Caching and tuning fun for high scalability
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This document presents techniques for caching and tuning to achieve high scalability, focusing on strategies for improving performance, reliability, and resource management for web applications. Key topics include various caching methods, the use of memcache and nginx, as well as tips for optimizing PHP and database queries. The content originates from a presentation by Wim Godden at Dynacon 2011.
Caching and tuning fun for high scalability
- 1. Caching and tuning fun for high scalability Wim Godden Cu.be Solutions
- 2. Notes about this presentation This presentation was presented at Dyncon 2011. It was designed to be presented live and as a result, many of the slides may seem odd when just looking at them without the spoken explanations. Also, the presentation had live benchmarks, which are ofcourse not present in the slides.
- 3. Who am I ? Wim Godden (@wimgtr)
- 4. Owner of Cu.be Solutions (http://cu.be)
- 5. PHP developer since 1997
- 8. Zend Framework Certified Engineer
- 10. Who are you ? Developers ?
- 12. Managers ?
- 14. Caching and tuning fun for high scalability Wim Godden Cu.be Solutions
- 15. Goals of this tutorial Everything about caching and tuning
- 16. A few techniques How-to
- 17. How-NOT-to -> Increase reliability, performance and scalability
- 18. 5 visitors/day -> 5 million visitors/day
- 19. (Don't expect miracle cure !)
- 20. LAMP
- 21. LAMP
- 22. Architecture
- 23. Our test site
- 24. Our base benchmark Apachebench = useful enough
- 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
- 29. Caching goals Source of information : Reduce # of request
- 30. Reduce the load Latency : Reduce for visitor
- 31. Reduce for Webserver load Network : Send less data to visitor
- 32. Hey, that's frontend !
- 33. Theory of caching DB
- 34. Theory of caching DB
- 35. Caching techniques #1 : Store entire pages Company Websites
- 36. Blogs
- 37. Full pages that don't change
- 38. Render -> Store in cache -> retrieve from cache
- 39. Caching techniques #1 : Store entire pages
- 40. Caching techniques #2 : Store parts of a page Most common technique
- 41. Usually a small block in a page
- 42. Best effect : reused on lots of pages
- 43. Caching techniques #2 : Store parts of a page
- 44. Caching techniques #3 : Store SQL queries ↔ SQL query cache Limited in size
- 45. Caching techniques #3 : Store SQL queries ↔ SQL query cache Limited in size
- 46. Resets on every insert/update/delete
- 47. Server and connection overhead Goal : not to get rid of DB
- 48. free up DB resources for more hits !
- 49. Caching techniques #3 : Store SQL queries
- 50. Caching techniques #4 : Store complex processing results Not just calculations
- 51. CPU intensive tasks : Config file parsing
- 52. XML file parsing
- 53. Loading CSV in an array Save resources -> more resources available
- 54. Caching techniques #4 : Store complex processing results
- 55. Caching techniques #xx : Your call Only limited by your imagination ! When you have data, think : Creating time ?
- 58. How to find cacheable data New projects : start from 'cache everything'
- 59. Existing projects : Look at MySQL slow query log
- 60. Make a complete query log (don't forget to turn it off !)
- 61. Check page loading times
- 62. Caching storage - MySQL query cache Use it
- 63. Don't rely on it
- 64. Good if you have : lots of reads
- 65. few different queries Bad if you have : lots of insert/update/delete
- 66. lots of different queries
- 67. Caching storage - Disk Data with few updates : good
- 68. Caching SQL queries : preferably not
- 69. DON'T use NFS or other network file systems especially for sessions
- 70. high latency
- 71. locking issues !
- 72. Caching storage - Disk / ramdisk Overhead : filesystem access
- 73. Limited number of files per directory -> Subdirectories Local 5 Webservers -> 5 local caches
- 74. -> Hard to scale
- 75. How will you keep them synchronized ? -> Don't say NFS or rsync !
- 76. Caching storage - Memcache Facebook, Twitter, Slashdot, … -> need we say more ?
- 77. Distributed memory caching system
- 78. Multiple machines ↔ 1 big memory-based hash-table
- 79. Key-value storage system Keys - max. 250bytes
- 80. Values - max. 1Mbyte
- 81. Caching storage - Memcache Facebook, Twitter, Slashdot, … -> need we say more ?
- 82. Distributed memory caching system
- 83. Multiple machines ↔ 1 big memory-based hash-table
- 84. Key-value storage system Keys - max. 250bytes
- 85. Values - max. 1Mbyte Extremely fast... non-blocking, UDP (!)
- 86. Memcache - where to install
- 87. Memcache - where to install
- 88. Memcache - installation & running it Installation Distribution package
- 89. PECL
- 90. Windows : binaries Running No config-files
- 91. memcached -d -m <mem> -l <ip> -p <port>
- 92. ex. : memcached -d -m 2048 -l 127.0.0.1 -p 11211
- 93. Caching storage - Memcache - some notes Not fault-tolerant It's a cache !
