Resin (software)

Resin is a web server and Java application server from Caucho Technology. In addition to Resin (GPL), Resin Pro is available for enterprise and production environments with a license. Resin supports the Java EE standard as well as a mod_php/PHP like engine called Quercus.
While Resin (GPL) is free for use in production, Resin Pro includes optimizations such as:
Although a Java-based server, key pieces of Resin's core networking are written in highly optimized C. Caucho states Java is the layer that allows Resin to be "full featured" while C provides the speed. Resin, which was released in 1999, predates Apache Tomcat, and is one of the most mature application servers and web servers.
Product features.
Resin Pro has been engineered to include:
Scalability
Development
Production Ready
"App Server"'
Web Server
Usage.
Resin's market share is small in the grand scheme of Java Application Servers, but some high traffic sites use it, such as Toronto Stock Exchange, Salesforce.com, Condé Nast (parent company of Wired, Vogue, GQ), CNET. NetCraft's February 2012 Survey stated Resin grew to 4,700,000 sites; Resin was the only Java-based web server mentioned.
A 2012-page on a Caucho wiki site describes a test procedure with results showing that tested 0k (empty HTML page), 1K, 8K and 64K byte files. At every level Resin matched or exceeded nginx web server performance.
Quercus.
Quercus is a Java-based implementation of the PHP language that is included with Resin. According to a slideshow presented by Emil Ong (from Caucho), to a San Francisco Java Meetup Group in April 2008 pertaining to Resin 3.1, an essential difference in the operation of Quercus between the Resin Open Source and the Resin Professional editions is that in Resin Professional the PHP is compiled to Java bytecode whereas in the open source version PHP is executed by an interpreter.
Caucho stated in 2007 that Quercus was faster than standard PHP 5 (PHP 8 with JIT is much faster than older PHP versions; PHP 5 is no longer supported) although this is only true for the JIT-compiled version in Resin Professional. Quercus ships with Resin.
Licensing.
One license covers all components of the Resin architecture.
Resin is provided in both an open source GPL license and a Pro version with enhancements for enterprises.