PEN: HTTP Load Balancer

This is performed on a CentOS 6.x 64 bit machine

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.

Configure Pen to load balance to Backend#1, Backend#2, Backend#3 web servers.

# install from EPEL
[root@dlp ~]# yum --enablerepo=epel -y install pen

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

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