HOWTO django + celery + rabbitmq simple setup for testing purpose

This setup is simply used for testing purpose and using the official First Steps with Celery and First Steps with Django as reference.

Installation

Step1. Install EPEL repository

Using yum search epel to find the exact package name for your distribution. Then use yum install to install EPEL.

Step2. Install Erlang

Erlang is required for RabbitMQ to work. Use yum install erlang to install it.

Step3. Install RabbitMQ

RabbitMQ is the message broker we chose. Use yum install rabbitmq-server to install it.

Step4. Install Celery

The installation of Celery is very easy. Just use pip install celery

Step5. Install Django

The installation of Django is also very easy. Just use pip install django

Configuration

First, setup a very basic Django project django-admin startproject proj
Then create a new proj/proj/celery.py module that defines the Celery instance:

file:proj/proj/celery.pyfrom __future__ import absolute_importimport osfrom celery import Celery# set the default Django settings module for the 'celery' program.os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'proj.settings')from django.conf import settingsapp = Celery('proj')# Using a string here means the worker will not have to# pickle the object when using Windows.app.config_from_object('django.conf:settings')app.autodiscover_tasks(lambda: settings.INSTALLED_APPS)@app.task(bind=True)def debug_task(self):    print('Request: {0!r}'.format(self.request))

Then you need to import this app in your proj/proj/__init__.py module. This ensures that the app is loaded when Django starts so that the @shared_task decorator (mentioned later) will use it:

File:proj/proj/__init__.pyfrom __future__ import absolute_import# This will make sure the app is always imported when# Django starts so that shared_task will use this app.from .celery import app as celery_app

Next, create a demoapp app in your proj project, using python manage.py startapp demoapp

Next, create a tasks.py in demoapp

IMPORTANT: Make sure the file name is tasks.py. Otherwise, it will not be autodiscovered.

The tasks you write will probably live in reusable apps, and reusable
apps cannot depend on the project itself, so you also cannot import
your app instance directly.

The @shared_task decorator lets you create tasks without having any
concrete app instance:

demoapp/tasks.py:from __future__ import absolute_importfrom celery import shared_task@shared_taskdef add(x, y):    return x + y@shared_taskdef mul(x, y):    return x * y@shared_taskdef xsum(numbers):    return sum(numbers)

Next, configure the broker and backend for Celery. To do this, since we’ve already told Celery to look for configuration in proj/settings.py, we will add the following to that file.

BROKER_URL = 'amqp://guest:guest@localhost:5672//'CELERY_RESULT_BACKEND = 'amqp'

Test

RabbitMQ

start rabbitmq and run it in background, rabbitmq-server -detached
stop rabbitmq, rabbitmqctl stop
check rabbitmq status, rabbitmqctl status

Celery

Start celery worker process, celery -A proj worker -l info

IMPORTANT:To test your @shared_task in tasks.py, you must using “python manage.py shell” to start a python shell. That will load the configuration in proj/_init_.py
Otherwise, if you start a python shell normally using “python”, then configuration in proj/_init_ will not be read, thus @shared_task will not function properly. For example, shared_task.ready() will raise AttributeError: ‘DisabledBackend’ object has no attribute ‘_get_task_meta_for’