Quickly Build an Asynchronous Email Service with Celery and Redis

Celery is a Python distributed task queue that provides a simple API for asynchronous processing. It relies on external message brokers such as RabbitMQ, Redis, or databases, with Redis being the recommended choice.

Installing Celery

Install via pip or easy_install, and add celery-with-redis when using Redis as the broker.

$ sudo pip install Celery
$ sudo easy_install Celery

Write a tasks.py file:

# tasks.py
import time
from celery import Celery

celery = Celery('tasks', broker='redis://localhost:6379/0')

@celery.task
def sendmail(mail):
    print('sending mail to %s...' % mail['to'])
    time.sleep(2.0)
    print('mail sent.')

Start a worker: $ celery -A tasks worker --loglevel=info Send a task from Python:

>> from tasks import sendmail
>>> sendmail.delay(dict(to='[email protected]'))

The worker logs show task receipt and execution, confirming Celery’s straightforward API and default settings (worker pool size equals CPU cores, default serialization with pickle, configurable to JSON).

Celery also supports advanced features such as chaining multiple tasks into atomic workflows and provides monitoring interfaces for further exploration.