Web Performance, Scalability, and Testing Techniques

Boston PHP Meetup Group – April 2011Jonathan Klein

jklein@csnstores.com @jonathanklein

What We’ll Cover

• Why Listen to Me?• Why Performance Matters• Measuring Server Side Performance• Speeding up the Server• Frontend Optimization• Measuring Full Page Load Time• Homework

What We’ll Cover

• Why Listen to Me?• Why Performance Matters• Measuring Server Side Performance• Speeding up the Server• Frontend Optimization• Measuring Full Page Load Time• Homework Fun Performance Adventure!

Introduction

• Senior Software Engineer/Performance Guy at CSN Stores

• Organizer of the Boston Web Performance Meetup Group

• CSN Stores Stats:– ~1400 requests/sec for static content– ~400 requests/sec for dynamic content– ~10 million unique visitors per month– On a typical Monday we serve 75,000,000 static files

Currently converting all store code to PHP

• Windows Server FreeBSD

• IIS Lighttpd

• ~100,000 lines of ASP Classic ~50,000 lines of PHP code

• ~5 weeks away from launch

Why Do We Care about Performance?

A Faster Website Will Make You More Money

Firefox

Firefox reduced the load time of their download page by 2.2 seconds

Downloads went up 15.4%

This could drive 60 MILLION yearly downloads

Google

Injected a 400ms delay into search0.44% fewer searches/user

0.76% after 6 weeks

After delay was removed, 0.21% fewer searches

Yahoo!

400ms delay

5-9% drop in full-page traffic

Direct Relationship Between Speed and Dollars

http://www.phpied.com/the-performance-business-pitch/

Server Side Monitoring

Lots of Options:• Paid:

– Coradiant– dynaTrace– Correlsense

• http://www.real-user-monitoring.com/ - Free Version

• Free:– Access Logs– Nagios– Ganglia– Hosted WebPagetest– Selenium/dynaTrace Ajax Edition

Server Side Monitoring

<?php$start = microtime(true);

…script content…

$end = microtime(true);

do_stuff(‘Description’, $end - $start);?>

WTH is do_stuff()?

• do_stuff() can do one of:– Log to a database (not ideal)

– Write to a text file (eww)

– Make a StatsD call over UDP (good) -http://codeascraft.etsy.com/2011/02/15/measure-anything-measure-everything/

StatsD/Graphite

Be Careful What You Watch

Averages can be misleading

Better to look at percentiles

What Does a Scalability Problem Look Like?

What Does a Scalability Problem Look Like?

What Does a Scalability Problem Look Like?

Ahh, much better!

What can you do?

• Start with the Database

• Run a database trace – Filter: Queries > 50ms– Filter: Reads > 1000– Start with the worst ones and optimize

Okay, I’ll “Optimize”

• Look at execution plan– Remove calls to remote servers

Database Optimizations

• Reduce Joins• Select * from Select Foo, Bar, Baz from…• Minimize/consolidate subqueries• Add indexes where needed– We added one index: Procedure dropped from 3.5

sec & 4500 reads to .06 sec and 130 reads!• Be careful with where clauses (don’t calculate

stuff in them)

Example

SELECT id, name, salary FROM employee WHERE salary < 25000;

NOT

SELECT id, name, salary FROM employee WHERE salary + 10000 < 35000;

Example

SELECT id, name, salary FROM employee WHERE salary < 25000;

NOT

SELECT id, name, salary FROM employee WHERE salary + 10000 < 35000;

Caching

The Fastest DB Query is the One That’s Never Made

Memcached

• Caching layer between database and webserver

• Can hold PHP objects and arrays

Memcached

$m = new Memcached();$m->pconnect(‘1.2.3.4', 11211);

$m->set(‘foo’, $bar, 600);

$baz = $m->get(‘foo’);

PHP Optimizations

Install APC

• APC – Alternative PHP Cache– Opcode Cache– User Cache– Awesome!

