h1. About amqp gem "!http://travis-ci.org/ruby-amqp/amqp.png!":http://travis-ci.org/ruby-amqp/amqp

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, Ruby 1.9.2, JRuby, REE and Rubinius, and is
licensed under the "Ruby License":http://www.ruby-lang.org/en/LICENSE.txt.
Versions 0.8.0 and later of amqp gem implement "AMQP 0.9.1":http://bit.ly/hw2ELX.


h2. I know what AMQP is, how do I get started?

See "Getting started with amqp gem" and "Documentation: tutorials, guides & API reference" sections below.


h2. What is AMQP?

AMQP is an "open standard for messaging middleware":http://www.amqp.org/confluence/display/AMQP/About+AMQP that
emphasizes interoperability between different technologies (for example, Java, .NET,
Ruby, Python, C and so on).

Key features of AMQP are very flexible yet simple routing and binary protocol
efficiency.


h2. 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:

 * A Web application may route messages to a Java app that works
   with SMS delivery gateways.

 * Periodically run (Cron-driven) application may notify other systems that
   there are some new results.

 * Content aggregators may update full-text search and geospatial search indexes
         by delegating actual indexing work to other applications over AMQP.

 * Companies may provide "Firehose-like" push APIs to their customers, partners
   or just general public.

 * A new shiny Ruby-based system may be integrated with an existing C++-based component
   using 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.



h2(Getting_started_with_amqp_gem). Getting started with amqp gem

h3. Install RabbitMQ

Please refer to "RabbitMQ installation guide":http://www.rabbitmq.com/install.html
Note that for Ubuntu and Debian we strongly advice that you use "RabbitMQ apt repository":http://www.rabbitmq.com/debian.html#apt
that has recent versions of RabbitMQ. Learn more in {file:docs/RabbitMQVersions.textile RabbitMQ versions} section.


h3. Install the gem

<pre>gem install amqp</pre>


h3. "Hello, World" example

<pre><code>
#!/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 {
      EM.stop { exit }
    }
  end

  exchange.publish "Hello, world!", :routing_key => queue.name
end
</code></pre>

(see "as a Gist":https://gist.github.com/910211)



h2(#Documentation_tutorials_guides_API_reference). Documentation: tutorials, guides & API reference

We believe that in order to be the best Ruby AMQP client out there, we need to care about documentation as much as
code readability, API beauty and autotomated testing across 5 Ruby implementations on 3 operating systems.


h3. Tutorials

We have written and maintain "Getting started guide":http://rdoc.info/github/ruby-amqp/amqp/master/file/docs/GettingStarted.textile that is written in form of a tutorial.
Check it out! If something isn't clear, every guide explains how to contact documentation authors.


h3. Examples

You can find many examples (both real-world cases and simple demonstrations)
under "examples directory":https://github.com/ruby-amqp/amqp/tree/master/examples 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.


h3. Guides

"Documentation guides":http://rdoc.info/github/ruby-amqp/amqp/master/file/docs/DocumentationGuidesIndex.textile describe
the library itself as well as AMQP usage scenarios, routing, error handing & recovery, broker-specific extensions, TLS support  and so on.


h3. API reference

"Reference documentation":http://rdoc.info/github/ruby-amqp/amqp/master/frames is up on rdoc.info and is updated daily.

*If you don't find your answer in documentation, we consider it a high severity bug* that you should "file to us":http://github.com/ruby-amqp/amqp/issues.


h2. How to use AMQP gem with Ruby on Rails, Merb, Sinatra and other web frameworks

To use AMQP gem from web applications, you would need to have EventMachine reactor running.
If you use "Thin":http://code.macournoyer.com/thin/ or "Goliath":https://github.com/postrank-labs/goliath/,
you are all set: those two servers use EventMachine under the hood.

With other web servers, you need to start EventMachine reactor in a separate thread like this:

<pre>Thread.new { EM.run }</pre>

Otherwise EventMachine will block current thread.


Then connect to AMQP broker:

<pre>amqp_connection = AMQP.connect(:host => "localhost", :user => "guest", :pass => "guest", :vhost => "/")</pre>

In a Ruby on Rails app, probably the best place for this code is initializer
(like config/initializers/amqp.rb). For Merb apps, it is config/init.rb. For
Sinatra and pure Rack applications, place it next to other configuration
code.