- 95. Lose shopping cart data
- 96. ...
- 97. Caching storage - Memcache - some notes Not fault-tolerant It's a cache !
- 99. Lose shopping cart data
- 100. … Different libraries Original : libmemcache
- 101. New : libmemcached (consistent hashing, UDP, binary protocol, …) Firewall your Memcache port !
- 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; }
- 104. Where's the data ? Memcache client decides (!)
- 105. 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 !
- 106. Memcache slabs (or why Memcache says it's full when it's not) Multiple slabs of different sizes : Slab 1 : 400 bytes
- 107. Slab 2 : 480 bytes (400 * 1.2)
- 108. Slab 3 : 576 bytes (480 * 1.2) (and so on...) Multiplier (1.2 here) can be configured
- 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 !
- 114. Memcache - Is it working ? Connect to it using telnet "stats" command ->
- 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
- 118. Memcache - tip Page with multiple blocks ? -> use Memcached::getMulti() Warning : what if you get some hits and some misses ?
- 119. Naming your keys Key names must be unique
- 120. Prefix / namespace your keys !
- 121. Only letters, numbers and underscore
- 122. md5() is useful -> BUT : harder to debug Use clear names
- 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
- 132. Cache stampeding
- 133. Memcache code ? DB
- 134. Cache warmup scripts Used to fill your cache when it's empty
- 135. Run it before starting Webserver !
- 136. 2 ways : Visit all URLs Error-prone
- 137. Hard to maintain Call all cache-updating methods Make sure you have a warmup script !
- 138. Cache stampeding - what about locking ? Seems like a nice idea, but... Lock in place
- 139. -> lots of new connections
- 140. -> memory spike
- 141. What if the process that created the lock fails ?
- 142. Quick word about expiration General rule : don't let things expire
- 143. Exception to the rule : things that have an end date (calendar items)
- 144. So... DON'T DELETE FROM CACHE (and don't expire unless usefull)
- 145. Time for... a break (15 min) After the break : Nginx Varnish Frontend caching Various tuning top tips
- 146. LAMP... -> LAMMP -> LANMMP
- 147. Nginx Web server
- 148. Reverse proxy
- 149. Lightweight, fast
- 150. 7.5% of all Websites
- 151. Nginx No threads, event-driven
- 152. Uses epoll / kqueue
- 153. Low memory footprint
- 154. 10000 active connections = normal
- 155. Nginx - a true alternative to Apache ? Not all Apache modules mod_auth_*
- 156. mod_dav*
- 157. … Basic modules are available
- 158. Some 3 rd party modules (needs recompilation !)
- 159. Nginx - Installation Packages
- 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; }
- 163. Nginx - phase 1 Move Apache to a different port (8080)
- 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 !
- 169. Nginx for PHP ? LANMMP to... LNMPP (ok, this is getting ridiculous)
- 170. Nginx with PHP In the past : spawn-fcgi (from Lighttpd)
- 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; }
- 174. Nginx + PHP-FPM features Graceful upgrade
- 175. Spawn new processes under high load
- 176. Chroot
- 177. Slow request log !
- 178. Nginx + PHP-FPM features Graceful upgrade
- 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
- 185. Varnish Not just a load balancer
- 186. Reverse proxy cache / http accelerator / …
- 187. Caches (parts of) pages in memory
- 188. Careful : uses threads
- 189. Nginx is faster (but doesn't have VCL)
- 190. Varnish - Installation & configuration Installation Packages
- 191. Source : ./configure && make && make install Configuration /etc/default/varnish
- 192. /etc/varnish/*.vcl
- 193. 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; } }
- 194. Varnish - backends + load balancing backend server1 { .host = "192.168.0.10"; .probe = { .url = "/"; .interval = 5s; .timeout = 1 s; .window = 5; .threshold = 3; } }
- 195. Varnish - VCL Varnish Configuration Language
- 196. DSL (Domain Specific Language) -> compiled to C Hooks into each request
- 197. Defines : Backends (web servers)
- 198. ACLs
- 199. Load balancing strategy Can be reloaded while running
- 200. Varnish - whatever you want Real-time statistics (varnishtop, varnishhist, ...)
- 201. ESI
- 202. Varnish - ESI Perfect for caching pages In your article page output : <esi:include src="/latest-news"/>
- 203. Varnish with ESI - hold on tight !
- 204. Varnish - what can/can't be cached ? Can : Static pages
- 205. Images, js, css
- 206. Pages or parts of pages that don't change often (ESI) Can't : POST requests
- 208. Very large files (it's not a file server !)
