GitHub - celery/py-amqp: amqplib fork (original) (raw)

Python AMQP 0.9.1 client library

About

This is a fork of amqplib which was originally written by Barry Pederson. It is maintained by the Celery project, and used by kombu as a pure python alternative when librabbitmq is not available.

This library should be API compatible with librabbitmq.

Differences from amqplib

• Supports draining events from multiple channels (Connection.drain_events)
• Support for timeouts
• Channels are restored after channel error, instead of having to close the connection.
• Support for heartbeats

  • Connection.heartbeat_tick(rate=2) must called at regular intervals (half of the heartbeat value if rate is 2).
  • Or some other scheme by using Connection.send_heartbeat.

• Supports RabbitMQ extensions:
  • Consumer Cancel Notifications
    * by default a cancel results in ChannelError being raised
    * but not if a on_cancel callback is passed to basic_consume.
  • Publisher confirms
    * Channel.confirm_select() enables publisher confirms.
    * Channel.events['basic_ack'].append(my_callback) adds a callback to be called when a message is confirmed. This callback is then called with the signature (delivery_tag, multiple).
  • Exchange-to-exchange bindings: exchange_bind / exchange_unbind.
    * Channel.confirm_select() enables publisher confirms.
    * Channel.events['basic_ack'].append(my_callback) adds a callback to be called when a message is confirmed. This callback is then called with the signature (delivery_tag, multiple).
  • Authentication Failure Notifications
    Instead of just closing the connection abruptly on invalid credentials, py-amqp will raise an AccessRefused error when connected to rabbitmq-server 3.2.0 or greater.
• Support for basic_return
• Uses AMQP 0-9-1 instead of 0-8.
  • Channel.access_request and ticket arguments to methodsremoved.
  • Supports the arguments argument to basic_consume.
  • internal argument to exchange_declare removed.
  • auto_delete argument to exchange_declare deprecated
  • insist argument to Connection removed.
  • Channel.alerts has been removed.
  • Support for Channel.basic_recover_async.
  • Channel.basic_recover deprecated.
• Exceptions renamed to have idiomatic names:
  • AMQPException -> AMQPError
  • AMQPConnectionException -> ConnectionError``
  • AMQPChannelException -> ChannelError``
  • Connection.known_hosts removed.
  • Connection no longer supports redirects.
  • exchange argument to queue_bind can now be empty to use the "default exchange".
• Adds Connection.is_alive that tries to detect whether the connection can still be used.
• Adds Connection.connection_errors and .channel_errors, a list of recoverable errors.
• Exposes the underlying socket as Connection.sock.
• Adds Channel.no_ack_consumers to keep track of consumer tags that set the no_ack flag.
• Slightly better at error recovery

Quick overview

Simple producer publishing messages to test queue using default exchange:

import amqp

with amqp.Connection('broker.example.com') as c: ch = c.channel() ch.basic_publish(amqp.Message('Hello World'), routing_key='test')

Producer publishing to test_exchange exchange with publisher confirms enabled and using virtual_host test_vhost:

import amqp

with amqp.Connection( 'broker.example.com', exchange='test_exchange', confirm_publish=True, virtual_host='test_vhost' ) as c: ch = c.channel() ch.basic_publish(amqp.Message('Hello World'), routing_key='test')

Consumer with acknowledgments enabled:

import amqp

with amqp.Connection('broker.example.com') as c: ch = c.channel() def on_message(message): print('Received message (delivery tag: {}): {}'.format(message.delivery_tag, message.body)) ch.basic_ack(message.delivery_tag) ch.basic_consume(queue='test', callback=on_message) while True: c.drain_events()

Consumer with acknowledgments disabled:

import amqp

with amqp.Connection('broker.example.com') as c: ch = c.channel() def on_message(message): print('Received message (delivery tag: {}): {}'.format(message.delivery_tag, message.body)) ch.basic_consume(queue='test', callback=on_message, no_ack=True) while True: c.drain_events()

Speedups

This library has experimental support of speedups. Speedups are implemented using Cython. To enable speedups, CELERY_ENABLE_SPEEDUPS environment variable must be set during building/installation. Currently speedups can be installed:

1. using source package (using --no-binary switch):

CELERY_ENABLE_SPEEDUPS=true pip install --no-binary :all: amqp

1. building directly source code:

CELERY_ENABLE_SPEEDUPS=true python setup.py install

Further

• Differences between AMQP 0.8 and 0.9.1

  http://www.rabbitmq.com/amqp-0-8-to-0-9-1.html

• AMQP 0.9.1 Quick Reference

  http://www.rabbitmq.com/amqp-0-9-1-quickref.html

• RabbitMQ Extensions

  http://www.rabbitmq.com/extensions.html

• For more information about AMQP, visit

  http://www.amqp.org

• For other Python client libraries see:

  http://www.rabbitmq.com/devtools.html#python-dev

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