This tutorial will help a user to learn how to install mod_jk module and what is mod_jk.mod_jk is basically Apache module which is used to connect the Servlet Container [also known as Web Container] with the Web Servers (i.e. Apache, iPlanet, Sun ONE). We use mod_jk module for loadbalancing and also use as a connector between Apache web server and Apache Tomcat together.

1- We use a package called libapache2-mod-jk to install mod_jk module in ubuntu.

2- To install apache module "mod_jk" we execute the below command in our terminal

 sudo apt-get install libapache2-mod-jk

3- Now we will enable mod_jk loading :Here we put a link in /etc/apache2/mods-enabled/jk.load which is mapped to /etc/apache2/mods-available/mod_jk.load. Which enables loading of mod_jk module when we restart apache.

Creating link in /etc/apache2/mods-enabled/jk.load

LoadModule jk_module /usr/lib/apache2/mods-available/mod_jk.load

5-Create mod_jk conf file and place it in /etc/apache2/mods-available/

<IfModule jk_module>

# Where to find workers.properties
# Update this path to match your conf directory location
JkWorkersFile /etc/apache2/jk_workers.properties

# Where to put jk logs
# Update this path to match your logs directory location
JkLogFile /var/log/apache2/mod_jk.log

# Set the jk log level [debug/error/info]
JkLogLevel info

# Select the log format
JkLogStampFormat "[%a %b %d %H:%M:%S %Y]"

# JkOptions indicate to send SSL KEY SIZE,
JkOptions +ForwardKeySize +ForwardURICompat -ForwardDirectories

# JkRequestLogFormat set the request format
JkRequestLogFormat "%w %V %T"

# Shm log file
JkShmFile /var/log/apache2/jk-runtime-status

</IfModule>

6- Enable mod_jk configurations: Here we put a link in /etc/apache2/mods-enabled/jk.conf which
is mapped to /etc/apache2/mods-available/mod_jk.conf. This will enable mod_jk configuration
when restart apache.

7- Now we will create a worker properties file: Which we place at the location below

/etc/apache2/mod_jk_workers.properties

here we define workers in the worker list.

# Define 1 real worker named ajp13
          worker.list=ajp13    

    # Set properties for worker named ajp13 to use ajp13 protocol,
    # and run on port 8009
         worker.ajp13.type=ajp13
         worker.ajp13.host=localhost 
         worker.ajp13.port=8009
         worker.ajp13.lbfactor=50
         worker.ajp13.cachesize=10
         worker.ajp13.cache_timeout=600
         worker.ajp13.socket_keepalive=1
         worker.ajp13.socket_timeout=30

8- now we will configure the url

<VirtualHost *:80>
    ...
    # Send everything for context "/context" to worker ajp13
    JkMount /context/ ajp13
    JkMount /context/* ajp13
    ...
   </VirtualHost>

9- Now restart Apache web server.

10- For more information see the link below:

https://tomcat.apache.org/tomcat-3.3-doc/mod_jk-howto.html