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Kombu is a messaging library for Python.

The aim of Kombu is to make messaging in Python as easy as possible byproviding an idiomatic high-level interface for the AMQ protocol, and alsoprovide proven and tested solutions to common messaging problems.

AMQP is the Advanced Message Queuing Protocol, an open standard protocolfor message orientation, queuing, routing, reliability and security,for which theRabbitMQ messaging server is the most popular implementation.

• Allows application authors to support several message serversolutions by using pluggable transports.

  • AMQP transport using thepy-amqp, orqpid-python libraries.
  • Virtual transports makes it really easy to add support for non-AMQPtransports. There is already built-in support forRedis,Amazon SQS,ZooKeeper,SoftLayer MQ,MongoDB andPyro.
  • In-memory transport for unit testing.

• Supports automatic encoding, serialization and compression of messagepayloads.

• Consistent exception handling across transports.

• The ability to ensure that an operation is performed by gracefullyhandling connection and channel errors.

• Several annoyances withamqplib has been fixed, like supportingtimeouts and the ability to wait for events on more than one channel.

• Projects already usingcarrot can easily be ported by usinga compatibility layer.

For an introduction to AMQP you should read the articleRabbits and warrens,and theWikipedia article about AMQP.

Kombu is using Sphinx, and the latest documentation can be found here:

https://kombu.readthedocs.io/

fromkombuimportConnection,Exchange,Queuemedia_exchange=Exchange('media','direct',durable=True)video_queue=Queue('video',exchange=media_exchange,routing_key='video')defprocess_media(body,message):print(body)message.ack()# connectionswithConnection('amqp://guest:guest@localhost//')asconn:# produceproducer=conn.Producer(serializer='json')producer.publish({'name':'/tmp/lolcat1.avi','size':1301013},exchange=media_exchange,routing_key='video',declare=[video_queue])# the declare above, makes sure the video queue is declared# so that the messages can be delivered.# It's a best practice in Kombu to have both publishers and# consumers declare the queue. You can also declare the# queue manually using:#     video_queue(conn).declare()# consumewithconn.Consumer(video_queue,callbacks=[process_media])asconsumer:# Process messages and handle events on all channelswhileTrue:conn.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')withconnection.Consumer([video_queue,image_queue],callbacks=[process_media])asconsumer:whileTrue:connection.drain_events()

Or handle channels manually:

withconnection.channel()aschannel:producer=Producer(channel, ...)consumer=Consumer(channel)

All objects can be used outside of with statements too,just remember to close the objects after use:

fromkombuimportConnection,Consumer,Producerconnection=Connection()# ...connection.release()consumer=Consumer(channel_or_connection, ...)consumer.register_callback(my_callback)consumer.consume()# ....consumer.cancel()

Exchange and Queue are simply declarations that can be pickledand used in configuration files etc.

They also support operations, but to do so they need to be boundto a channel.

Binding exchanges and queues to a connection will make it usethat connections default channel.

>>> exchange = Exchange('tasks', 'direct')>>> connection = Connection()>>> bound_exchange = exchange(connection)>>> 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.

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 beconfigured to use one of several routing algorithms. The exchangeroutes the messages to consumers by matching the routing key in themessage with the routing key the consumer provides when binding tothe exchange.

• Consumers

  Consumers declares a queue, binds it to a exchange and receivesmessages from it.

• Queues

  Queues receive messages sent to exchanges. The queues are declaredby consumers.

• Routing keys

  Every message has a routing key. The interpretation of the routingkey depends on the exchange type. There are four default exchangetypes defined by the AMQP standard, and vendors can define customtypes (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 andthe routing_key attribute of the consumer are identical.

  • Fan-out exchange

    Always matches, even if the binding does not have a routingkey.

  • Topic exchange

    Matches the routing key property of the message by a primitivepattern matching scheme. The message routing key then consistsof words separated by dots (".", like domain names), andtwo special characters are available; star ("*") and hash("#"). The star matches any word, and the hash matcheszero or more words. For example "*.stock.#" matches therouting keys "usd.stock" and "eur.stock.db" but not"stock.nasdaq".

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 itby doing the following,:

$ python setup.py build# python setup.py install # as root

Join the`celery-users`_ mailing list.

If you have any suggestions, bug reports or annoyances please report themto our issue tracker athttps://github.com/celery/kombu/issues/

Development of Kombu happens at Github:https://github.com/celery/kombu

You are highly encouraged to participate in the development. If you don'tlike Github (for some reason) you're welcome to send regular patches.

This software is licensed under the New BSD License. See the LICENSEfile in the top distribution directory for the full license text.

The maintainers of kombu and thousands of other packages are working with Tidelift to deliver commercial support and maintenance for the open source dependencies you use to build your applications. Save time, reduce risk, and improve code health, while paying the maintainers of the exact dependencies you use. [Learn more.](https://tidelift.com/subscription/pkg/pypi-kombu?utm_source=pypi-kombu&utm_medium=referral&utm_campaign=readme&utm_term=repo)

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