Link Apache to Jboss with mod_jk

Using Mod_jk 1.2 with JBoss

Using mod_jk 1.2.x with JBoss/Tomcat bundle and Apache2

Quick Overview

  1. Download Apache2
  2. Download modjk 1.2.x
  3. Change the main Apache config to include modjk config
  4. Create the modjk config
  5. Configure the modjk workers (which JBoss/Tomcat nodes Apache uses)
  6. Configure the Apache URIs served by modjk (the applications served by JBoss/Tomcat)
  7. Restart Apache
  8. Configure Tomcat (Give each JBoss/Tomcat a jvmRoute for session stickness)
  9. Restart JBoss
  10. Test it

More Details

This wiki outlines the various steps required to install a basic load-balancing solution based on JBoss/Tomcat and mod_jk 1.2.

Step #1: Download Apache2 Web Server
Get the latest Apache2 package from and install it. We require no special configuration, just use the default settings. In the following steps, APACHE_HOME will represent the Apache install directory.

Step #2: Download mod_jk 1.2.x
Download the latest package available from Tomcats’s ‘Download Tomcat connector section’ page . Always download the latest stable release if possible.
Rename the lib and drop it in APACHE_HOME/modules directory.
NOTE: Don’t use any release prior to mod_jk 1.2.15. Earlier releases are fairly buggy.

Note: Darwin Ports supports the installation of mod_jk on OS X. See for more info.

Step #3: Setup Apache to use modjk
Add this line at the very bottom in APACHE_HOME/conf/httpd.conf :

Step #4: Create the modjk config
Under APACHE_HOME/conf, create mod-jk.conf and populate it as follows:

mod_jk is ready to forward requests to JBoss instances. We need now to setup the workers

Step #5: Configuring workers
Under APACHE_HOME/conf, create and populate it as follows:

Important: Please review for the directive descriptions. Especially lookout for the comments on cachsize for Apache 1.3.x.

(1) You should only set the connection_pool_size if the number of allowed connection to the Httpd is higher than maxThreads in server.xml

If you specify worker.loadbalancer.sticky_session=Off, each request will be load balanced between node1 and node2. But when a user opens a Session on one server, it is a good idea to always forward this user’s requests to the same server. Otherwise the user’s session data would need to be synchronized between both servers. This is called a “sticky session”, as the client is always using the same server he reached on his first request. Session stickiness is enabled by default.

Side Note: a non-loadbalanced setup with a single node required the “worker.list=node1” entry before mod_jk would function correctly. Without this setting I would only get a 500 error and no other useful messages in log or otherwise. -Harlequin516

Side Note: I tried both loadbalanced and single node methods on Fedora 4. Both setups causing jk.shm errno=13 and jk-runtime-status errno=13 in the mod_jk.log. Could only get 500 errors. As a last resort disabled selinux on apache server. Restarted service and connection was made first try. -paulbrown

Step #6: Create the URI to worker map file
Create a file in the APACHE_HOME/conf directory. This file should contain the URL mappings you want Apache to forward to Tomcat. The format of the file is /url=worker_name. To get things started, paste this example into the file you created:

This will configure mod_jk to forward requests to /jmx-console and /web-console to Tomcat. Step #7: Restart Apache
Step #8: Configure Tomcat
To complete the configuration, we also need to name each node accordingly to the names specified in
Edit JBOSS_HOME/server/all/deploy/jbossweb-tomcat50.sar/server.xml (replace /all with your own server name)
Locate the <Engine….> element and add an attribute jvmRoute:

The jvmRoute attribute must match the name specified in In the server.xml file, make sure that the AJP 1.3 Connector is uncommented, e.g.:

If you are only accepting requests via mod_jk, you can comment out the regular HTTP Connector; Tomcat then won’t listen on port 8080.

Step #9: Activate the UseJK Valve in JBoss (not needed with Tomcat Standalone)
Finally, we need to tell Tomcat to add the jvmRoute value to its session cookies so that mod_jk can route incoming requests.
Edit JBOSS_HOME/server/all/deploy/jbossweb-tomcat50.sar/META-INF/jboss-service.xml (replace /all with your own server name)
Locate the <attribute> element with a name of UseJK, and set its value to “true”:

Note that tomcat version can be 50 or 55 depending on the AS that you use. Step #10: Restart JBoss AS.

Step #11: Access the JBoss AS web-console through Apache by browsing to http://localhost/web-console and you should see the JBoss web console page.

Note: to use mod_jk with Jboss 2 (e.g. jboss 2.4.6), you must edit jboss.jcml. Add the ‘jvmRoute=<<myWorker>>’ to the Engine element under the EmbeddedCatalinaSX? mbean.

Apache Install on Linux

Download $ lynx
Extract $ gzip -d httpd-NN.tar.gz
$ tar xvf httpd-NN.tar
$ cd httpd-NN
Configure $ ./configure --prefix=PREFIX
Compile $ make
Install $ make install
Customize $ vi PREFIX/conf/httpd.conf
Test $ PREFIX/bin/apachectl -k start

Logitech Problems

Recently found that using a Logitech Classic Keyboard 200 interfered with Windows 2000 removable USB operations. Unclear why but unplugged keyboard and am returning it. Fixed.

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