Author: ZIADI Mohamed Ali

What is Varnish ? Varnish is an HTTP cache server. It considered as an HTTP accelerator or sometimes a reversy-proxy between application servers and clients. It is designed for content-heavy dynamic web sites and highly consumed APIs. According to the rules which are defined by system administrator and site developers, it allows alleviating server load and serving queries faster by caching data. Examples of web sites using Varnish: Wikipedia, Facebook, Twitter, Vimeo, Tumblr, The New York Times, The Guardian, The Hindu, Corriere della Sera… In 2012, 5% of the top 10000 sites in the web used the software. How it works ?   As mentionned in the figure, Varnish is between the client and the web server. Let’s consider that we are using Apache as web server: Varnsih will listen on port 80 and Apache will move to another port (8080) Apache will be considered as a backend to Varnish   Installation [root@server varnish]# yum install varnish Related packages are: [root@server varnish]# rpm -qa | grep varnish varnish-libs-4.0.3-3.el7.x86_64 varnish-4.0.3-3.el7.x86_64 Related files are: [root@server varnish]# tree /etc/varnish/ /etc/varnish/ |___ default.vcl |___ secret |___ varnish.params 0 directories, 3 files   Configuration The file /etc/varnish/default.vcl is written in VCL (Varnish Cache Language) and contains blocks defining how varnish is working when receiving, fechting/asking the backend and delivering responses. Each block begins with a little description explaining it’s role. Edit /etc/varnish/default.vcl and modify/add...