How to Install and Configure Varnish on CentOS?

What is Varnish?

Varnish is a HTTP proxy cache or an HTTP accelerator designed to cache http requests to make dynamic websites a lot faster

Steps to install Varnish on CentOS

Execute the following command to get the rpm for varnish

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

Then install varnish using this command

yum install varnish

Modify the VARNISH_LISTEN_PORT=6081 line to port 80

VARNISH_LISTEN_PORT=80

Save the file and edit varnish default configuration file using the following command

vi /etc/varnish/default.vcl

Modify the default backend default port to port 81 instead, so the backend section should look like the following

backend default {
 .host = "127.0.0.1";
 .port = "81";
}

6. Edit the apache httpd.conf to configure apache to listen on port 81 instead

To edit the file execute the following command

vi /etc/httpd/conf/httpd.conf

Modify the Listen line to look the the following

Listen 81

7. Modify the iptables firewall to allow connections on port 81

Edit the iptables configuration file using the command

vi /etc/sysconfig/iptables

Add the following 2 lines before the COMMIT

-A INPUT -m state --state NEW -m tcp -p tcp --dport 81 -j ACCEPT

-A OUTPUT -m state --state NEW -m tcp -p tcp --dport 81 -j ACCEPT

Save the file then restart iptables

service iptables restart

Configure SELinux to allow connecting to apache on port 81 then restart apache

vi /etc/selinux/config

Modify SELINUX=enforcing to

SELINUX=permissive

Save the file then restart apache using the command

service httpd restart

Configure Varnish to run on startup

chkconfig varnish on

Then start Varnish

service varnish start

Try visiting your site and refresh the page multiple times to make sure it was cached, then using firebug go to the Net tab you should see under the fetched resources that it was served by varnish

I hope you've enjoyed this tutorial and stay tuned for more to come