Caching has been a 'hot' topic for a few years. But caching takes more than merely taking data and putting it in a cache : the right caching techniques can improve performance and reduce load significantly. But we'll also look at some major pitfalls, showing that caching the wrong way can bring down your site. If you're looking for a clear explanation about various caching techniques and tools like Memcached, Nginx and Varnish, as well as ways to deploy them in an efficient way, this talk is for you.

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

4. Owner of Cu.be Solutions (http://cu.be)

5. PHP developer since 1997

6. Developer of OpenX

7. Zend Certified Engineer

8. Zend Framework Certified Engineer

9. MySQL Certified Developer

11. System/network engineers ?

12. Managers ?

13. Caching experience ?

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

18. 5 visitors/day -> 5 million visitors/day

19. (Don't expect miracle cure !)

20. LAMP

21. LAMP

22. Architecture

23. Our test site

25. Result ?

26. Caching

27. What's caching ?

28. What is caching ? select * from article join user on article.user_id = user.id order by created desc limit 10

32. Hey, that's frontend !

33. Theory of caching DB

34. Theory of caching DB

36. Blogs

37. Full pages that don't change

38. Render -> Store in cache -> retrieve from cache

41. Usually a small block in a page

42. Best effect : reused on lots of pages

46. Resets on every insert/update/delete

48. free up DB resources for more hits !

52. XML file parsing

56. Modification frequency ?

57. Retrieval frequency ?

60. Make a complete query log (don't forget to turn it off !)

61. Check page loading times

63. Don't rely on it

66. lots of different queries

68. Caching SQL queries : preferably not

70. high latency

71. locking issues !

74. -> Hard to scale

77. Distributed memory caching system

78. Multiple machines ↔ 1 big memory-based hash-table

80. Values - max. 1Mbyte

82. Distributed memory caching system

83. Multiple machines ↔ 1 big memory-based hash-table

86. Memcache - where to install

87. Memcache - where to install

89. PECL

91. memcached -d -m <mem> -l <ip> -p <port>

92. ex. : memcached -d -m 2048 -l 127.0.0.1 -p 11211

94. Lose session data

95. Lose shopping cart data

96. ...

98. Lose session data

99. Lose shopping cart data

102. Caching in PHP <?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;

103. Let's give that a go ! /** * Retrieves the 10 highest rated articles * @return array List of highest rated articles */ static public function getTopRatedArticleList () { if (!$articleList = $cache->load( 'topRatedArticleList' )) { $articleList = self :: getTopRatedArticleListUncached (); $cache->save($articleList, 'topRatedArticleList' ); } return $articleList; }

107. Slab 2 : 480 bytes (400 * 1.2)

109. Each larger slab has room for fewer items (chunks)

110. -> Store a lot of very large objects

111. -> Large slabs might be full

112. -> Rest of slabs might be free

113. -> Try to store more -> eviction of data !

115. 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

116. Memcache - backing up

117. Memcache - deleting <?php $memcache = new Memcache(); $memcache->delete( 'myKey' ); $myData = $memcache->get( 'myKey' ); // $myData === false

120. Prefix / namespace your keys !

121. Only letters, numbers and underscore

123. Document your key names !

124. Updating data

125. Updating data

126. Adding/updating data $memcache->delete( 'ArticleDetails__Toshiba_32C100U_32_Inch' ); $memcache->delete( 'Homepage_Popular_Product_List' );

127. Adding/updating data

128. Adding/updating data - Why it crashed

129. Adding/updating data - Why it crashed

130. Adding/updating data - Why it crashed

131. Cache stampeding elePHPants

132. Cache stampeding

133. Memcache code ? DB

135. Run it before starting Webserver !

139. -> lots of new connections

140. -> memory spike

141. What if the process that created the lock fails ?

143. Exception to the rule : things that have an end date (calendar items)

148. Reverse proxy

149. Lightweight, fast

150. 7.5% of all Websites

152. Uses epoll / kqueue

153. Low memory footprint

154. 10000 active connections = normal

156. mod_dav*

158. Some 3 rd party modules (needs recompilation !)

160. Win32 binaries

161. Build from source (./configure; make; make install)

162. 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; }

164. Put Nginx at port 80

165. Nginx serves all statics (images, css, js, …)

166. Forward dynamic requests to Apache

167. 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; } }

168. Nginx - let's give that a go !

171. Now : PHP-FPM (in PHP 5.3.3 !)

172. Runs on port 9000

173. Nginx connects using fastcgi method location / { fastcgi_pass 127.0.0.1:9000; fastcgi_index index.php; include fastcgi_params; fastcgi_param SCRIPT_NAME $fastcgi_script_name; fastcgi_param SCRIPT_FILENAME /home/www.phpbenelux.eu/$fastcgi_script_name; fastcgi_param SERVER_NAME $host; fastcgi_intercept_errors on; }

