Pen - smtp load balancer

This is pen, a load balancer for "simple" tcp based protocols such as http or smtp. It allows several servers to appear as one to the outside and automatically detects servers that are down and distributes clients among the available servers. This gives high availability and scalable performance.

In this senaerio  we have two server ( server A and server B )  

server A = Load balancer with pen installed
eth0 = 192.168.50.156
 
server B = postfix with two instances of psotfix installed (  http://advosys.ca/papers/postfix-instance.html )
eth0 = 192.168.50.124
eth0:1  = 192.168.50.125

postfix  should be listening
[root@smtptestserver ~]# netstat -tupln |grep 25
tcp        0      0 192.168.50.125:25           0.0.0.0:*                   LISTEN      12077/master
tcp        0      0 192.168.50.124:25           0.0.0.0:*                   LISTEN      11910/master on both server


Installation of Pen on Server A
Downlaod the rpm from here

ftp://194.199.20.114/linux/dag/redhat/el5/en/i386/dag/RPMS/pen-0.17.2-1.el5.rf.i386.rpm
rpm -ivh  pen-0.17.2-1.el5.rf.i386.rpm

This should install   /usr/bin/pen

now we need to tell pen to listen port 25 for all  incomning connections  and to distribute those connection to 50 .125 and 50.124

/usr/bin/pen 192.168.50.156:25 -l /var/log/pen/pen.log -p /var/run/pen.pid -r 192.168.50.124:25 192.168.50.125:25

# netstat -tupln |grep pen
tcp        0      0 192.168.50.156:25           0.0.0.0:*                   LISTEN      14505/pen

Now try
telnet 192.168.50.156 25 from any local system   it should take you to either    192.168.50.124 or  192.168.50.124