1. Caching and tuning fun
for high scalability
Wim Godden
Cu.be Solutions

2. Who am I ?
Wim Godden (@wimgtr)
Founder of Cu.be Solutions (http://cu.be)
Open Source developer since 1997
Developer of OpenX, PHPCompatibility, Nginx extensions, ...
Zend / ZF Certified Engineer
MySQL Certified Developer
Speaker at PHP and Open Source conferences

3. Who are you ?
Developers ?
System/network engineers ?
Managers ?
Caching experience ?

4. Goals of this tutorial
Everything about caching and tuning
A few techniques
How-to
How-NOT-to
→ Increase reliability, performance and scalability
5 visitors/day → 5 million visitors/day
(Don't expect miracle cure !)

5. LAMP

6. Architecture

7. Test page
3 DB-queries
select firstname, lastname, email from user where user_id = 5;
select title, createddate, body from article order by createddate desc limit 5;
select title, createddate, body from article order by score desc limit 5;
Page just outputs result

8. Our base benchmark
Apachebench = useful enough
Result ?
Single webserver Proxy
Static PHP Static PHP
Apache + PHP 3900 17.5 6700 17.5
Limit :
CPU, network
or disk
Limit :
database

9. CachingCaching

10. What is caching ?
CACHECACHE

11. What is caching ?
x = 5, y = 2
n = 50
Same result
CACHECACHE
select
*
from
article
join user
on article.user_id = user.id
order by
created desc
limit
10
Doesn't change
all the time

12. Theory of caching
DB
Cache
$data = get('key')
false
GET /page
Page
select data from
table
$data = returned result
set('key', $data)
if ($data == false)

13. Theory of caching
DB
Cache
HIT

14. Caching goals - 1st
goal
Reduce # of concurrent request
Reduce the load

15. Caching goals - 2nd
goal

16. Some figures
Pageviews : 5000 (4000 on 10 pages)
Avg. loading time : 200ms
Cache 10 pages
Avg. loading time : 20ms
→ Total avg. loading time : 56ms
Worth it ?

17. Caching goals - 3rd
goal
Send less data across the network / Internet
You benefit → lower bill from upstream provider
Users benefit → faster page load
Wait a second... that's mostly frontend stuff !

18. Caching techniques
#1 : Store entire pages
Company Websites
Blogs
Full pages that don't change
Render → Store in cache → retrieve from cache

19. Caching techniques
#2 : Store parts of a page
Most common technique
Usually a small block in a page
Best effect : reused on lots of pages
Can be inserted on dynamic pages

20. Caching techniques
#3 : Store SQL queries
↔ SQL query cache
Limited in size

21. Caching techniques
#3 : Store SQL queries
↔ SQL query cache
Limited in size
Resets on every insert/update/delete
Server and connection overhead
Goal :
not to get rid of DB
free up DB resources for more hits !
Better :
store returned object
store group of objects

22. Caching techniques
#4 : Store complex PHP results
Not just calculations
CPU intensive tasks :
Config file parsing
XML file parsing
Loading CSV in an array
Save resources → more resources available

23. Caching techniques
#xx : Your call
Only limited by your imagination !
When you have data, think :
Creating time ?
Modification frequency ?
Retrieval frequency ?

24. How to find cacheable data
New projects : start from 'cache everything'
Existing projects :
Look at MySQL slow query log
Make a complete query log (don't forget to turn it off !)
→ Use Percona Toolkit (pt-query-digest)
Check page loading times

25. Caching storage - MySQL query cache
Use it
Don't rely on it
Good if you have :
lots of reads
few different queries
Bad if you have :
lots of insert/update/delete
lots of different queries

26. Caching storage - Database memory tables
Tables stored in memory
In MySQL : memory/heap table
↔ temporary table :
memory tables are persistent
temporary tables are session-specific
Faster than disk-based tables
Can be joined with disk-based tables
But :
default 16MByte limit
master-slave = trouble
if you don't need join → overhead of DB software
So : don't use it unless you need to join

