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Varnish to the rescue Leszek Krupiński

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@leafnode PHPers Manual Consultant Architect

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intro

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web 1. User 2. Browser 3. Server

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user is impatient

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fast!

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100ms

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1s = -11% Page Views -16% User Satisfaction -7% Conversion

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1-5s ! 32% consumers lost

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(2012) average: 2.45s

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Optimize application

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• Frameworks • Limits • Time-consuming operations • Cost

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Maybe it’s not needed?

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Cache!

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Many levels, many solutions

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But… my site is very dynamic!

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1s TTL

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From 20 rq/s to 1 rq/s in single apt-get install

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Fresh content takes most hits

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Varnish The Web Accelerator

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Architecture

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Works with the kernel not against it

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mmap, threads, epoll, kqueue

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Backends: memory, file

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If it fits in memory, use memory

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Works on HTTP headers

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Cache-control, If-Modified-Since, Expires, Pragma, If-None-Match, Etag, Vary, Age

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Varnish uses language both browser and backend know

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In-memory logs

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75 000 rq/s at TMECC 143 000 rq/s at Redpill-Linpro

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Do I need a lot of memory?

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Nope

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Fresh content takes most hits

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Take that, slashdot effect!

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Configuration

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Lots of possibilities

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Unfortunately, lots of possibilities

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Varnish Configuration Language

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Compiled directly to C

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Hook-like configuration

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vcl_fetch vcl_recv vcl_hit vcl_miss vcl_hash vcl_pass vcl_deliver vcl_error

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restart

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Objects req, bereq, resp, beresp, obj

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Defaults

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vcl_recv

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vcl_hash

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VMods

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throttle, cookie, shield, redis, memcached, curl, url code, redirect…

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Varnish: load balancer failover system

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Directors

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Default: random

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Round-robin, client, hash, dns

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Health check

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Saint mode

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Grace mode

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Two hard things

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Invalidate cache

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Ban list Efficient way to invalidate cache

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Over HTTP

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Use PURGE header

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Real life issues

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Cookies

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Varnish does not cache when cookies are involved

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Ignore cookies

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Pick cookies

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Pick URLs

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Redirects

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POST

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PHP sessions

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CURL VMod

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PHP + memcached

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mobile detection

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mobile detection II

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VMod: DeviceAtlas Mobile Detection

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Cache “one-time” data

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Example: dynamic image resizing

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1B pictures 10 sizes

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apache + moddims

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Fresh content takes most hits

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Different TTL for different parts?

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ESI!

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Testing?

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jQuery plugin

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Just in! Varnish 4.0

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Log query language, background fetch, byte counters, security improvements

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