NRW08

Thomas WeinertOptimizing Your Frontend Performance

About Me● Application Developer

– PHP– XSLT/XPath– (some) Javascript

● papaya CMS– PHP based Content Management System– uses XSLT for Templates

How to scale you webpage?● Hardware● Backend● Frontend

Hardware● More hardware● Better hardware● Moores Law

– Transistors doubling every 18 months– Transistors != Performance

● Distributed systems are complex● Think about environment

Backend● External data sources are slow

– SQL– Files– Network

● Locking is slower● Memory is faster

– but less secure

Mini/Micro Optimisations● Myths

– echo vs. print– ' vs. "

● Objects vs. functions vs. linear source● Template systems

Mini/Micro Optimisations

DON'T DO IT

Yahoo!● Yahoo!'s Exceptional Performance team

– Yahoo!'s Exceptional Performance team evangelizes best practices for improving web performance. They conduct research, build tools, write articles and blogs, and speak at conferences. Their best practices center around the rules for high performance web sites.

– http://developer.yahoo.com/performance/

Results● 80% of the end-user response time is spent on

the front-end.

Firebug● Firefox extension● Analyze and manipulate

– requests, page structure, CSS● Javascript debugger

YSlow● Why (is your web page) slow● Set of rules● Firebug extension

Yslow: Performance View

Yslow: Stats

Yslow: Components

Yslow: Tools● Print View● JSLint

Make Fewer HTTP Requests● Combined files

– CSS– JavaScript

● CSS sprites

Combined files● Release process● CSS

– Consider URLs● JavaScript

– Minify– Obfuscate

CSS Sprites● Elements with fixed size● Background image● Disable repeat● Negative positions

CSS Icons● Raster of icons● No repeat● Fixed size

<div> or <span>

CSS Backgrounds● Gradient● Repeat in one

direction

Minify Javascript● Most JS libraries provide a minified version● YUI Compressor:

http://developer.yahoo.com/yui/compressor/– JS and CSS

● Packer– Webpage, .Net, Perl, PHP– http://dean.edwards.name/packer/

#2 Use A CDN● Content Delivery Network

– Akamai Technologies– Mirror Image Internet– Limelight Networks

● Bring the content to your users– Geographic distance– Physics is still here

● Only for large sites● Dynamic content is complex

Headers● Expires● Cache-Control

– Session-Management● 304 Not Modified

Expires● Apache mod_expire●

● <IfModule mod_expires.c>● ExpiresDefault "access plus 1 month"● ExpiresActive on● </IfModule>

Cache-Control● None

– no caching– default for sessions

● Private– cacheable in browser cache

● Public– cacheable in browser cache and proxies

304 Not Modified● Send Etag and Modfication date

– Etag: "some hash"– Last-Modified: Thu, 12 Sep 2008 11:00:00 GMT

● Request headers– If-Modified-Since: Tue, 12 Sep 2008 11:00:00 GMT– If-None-Match: "some hash"

● Response headers– HTTP/1.1 304 Not Modified

HTTPFox● Firefox Extension● Log of all HTTP requests● Not only displayed content

Gzip Components● Gzip != Zip

– only compression– no packaging– tar.gz

● Good browser support– Accept-Encoding: gzip, deflate– Content-Encoding: gzip–

Gzip in Apache● mod_gzip● mod_deflate

– filter chain, works on dynamic content, too●

– http://httpd.apache.org/docs/2.2/mod/mod_deflate.html

Gzip In PHP 5● <?php● ob_start('ob_gzhandler');● ...

Gzip In PHP 5● <?php● if (function_exists('ob_gzhandler')) {● ob_start('ob_gzhandler');● }● ...

Configure ETags● Browser still asks webserver● Server specific

– CDN– Load balancer with multiple servers

● Apache– FileETag none

● IIS– http://support.microsoft.com/?id=922733

Split requests across domains● HTTP 1.1 suggests 2 parallel requests per

domain● Separate content by function

– www.domain.tld– themes.domain.tld– usercontent.domain.tld (security)

● Optimisation tools change the option● Consider cookie domains

Reduce DNS Lookups● DNS maps host names to ips● Needs time

– 20-120 milliseconds● Cached in browser

Avoid Redirects● Obviously addition requests● Only cached with explicit headers●

● http://www.domain.tld– → http://www.domain.tld/

Put Stylesheets at the Top● Progressive display of the page● Page appears to load faster● W3C specifications

Put Scripts at the Bottom● Scripts block parallel downloads

– defer attribute in MSIE● onload() event

– used by most libraries●

● Problem: document.write()– Counter– Banners

Avoid CSS Expressions● MSIE from version 5

– cross browser experience● JavaScript inside CSS● Evaluated

– page render– resize– scrolling– mouse movements (hover)

JavaScript And CSS Files● Do not embed JS/CSS in your pages

– No <script>...</script>– No <style>...</style>

● Seperate caching headers● Revision parameter (style.css?rev=1234)

– Get parameter– Unique URL for browser

Remove Duplicate Scripts● Team size● Standard scripts

– XMLRPC, JQuery, Prototype● Script module for your template system

● $templatesystem->addScript('foo.js');

Make Ajax Cacheable● Often AJAX applications avoid caching

– http://some.domain.tld/ajax.file?t=randomvalue● A lot of requests● Use more static URLs

Questions?

References● Slides: http://www.abasketfulofpapayas.de/● Yahoo Performance Team

– http://developer.yahoo.com/performance/● JS minimize

– http://developer.yahoo.com/yui/compressor/– http://dean.edwards.name/packer/

● Apache GZIP– http://httpd.apache.org/docs/2.2/mod/mod_deflate.html

● No Etag in IIS– http://support.microsoft.com/?id=922733