27. Caching storage - Opcode caching
DO !

28. Caching storage - Opcode caching
APC
De-facto standard
Will be in PHP core in 5.4 ? 5.5 ? 6.0 ?
PECL or packages

29. Caching storage - Opcode caching
Zend Optimizer+
Will be in PHP core in 5.5
APC
eAccelerator

30. Caching storage - Opcode caching
Zend Optimizer+
Will be in PHP core in 5.5
APC
eAccelerator
PHP PHP + Zend O+ PHP + APC
42.18 req/sec 206.20 req/sec 211.49 req/sec

31. Caching storage - Disk
Data with few updates : good
Caching SQL queries : preferably not
DON'T use NFS or other network file systems
high latency
possible problem for sessions : locking issues !

32. Caching storage - Memory disk (ramdisk)
Usually faster than physical disk
But : OS file caching makes difference minimal
(if you have enough memory)

33. Caching storage - Disk / ramdisk
Overhead : filesystem
Limited number of files per directory
→ Subdirectories
Local
5 Webservers → 5 local caches
How will you keep them synchronized ?
→ Don't say NFS or rsync !

34. Caching storage - Memcache(d)
Facebook, Twitter, YouTube, … → need we say more ?
Distributed memory caching system
Multiple machines ↔ 1 big memory-based hash-table
Key-value storage system
Keys - max. 250bytes
Values - max. 1Mbyte

35. Caching storage - Memcache(d)
Facebook, Twitter, YouTube, … → need we say more ?
Distributed memory caching system
Multiple machines ↔ 1 big memory-based hash-table
Key-value storage system
Keys - max. 250bytes
Values - max. 1Mbyte
Extremely fast... non-blocking, UDP (!)

36. Memcache - where to install

37. Memcache - where to install

38. Memcache - installation & running it
Installation
Distribution package
PECL
Windows : binaries
Running
No config-files
memcached -d -m <mem> -l <ip> -p <port>
ex. : memcached -d -m 2048 -l 172.16.1.91 -p 11211

39. Caching storage - Memcache - some notes
Not fault-tolerant
It's a cache !
Lose session data
Lose shopping cart data
...

40. Caching storage - Memcache - some notes
Not fault-tolerant
It's a cache !
Lose session data
Lose shopping cart data
…
Different libraries
Original : libmemcache
New : libmemcached (consistent hashing, UDP, binary protocol, …)
Firewall your Memcache port !

41. Memcache in code
<?php
$memcache = new Memcache();
$memcache->addServer('172.16.0.1', 11211);
$memcache->addServer('172.16.0.2', 11211);
$myData = $memcache->get('myKey');
if ($myData === false) {
$myData = GetMyDataFromDB();
// Put it in Memcache as 'myKey', without compression, with no expiration
$memcache->set('myKey', $myData, false, 0);
}
echo $myData;
Careful : false is a valid value !

42. Memcache in code
<?php
$memcache = new Memcache();
$memcache->addServer('172.16.0.1', 11211);
$memcache->addServer('172.16.0.2', 11211);
$myData = $memcache->get('myKey');
if ($memcache->getResultCode() == Memcached::RES_NOTSTORED) {
$myData = GetMyDataFromDB();
// Put it in Memcache as 'myKey', without compression, with no expiration
$memcache->set('myKey', $myData, false, 0);
}
echo $myData;

43. Benchmark with Memcache
Single webserver Proxy
Static PHP Static PHP
Apache + PHP 3900 17.5 6700 17.5
Apache + PHP + MC 3900 55 6700 108

44. Where's the data ?
Memcache client decides (!)
2 hashing algorithms :
Traditional
Server failure → all data must be rehashed
Consistent
Server failure → 1/x of data must be rehashed (x = # of servers)
No replication !

