Tech Geeking: Ruby Rails Mongrel Thin Zed Shaw
Perm URL with updates: http://xahlee.info/comp/ruby_rails_mongrel_thin_zed_shaw.html
Mongrel (web server) is a thin web server, written in Ruby, by Zed Shaw.
Here's a interesting characteristic:
… It is used to run Ruby web applications and presents a standard HTTP interface. This makes layering other servers in front of it possible using a web proxy, a load balancer, or a combination of both, instead of having to use more conventional methods employed to run scripts such as FastCGI or SCGI to communicate.
This is made possible by integrating a custom high-performance HTTP request parser implemented using Ragel.
Mongrel was the first web server used by Twitter, and inspired Node.js according to Ryan Dahl 
Shaw subsequently created Mongrel2, an open-source “language agnostic” web server and the successor to Mongrel server.
After the original author Zed Shaw left the Ruby on Rails-scene the releases of Mongrel stopped. The current release 1.1.5 is no longer able to install in Ruby versions higher than 1.9.2 …
A new and maintained server, called Thin, uses the Mongrel parser.
“Thin”, home page at 〔http://code.macournoyer.com/thin/〕
The guy, Zed Shaw, seems quite a colorful character. He is all pissed at the Ruby community, and left the Ruby community, and started Mongrel2 webserver, and one of its specific mantra, burned into its official doc, is “language agnostic”.
TechCrunch reports: 〔Zed Shaw Puts The Smack Down On The Rails Community By Michael Arrington. @ techcrunch.com…〕
Zed has removed the article. It's quite scathing. Here's a local copy saved from web archive: Rails_Is_A_Ghetto_by_Zed_Shaw_2007-12-31.txt. A very entertaining read, as well as getting you into some of the guts of Ruby community.
Zed's website: http://www.zedshaw.com/