The Undertow subsystem allows you to configure the web server and servlet container settings. It implements the Java Servlet 3.1 Specification as well as websockets and supports HTTP Upgrade and using high performance non-blocking handlers in servlet deployments. The Undertow subsystem also has the ability to act as a high performance reverse proxy which supports mod_cluster.

Within the Undertow subsystem, there are six main components to configure:

  1. Global Settings
  2. Buffer Caches
  3. Server
  4. Servlet Container
  5. Filters
  6. Handlers

Important
The Undertow subsystem also relies on the IO subsystem to provide XNIO workers and buffer pools. The IO subsystem is configured separately and provides a default configuration which should give optimal performance in most cases.