Jetty/Howto/Configure AJP13

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Configuring AJP13 Using mod_jk or mod_proxy_ajp

The Apache web server is frequently used as a server in front of a servlet container. While there are no real technical reasons to front Jetty with Apache, you might choose to do so for software load balancing, to fit with a corporate infrastructure, or simply to stick with a known deployment structure.

There are three main ways to connect Apache to Jetty:

  1. Using Apache mod_proxy and a normal Jetty HTTP connector.
  2. Using Apache mod_proxy_ajp and the Jetty AJP connector.
  3. Using Apache mod_jk and the Jetty AJP connector.

We recommend using the HTTP connectors for the following reasons:

  • Jetty performs significantly better with HTTP.
  • The AJP protocol is poorly documented and has many version irregularities.

If you must use AJP, the mod_proxy_ajp module is better than mod_jk. Previously, the load balancing capabilities of mod_jk meant that you had to use (tolerate) it, but with Apache 2.2, mod_proxy_balancer is available and works over HTTP and AJP connectors.

Using HTTP

We recommend this mechanism to connect Apache and Jetty.

To configure Apache to use mod_proxy, mod_proxy_http and/or mod_proxy_balancer with HTTP, see Configuring mod_proxy.

Using AJP

We do NOT recommend AJP. Use HTTP and mod_proxy instead (see above).

We do not recommend AJP for these reasons:

  • Historically mod_jk has had intermittent maintenance and bad versioning practices. This make it difficult to select a known, good version that is fully compatible with the AJP connector you are running.
  • The mod_proxy plugin is more actively maintained and the mod_proxy_balancer supports a richer set of options for load balancing.
  • Jetty is optimized to deal with the text-based HTTP protocol, and the servlet API also exposes the text nature of HTTP to the application. There are no measurable benefits for using Apache to convert text HTTP to the binary AJP protocol, only for Jetty to have to convert back. Some tests have shown 15% more throughput with mod_proxy than with mod_ajp.
  • With cometd style applications, neither mod_jk nor mod_proxy scale well. However, mod_proxy does make greater use of connections, so it is a better choice for moderate comet load. For full comet scaling, you should either directly expose Jetty to the Internet, or use an async load balancer like Nginx.

Note however that the Jetty team still supports AJP, and we will strive to fix any issues found.

The Jetty AJP Connector

To use AJP with either mod_jk or mod_proxy_ajp, you need to configure Jetty with an AJP13 connector. You can do so by adding etc/jetty-ajp.xml to the command line. You can also modify an existing jetty.xml file with:

 <Call name=<span class="code-quote">"addConnector"</span>>
     <New class=<span class="code-quote">"org.eclipse.jetty.ajp.Ajp13SocketConnector"</span>>
       <Set name=<span class="code-quote">"port"</span>>8009</Set>

The full options for the Ajp13SocketConnector are available in the javadoc.


With Apache 2.2 mod_proxy_ajp is an extension of the mod_proxy module, and works in conjunction with the mod_proxy_balancer module. Prior to 2.2, mod_proxy did not support AJP.


Apache Win32 Linux (Ubuntu)
Apache 1.3 no mod_proxy_ajp bundled no mod_proxy_ajp bundled
Apache 2.0 (2.0.59) no mod_proxy_ajp bundled
no mod_proxy_ajp bundled
Apache 2.2




The configuration of mod_proxy_ajp is identical to the [[JETTY/Howto_Configure_mod_proxy configuration of mod_proxy], except that you can use ajp:// as a protocol instead of http:// when specifying destinations (workers) in ProxyPass and BalancerMember elements.

Apache 2.2 normally bundles mod_proxy, mod_proxy_ajp and mod_proxy_balancer, so often you do not need to install them separately. If they are separately bundled by your operating system (for example, as RPMs or Debians), ensure that they are installed.

The Apache configuration structure can vary greatly with operating system distros, and there might be some template configurations for mod_proxy. If not, add the entry below in your httpd.conf apache configuration file located in <apache-root>/conf/ directory:

 LoadModule proxy_module modules/
 LoadModule proxy_ajp_module modules/
 LoadModule proxy_balancer_module modules/
 # always keep the host header
 ProxyPreserveHost On
 # map to cluster
 ProxyPass /test balancer:</nowiki><span class="code-comment">//my_cluster/test stickysession=JSESSIONID nofailover=On
 </span>ProxyPass /demo balancer:<span class="code-comment">//my_cluster/demo stickysession=JSESSIONID nofailover=On
 # define the balancer, with http and/ or ajp connections
 <Proxy balancer:</nowiki><span class="code-comment">//my_cluster>
 </span>    BalancerMember ajp:<span class="code-comment">//yourjettyhost1:8009
 </span>    BalancerMember ajp:<span class="code-comment">//yourjettyhost2:8009


  • LoadModule–tells your Apache server to load a module library, and shows where it is located.
  • ProxyPreserveHost On–keeps the original Host Header. WE HIGHLY RECOMMENDED THIS FOR ALL PROXY CONFIGURATIONS.
  • ProxyPass–Maps a path to a proxied destination. The destination might be a http:// or ajp:// URL to directly map to a single server, or it might be a balancer:// URL to map to a cluster.
  • 'Proxy balancer://–defines the nodes (workers) in the cluster. Each member might be a {http://}} or ajp:// URL or another balancer:// URL for a cascaded load balancing configuration.


We do NOT recommend using mod_jk.


Apache mod_jk Win32 Linux (Ubuntu)
Apache 1.3 No HTTPD Binary Available
mod_jk-1.2.14 Not yet tested
mod_jk-1.2.15 Not yet tested
mod_jk-1.2.18 Not yet tested
mod_jk-1.2.19 Not yet tested
Apache 2.0 (2.0.59)
mod_jk-1.2.14 Check.png
mod_jk-1.2.15 Check.png
mod_jk-1.2.18 Check.png
mod_jk-1.2.19 Check.png
Apache 2.2
mod_jk-1.2.14 No Binary Available
mod_jk-1.2.15 No Binary Available
mod_jk-1.2.18 Check.png
mod_jk-1.2.19 Check.png

Configuring Apache HTTPD Server with mod_jk

To configure an Apache HTTPD server with mod_jk:

  1. Put into your <apache-root>/modules/ directory.
  2. Download here:
  3. Add the entry below in your httpd.conf apache configuration file located in <apache-root>/conf/ directory.
<IfModule !mod_jk.c>   LoadModule jk_module modules/   </IfModule>   <IfModule mod_jk.c>   JkWorkersFile "conf/"   JkLogFile "logs/mod_jk.log"   JkLogLevel info   JkLogStampFormat "[%a %b %d %H:%M:%S %Y] "   JkOptions +ForwardKeySize +ForwardURICompat   </IfModule>

* LoadModule jk_module modules/ tells your Apache server to load the mod_jk libray and where to find it.
* JkWorkersFile conf/ tells mod_jk where your is located.
* JkLogFile logs/mod_jk.log tells mod_jk where to write mod_jk related Logs.
  1. After adding the mod_jk configuration you can add a VirtualHost entry in the same file (httpd.conf) as long as it is located below your mod_jk configuration entry:
 <VirtualHost host:*>
 	ServerName yourserver
  	ServerAdmin user@yourserver
  	## You can add further entries concerning log-files, log-level, URL-rewriting, ...
  	## Pass requests through to jetty worker
  	JkMount /* jetty
  1. Add a worker file in your <apache-root>/conf/.
  1. Add the entries below, and make sure to specify your IP address or hostname in property entry to where your jetty application is runnning.
 worker.jetty.port=8009<server name or ip where your jetty will be running>