Ruby amqp gem: the asynchronous Ruby RabbitMQ client

Ruby amqp gem is a feature-rich,
EventMachine-based RabbitMQ client with batteries included.

It’s the original RabbitMQ client for Ruby. These days there are very
solid alternatives available: Bunny for MRI and March Hare for JRuby.

It implement AMQP
0.9.1 and
support RabbitMQ extensions to AMQP
0.9.1.

A Word of Warning: Use This Only If You Already Use EventMachine

Unless you already use EventMachine, there is no real reason to
use this client. Consider Bunny or March Hare instead.

amqp gem brings in a fair share of EventMachine complexity which
cannot be fully eliminated. Event loop blocking, writes that happen
at the end of loop tick, uncaught exceptions in event loop silently killing it:
it’s not worth the pain unless you’ve already deeply invested in EventMachine
and understand how it works.

So, just use Bunny or March Hare. You will be much happier.

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

See Getting started with amqp gem and other amqp gem documentation guides.
We recommend that you read AMQP 0.9.1 Model Explained, too.

What is RabbitMQ?

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

Key features of RabbitMQ are very flexible yet simple routing and
binary protocol efficiency. RabbitMQ supports many sophisticated
features, for example, message acknowledgements, queue length limit,
message TTL, 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 guides. Note that for Ubuntu and Debian we strongly advice that you
use the Cloudsmith apt repository that has recent versions of RabbitMQ.

Install the gem

On Microsoft Windows

gem install eventmachine
gem install amqp

On other OSes

gem install amqp

“Hello, World” example

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

require 'amqp'

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

  ch  = AMQP::Channel.new(connection)
  q   = ch.queue("amqpgem.examples.hello_world", :auto_delete => true)
  x   = ch.default_exchange

  q.subscribe do |metadata, payload|
    puts "Received a message: #{payload}. Disconnecting..."

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

  x.publish "Hello, world!", :routing_key => q.name
end

Getting started guide explains this and two more examples in detail,
and is written in a form of a tutorial. See AMQP 0.9.1 Model Explained if you want
to learn more about RabbitMQ protocol principles & concepts.

Supported Ruby Versions

Modern amqp gem release series support

• Ruby 2.4
• Ruby 2.3
• Ruby 2.2

The last series to support Ruby 1.9 was 1.5.x.

JRuby users should use March Hare.

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 Concepts will introduce you to protocol concepts
in less than 5 minutes.

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.

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.

API reference

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

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

We cover Web application integration for multiple Ruby Web servers in Connecting to the broker guide.

Community

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

Maintainer Information

amqp gem is maintained by Michael Klishin.

Continuous Integration

Links

• API reference
• Documentation guides
• Code Examples
• Issue tracker
• Continous integration status

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.
• Copyright © 2008 - 2010 Aman Gupta.
• Contributions from Jakub Stastny are Copyright © 2011-2012 VMware, Inc.
• Copyright © 2010 — 2017 ruby-amqp group members.

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

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

Documentation Resources

• AMQP 0.9.1 Model Explained
• RabbitMQ tutorials that demonstrate interoperability