45. Memcached ? Couchbase ? Redis ? … ?
Memcached Couchbase Redis
Purpose Key-value store Document store Key-value store
Additional indexes No Yes No
Replication No Master-master
Master-slave
Master-slave
Persistency No Yes Yes
Interesting read : http://kkovacs.eu/cassandra-vs-mongodb-vs-couchdb-vs-redis
(Cassandra vs MongoDB vs CouchDB vs Redis vs Riak vs HBase vs Couchbase
vs Neo4j vs Hypertable vs ElasticSearch vs Accumulo vs VoltDB vs Scalaris
comparison)

46. Memcache slabs
(or why Memcache says it's full when it's not)
Multiple slabs of different sizes :
Slab 1 : 400 bytes
Slab 2 : 480 bytes (400 * 1.2)
Slab 3 : 576 bytes (480 * 1.2) (and so on...)
Multiplier (1.2 here) can be configured
Store a lot of very large objects
→ Large slabs : full
→ Rest : free
→ Eviction of data !

47. Memcache - Is it working ?
Connect to it using telnet
"stats" command →
Use Cacti or other monitoring tools
STAT pid 2941
STAT uptime 10878
STAT time 1296074240
STAT version 1.4.5
STAT pointer_size 64
STAT rusage_user 20.089945
STAT rusage_system 58.499106
STAT curr_connections 16
STAT total_connections 276950
STAT connection_structures 96
STAT cmd_get 276931
STAT cmd_set 584148
STAT cmd_flush 0
STAT get_hits 211106
STAT get_misses 65825
STAT delete_misses 101
STAT delete_hits 276829
STAT incr_misses 0
STAT incr_hits 0
STAT decr_misses 0
STAT decr_hits 0
STAT cas_misses 0
STAT cas_hits 0
STAT cas_badval 0
STAT auth_cmds 0
STAT auth_errors 0
STAT bytes_read 613193860
STAT bytes_written 553991373
STAT limit_maxbytes 268435456
STAT accepting_conns 1
STAT listen_disabled_num 0
STAT threads 4
STAT conn_yields 0
STAT bytes 20418140
STAT curr_items 65826
STAT total_items 553856
STAT evictions 0
STAT reclaimed 0

48. Memcache - backing up

49. Memcache - deleting
<?php
$memcache = new Memcache();
$memcache->delete('myKey');

50. Memcache - caching a page
<?php
$output = $memcache->get('page_' . $page_id);
if ($output === false) {
ob_start();
GetMyPageInRegularWay($page_id);
$output = ob_get_contents();
ob_end_clean();
$memcache->set('page_' . $page_id, $output, false, 600); // Cache 10 mins
}
echo $output;

51. Memcache - tip
Page with multiple blocks ?
→ use Memcached::getMulti()
But : what if you get some hits and some misses ?
getMulti($array)
Hashing
algorithm

52. Naming your keys
Key names must be unique
Prefix / namespace your keys !
Only letters, numbers and underscore
Why ? → Change caching layer
md5() is useful
→ BUT : harder to debug
Use clear names
Document your key names !

53. Updating data

54. Updating data
LCD_Popular_Product_List

55. Adding/updating data
$memcache->delete('ArticleDetails__Toshiba_32C100U_32_Inch');
$memcache->delete('LCD_Popular_Product_List');

56. Adding/updating data

57. Adding/updating data - Why it crashed

58. Adding/updating data - Why it crashed

59. Adding/updating data - Why it crashed

60. Cache stampeding

61. Cache stampeding

62. Memcache code ?
DB
Visitor interface Admin interface
Memcache code

63. Cache warmup scripts
Used to fill your cache when it's empty
Run it before starting Webserver !
2 ways :
Visit all URLs
Error-prone
Hard to maintain
Call all cache-updating methods
Make sure you have a warmup script !

64. Cache stampeding - what about locking ?
Seems like a nice idea, but...
While lock in place
What if the process that created the lock fails ?

65. Quick word about expiration
General rule : don't let things expire
Exception to the rule : things that have an end date (calendar
items)

66. So...
DON'T DELETE FROM CACHE
&
DON'T EXPIRE FROM CACHE
(unless you know you'll never store it again)

67. Time for...
a break (15 min)
After the break :
Byebye Apache
Reverse proxying
The importance of frontend
lots of hints & tips...