175. Spawn new processes under high load

176. Chroot

177. Slow request log !

179. Spawn new processed under high load

180. Chroot

181. Slow request log !

182. fastcgi_finish_request() -> offline processing

183. Nginx + PHP-FPM - performance ?

184. LAMP

186. Reverse proxy cache / http accelerator / …

187. Caches (parts of) pages in memory

189. Nginx is faster (but doesn't have VCL)

192. /etc/varnish/*.vcl

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

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

198. ACLs

201. ESI

203. Varnish with ESI - hold on tight !

205. Images, js, css

207. Requests with Set-Cookie

208. Very large files (it's not a file server !)

209. User-specific content

211. Set AllowOverride to None

214. Don't mod_proxy -> use Nginx or Varnish !

215. High load on an SSL-site ? -> put SSL on a reverse proxy

217. Use an opcode cache

218. Caching storage - Opcode caching

220. Use an opcode cache

223. Let's see what difference opcode caching and profilers make...

224. KCachegrind is your friend

227. Select the right storage engine

228. Don't use persistent connect

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

231. Expires/Cache-Control header

232. HTTP 304 First request Next requests

233. HTTP 304 with ETag First request Next requests

235. Seconds to expiry

237. Date to expire on

238. Used by old proxies

239. Requires clock to be accurate !

242. HTTP/1.1 : &quot;Cache-Control: no-store&quot;

244. Test frontend

245. Check what requests frontend sends to backend

247. Use inline images in CSS/XHTML (not supported on all browsers yet)

248. 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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////........MEl0nGVUC6tObNnPceSFBaQVMJAxC4lo3gNOrUaFnTHoAxNm3XVxPfRq139e8BEGAjWD5bgIALw287T8AcAXLly2kjOACdc17higXSIKDO/Lpv7Qq4bw7APgBq8eOzX69InrZ6xe3dbxZffyTGkb8tdx8F+b0Xn2sFsCSBAgTM5lp63RHYnoHUudZgRgkGOGCB+43nGk4OGcQTabKx5dyJKJ7ImoUNCaRRAZYN1ppsrT3Y2gIwyjSQBAtUpABml/0IJGYd6VjQUDH9uBFkGxGm5I8dPQaRUAQUMBdhhBV25ZYUJZBcSAtSJBddWZZ5UAGPOTXlgkNVOSZdBxEwIkYu7VhYnAol5GaadRqF0Uaz0TgXnX2umVFyGakJUUAAADs=); margin-left: 4px; } <img border=0 src=&quot;data:image/gif;base64,R0lGODlhHwAfAPcAAAAAAIxKAKVjCLW1tb29tcbGvc7OxtZ7ANbWztbW1tbe1t7e1uelMefn1ufn3ufn5+fv3u+MAO/v5+/v7/fGCPf35/f37//nY/......Uaz0TgXnX2umVFyGakJUUAAADs=&quot;>

250. Use inline images in CSS (not supported on all browsers yet)

251. Use CSS Sprites

252. CSS Sprites

253. Tuning content - CSS sprites

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

256. Use inline images in CSS (not supported on all browsers yet)

260. Have a favicon.ico (don't 404 it !)

262. Split requests across subdomains

263. Put statics on a separate subdomain (without cookies !) www.phpbenelux.eu www.phpbenelux.eu images.phpbenelux.eu

268. HttpGzipModule in Nginx (HttpGzipStaticModule for pre-zipped statics !)

269. No native support in Varnish

272. Try to avoid redirects anyway

274. Watch the logging process ->

275. Logging = disk I/O -> can kill your site !

276. Slashdot effect

278. Use a cache abstraction layer (disk -> Memcache)

279. Don't install for the worst -> prepare for the worst

280. Have a test-setup

284. Slides http://www.slideshare.net/wimg

285. Twitter @wimgtr

286. E-mail [email_address]