Celery (software)

Celery is an open source asynchronous task queue or job queue which is based on distributed message passing. While it supports scheduling, its focus is on operations in real time.
Overview.
The execution units, called "tasks", are executed concurrently on one or more worker nodes using multiprocessing, eventlet or gevent. Tasks can execute asynchronously (in the background) or synchronously (wait until ready). Celery is used in production systems, for instance Instagram, to process millions of tasks every day.
Technology.
Celery is written in Python, but the protocol can be implemented in any language. It can also operate with other languages using webhooks. There is also a Ruby-Client called RCelery, a PHP client, a Go client, and a Node.js client.
The recommended message brokers are RabbitMQ or Redis. Additionally, MongoDB, Amazon SQS, CouchDB, IronMQ, and databases (using SQLAlchemy or the Django ORM) are supported in status "experimental".