68. LAMP...
→ LAMMP
→ LANMMP

69. Nginx
Web server
Reverse proxy
Lightweight, fast
12.81% of all Websites

70. Nginx
No threads, event-driven
Uses epoll / kqueue
Low memory footprint
10000 active connections = normal

71. Nginx - a true alternative to Apache ?
Not all Apache modules
mod_auth_*
mod_dav*
…
Basic modules are available
Lots of 3rd
party modules (needs recompilation !)

72. Nginx - Installation
Packages
Win32 binaries
→ Not for production !
Build from source (./configure; make; make install)

73. Nginx - Configuration
server {
listen 80;
server_name www.domain.ext *.domain.ext;
index index.html;
root /home/domain.ext/www;
}
server {
listen 80;
server_name photo.domain.ext;
index index.html;
root /home/domain.ext/photo;
}

74. Nginx - phase 1
Move Apache to a different port (8080)
Put Nginx at port 80
Nginx serves all statics (images, css, js, …)
Forward dynamic requests to Apache

75. Nginx for static files only
server {
listen 80;
server_name www.domain.ext;
location ~* ^.*.(jpg|jpeg|gif|png|ico|css|zip|tgz|gz|rar|bz2|doc|xls|pdf|ppt|txt|tar|rtf|js)$ {
expires 30d;
root /home/www.domain.ext;
}
location / {
proxy_pass http://www.domain.ext:8080;
proxy_pass_header Set-Cookie;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header Host $host;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
}
}

76. Nginx for PHP ?
Bottleneck = PHP ? Keep it in Apache
Bottleneck = memory ? Go for it !
LANMMP to... LNMPP
(ok, this is getting ridiculous)

77. Nginx with PHP-FPM
Since PHP 5.3.3
Runs on port 9000
Nginx connects using fastcgi method
location / {
fastcgi_pass 127.0.0.1:9000;
fastcgi_index index.php;
include fastcgi_params;
fastcgi_param SCRIPT_NAME $fastcgi_script_name;
fastcgi_param SCRIPT_FILENAME /home/www.domain.ext/$fastcgi_script_name;
fastcgi_param SERVER_NAME $host;
fastcgi_intercept_errors on;
}

78. Nginx + PHP-FPM features
Graceful upgrade
Spawn new processes under high load
Chroot
Slow request log !

79. Nginx + PHP-FPM features
Graceful upgrade
Spawn new processes under high load
Chroot
Slow request log !
fastcgi_finish_request() → offline processing

80. Nginx + PHP-FPM - performance ?
Single webserver Proxy
Static PHP Static PHP
Apache + PHP 3900 17.5 6700 17.5
Apache + PHP + MC 3900 55 6700 108
Nginx + PHP-FPM + MC 11700 57 11200 112
Limit :
single-threaded
Apachebench

81. Nginx + PHP-FPM - performance ?
Single webserver Proxy
Static PHP Static PHP
Apache + PHP 3900 17.5 6700 17.5
Apache + PHP + MC 3900 55 6700 108
Nginx + PHP-FPM + MC 11700 57 11200 112
Apache (tuned) +
PHP/MC
10600 55 11400 108
Limit :
single-threaded
Apachebench

82. Reverse proxy time...

83. Varnish
Not just a load balancer
Reverse proxy cache / http accelerator / …
Caches (parts of) pages in memory
Careful :
uses threads (like Apache)
Nginx usually scales better (but doesn't have VCL)

84. Varnish - Installation & configuration
Installation
Packages
Source : ./configure && make && make install
Configuration
/etc/default/varnish
/etc/varnish/*.vcl

85. Varnish - backends + load balancing
backend server1 {
.host = "192.168.0.10";
}
backend server2 {
.host = "192.168.0.11";
}
director example_director round-robin {
{
.backend = server1;
}
{
.backend = server2;
}
}

86. Varnish - backends + load balancing
backend server1 {
.host = "192.168.0.10";
.probe = {
.url = "/";
.interval = 5s;
.timeout = 1 s;
.window = 5;
.threshold = 3;
}
}

