Which message broker was used in Celery for task processing?

In Celery, the message broker most commonly used for task processing is RabbitMQ or Redis.

RabbitMQ is a full-featured message broker supporting complex routing and delivery guarantees. Redis is a simpler and faster option, often used for small projects or when high performance is required.

Example of setting up Celery with RabbitMQ:

from celery import Celery

app = Celery('tasks', broker='pyamqp://guest@localhost//')

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

Here, pyamqp://guest@localhost// is the connection URL to RabbitMQ.

Thus, the message broker in Celery is responsible for transmitting and routing tasks between producers and workers.