Dynamically Schedule Celery Beat task with Flask

Question

I want to be able to let the user of my application start/stop periodic crontab style tasks with Celery beat. Right now I run Celery with

venv/bin/celery worker -A celery_worker.celery --loglevel=info

I got Celery Beat running with this simple example:

@celery.task
def add(x, y):
    return x + y

on my config file:

CELERYBEAT_SCHEDULE = {
    'add-every-30-seconds': {
        'task': 'app.email.add',
        'schedule': timedelta(seconds=30),
        'args': (16, 16)
    },
}
CELERY_TIMEZONE = 'UTC'

then I run the Celery beat worker with

celery -A celery_worker.celery beat -s ~/Documents/cesco-automation/power/celerybeat-schedule

And it works perfectly! But I need to have more control over the schedule.

Also on my app shell, I am able to do this.

>>>add.apply_async([80,800],countdown=30)

>>> from datetime import datetime, timedelta     
>>> tomorrow = datetime.now() + timedelta(days=1)
>>> add.apply_async(args=[10, 10], eta=tomorrow)

Which is great, but I am developing a home-automation app, so I also need to stop the tasks. How do I do this??

I have also found this link that mention about a django custom scheduler classes. Which is exactly what I need. On the Celery docs it mentions the -S flag, but I dont know how to properly add the class to my Flask app. How can I use it with Flask??

Do I really need Celery Beat? Are there other option other the crontab? Crontab seems not to be sharp enough.

The default celery scheduler kinda sucks. Don't even get me started on dealing with timezones with it. I would use a database scheduler, can look at the one for django celery.readthedocs.org/en/latest/userguide/… — reptilicus
I have mention the same doc on the question, but do not know how to make it work. Can I use the Django scheduler on my Flask app? How? — CESCO
@CESCO, Hi, have you tried using django scheduler in flask app ? if yes, please share — Saad Abdullah
well, i found something...and its working fine...incase anyone need github.com/tuomur/celery_sqlalchemy_scheduler — Saad Abdullah

Jakub Czaplicki Jakub Czaplicki · Accepted Answer · 2016-05-21T19:30:19

This functionality will be available in Celery ver.4.0. Dynamic task scheduling is only currently supported in the development version : http://docs.celeryproject.org/en/master/userguide/periodic-tasks.html#beat-entries

Dynamically Schedule Celery Beat task with Flask

2 Answers