Installing HA-Proxy on Cent OS 7

This example assumes that firewall and selinux is disabled. We are going to use the following three servers.

Apache1: 192.168.124.2 apache1.example.com
Apache2: 192.168.124.3 apache2.example.com
HAProxy: 192.168.124.10 haproxy.example.com



All three servers should be able to reach each other. Enter the following in the /etc/hosts file in all three nodes

192.168.124.2 apache1.example.com apache1
192.168.124.3 apache2.example.com apache2
192.168.124.10 haproxy.example.com haproxy

Now install apache service on the two apache nodes using the following command

#yum install httpd -y

Create a sample HTML file in the apache nodes in differentiate them and start the httpd service

#systemctl start httpd.service


Install and enable Epel repository on the haproxy node

#yum install epel-release -y

Install HA proxy

#yum install haproxy -y

The default configuration file haproxy.cfg is located in /etc/haproxy/

Lets make a backup of the original file

#cd /etc/haproxy

#cp haproxy.cfg haproxy.cfg.bkp


Now lets edit the configuration file. We need to clear the existing frontend/backend config and create our own config

Delete the following lines in haproxy.cfg

------------------------------------------------------------------------
frontend  main *:5000
    acl url_static       path_beg       -i /static /images /javascript /stylesheets
    acl url_static       path_end       -i .jpg .gif .png .css .js

    use_backend static          if url_static
    default_backend             app

backend static
    balance     roundrobin
    server      static 127.0.0.1:4331 check

backend app
    balance     roundrobin
    server  app1 127.0.0.1:5001 check
    server  app2 127.0.0.1:5002 check
    server  app3 127.0.0.1:5003 check
    server  app4 127.0.0.1:5004 check
------------------------------------------------------------------------

Now add the following lines
-------------------------------------------------------------------------
#webapp1 is the name we give for our frontend
frontend webapp1
#Makes the haproxy service listen on port number 80
bind *:80
#defining the backen name
default_backend webapp1_servers
#send X-Forwarded-For header
option  forwardfor


#Backend configuration
backend webapp1_servers
#Load balencing protocol
balance     roundrobin
server  apache1 192.168.124.89:80 check
server  apache2 192.168.124.51:80 check
-------------------------------------------------------------------------

Note: The X-Forwarded-For request header helps you identify the IP address of a client when you use an HTTP or HTTPS load balancer. Because load balancers intercept traffic between clients and servers, your server access logs contain only the IP address of the load balancer.





Save the config file and restart haproxy service

#systemctl restart haproxy.service


Now hit the haprosy node's IP address in the browser and it should direct us to one of the web servers.