Apache JServ Protocol

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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.

It also supports some monitoring in that the web server can ping the application server. Web implementors typically use AJP in a load-balanced deployment where one or more front-end web servers feed requests into one or more application servers. Sessions are redirected to the correct application server using a routing mechanism wherein each application server instance gets a name (called a route). In this scenario the web server functions as a reverse proxy for the application server.

AJP runs in Apache HTTP Server 1.x using the mod_jk plugin and in Apache 2.x using the provided Proxy AJP, mod_proxy and proxy balancer modules together. Implementations exist for the not-yet-released lighttpd version 1.5,[1] nginx,[2] Grizzly 2.1,[3] and the Internet Information Server.[4]

The Apache Tomcat and JBoss AS/WildFly servlet containers support AJP.


Alexei Kosut originally developed the Apache JServ Protocol in July 1997[5] but the version 1.0 specification was published later on July 29, 1998.[6] He also wrote the first implementations of it in the same month, with the releases of the Apache JServ Servlet Engine 0.9 and the Apache mod_jserv 0.9a (released on July 30, 1997).[7]

The specification was updated to version 1.1 on September 9, 1998.[8] Also in 1998, a revamped protocol was created and published in specification versions 2[9] and 2.1,[5] however it was never adopted.

The current specification remains at version 1.3,[10] however there is a published extension proposal.[11]

See also


  1. ^ lighttpd ModProxyCore
  2. ^ Weibin Yao: nginx_ajp_module
  3. ^ "AJP". Grizzly 2.3 User's Guide. java.net. Retrieved 2013-04-29. 
  4. ^ BonCode AJP 1.3 Connector
  5. ^ a b Barbieri, Federico; Fumagalli, Pierpaolo; Kluft, Ian; Korthof, Ed; Mazzocchi, Stefano; Pool, Martin (June 30, 1998). "Apache JServ Protocol Version 2.1". Java Apache Project. Archived from the original on 2003-08-04. 
  6. ^ Kosut, Alexei (July 29, 1998). "Apache JServ Protocol Version 1.0". Java Apache Project. Archived from the original on 2003-04-15. 
  7. ^ "History of Changes - Apache JServ Project". Java Apache Project. Archived from the original on 2003-04-16. 
  8. ^ Kosut, Alexei (September 9, 1998). "Apache JServ Protocol Version 1.1". Java Apache Project. Archived from the original on 2003-08-04. 
  9. ^ Kluft, Ian; Korthof, Ed; Mazzocchi, Stefano (February 15, 1998). "Apache JServ Protocol Version 2". Java Apache Project. Archived from the original on 2003-08-05. 
  10. ^ "AJP Protocol Reference - AJPv13". Apache Tomcat. Retrieved 2016-08-20. 
  11. ^ "AJP Protocol Reference - AJPv13 Extension Proposal". Apache Tomcat. Retrieved 2016-08-20. 

External links