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EventMachine: fast, simple event-processing library for Ruby programs

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About EventMachine Build Status Code Climate Maintainability

What is EventMachine

EventMachine is an event-driven I/O and lightweight concurrency library for Ruby. It provides event-driven I/O using the Reactor pattern, much like JBoss Netty, Apache MINA, Python's Twisted, Node.js, libevent and libev.

EventMachine is designed to simultaneously meet two key needs:

  • Extremely high scalability, performance and stability for the most demanding production environments.
  • An API that eliminates the complexities of high-performance threaded network programming, allowing engineers to concentrate on their application logic.

This unique combination makes EventMachine a premier choice for designers of critical networked applications, including Web servers and proxies, email and IM production systems, authentication/authorization processors, and many more.

EventMachine has been around since the early 2000s and is a mature and battle-tested library.

What EventMachine is good for?

What platforms are supported by EventMachine?

EventMachine supports Ruby 2.0.0 through 2.7, JRuby and works well on Windows as well as many operating systems from the Unix family (Linux, Mac OS X, BSD flavors).

Install the gem

Install it with RubyGems

gem install eventmachine

or add this to your Gemfile if you use Bundler:

gem 'eventmachine'

Getting started

For an introduction to EventMachine, check out:

Server example: Echo server

Here's a fully-functional echo server written with EventMachine:

 require 'eventmachine'

module EchoServer def post_init puts "-- someone connected to the echo server!" end

def receive_data data send_data ">>>you sent: #{data}" close_connection if data =~ /quit/i end

def unbind puts "-- someone disconnected from the echo server!" end end

Note that this will block current thread. { EventMachine.start_server "", 8081, EchoServer }

EventMachine documentation

Currently we only have reference documentation and a wiki.

Community and where to get help

  • Join the mailing list (Google Group)
  • Join IRC channel #eventmachine on

License and copyright

EventMachine is copyrighted free software made available under the terms of either the GPL or Ruby's License.

Copyright: (C) 2006-07 by Francis Cianfrocca. All Rights Reserved.


If you are unhappy with EventMachine and want to use Ruby, check out Celluloid.

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