87. Varnish - VCL
Varnish Configuration Language
DSL (Domain Specific Language)
→ compiled to C
Hooks into each request
Defines :
Backends (web servers)
ACLs
Load balancing strategy
Can be reloaded while running

88. Varnish - whatever you want
Real-time statistics (varnishtop, varnishhist, ...)
ESI

89. Article content page
/page/732
Article content (TTL : 15 min)
/article/732
Varnish - ESI
Perfect for caching pages
Header (TTL : 60 min)
/top
Latest news (TTL : 2 min) /news
Navigation
(TTL :
60 min)
/nav
In your /page/732 output :
<esi:include src="/top"/>
<esi:include src="/nav"/>
<esi:include src="/news"/>
<esi:include src="/article/732"/>
In your Varnish config :
sub vcl_fetch {
if (req.url == "/news") {
esi; /* Do ESI processing */
set obj.ttl = 2m;
} elseif (req.url == "/nav") {
esi;
set obj.ttl = 1m;
} elseif ….
….
}

90. Varnish with ESI - hold on tight !
Single webserver Proxy
Static PHP Static PHP
Apache + PHP 3900 17.5 6700 17.5
Apache + PHP + MC 3900 55 6700 108
Nginx + PHP-FPM + MC 11700 57 11200 112
Varnish - - 11200 4200

91. Varnish - what can/can't be cached ?
Can :
Static pages
Images, js, css
Pages or parts of pages that don't change often (ESI)
Can't :
POST requests
Very large files (it's not a file server !)
Requests with Set-Cookie
User-specific content

92. ESI → no caching on user-specific content ?
Logged in as : Wim Godden
5 messages
TTL = 5minTTL=1h
TTL = 0s ?

93. Coming soon...
Based on Nginx
Reduces load by 50 – 95%
Requires code changes !
Well-built project → few changes
Effect on webservers and database servers

94. Requesting /page (1st
time)
Nginx
Shared memory
1
2
3
4
/page
/page

95. Requesting /page ESI subrequests (1st
time)
Nginx
1
2
3
/menu
/news
/top (in ESI session)

96. Requesting /page (next time)
Nginx
Shared memory
1
2
/page
/menu
/news
/top (in ESI session)
/page

97. New message is sent...
POST /send
DB
insert into...
set(...)
top (in ESI session)

98. Advantages
No repeated GET hits to webserver anymore !
At login : POST → warm up the cache !
No repeated hits for user-specific content
Not even for non-specific content

99. News added
addnews() method
DB
insert into...
set(...)
Memcache key /news

100. How many Memcache requests ?
Logged in as : Wim Godden
5 messages
<scl:include key="news" src="/news" ttl="5m" />
<scl:include
key="menu"
src="/menu"
ttl="1h" />
<scl:include key="top" src="/top" session="true" ttl="1h" />

101. First release : ESI
Part of the ESI 1.0 spec
Only relevant features implemented
Extension for dynamic session support
But : unavailable for copyright reasons

102. Rebuilt from scratch : SCL
Session-specific Caching Language
Language details :
Control structures : if/else, switch/case, foreach
Variable handling
Strings : concatenation, substring, ...

103. What's the result ?

104. Figures
Second customer (already using Nginx + Memcache) :
No. of web servers : 72 → 8
No. of db servers : 15 → 4
Total : 87 → 12 (86% reduction !)
Latest customer :
Total no. of servers : 1350 → 380
72% reduction → €1.5 million / year

105. A real example : vBulletin
DB Server Load Web Server Load Max Requests/sec (1 = 282)
0
5
10
15
20
25
30
35
Standard install
With Memcached
Nginx + SCL + memcached

106. Availability
Good news :
It will become Open Source
It's solid : stable at 3 customers, being installed at 1 more
Bad news :
First customer holds copyrights
Total rebuild
→ Open Source release
Beta : Sep 2013
Final : End 2013 (on Github !)

