AMQP Messaging Framework for Python
Project description
- Version:
- 0.9.5
Introduction
Kombu is an AMQP messaging queue framework. AMQP is the Advanced Message Queuing Protocol, an open standard protocol for message orientation, queuing, routing, reliability and security.
The aim of Kombu is to make messaging in Python as easy as possible by providing a high-level interface for producing and consuming messages, and provide tested and proven implementations of common messaging patterns.
Kombu has pluggable messaging transports, so it is possible to support several messaging systems. Currently, there is support for AMQP (py-amqplib, pika), Redis, and Beanstalk. Also there’s an in-memory transport for testing purposes.
There are also transports available as plug-ins, like kombu-sqlalchemy (SQLAlchemy transport), or django-kombu (transport using the Django ORM).
Before you start playing with Kombu, you should probably read up on AMQP, and you could start with the excellent article about using RabbitMQ under Python, Rabbits and warrens. For more detailed information, you can refer to the Wikipedia article about AMQP.
Documentation
Kombu is using Sphinx, and the latest documentation is available at GitHub:
Quick overview
from kombu.connection BrokerConnection
from kombu.messaging import Exchange, Queue, Consumer, Producer
media_exchange = Exchange("media", "direct", durable=True)
video_queue = Queue("video", exchange=media_exchange, key="video")
# connections/channels
connection = BrokerConnection("localhost", "guest", "guest", "/")
channel = connection.channel()
# produce
producer = Producer(channel, exchange=media_exchange, serializer="json")
producer.publish({"name": "/tmp/lolcat1.avi", "size": 1301013})
# consume
consumer = Consumer(channel, video_queue)
consumer.register_callback(process_media)
consumer.consume()
# Process messages on all channels
while True:
connection.drain_events()
# Consume from several queues on the same channel:
video_queue = Queue("video", exchange=media_exchange, key="video")
image_queue = Queue("image", exchange=media_exchange, key="image")
consumer = Consumer(channel, [video_queue, image_queue])
consumer.consume()
while True:
connection.drain_events()
Exchange and Queue are simply declarations that can be pickled and used in configuaration files etc.
They also support operations, but to do so they need to be bound to a channel:
>>> exchange = Exchange("tasks", "direct")
>>> connection = BrokerConnection()
>>> channel = connection.channel()
>>> bound_exchange = exchange(channel)
>>> bound_exchange.delete()
# the original exchange is not affected, and stays unbound.
>>> exchange.delete()
raise NotBoundError: Can't call delete on Exchange not bound to
a channel.
Installation
You can install Kombu either via the Python Package Index (PyPI) or from source.
To install using pip,:
$ pip install kombu
To install using easy_install,:
$ easy_install kombu
If you have downloaded a source tarball you can install it by doing the following,:
$ python setup.py build # python setup.py install # as root
Terminology
There are some concepts you should be familiar with before starting:
Producers
Producers sends messages to an exchange.
Exchanges
Messages are sent to exchanges. Exchanges are named and can be configured to use one of several routing algorithms. The exchange routes the messages to consumers by matching the routing key in the message with the routing key the consumer provides when binding to the exchange.
Consumers
Consumers declares a queue, binds it to a exchange and receives messages from it.
Queues
Queues receive messages sent to exchanges. The queues are declared by consumers.
Routing keys
Every message has a routing key. The interpretation of the routing key depends on the exchange type. There are four default exchange types defined by the AMQP standard, and vendors can define custom types (so see your vendors manual for details).
These are the default exchange types defined by AMQP/0.8:
Direct exchange
Matches if the routing key property of the message and the routing_key attribute of the consumer are identical.
Fan-out exchange
Always matches, even if the binding does not have a routing key.
Topic exchange
Matches the routing key property of the message by a primitive pattern matching scheme. The message routing key then consists of words separated by dots (“.”, like domain names), and two special characters are available; star (“*”) and hash (“#”). The star matches any word, and the hash matches zero or more words. For example “*.stock.#” matches the routing keys “usd.stock” and “eur.stock.db” but not “stock.nasdaq”.
Getting Help
Mailing list
Join the carrot-users mailing list.
Bug tracker
If you have any suggestions, bug reports or annoyances please report them to our issue tracker at http://github.com/ask/kombu/issues/
Contributing
Development of Kombu happens at Github: http://github.com/ask/kombu
You are highly encouraged to participate in the development. If you don’t like Github (for some reason) you’re welcome to send regular patches.
License
This software is licensed under the New BSD License. See the LICENSE file in the top distribution directory for the full license text.
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