Varnish is a reverse proxy caching system that stores cached content in memory to serve web requests very quickly. It works by checking for cached content on common requests and serving it directly if there, otherwise fetching the requested content from the backend server and caching it for future requests. Key advantages are reduced CPU usage and faster response times. Varnish installation involves changing the Apache port, configuring the Varnish default VCL file to point to Apache, and starting both services. Status can be checked using cURL commands.

1. Cache
Varnish Caching Technique
Created by: Pankaj Chauhan

2. What is Varnish?
lVarnish is a reverse
proxy caching system. It
acts as an operator or
security guard.
lBecause when web
request comes then it

3. How It Works
lVarnish caching stores
it's cache in the memory
not so much on hard
drive.
lDue to that it can able to
serve hundred or more

4. Extra Advantage
lVarnish caching has
these other advance
like.. saving the CPU
time, File lookup and
database request for
content.

5. Varnish used before
with server

6. Varnish Method
Mostly used method:
1. vcl_init
2. vcl_recv
3. vcl_hit
4. vcl_miss
5. vcl_fetch
6. vcl_deliver

7. Varnish installation step with
ubuntu 14.04 + Apache
1. Sudo apt-get update
2. Sudo apt-get install varnish
3. Need to change port of apache
sudo nano /etc/apache2/ports.config
change 80 to 8080
4. Change varnish server host also you
can appy method here for caching.
sudo nano /etc/varnish/default.vcl
backend default {
.host = "127.0.0.1";
.port = "8080";

8. Continue...
5. sudo nano /etc/default/varnish
DAEMON_OPTS="-a :80
-T localhost:6082
-f /etc/varnish/default.vcl
-S /etc/varnish/secret
-s malloc,256m"
6. Restart apache and varnish
/etc/init.d/apache2 restart
/etc/init.d/varnish restart

9. How can checking varnish
status
curl -I http://localhost:8080
status like as:
HTTP/1.1 503 Service Unavailable
Server: Varnish
Content-Type: text/html; charset=utf-8
Retry-After: 5
Content-Length: 417
Accept-Ranges: bytes
Date: Tue, 27 Dec 2016 10:52:15 GMT
X-Varnish: 70237562
Age: 0
Via: 1.1 varnish

10. lThank You