# About EventMachine [![Build Status](https://travis-ci.org/eventmachine/eventmachine.svg?branch=master)](https://travis-ci.org/eventmachine/eventmachine) [![Code Climate Maintainability](https://api.codeclimate.com/v1/badges/e9b0603462905d5b9118/maintainability)](https://codeclimate.com/github/eventmachine/eventmachine/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](http://en.wikipedia.org/wiki/Reactor_pattern), much like [JBoss Netty](http://www.jboss.org/netty), [Apache MINA](http://mina.apache.org/), Python's [Twisted](http://twistedmatrix.com), [Node.js](http://nodejs.org), 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? ## * Scalable event-driven servers. Examples: [Thin](http://code.macournoyer.com/thin/) or [Goliath](https://github.com/postrank-labs/goliath/). * Scalable asynchronous clients for various protocols, RESTful APIs and so on. Examples: [em-http-request](https://github.com/igrigorik/em-http-request) or [amqp gem](https://github.com/ruby-amqp/amqp). * Efficient network proxies with custom logic. Examples: [Proxymachine](https://github.com/mojombo/proxymachine/). * File and network monitoring tools. Examples: [eventmachine-tail](https://github.com/jordansissel/eventmachine-tail) and [logstash](https://github.com/logstash/logstash). ## What platforms are supported by EventMachine? ## EventMachine supports Ruby 1.8.7 through 2.6, REE, 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](https://rubygems.org/) gem install eventmachine or add this to your Gemfile if you use [Bundler](http://gembundler.com/): gem "eventmachine" ## Getting started ## For an introduction to EventMachine, check out: * [blog post about EventMachine by Ilya Grigorik](http://www.igvita.com/2008/05/27/ruby-eventmachine-the-speed-demon/). * [EventMachine Introductions by Dan Sinclair](http://everburning.com/news/eventmachine-introductions.html). ### Server example: Echo server ### Here's a fully-functional echo server written with EventMachine: ```ruby 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.run { EventMachine.start_server "127.0.0.1", 8081, EchoServer } ``` ## EventMachine documentation ## Currently we only have [reference documentation](http://rdoc.info/github/eventmachine/eventmachine/frames) and a [wiki](https://github.com/eventmachine/eventmachine/wiki). ## Community and where to get help ## * Join the [mailing list](http://groups.google.com/group/eventmachine) (Google Group) * Join IRC channel #eventmachine on irc.freenode.net ## 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. ## Alternatives ## If you are unhappy with EventMachine and want to use Ruby, check out [Celluloid](https://celluloid.io/).