Opcode cache

User Cache

<?php$bar = 'BAR';apc_store('foo', $bar);var_dump(apc_fetch('foo'));?>

Outputs…

string(3) "BAR"

PHP Code Optimizations

• Set the max loop value before the loop:$max = count($rows);for ($i = 0; $i < $max; $i++) {

echo $i;}

• require_once() is slow• Minimize use of define()• Yes, single quotes are slightly faster than double

quotes

PHP Code Optimizations

• Could go on and on…– http://www.wmtips.com/php/tips-optimizing-php-code.htm

• Minimal returns

• Find the hotspots in your application and fix them

Example…

• Homepage takes 5 seconds to load

• Optimize PHP…– Reduce PHP execution time by 50%!

• But wait! PHP execution was only taking 100ms– Saves you 50ms in load time– 1% of total page load

HipHop for PHP

• Built by Facebook and Open Sourced

• Compiles PHP into C++

• Currently supports PHP 5.2

• http://developers.facebook.com/blog/post/358/• https://github.com/facebook/hiphop-php

Webserver Considerations

Webserver Optimizations

• Pick the right one– Lighttpd/Nginx instead of Apache– Designed to solve the C10K problem

• Lighttpd Used By:– Youtube– Wikipedia– Meebo

Lighttpd Benefits

• Event driven model:“Unlike traditional servers, Nginx doesn't rely on threads to handle requests. Instead it uses a much more scalable event-driven (asynchronous) architecture. This architecture uses small, but more importantly, predictable amounts of memory under load.”- http://wiki.nginx.org/

• FastCGI + spawn-fcgi– PHP Process Management– Many child processes – scale out application tier.

If you are stuck on Apache…

• mod_deflate– Gzips content for faster transfer times

• mod_pagespeed– Automatic performance improvements

• KeepAlives on– Server won’t create a new connection for every

resource

Load Testing

JMeter

JMeter

JMeter

Frontend Optimization

Client side Optimization is Critical

• 80-90% of load time takes place on the client

• For mobile 97%

Best Practices

• Reduce HTTP Requests– Combine CSS, JS– Use image sprites

.classname { background: url(sprite.png) no-repeat 0 -432px;}

Best Practices

• Minify CSS/JS– Strip comments and whitespace– Automate this – YUI Compressor• http://developer.yahoo.com/yui/compressor/

• Gzip all text– HTML– CSS– JS

• Optimize Images…

Image Optimization

• For graphics use PNG8 (256 color limitation)– No more .gif (unless animated)

• JPEGs can be saved at lower quality (75%-80%)

• Smush all images

Smush Your Images! - smushit.com

JPEG Quality

100% 80%

182 KB 48 KB

Measuring Frontend Performance

How Do You Measure Load Time?

• Google Webmaster Tools• WebPagetest (www.webpagetest.org)• Yottaa.com• Firebug• YSlow• PageSpeed• Dynatrace Ajax Edition

CDN – Content Delivery Network

Lots of Options

• Amazon CloudFront• MaxCDN• Limelight• Level3• Akamai• Cotendo

Expires Headers

• Set a far future date on static resources– CSS/JS/Images

• Release new version by changing the filename

• Benefits repeat visitors and repeat page views

Google Page Speed

Firebug Net Panel

Webmaster tools

Webmaster tools

Resources

• http://www.webperformancecentral.com/wiki/WebPagetest/Optimization_Help

• http://developer.yahoo.com/performance/• http://code.google.com/speed/• High Performance Websites (Book)• Even Faster Websites (Book)

Conclusion

“Speed is the most important feature. If your application is slow, people won’t use it. I see this more with mainstream users than I do with power users...If something is slow, they’re just gone.”

- Fred Wilson (10 Golden Principles of Web Apps)

Conclusion

“Speed is the most important feature. If your application is slow, people won’t use it. I see this more with mainstream users than I do with power users...If something is slow, they’re just gone.”

- Fred Wilson (10 Golden Principles of Web Apps)

?>We’re Hiring!

www.csnstores.com/careers

Get In Touch:www.meetup.com/Web-Performance-Boston/

jklein@csnstores.com@jonathanklein