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Varnish to the rescue
Leszek Krupiński
@leafnode
PHPers Manual
Consultant Architect
intro
web
1. User 2. Browser 3. Server
user is impatient
fast!
100ms
1s =
-11% Page Views -16% User Satisfaction
-7% Conversion
1-5s !
32% consumers lost
(2012)
average: 2.45s
Optimize application
• Frameworks • Limits • Time-consuming operations • Cost
Maybe it’s not needed?
Cache!
Many levels, many solutions
But… my site is very dynamic!
1s TTL
From 20 rq/s to 1 rq/s in single apt-get install
Fresh content takes most hits
Varnish The Web Accelerator
Architecture
Works with the kernel not against it
mmap, threads, epoll, kqueue
Backends: memory, file
If it fits in memory, use memory
Works on HTTP headers
Cache-control, If-Modified-Since, Expires, Pragma, If-None-Match, Etag,
Vary, Age
Varnish uses language both browser and
backend know
In-memory logs
75 000 rq/s at TMECC 143 000 rq/s at Redpill-Linpro
Do I need a lot of memory?
Nope
Fresh content takes most hits
Take that, slashdot effect!
Configuration
Lots of possibilities
Unfortunately, lots of possibilities
Varnish Configuration
Language
Compiled directly to C
Hook-like configuration
vcl_fetch vcl_recv
vcl_hit vcl_miss
vcl_hash vcl_pass
vcl_deliver vcl_error
restart
Objects
req, bereq, resp, beresp, obj
Defaults
vcl_recv
vcl_hash
VMods
throttle, cookie, shield, redis, memcached, curl,
url code, redirect…
Varnish: load balancer
failover system
Directors
Default: random
Round-robin, client, hash, dns
Health check
Saint mode
Grace mode
Two hard things
Invalidate cache
Ban listEfficient way to invalidate cache
Over HTTP
Use PURGE header
Real life issues
Cookies
Varnish does not cache when cookies
are involved
Ignore cookies
Pick cookies
Pick URLs
Redirects
POST
PHP sessions
CURL VMod
PHP + memcached
mobile detection
mobile detection II
VMod: DeviceAtlas Mobile Detection
Cache “one-time” data
Example: dynamic image resizing
1B pictures 10 sizes
apache + moddims
Fresh content takes most hits
Different TTL for different parts?
ESI!
Testing?
jQuery plugin
Just in! Varnish 4.0
Log query language, background fetch, byte
counters, security improvements