107. Time to tune...

108. PHP speed - some tips
Upgrade PHP - every minor release has 5-15% speed gain !
Use an opcode cache (Zend O+, APC, eAccelerator, XCache)
Profile your code
XHProf
Xdebug
But : turn off profilers on acceptance/production platforms !

109. KCachegrind is your friend

110. PHP speed - some tips
Most performance issues are in DB queries → look there first !
Log PHP errors and review those logs !
Shorter code != faster code → keep your code readable !
Hardware cost < Manpower cost
→ 1 more server < 30 mandays of labor
Keep micro-optimizations in code = last thing on list

111. Apache - tuning tips
Disable unused modules → fixes 10% of performance issues
Set AllowOverride to None. Enable only where needed !
Disable SymLinksIfOwnerMatch. Enable only where needed !
MinSpareServers, MaxSpareServers, StartServers, MaxClients,
MPM selection → a whole session of its own ;-)
Don't mod_proxy → use Nginx or Varnish !
High load on an SSL-site ? → put SSL on a reverse proxy

112. DB speed - some tips
Avoid dynamic functions
Ex. : select id from calendar where startDate > curdate()
Better : select id from calendar where startDate > "2013-05-14"
Use same types for joins
i.e. don't join decimal with int, bigint with int, etc.
RAND() is evil !
count(*) is evil in InnoDB without a where clause !
Persistent connect is sort-of evil
Index, index, index !
→ But only on fields that are used in where, order by, group by !

113. Caching & Tuning @ frontend
http://www.websiteoptimization.com/speed/tweak/average-web-page/

114. Caching in the browser
HTTP 304 (Not modified)
Expires/Cache-Control header
2 notes :
Don't use POST if you want to cache
Don't cache user-specific pages in browser (security !)

115. HTTP 304
Browser Server
No header
Last Modified: Fri 28 Jan 2011 08:31:01 GMT
If-Modified-Since: Fri 28 Jan 2011 08:31:01 GMT
200 OK / 304 Not Modified
First request
Next requests

116. HTTP 304 with ETag
Browser Server
No header
Etag: 8a53321-4b-43f0b6dd972c0
If-None-Match: 8a53321-4b-43f0b6dd972c0
200 OK / 304 Not Modified
First request
Next requests

117. Expires/Cache-control header
Cache-Control
HTTP/1.1
Seconds to expiry
Used by browsers
Browser Server
No header
Expires: Fri 29 Nov 2011 12:11:08 GMT
Cache-Control: max-age=86400
First request
Next requests No requests until item expires
Expires
HTTP/1.0
Date to expire on
Used by old proxies
Requires clock to be accurate !

118. Pragma: no-cache = evil
"Pragma: no-cache" doesn't make it uncacheable
Don't want caching on a page ?
HTTP/1.0 : "Expires : Fri, 30 Oct 1998 00:00:00 GMT" (in the past)
HTTP/1.1 : "Cache-Control: no-store"

119. Frontend tuning
1. You optimize backend
2. Frontend engineers messes up → havoc on backend
3. Don't forget : frontend sends requests to backend !
SO...
Care about frontend
Test frontend
Check what requests frontend sends to backend

120. Tuning frontend
Minimize requests
Combine CSS/JavaScript files
Use inline images in CSS/XHTML (not supported on all browsers yet)

