What is AJP? A short introduction

• AJP is used to communicate between the web server and the servlet container
• The Apache JServ Protocol (AJP) is a binary protocol that can proxy inbound requests from a web server through to an application server that sits behind the web server. The web server is a “reverse proxy,” meaning, its purpose is to handle incoming traffic from the Internet on behalf of the application server.
• Gal Shachor was the original designer of this protocol. There is, apparently, no current documentation of how the protocol works.
• Apache JServ is a 100% pure Java servlet engine fully compliant with the JavaSoft Java Servlet APIs 2.0 specification
• Web implementers typically use AJP in a load-balanced deployment where one or more front-end web servers feed requests into one or more application servers.
• AJP runs in Apache HTTP Server using the mod_jk plugin.
• When it was developed the goals of this protocol was
  • Increasing performance (speed, specifically).
  • Adding support for SSL, so that isSecure() and getScheme() will function correctly within the servlet container.
• A binary format was presumably chosen over the more readable plain text for reasons of performance.