRONOS_BREAD_CRUMB is defined to detect which tasks have to be deleted after being installed.


$ pip install django-kronos

... and add kronos to INSTALLED_APPS.


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Johannes Gorset made this. You should tweet me if you can't get it to work. In fact, you should tweet me anyway.