Varnish Cache is a powerful open source HTTP accelerator that can be installed infront of any Webserver. Varnish Cache can improve overall performance of your web server by caching contents. The Varnish cache stores the copy of user request’s and serves the same page when the user revisits the webpage.

Installing Varnish Cache on Centos.
==========================
The Varnish Cache can be installed from Official Varnish repository.

Run the below command to enable Varnish Repo in Centos6

wget http://repo.varnish-cache.org/redhat/varnish-3.0/el5/noarch/varnish-release-3.0-1.noarch.rpm
rpm –nosignature -i varnish-release-3.0-1.noarch.rpm

Now you can install varnish using yum command

yum install varnish

Configurations
In this tutorial I am using nginx as Webserver.

The first step is changing nginx default port.

Open the configuration file

vim /etc/nginx/conf.d/default.conf

Replace the port 80 to 8080.

# The default serverserver {

listen 8080;

server_name ntn-blog.com;

Add a firewall rule to allow this port in iptables

iptables -I INPUT -p tcp –dport 8080 –syn -j ACCEPT

Now we are going to configure Varnish to run on port 8O.

The main configuration file for Varnish is /etc/sysconfig/varnish

Open the configuration file

vim /etc/sysconfig/varnish

Change the below parameters

VARNISH_LISTEN_PORT=80

VARNISH_STORAGE_SIZE=512M

And another configuration file is /etc/sysconfig/varnish which is used to communicate with nginx webserver running on port 8080.

Open up the configuration file

vim /etc/sysconfig/varnish

Modify the parameters as given below

backend default {.host = “127.0.0.1″;

.port = “8080″;

}

Finally restart the services

service nginx restart
service varnish restart

Test the installation by running below command in server

curl -I ntn-blog.com

You will get output like this.HTTP/1.1 200 OK

Server: nginx/1.0.15Content-Type: text/html; charset=UTF-8X-Powered-By: PHP/5.3.3X-Pingback: http://ntn-blog.com/xmlrpc.php
Content-Length: 7993

Date: Tue, 19 Nov 2013 14:15:16 GMT

X-Varnish: 274529218

Age: 0

Via: 1.1 varnish

Connection: keep-alive

Thats all …… 🙂