How to route tasks to different queues with Celery and Django

Question

I am using the following stack:

Python 3.6
Celery v4.2.1 (Broker: RabbitMQ v3.6.0)
Django v2.0.4.

According Celery's documentation, running scheduled tasks on different queues should be as easy as defining the corresponding queues for the tasks on CELERY_ROUTES, nonetheless all tasks seem to be executed on Celery's default queue.

This is the configuration on my_app/settings.py:

CELERY_BROKER_URL = "amqp://guest:guest@localhost:5672//"
CELERY_ROUTES = {
 'app1.tasks.*': {'queue': 'queue1'},
 'app2.tasks.*': {'queue': 'queue2'},
}
CELERY_BEAT_SCHEDULE = {
    'app1_test': {
        'task': 'app1.tasks.app1_test',
        'schedule': 15,
    },
    'app2_test': {
        'task': 'app2.tasks.app2_test',
        'schedule': 15,
    },

}

The tasks are just simple scripts for testing routing:

File app1/tasks.py:

from my_app.celery import app
import time


@app.task()
def app1_test():
    print('I am app1_test task!')
    time.sleep(10)

File app2/tasks.py:

from my_app.celery import app
import time


@app.task()
def app2_test():
    print('I am app2_test task!')
    time.sleep(10)

When I run Celery with all the required queues:

celery -A my_app worker -B -l info -Q celery,queue1,queue2

RabbitMQ will show that only the default queue "celery" is running the tasks:

sudo rabbitmqctl list_queues
# Tasks executed by each queue:
#  - celery 2
#  - queue1 0
#  - queue2 0

Does somebody know how to fix this unexpected behavior?

Regards,

Ander Ander · Accepted Answer · 2018-08-09T19:03:47

I have got it working, there are few things to note here:

According Celery's 4.2.0 documentation, CELERY_ROUTES should be the variable to define queue routing, but it only works for me using CELERY_TASK_ROUTES instead. The task routing seems to be independent from Celery Beat, therefore this will only work for tasks scheduled manually:

app1_test.delay()
app2_test.delay()

or

app1_test.apply_async()
app2_test.apply_async()

To make it work with Celery Beat, we just need to define the queues explicitly in the CELERY_BEAT_SCHEDULE variable. The final setup of the file my_app/settings.py would be as follows:

CELERY_BROKER_URL = "amqp://guest:guest@localhost:5672//"
CELERY_TASK_ROUTES = {
 'app1.tasks.*': {'queue': 'queue1'},
 'app2.tasks.*': {'queue': 'queue2'},
}
CELERY_BEAT_SCHEDULE = {
    'app1_test': {
        'task': 'app1.tasks.app1_test',
        'schedule': 15,
        'options': {'queue': 'queue1'}
    },
    'app2_test': {
        'task': 'app2.tasks.app2_test',
        'schedule': 15,
        'options': {'queue': 'queue2'}
    },

}

I hope this saves some time to other developers.

How to route tasks to different queues with Celery and Django

3 Answers