- 210. Apache - tuning tips Disable unused modules -> fixes 10% of performance issues
- 211. Set AllowOverride to None
- 212. Disable SymLinksIfOwnerMatch Site in /var/www/domain.com/subdomain/html
- 213. Check on /var, /var/www, /var/www/domain.com, etc. MinSpareServers, MaxSpareServers, StartServers, MaxClients, MPM selection -> a whole session of its own ;-)
- 214. Don't mod_proxy -> use Nginx or Varnish !
- 215. High load on an SSL-site ? -> put SSL on a reverse proxy
- 216. PHP speed - some tips Upgrade PHP - every minor release has 5-15% speed gain !
- 217. Use an opcode cache
- 218. Caching storage - Opcode caching
- 219. PHP speed - some tips Upgrade PHP - every minor release has 5-15% speed gain !
- 220. Use an opcode cache
- 221. Profile your code XHProf
- 222. Xdebug But : turn off profilers on acceptance/production platforms !
- 223. Let's see what difference opcode caching and profilers make...
- 224. KCachegrind is your friend
- 225. DB speed - some tips Avoid NOW() -> use PHP date("Y-m-d") as a parameter Why ? Query cache ! Index, index, index ! (where needed only)
- 226. Use same types for joins i.e. don't join decimal with int RAND() is evil !
- 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/
- 230. Caching in the browser HTTP 304 (Not modified)
- 232. HTTP 304 First request Next requests
- 233. HTTP 304 with ETag First request Next requests
- 234. Expires/Cache-control header Cache-Control HTTP/1.1
- 235. Seconds to expiry
- 236. Used by browsers First request Next requests No requests until item expires Expires HTTP/1.0
- 237. Date to expire on
- 238. Used by old proxies
- 239. Requires clock to be accurate !
- 240. Pragma: no-cache = evil "Pragma: no cache" doesn't make it uncacheable
- 241. Don't want caching on a page ? HTTP/1.0 : "Expires : Fri, 30 Oct 1998 00:00:00 GMT" (in the past)
- 242. HTTP/1.1 : "Cache-Control: no-store"
- 243. 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
- 244. Test frontend
- 245. Check what requests frontend sends to backend
- 246. Tuning frontend Minimize requests Combine CSS/JavaScript files
- 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="data:image/gif;base64,R0lGODlhHwAfAPcAAAAAAIxKAKVjCLW1tb29tcbGvc7OxtZ7ANbWztbW1tbe1t7e1uelMefn1ufn3ufn5+fv3u+MAO/v5+/v7/fGCPf35/f37//nY/......Uaz0TgXnX2umVFyGakJUUAAADs=">
- 249. Tuning frontend Minimize requests Combine CSS/JavaScript files
- 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
- 255. Tuning frontend Minimize requests Combine CSS/JavaScript files
- 256. Use inline images in CSS (not supported on all browsers yet)
- 257. Use CSS Sprites (horizontally if possible) Put CSS at top
- 258. Put JavaScript at bottom Max. no connections
- 259. Especially if JavaScript does Ajax (advertising-scripts, …) ! Avoid iFrames Again : max no. of connections Don't scale images in HTML
- 260. Have a favicon.ico (don't 404 it !)
- 261. Tuning frontend Use GET for Ajax retrieval requests (and cache them !)
- 262. Split requests across subdomains
- 263. Put statics on a separate subdomain (without cookies !) www.phpbenelux.eu www.phpbenelux.eu images.phpbenelux.eu
- 264. Tuning miscellaneous Avoid DNS lookups Frontend : don't use too many subdomains (2 = ideal)
- 265. Backend : Turn off DNS resolution in Apache : HostnameLookups Off
- 266. If your app uses external data Run a local DNS cache (timeout danger !)
- 267. Make sure you can trust DNS servers (preferable run your own) Compress non-binary content (GZIP) mod_deflate in Apache
- 268. HttpGzipModule in Nginx (HttpGzipStaticModule for pre-zipped statics !)
- 269. No native support in Varnish
- 270. What else can kill your site ? Redirect loops Multiple requests More load on Webserver
- 271. More PHP to process Additional latency for visitor
- 272. Try to avoid redirects anyway
- 273. -> In ZF : use $this->_forward instead of $this->_redirect Watch your logs, but equally important...
- 274. Watch the logging process ->
- 275. Logging = disk I/O -> can kill your site !
- 276. Slashdot effect
- 277. Above all else... be prepared ! Have a monitoring system
- 278. Use a cache abstraction layer (disk -> Memcache)
- 279. Don't install for the worst -> prepare for the worst
- 280. Have a test-setup
- 281. Have fallbacks Turn off non-critical functionality
- 282. Questions ?
- 283. Contact Web http://techblog.wimgodden.be
- 285. Twitter @wimgtr
- 287. Please... Rate my talk : http://joind.in/2950
- 288. Thanks !