Pen Load Balancer: How to setup pen load balancer and Failover

Install Pen to configure Load Balance server. Pen is a light weight simple load balancer. This example shows to configure on the environment like follows. 

192.168.2.56 ------ Pen Server
192.168.2.55 ------ Web Server1
192.168.2.100 ----- Web Server2
192.168.2.95  ----- Web Server3

Set index.html in Document Root -- For testing from which server its resolving

set hostname if needed 

set ip in /etc/hosts  --------------- For basic dns resolution 

Here use IP Based virtual hosting ---------- no need of any virtual hosting if it is not a website, instead if it is a cgi just make change in httpd.conf as follows

Listen 192.168.2.55:80  ------ in each host

#
# ScriptAlias: This controls which directories contain server scripts.
# ScriptAliases are essentially the same as Aliases, except that
# documents in the realname directory are treated as applications and
# run by the server when requested rather than as documents sent to the client.
# The same rules about trailing "/" apply to ScriptAlias directives as to
# Alias.
#
ScriptAlias /cgi-bin/ "/var/www/cgi-bin/"
#
# "/var/www/cgi-bin" should be changed to whatever your ScriptAliased
# CGI directory exists, if you have that configured.
#
#<Directory "/var/www/cgi-bin">
#    AllowOverride None
#    Options None
#    Order allow,deny
#    Allow from all
#</Directory>
<Directory "/var/www/cgi-bin">
  AllowOverride None
  Options None
  Order allow,deny
  Allow from all
  Options +ExecCGI
  AuthName "CGI Authentication"
  AuthType Basic
  AuthUserFile /etc/httpd/passwd
  require valid-user
</Directory>

OR

In httpd.conf make // Listen 192.168.2.55:80 and etc,

# yum install httpd
# service httpd start
# chkconfig httpd on

# wget http://siag.nu/pub/pen/pen-0.18.0.tar.gz

# tar -xvzf pen-0.18.0.tar.gz

# cd pen-0.18.0/

# ./configure

# make

# make install

# service httpd stop
 
Bcz We have to run pen in port 80 or when starting pen it will conflict with httpd server port

# ls /usr/local/bin/

# /usr/local/bin/pen -r -b2 192.168.2.56:80 192.168.2.55:80 192.168.2.100:80 192.168.2.95:80

the -r flag denotes 'round robin'.

In Browser take http://192.168.2.56/  it will connect to any of the above three web servers. Either than load balancing pen also povide Failover as well.
 
To check this stop apache in any of the above web server, then pen will automatically failover to next available web server.

Point it to a web site it will work for load balancing the same.