This document describes the current stable version of Celery (5.3). For development docs, go here.

Introduction to Celery

What’s a Task Queue?

Task queues are used as a mechanism to distribute work across threads or machines.

A task queue’s input is a unit of work called a task. Dedicated worker processes constantly monitor task queues for new work to perform.

Celery communicates via messages, usually using a broker to mediate between clients and workers. To initiate a task the client adds a message to the queue, the broker then delivers that message to a worker.

A Celery system can consist of multiple workers and brokers, giving way to high availability and horizontal scaling.

Celery is written in Python, but the protocol can be implemented in any language. In addition to Python there’s node-celery and node-celery-ts for Node.js, and a PHP client.

Language interoperability can also be achieved exposing an HTTP endpoint and having a task that requests it (webhooks).

What do I need?

Celery requires a message transport to send and receive messages. The RabbitMQ and Redis broker transports are feature complete, but there’s also support for a myriad of other experimental solutions, including using SQLite for local development.

Celery can run on a single machine, on multiple machines, or even across data centers.

Get Started

If this is the first time you’re trying to use Celery, or if you haven’t kept up with development in the 3.1 version and are coming from previous versions, then you should read our getting started tutorials:

Celery is…

Features

Framework Integration

Celery is easy to integrate with web frameworks, some of them even have integration packages:

For Django see First steps with Django.

The integration packages aren’t strictly necessary, but they can make development easier, and sometimes they add important hooks like closing database connections at fork(2).

Quick Jump

Installation

You can install Celery either via the Python Package Index (PyPI) or from source.

To install using pip:

$ pip install -U Celery

Bundles

Celery also defines a group of bundles that can be used to install Celery and the dependencies for a given feature.

You can specify these in your requirements or on the pip command-line by using brackets. Multiple bundles can be specified by separating them by commas.

$ pip install "celery[librabbitmq]"

$ pip install "celery[librabbitmq,redis,auth,msgpack]"

The following bundles are available:

Serializers

celery[auth]:

for using the auth security serializer.

celery[msgpack]:

for using the msgpack serializer.

celery[yaml]:

for using the yaml serializer.

Concurrency

celery[eventlet]:

for using the eventlet pool.

celery[gevent]:

for using the gevent pool.

Transports and Backends

celery[librabbitmq]:

for using the librabbitmq C library.

celery[redis]:

for using Redis as a message transport or as a result backend.

celery[sqs]:

for using Amazon SQS as a message transport (experimental).

celery[tblib]:

for using the task_remote_tracebacks feature.

celery[memcache]:

for using Memcached as a result backend (using pylibmc)

celery[pymemcache]:

for using Memcached as a result backend (pure-Python implementation).

celery[cassandra]:

for using Apache Cassandra/Astra DB as a result backend with DataStax driver.

celery[couchbase]:

for using Couchbase as a result backend.

celery[arangodb]:

for using ArangoDB as a result backend.

celery[elasticsearch]:

for using Elasticsearch as a result backend.

celery[riak]:

for using Riak as a result backend.

celery[dynamodb]:

for using AWS DynamoDB as a result backend.

celery[zookeeper]:

for using Zookeeper as a message transport.

celery[sqlalchemy]:

for using SQLAlchemy as a result backend (supported).

celery[pyro]:

for using the Pyro4 message transport (experimental).

celery[slmq]:

for using the SoftLayer Message Queue transport (experimental).

celery[consul]:

for using the Consul.io Key/Value store as a message transport or result backend (experimental).

celery[django]:

specifies the lowest version possible for Django support.

You should probably not use this in your requirements, it’s here for informational purposes only.

Downloading and installing from source

Download the latest version of Celery from PyPI:

https://pypi.org/project/celery/

You can install it by doing the following,:

$ tar xvfz celery-0.0.0.tar.gz
$ cd celery-0.0.0
$ python setup.py build
# python setup.py install

The last command must be executed as a privileged user if you aren’t currently using a virtualenv.

Using the development version

With pip

The Celery development version also requires the development versions of kombu, amqp, billiard, and vine.

You can install the latest snapshot of these using the following pip commands:

$ pip install https://github.com/celery/celery/zipball/main#egg=celery
$ pip install https://github.com/celery/billiard/zipball/main#egg=billiard
$ pip install https://github.com/celery/py-amqp/zipball/main#egg=amqp
$ pip install https://github.com/celery/kombu/zipball/main#egg=kombu
$ pip install https://github.com/celery/vine/zipball/main#egg=vine

With git

Please see the Contributing section.