CentOS 6
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Pen : HTTP Load Balancing
2015/01/31
 
Install pen which is lightweight simple Load Balancing software.
It is TCP protocol based, so it's possible to balance not only HTTP but SMTP, FTP, LDAP and so on.
This example is based on the environment like follows.
        |
--------+--------------------------------------------------------------------
        |
        +-------------------+--------------------+--------------------+
        |10.0.0.30          |10.0.0.51           |10.0.0.52           |10.0.0.53
 +------+-----+     +-------+------+     +-------+------+     +-------+------+
 |  Frontend  |     |   Backend#1  |     |   Backend#2  |     |   Backend#3  |
 | Pen Server |     |  Web Server  |     |  Web Server  |     |  Web Server  |
 +------------+     +--------------+     +--------------+     +--------------+

 
Configure Pen to load balance to Backend#1, Backend#2, Backend#3 web servers.
[1] Install Pen.
# install from EPEL

[root@dlp ~]#
yum --enablerepo=epel -y install pen
[2] Configure Pen.
[root@dlp ~]#
vi /etc/pen.conf
# create new

# log file

LOGFILE=/var/log/pen.log
# statics report file

WEBFILE=/var/www/pen/webstats.html
# control port

CONTROL=127.0.0.1:10080
# max connections

MAX_CONNECTIONS=256
# sebd X-Forwarded-For header

XFORWARDEDFOR=true
# Round-Robin mode

ROUNDROBIN=true
# listenning port

PORT=80
# number of backends

BACKEND=3
# define backend servers

SERVER1=10.0.0.51:80
SERVER2=10.0.0.52:80
SERVER2=10.0.0.53:80
# create an init script

[root@dlp ~]#
vi /etc/rc.d/init.d/pend
#!/bin/bash

# pend: Start/Stop Pend
# chkconfig: - 90 10
# description: Pen is a light weight simple load balancer.
# pidfile: /var/run/pen.pid

. /etc/rc.d/init.d/functions
. /etc/pen.conf

LOCKFILE="/var/lock/subsys/pen"
PID=/var/run/pen.pid
PROG=/usr/bin/pen
PROGNAME=Pend

RETVAL=0
start() {
    SERVER=`grep "^SERVER" /etc/pen.conf | cut -d= -f2`
    [ $XFORWARDEDFOR = "true" ] && SERVER="-H $SERVER"
    [ $ROUNDROBIN = "true" ] && SERVER="-r $SERVER"
    [ $SSLCERTS ] && SERVER="-E $SSLCERTS $SERVER"

    echo -n $"Starting $PROGNAME: "
    daemon $PROG -w $WEBFILE -x $MAX_CONNECTIONS -p $PID -l $LOGFILE -C $CONTROL -S $BACKEND $PORT $SERVER
    RETVAL=$?
    echo
    [ $RETVAL -eq 0 ] && touch $LOCKFILE
    return $RETVAL
}
stop() {
    echo -n $"Stopping $PROGNAME: "
    killproc $PROG
    RETVAL=$?
    echo
    [ $RETVAL -eq 0 ] && rm -f $PID $LOCKFILE
    return $RETVAL
}
case "$1" in
    start)
        start
        ;;
    stop)
        stop
        ;;
    status)
        status -p "$PID" -l $PROG $PROGNAME
        ;;
    restart)
        stop
        start
        ;;
    *)
        echo $"Usage: $0 {start|stop|status|restart}"
        exit 1
esac
exit $?

[root@dlp ~]#
chmod 755 /etc/rc.d/init.d/pend

[root@dlp ~]#
/etc/rc.d/init.d/pend start

Starting Pend: [ OK ]
[root@dlp ~]#
chkconfig --add pend

[root@dlp ~]#
chkconfig pend on

[3] Configure httpd on backend servers to record logs of X-Forwarded-For.
[root@www ~]#
vi /etc/httpd/conf/httpd.conf
# line 497: change

LogFormat "
\"%{X-Forwarded-For}i\"
%l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\"" combined
[root@www ~]#
/etc/rc.d/init.d/httpd restart

[4] Make sure all works fine to access to the frontend server from a Client with HTTP like follows.
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