Introduction
Varnish is an open source reverse HTTP proxy, an HTTP accelerator, and a useful tool for speeding up an Apache server. Varnish is also known as front-end web caching software that you put in front of an Apache web server to speed it up.
Varnish can increase the performance of your website and prevent the Apache server from overloading in case of high server traffic.
Varnish features
- Reduces CPU load on the Apache web server.
- Web browser will load your website faster since the cache is stored in RAM.
- Supports load balancing.
In this article I will explain how to install and use Varnish as a front-end to an Apache web server.
Requirements
- A server running CentOS 7 with Apache installed
- A static IP address for your server
Install Varnish
Before installing Varnish, you will have to install the EPEL repository. You can do this by running the following command:
sudo yum install -y epel-release
Once the installation is finished you will be able to install Varnish.
sudo yum install -y varnish
After installation, you will need to start Varnish and enable it to start on boot.
To do this, run:
sudo systemctl start varnish
sudo systemctl enable varnish
To check the status of Varnish, run the following command:
sudo systemctl status varnish
Check the version of Varnish that is running:
sudo varnishd -V
Configure Varnish
The Varnish configuration file will be located in the /etc/varnish directory in CentOS 7. To make Varnish work in front of Apache, you will need to set up some basic configurations.
By default Varnish listens on port 6081. You will need to change port 6081 to 80 so that website requests access the Varnish cache first. You can do this by editing the varnish.params config file.
sudo nano /etc/varnish/varnish.params
Change VARNISH_LISTEN_PORT from 6081 to 80:
VARNISH_LISTEN_PORT=80
Save the file, then open the default.vcl file. This file tells varnish to look for the server content:
sudo nano /etc/varnish/default.vcl
Tell Varnish to get the content on port 8080.
backend default {
.host = "127.0.0.1";
.port = "8080";
}
Configure Apache to work with Varnish
By default Apache listens on port 80. Now, you need to make Apache to run behind Varnish caching by changing the default Apache port to 8080.
To do this, edit the httpd.conf config file:
sudo nano /etc/httpd/conf/httpd.conf
Search for Listen 80 and replace it with Listen 8080:
Listen 8080
Save and close the file, then restart Apache and Varnish to reflect the changes.
sudo apachectl restart
sudo systemctl restart varnish
Test Varnish
Now you should have Varnish and Apache running together. To verify that Varnish is on and working, you can use the curl command to view the HTTP header:
curl -I http://localhost
You should see the output something like this:
HTTP/1.1 200 OK
Date: Wed, 04 Nov 2015 10:21:07 GMT
Server: Apache/2.4.6 (CentOS)
Last-Modified: Fri, 02 Oct 2015 10:36:53 GMT
ETag: "6c-5211cdbf61c14"
Content-Length: 108
Content-Type: text/html; charset=UTF-8
X-Varnish: 32770
Age: 0
Via: 1.1 varnish-v4
Connection: keep-alive
Additional information on Varnish can be located at the Official Varnish Website
By Victor C.