If you want to integrate AMQP with "Thin":http://code.macournoyer.com/thin/, "Goliath":https://github.com/postrank-labs/goliath/ or
some other EventMachine-based software which already runs an event loop, you might want to use following code:

<pre>EM.next_tick { AMQP.connect(...) }</pre>

So in case EventMachine reactor isn't running yet on server/application boot,
connection won't fail but instead wait for reactor to start.

Same separate thread technique can be used to make EventMachine play nicely with other
libraries that would block current thread (like "File::Tail":http://rubygems.org/gems/file-tail).


h2. Using amqp gem in your app/library using Bundler

With Bundler, add this line to your Gemfile:

<pre>gem "amqp"</pre>

If you want to use edge version (usually there is no need to):

<pre>
gem "amqp", :git => "git://github.com/ruby-amqp/amqp.git", :branch => "master"
</pre>



h2. How does amqp gem relate to amq-client gem, amq-protocol and libraries like bunny?

See "this page about AMQP gems family":https://github.com/ruby-amqp/amq-client/blob/master/README.textile


h2. How can I learn more?

h3. AMQP resources

 * "RabbitMQ tutorials":http://www.rabbitmq.com/getstarted.html that demonstrate interoperability
 * "Wikipedia page on AMQP":http://en.wikipedia.org/wiki/Advanced_Message_Queuing_Protocol
 * "AMQP quick reference":http://www.rabbitmq.com/amqp-0-9-1-quickref.html
 * John O'Hara on the "history of AMQP":http://www.acmqueue.org/modules.php?name=Content&pa=showpage&pid=485

h3. Messaging and distributed systems resources

 * "Enterprise Integration Patterns":http://www.eaipatterns.com/, a book about messaging and use of messaging in systems integration.

 * "A Critique of the Remote Procedure Call Paradigm":http://www.cs.vu.nl/~ast/publications/euteco-1988.pdf
 * "A Note on Distributed Computing":http://research.sun.com/techrep/1994/smli_tr-94-29.pdf
 * "Convenience Over Correctness":http://steve.vinoski.net/pdf/IEEE-Convenience_Over_Correctness.pdf
 * Joe Armstrong on "Erlang messaging vs RPC":http://armstrongonsoftware.blogspot.com/2008/05/road-we-didnt-go-down.html


h2. Community

 * "Ruby AMQP mailing list":http://groups.google.com/group/ruby-amqp
 * "RabbitMQ mailing list":https://lists.rabbitmq.com/cgi-bin/mailman/listinfo/rabbitmq-discuss (AMQP community epicenter).
 * "Jabber room for contributors":xmpp://amqp-dev@conf.netlab.cz


h2. License

AMQP gem is licensed under the "Ruby License":http://www.ruby-lang.org/en/LICENSE.txt.



h2. Credits and copyright information

* The Original Code is "tmm1/amqp":http://github.com/tmm1/amqp.
* The Initial Developer of the Original Code is Aman Gupta.
* Copyright (c) 2008 - 2010 "Aman Gupta":http://github.com/tmm1.
* Contributions from "Jakub Stastny":http://github.com/botanicus are Copyright (c) 2011 VMware, Inc.
* Copyright (c) 2010 — 2011 "ruby-amqp":https://github.com/ruby-amqp group members.

Currently maintained by "ruby-amqp":https://github.com/ruby-amqp group members
Special thanks to Dmitriy Samovskiy, Ben Hood and Tony Garnock-Jones.



h2. FAQ

h3. So, does amqp gem only work with RabbitMQ?

This library was tested primarily with "RabbitMQ":http://rabbitmq.com, although it should be compatible with any
server implementing the "AMQP 0.9.1 spec":http://bit.ly/hw2ELX. For AMQP 0.8.0 brokers,
use version 0.7.


h2. Links

* "API reference":http://rdoc.info/github/ruby-amqp/amqp/master/frames
* "Examples":https://github.com/ruby-amqp/amq-protocol/tree/master/examples/
* "Issue tracker":http://github.com/ruby-amqp/amqp/issues
* "Continous integration server":http://travis-ci.org/#!/ruby-amqp/amqp