Running tasks in Django Celery at specified time?

Question

Snippet from my tasks.py file are as follows:

from celery.task.schedules import crontab
from celery.decorators import periodic_task

@periodic_task(
    run_every=crontab(minute='15, 45', hour='0, 7, 15'),
)
def task1():
    send_mail()

I want the script in task1() to be triggered only at 00:15, 7:15 and 15:45, whereas with the current settings it's triggered at 00:15, 00:45, 7:15, 7:45, 15:15 and 15:45.

How do I do this ? Also, let me know if there is a better approach!

Can you use the decorator multiple times to achieve what you want? — voodoo-burger, Nov 25 '19 at 12:27
@voodoo-burger You mean same decorator multiple times (with different arguments) ? That won't work!! — Virat, Nov 25 '19 at 12:43

Virat · Accepted Answer · 2019-11-26T16:36:21.280

1

After reading through the documentation, and borrowing some ideas from here, I went about solving this as follows:

Removing the periodic_task decorator and updating the tasks.py as:

from celery.task.schedules import crontab
from celery.decorators import periodic_task

@task
def task1():
    send_mail()

Add the beat schedule in celery.py as:

app.conf.beat_schedule = {
    'alert': {
        'task': 'app.tasks.task1',
        'schedule': crontab(minute='15', hour='0, 7')
    },
    'custom_alert': {
        'task': 'app.tasks.task1',
        'schedule': crontab(minute='45', hour='15')
    }
}

With these settings, the script in task1() is getting triggered only at desired time (0:15, 7:15 and 15:45)!

edited Nov 26 '19 at 16:36

answered Nov 26 '19 at 07:04

Virat

129
4
20

1

I don't think you should have to define the beat schedule twice. Otherwise this is the better solution. – schillingt Nov 26 '19 at 14:10
@schillingt Thanks for pointing it out! Updated the answer, following your suggestion. – Virat Nov 26 '19 at 16:37

score 0 · Answer 2 · answered Nov 25 '19 at 16:28

0

You have two options. One is to define the decorated function a few times:

def _task1():
    send_mail()

task1_a = @periodic_task(
    _task1,
    run_every=crontab(minute='15', hour='0, 7'),
)
task1_b = @periodic_task(
    _task1,
    run_every=crontab(minute='45', hour='15'),
)

The other option is to define a custom schedule implementing celery's schedule interface.

answered Nov 25 '19 at 16:28

schillingt

13,493
2
32
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I don't think we can assign decorators to variables! I am exploring the second option, but can you please elaborate more on the first method ? – Virat Nov 26 '19 at 05:24
1

Yes you can. Python is a language that has first-class functions. They are effectively objects in their own right. All a decorator does is wrap the internal function. So rather than defining the internal function twice or creating a new function that calls the internal, you use the decorator twice to wrap the function creating two new functions. – schillingt Nov 26 '19 at 14:09
Although I'm aware of first-class functions in Python, I didn't think it was possible to use decorators this way! As for the given question, the first method ( that of assigning decorators to variables) throws a syntax error. – Virat Nov 26 '19 at 16:47

Running tasks in Django Celery at specified time?

2 Answers2