About Ruby amqp gem

Ruby amqp gem is a widely used, feature-rich, well-maintained asynchronous AMQP 0.9.1 client with batteries included. This library works with Ruby 1.8.7 (except p249, see the FAQ), Ruby 1.9.2, Ruby 1.9.3-preview1, JRuby (highly recommended to Microsoft Windows users), REE and Rubinius, and is licensed under the Ruby License

Versions 0.8.0.RC13 and later of amqp gem implement AMQP 0.9.1 (see also AMQP 0.9.1 spec document) and support RabbitMQ extensions to AMQP 0.9.1.

I know what AMQP is, how do I get started?

See Getting started with amqp gem and other documentation guides.

What is AMQP?

AMQP is an open standard for messaging middleware that emphasizes interoperability between different technologies (for example, Java, .NET, Ruby, Python, Node.js, Erlang, C and so on).

Key features of AMQP are very flexible yet simple routing and binary protocol efficiency. AMQP supports many sophisticated features, for example, message acknowledgements, returning of messages to producer, redelivery of messages that couldn't be processed, load balancing between message consumers and so on.

What is amqp gem good for?

One can use amqp gem to make Ruby applications interoperate with other applications (both Ruby and not). Complexity and size may vary from simple work queues to complex multi-stage data processing workflows that involve dozens or hundreds of applications built with all kinds of technologies.

Specific examples:

Events collectors, metrics & analytics applications can aggregate events produced by various applications (Web and not) in the company network.
A Web application may route messages to a Java app that works with SMS delivery gateways.
MMO games can use flexible routing AMQP provides to propagate event notifications to players and locations.
Price updates from public markets or other sources can be distributed between interested parties, from trading systems to points of sale in a specific geographic region.
Content aggregators may update full-text search and geospatial search indexes by delegating actual indexing work to other applications over AMQP.
Companies may provide streaming/push APIs to their customers, partners or just general public.
Continuous integration systems can distribute builds between multiple machines with various hardware and software configurations using advanced routing features of AMQP.
An application that watches updates from a real-time stream (be it markets data or Twitter stream) can propagate updates to interested parties, including Web applications that display that information in the real time.

Getting started with Ruby amqp gem

Install RabbitMQ

Please refer to the RabbitMQ installation guide. Note that for Ubuntu and Debian we strongly advice that you use RabbitMQ apt repository that has recent versions of RabbitMQ. RabbitMQ packages Ubuntu and Debian ship with are outdated even in recent (10.10) releases. Learn more in the RabbitMQ versions guide.

Install the gem

On Microsoft Windows 7

gem install eventmachine --pre
gem install amqp --pre

On other OSes or JRuby:

gem install amqp --pre

"Hello, World" example

#!/usr/bin/env ruby
# encoding: utf-8

require "rubygems"
# or
#
# require "bundler"
# Bundler.setup
#
# if you use Bundler

require 'amqp'

EventMachine.run do
  connection = AMQP.connect(:host => '127.0.0.1')
  puts "Connected to AMQP broker. Running #{AMQP::VERSION} version of the gem..."

  channel  = AMQP::Channel.new(connection)
  queue    = channel.queue("amqpgem.examples.hello_world", :auto_delete => true)
  exchange = channel.direct("")

  queue.subscribe do |payload|
    puts "Received a message: #{payload}. Disconnecting..."

    connection.close {
      EventMachine.stop { exit }
    }
  end

  exchange.publish "Hello, world!", :routing_key => queue.name
end

Getting started guide explains this and two more examples in detail, and is written in a form of a tutorial. See AMQP Model Explained if you want to learn more about AMQP principles & concepts.

Documentation: tutorials, guides & API reference

We believe that in order to be a library our users really love, we need to care about documentation as much as (or more) code readability, API beauty and autotomated testing across 5 Ruby implementations on multiple operating systems. We do care about our documentation: if you don't find your answer in documentation, we consider it a high severity bug that you should file to us. Or just complain to @rubyamqp on Twitter.

Tutorials

Getting started guide is written as a tutorial that walks you through 3 examples:

The "Hello, world" of messaging, 1-to-1 communication
Blabbr, a Twitter-like example of broadcasting (1-to-many communication)
Weathr, an example of sophisticated routing capabilities AMQP 0.9.1 has to offer (1-to-many or many-to-many communication)

all in under 20 minutes. AMQP 0.9.1 Protocol Tutorial will introduce you to protocol concepts in less than 5 minutes.

Examples

You can find many examples (both real-world cases and simple demonstrations) under examples directory in the repository. Note that those examples are written against version 0.8.0.rc1 and later. 0.6.x and 0.7.x may not support certain AMQP protocol or "DSL syntax" features.

There is also a work-in-progress Messaging Patterns and Use Cases With AMQP documentation guide.

Documentation guides

Documentation guides describe the library itself as well as AMQP concepts, usage scenarios, topics like working with exchanges and queues, error handing & recovery, broker-specific extensions, TLS support, troubleshooting and so on. Most of the documentation is in these guides.

API reference

API reference is up on rubydoc.info and is updated daily.

How to use AMQP gem with Ruby on Rails, Merb, Sinatra and other web frameworks

We cover this subject for multiple Ruby application servers in Connecting to the broker guide, take a look and let us know what wasn't clear.

Migration from amqp gem 0.6.x and 0.7.x

Upgrading from amqp gem 0.6.x and 0.7.x to to 0.8.0.RCs is straightforward, please see amqp gem 0.8.0 migration guide. The same guide explains amqp gem versions history and why you would want to upgrade.

Community

Join Ruby AMQP mailing list
Follow @rubyamqp on Twitter for Ruby AMQP ecosystem updates.
Join also RabbitMQ mailing list (AMQP community epicenter).
Stop by #rabbitmq on irc.freenode.net. You can use Web IRC client if you don't have IRC client installed.

License

AMQP gem is licensed under the Ruby License.

Credits and copyright information

The Original Code is tmm1/amqp.
The Initial Developer of the Original Code is Aman Gupta.

Currently maintained by ruby-amqp group members Special thanks to Dmitriy Samovskiy, Ben Hood and Tony Garnock-Jones.

How can I learn more about AMQP and messaging in general?

AMQP resources

RabbitMQ tutorials that demonstrate interoperability
Wikipedia page on AMQP
AMQP quick reference
John O'Hara on the history of AMQP

Messaging and distributed systems resources

Enterprise Integration Patterns, a book about messaging and use of messaging in systems integration.
A Critique of the Remote Procedure Call Paradigm
A Note on Distributed Computing
Convenience Over Correctness
Joe Armstrong on Erlang messaging vs RPC

(Very) Short FAQ

So, does amqp gem only work with RabbitMQ?

This library is developed and tested primarily with RabbitMQ, although it should be compatible with any server implementing the AMQP 0.9.1 spec. For AMQP 0.8 brokers, use amqp gem version 0.7.x.

Why isn't Ruby 1.8.7.-p249 supported? Will it be supported in the future?

In order to make code like the following (pseudo-synchronous) work

conn = AMQP.connect
ch   = AMQP::Channel.new(conn)

ex   = ch.default_exchange
ex.publish(some_data)

and not be affected by this Ruby 1.8.7-p249-specific bug (super called outside of method), we need to avoid any inheritance for key amqp gem classes: Channel, Queue, Exchange. This will take a moderate refactoring effort, and is likely to happen in 0.8.0.RC15.

How does amqp gem relate to amq-client gem, amq-protocol and libraries like bunny?

See this page about AMQP gems family

celldee/amqp