Running “unique” tasks with celery

Question

I use celery to update RSS feeds in my news aggregation site. I use one @task for each feed, and things seem to work nicely.

There\'s a detail that I\'m not sure to

Answer 1

Using https://pypi.python.org/pypi/celery_once seems to do the job really nice, including reporting errors and testing against some parameters for uniqueness.

You can do things like:

from celery_once import QueueOnce
from myapp.celery import app
from time import sleep

@app.task(base=QueueOnce, once=dict(keys=('customer_id',)))
def start_billing(customer_id, year, month):
    sleep(30)
    return "Done!"

which just needs the following settings in your project:

ONCE_REDIS_URL = 'redis://localhost:6379/0'
ONCE_DEFAULT_TIMEOUT = 60 * 60  # remove lock after 1 hour in case it was stale