Scientific Linux 6
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Pen - Load Balance
2011/06/05
 
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. 
        (1)  gw.srv.world         [10.0.0.50]  -  Pen Server
        (2)  www01.srv.world   [10.0.0.51]  -  Web Server#1
        (3)  www02.srv.world   [10.0.0.52]  -  Web Server#2
[1] Install and Configure Pen
[root@gw ~]#
yum --enablerepo=epel -y install pen
 
# install from EPEL
[root@gw ~]#
vi /etc/pen.conf
# create new

# log file

LOGFILE=/var/log/pen.log
# output file of status

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

CONTROL=127.0.0.1:10080
# max connections

MAX_CONNECTIONS=500
# listen port

PORT=80
# backend servers

BACKEND=2
# IP address of a backend

SERVER1=10.0.0.51:80
# IP address of a backend

SERVER2=10.0.0.52:80
[root@gw ~]#
vi /etc/rc.d/init.d/pend
# create init script

# this is an example

#!/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/sysconfig/network
. /etc/pen.conf

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

RETVAL=0
start() {
   echo -n $"Starting Pend: "
   SERVER=`grep "^SERVER" /etc/pen.conf | cut -d= -f2`
   daemon $PROG -w $WEBFILE -x $MAX_CONNECTIONS -p $PID -l $LOGFILE -C $CONTROL -S $BACKEND -r $PORT $SERVER
   RETVAL=$?
   echo
   [ $RETVAL -eq 0 ] && touch $LOCKFILE
   return $RETVAL
}
stop() {
   echo -n $"Stopping Pend: "
   killproc $PROG
   RETVAL=$?
   echo
   [ $RETVAL -eq 0 ] && rm -f $PID $LOCKFILE
   return $RETVAL
}
case "$1" in
   start)
      start
      ;;
   stop)
      stop
      ;;
   status)
      status pend
      ;;
   restart)
      stop
      start
      ;;
   *)
      echo $"Usage: $0 {start|stop|status|restart}"
      exit 1
esac
exit $?
[root@gw ~]#
vi /etc/logrotate.d/pen
# setting of logrotation
# this is an example

/var/log/pen.log {
   daily
   copytruncate
   compress
   notifempty
   missingok
   postrotate
     /etc/rc.d/init.d/pend restart 2>&1 > /dev/null || true
   endscript
}
[root@gw ~]#
chmod 755 /etc/rc.d/init.d/pend

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

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

[root@gw ~]#
chkconfig pend on

[2] Access to the URL you set and make sure backend server answers normally like follows.
[3] Shutdown other httpd manually and make sure another httpd answers normally like follows.
[4] Configure the tool that it's possible to watch Pen's status.
[root@gw ~]#
cp /usr/share/doc/pen-*/penstats /var/www/pen

[root@gw ~]#
vi /var/www/pen/penstats
# line 4: change

PIDFILE=
/var/run/pen.pid
# line 5: change

WEBFILE=
/var/www/pen/webstats.html
[root@gw ~]#
vi /etc/httpd/conf.d/pen.conf
# change

Alias
/pen/ /var/www/pen/
<Directory /var/www/pen/>
   DirectoryIndex penctl.cgi
   Options ExecCGI
   order deny,allow
   deny from all
   allow from 127.0.0.1
10.0.0.0/24
 
# IP address you permit

</Directory>
[root@gw ~]#
/etc/rc.d/init.d/httpd restart

Stopping httpd:
[ OK ]

Starting httpd:
[ OK ]

[root@gw ~]#
chmod 755 /var/www/pen/penstats

[root@gw ~]#
/var/www/pen/penstats > /dev/null
 
# run

[root@gw ~]#
crontab -e
# update by 5 minutes

*/5 * * * * /var/www/pen/penstats > /dev/null
[5] Access to "http://(pen's hostname or IP address):(httpd listen port)/pen/webstats.html" and make sure following site is shown normally.
 
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