Configuration file mod_rewrite load balancing

Tomcat - Extra Features example from a Well House Consultants training course
More on Tomcat - Extra Features [link]

This example is described in the following article(s):
• Clustering, load balancing, mod_rewrite and mod_proxy - [link]
• mod_rewrite for newcomers - [link]

Source code: mod_rewrite-load_balance Module: A900

::::::::::::::
balance.conf
::::::::::::::
SHARE162 192.168.200.162:8080
SHARE152 192.168.200.152:8080
FIRST 192.168.200.162:8080|192.168.200.152:8080

::::::::::::::
phpbal.conf
::::::::::::::
local 192.168.200.67:80
live www.wellho.net:80
FIRST 192.168.200.67:80|www.wellho.net:80

1. httpd.conf - selecting a random (Tomcat) server for each request

RewriteMap SERVERS rnd:/usr/local/apache2/conf/balance.conf
<Location /tommy>
RewriteEngine On
RewriteRule /tommy/(.*) http://${SERVERS:FIRST}/latmjdemo/$1 [P]
</Location>
ProxyPassReverse /tommy http://192.168.200.152:8080/latmjdemo
ProxyPassReverse /tommy http://192.168.200.162:8080/latmjdemo
# Note - engine names in Tomcat server.xml file are SHARE152 and SHARE162

2. httpd.conf - selecting a random server at first hit, then using the
same server if URL includes a jsessionid.

RewriteMap SERVERS rnd:/usr/local/apache2/conf/balance.conf
<Location /tommy>
RewriteEngine On
RewriteRule /tommy/(.*);jsessionid=(SHARE\d+) http://${SERVERS:$2}/latmjdemo/$1;jsessionid=$2 [P,L]
RewriteRule /tommy/(.*) http://${SERVERS:FIRST}/latmjdemo/$1 [P]
</Location>
ProxyPassReverse /tommy http://192.168.200.152:8080/latmjdemo
ProxyPassReverse /tommy http://192.168.200.162:8080/latmjdemo

3. httpd.conf - selecting a random server at first but then returning to the
same server based on a cookie set on the first page.

RewriteMap SERVERS rnd:/usr/local/apache2/conf/phpbal.conf
<Location /booze>
RewriteEngine On
# Next line historic - for URL rewrite stuff under Java
# RewriteRule /booze/(.*);jsessionid=(SHARE\d+) http://${SERVERS:$2}/latmjdemo/$1;jsessionid=$2 [P,L]
RewriteCond %{HTTP_COOKIE} "what=(\w+)-(\w+)"
RewriteRule /booze/(.*) http://${SERVERS:%1}/demo/$1 [P,L]
RewriteRule /booze/(.*) http://${SERVERS:FIRST}/demo/$1 [P]
</Location>
ProxyPassReverse /booze http://192.168.200.67:80/demo
ProxyPassReverse /booze http://www.wellho.net:80/demo

This example (no. 3) was tested with a PHP page on the server as we had
a lot of PHP Cookie apps and servers lying to hand ;-)

====================================
pubsales.php4 - The testing PHP script
====================================

<?php
$free = array("beer","wine","lager","brandy","vodka");
$first = 0;
if (! is_string($_COOKIE[what])) {
        $drink = $free[rand(0,count($free)-1)];
### Change local to live on second machine so it shows
### up differently in tests. Also make some other
### changes to the page for testing so you can tell
### the servers apart easily.
        setcookie("what","local-".$drink);
        $first = 1;
?>
<html>
<body bgcolor=green><h1>Have a <?= $drink ?> on us</h1></body>
</html>
<?php
        } else {
        $drink = $_COOKIE[what];
?>
<html>
<body bgcolor=fucshia text=white><h1>Did you like your free <?= $drink ?>?</h1>
The Bar is open if you want to purchase another</body>
</html>
<?php } ?>

Learn about this subject

This module and example are covered on the following public courses:
* Deploying Apache and Tomcat
* Deploying Java Applications on Linux / Unix
Also available on on site courses for larger groups

Books covering this topic

Yes. We have over 700 books in our library. Books covering Lamp deployment are listed here and when you've selected a relevant book we'll link you on to Amazon to order.

Other Examples

This example comes from our "Tomcat - Extra Features" training module. You'll find a description of the topic and some other closely related examples on the "Tomcat - Extra Features" module index page.

Full description of the source code

You can learn more about this example on the training courses listed on this page, on which you'll be given a full set of training notes.

Many other training modules are available for download (for limited use) from our download centre under an Open Training Notes License.

Other resources

• Our Solutions centre provides a number of longer technical articles.
• Our Opentalk forum archive provides a question and answer centre.
• The Horse's mouth provides a daily tip or thought.
• Further resources are available via the resources centre.
• All of these resources can be searched through through our search engine
• And there's a global index here.

Purpose of this website

This is a sample program, class demonstration or answer from a training course. It's main purpose is to provide an after-course service to customers who have attended our public private or on site courses, but the examples are made generally available under conditions described below.

Web site author

This web site is written and maintained by Well House Consultants.

Conditions of use

Past attendees on our training courses are welcome to use individual examples in the course of their programming, but must check the examples they use to ensure that they are suitable for their job. Remember that some of our examples show you how not to do things - check in your notes. Well House Consultants take no responsibility for the suitability of these example programs to customer's needs.

This program is copyright Well House Consultants Ltd. You are forbidden from using it for running your own training courses without our prior written permission. See our page on courseware provision for more details.

Any of our images within this code may NOT be reused on a public URL without our prior permission. For Bona Fide personal use, we will often grant you permission provided that you provide a link back. Commercial use on a website will incur a license fee for each image used - details on request.