steam learn : varnish or how to reduce the load of your web server

22th of January, 2015

How to reduce the load of your web server

With Varnish

by Clément Beudot


Introduction

● What is Varnish

● Purpose of Varnish

● Varnish Request Life Cycle

● Performances : Apache vs Varnish

● Strength & Limitations

● Advanced features


Quick Quiz !

Calculate, without using your smartphone

45 x 12


Quick Quiz !

Calculate, without using your smartphone

45 x 12 = 540


Recurring Content


What is Varnish

● HTTP Reverse Proxy (HTTP Accelerator)● Varnish 1.0 released in 2006, now version 4.0.2● Varnish written in C

CLIENT VARNISH Web Server


Purpose of Varnish

● Scaling at thousands of req/s

● Caching recurring content

● Caching static resources

● Reducing load of your web servers


Varnish Request Life Cycle

Few words to know first before seeing it !

1. HIT : requested resource has been found in the cache

2. MISS : requested resource not found.

3. PASS : bypass of varnish

4. PIPE : direct passthrough to the backend (streams)



Cache Miss

RECV

HASH PIPE

HIT MISS

PASS

FETCH

DELIVER

WEB SERVER



Cache Hit

RECV

HASH PIPE

HIT MISS

PASS

FETCH

DELIVER

WEB SERVER



Cache Pass

RECV

HASH PIPE

HIT MISS

PASS

FETCH

DELIVER

WEB SERVER



Cache Pipe

RECV

HASH PIPE

HIT MISS

PASS

FETCH

DELIVER

WEB SERVER


Performances : Apache vs VarnishUsing Varnish on a low complexity page

** SIEGE 2.70** Preparing 200 concurrent users.

Transactions: 2298 hitsAvailability: 100.00 %Elapsed time: 29.83 secsData transferred: 5.70 MBResponse time: 0.00 secsTransaction rate: 77.04 trans/secLongest transaction: 0.01 secsShortest transaction: 0.00 secs




Performances : Apache vs VarnishUsing Varnish on high complexity page


Transactions: 2298 hitsAvailability: 100.00 %Elapsed time: 29.83 secsData transferred: 5.70 MBResponse time: 0.00 secsTransaction rate: 77.04 trans/secLongest transaction: 0.01Shortest transaction: 0.00






Performances : Apache vs VarnishReally easy for Varnish !


Varnish Strengths

● Scaling to thousands of reqs/ s

● Load Balancing capability with Backend Health Check

● Ability to Manage the request life cycle

● Easy to partially integrate in your S.I


Varnish Limitations

● HTTPS

● Only designed for GET & HEAD request

● Hates Cookies & HTTP Auth Headers

● Not recommended on 32 bits servers

● Using Varnish for a logged user on your website


Varnish Limitations


Varnish : Advanced Features & Assets

● E.S.I. Support

● Control varnish via CLI or dedicated modules

● “Always online”


How to reduce the load of your web server with varnish - Summary

● HTTP Accelerator / HTTP Reverse Proxy

● Get rid of recurring content cost

● Scale at “nearly” zero cost

● And finally … reduce the load of your web server by

avoiding unnecessary calculation.


How to reduce the load of your web server with varnish

Thank You


How to reduce the load of your web server with varnish

Questions ?How to install it ?

Do I really need Varnish ?Can I cache in a file instead ofRAM ?

How I can change the

TTL for a page ?

What if all m

y

backends are dead ?Can I use varnish for my

logged users ?

Is Varnish really useful

for static content ?

Can I load balance on

multiple backends ?

How much RAM do I need ?


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