EventMachine

EventMachine is a software system designed for writing highly scalable applications for Ruby. It provides event-driven I/O using the reactor pattern. EventMachine is the most popular library for concurrent computing in the Ruby programming language.

Example uses
EventMachine has been used to build a number of different libraries and frameworks in which concurrency is a performance concern. Some examples include:
 * critical networked applications
 * web servers and proxies
 * email and IM production systems
 * authentication/authorization processors