121. Frontend tuning - inline CSS/XHTML images
#navbar span {
width: 31px;
height: 31px;
display: inline;
float: left;
margin-right: 4px;
}
.home { background-image:
url(data:image/gif;base64,R0lGODlhHwAfAPcAAAAAAIxKAKVjCLW1tb29tcbGvc7OxtZ7ANbWztbW1tbe1t7e1uelMefn1ufn3ufn5+fv3u
+MAO/v5+/v7/fGCPf35/f37//nY////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////........MEl0nGVUC6tObNnPceSFBaQVMJAxC4lo3gNOrUaFnTHoAxNm3XVxPfRq139e8BEGAjWD5bgI
ALw287T8AcAXLly2kjOACdc17higXSIKDO/Lpv7Qq4bw7APgBq8eOzX69InrZ6xe3dbxZffyTGkb8tdx8F+b0Xn2sFsCSBAgTM5lp63RH
YnoHUudZgRgkGOGCB+43nGk4OGcQTabKx5dyJKJ7ImoUNCaRRAZYN1ppsrT3Y2gIwyjSQBAtUpABml/0IJGYd6VjQUDH9uBFkGx
Gm5I8dPQaRUAQUMBdhhBV25ZYUJZBcSAtSJBddWZZ5UAGPOTXlgkNVOSZdBxEwIkYu7VhYnAol5GaadRqF0Uaz0TgXnX2umV
FyGakJUUAAADs=); margin-left: 4px; }
<img border=0
src="data:image/gif;base64,R0lGODlhHwAfAPcAAAAAAIxKAKVjCLW1tb29tcbGvc7OxtZ7ANbWztbW1tbe1t7e1uelMefn1ufn3ufn5+fv
3u+MAO/v5+/v7/fGCPf35/f37//nY/......Uaz0TgXnX2umVFyGakJUUAAADs=">

122. Tuning frontend
Minimize requests
Combine CSS/JavaScript files
Use inline images in CSS/XHTML (not supported on all browsers yet)
Use CSS Sprites

123. CSS Sprites

124. Tuning content - CSS sprites

125. Tuning content - CSS sprites
11 images
11 HTTP requests
24KByte
1 image
1 HTTP requests
14KByte

126. Tuning frontend
Minimize requests
Combine CSS/JavaScript files
Use inline images in CSS/XHTML (not supported on all browsers yet)
Use CSS Sprites (horizontally if possible)
Put CSS at top
Put JavaScript at bottom
Max. no connections
Especially if JavaScript does Ajax (advertising-scripts, …) !
Avoid iFrames
Again : max no. of connections
Don't scale images in HTML
Have a favicon.ico (don't 404 it !)
→ see my blog

127. Tuning frontend
Don't use inline CSS/JavaScript
CSS/JavaScript need to be external files (minified, merged)
Why ? → Cacheable by browser / reverse proxy
Use GET for Ajax retrieval requests (and cache them !)
Optimize images (average 50-60% !)
Split requests across subdomains
Put statics on a separate subdomain (without cookies !)
www.domain.ext
Max. 2
requests
www.domain.ext
Max. 2
requests
Max. 2
requests
images.domain.ext

128. Tuning miscellaneous
Avoid DNS lookups
Frontend : don't use too many subdomains (2 = ideal)
Backend :
Turn off DNS resolution in Apache : HostnameLookups Off
If your app uses external data
Run a local DNS cache (timeout danger !)
Make sure you can trust DNS servers (preferable run your own)
Compress non-binary content (GZIP)
mod_deflate in Apache
HttpGzipModule in Nginx (HttpGzipStaticModule for pre-zipped statics !)
No native support in Varnish

129. What else can kill your site ?
Redirect loops
Multiple requests
More load on Webserver
More PHP to process
Additional latency for visitor
Try to avoid redirects anyway
→ In ZF : use $this->_forward instead of $this->_redirect
Watch your logs, but equally important...
Watch the logging process →
Logging = disk I/O → can kill your server !

130. Above all else... be prepared !
Have a monitoring system
Use a cache abstraction layer (disk → Memcache)
Don't install for the worst → prepare for the worst
Have a test-setup
Have fallbacks
→ Turn off non-critical functionality

131. So...
Cache
But : never delete, always push !
Have a warmup script
Monitor your cache
Have an abstraction layer
Apache = fine, Nginx = better
Static pages ? Use Varnish
Tune your frontend → impact on backend !

132. Questions ?

133. Questions ?

134. Contact
Twitter @wimgtr
Web http://techblog.wimgodden.be
Slides http://www.slideshare.net/wimg
E-mail wim.godden@cu.be
Please...
Rate my talk : http://joind.in/8195

135. Thanks !
Please...
Rate my talk : http://joind.in/8195