Those of you who have worked with previous versions of WildFly will know that historically, JBoss has always included Tomcat, or a fork of Tomcat (named JBoss Web), as the application server's web container.
The decision to replace JBoss Web came about as a new web container was required, one that supports new Java EE 7 requirements, such as web sockets and an HTTP upgrade. It was also decided that the new web server should be lightweight and flexible, and have better performance. The resulting server is super responsive, can scale to over a million connections, and has exceptional throughput.
Undertow is written in Java and based on the Non-blocking Input/Output API (often referred to as New Input/Output or just NIO). With a composition-based architecture and built using a fluent builder API, Undertow can be easily configured, giving you as much or as little functionality as you need. By chaining handlers together, you can build anything from...