Varnish is a web application accelerator developed for content heavy dynamic websites and heavily consumed API’s. You install it in front of any server that speaks HTTP and configure it to cache the contents. Varnish Cache is really, really fast. It typically speeds up delivery with a factor of 300 – 1000x, depending on your architecture Varnish is a superior caching engine for your Web applications. It will get them to work at blazing speeds with minimal configuration.
Why Varnish
Varnish has several advantages over other caching engines. Varnish act independently acts as a transparent go-between between the users and the web server backend. The advantages of Varnish are many, with the main ones being
- Savings in server infrastructure
- Lightweight, easy to set up and configuration
- Highly customisable with an easy configuration syntax
- Protection against outages—if your server fails, Varnish Cache continues to serve cached content
- Highly customisable with an easy configuration syntax
- Admin dashboard and other utilities for logging and performance evaluation
There are only a few limitations to this tool. Varnish does not support the HTTPS protocol, but it can be configured as an HTTP reverse proxy using Pound for internal caching.
It is recommended that users refer to the documentation for the exact version to avoid mistakes. Varnish is a powerful tool and allows you to do a lot more. For instance, it can be used to give temporary 301 redirections or serve your site while the backend server is down for maintenance.
Installing varnish
Let us go through the steps to install and configure Varnish.
Run the following commands as root to download and install the latest version of Varnish:
With this, Varnish is already running on your server and has started to cache. The Varnish configuration file is generally located at /etc/varnish/default.vcl. Varnish has several built-in sub-routines, which are called the several stages of the caching fetch process. We can also define custom sub-routines, which can be called within these built-in sub-routines.
Source: http://www.aditmicrosys.com/
