When dynamic becomes static: the next step in web caching techniques

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Although tools like Varnish can improve performance and scalability for static sites, when user-specific content is needed, a hit to the PHP/Ruby/Python/.Net backend is still required, causing scalability issues. We'll look at a brand-new Nginx module which implements an ultra-fast and scalable solution to this problem, changing the way developers think about designing sites with user-specific content.

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When dynamic becomes static: the next step in web caching techniques

  1. 1. When dynamic becomes static – the next step in web caching techniques Wim Godden Cu.be Solutions
  2. 2. Disclaimer The next step As in : what you will be doing in the future Not as in : go home and run it ;-) Language of choice : PHP But : think Perl, Python, Ruby, Java, .Net, …
  3. 3. Who am I ? Wim Godden (@wimgtr) Founder of Cu.be Solutions (http://cu.be) Open source developer since 1997 Developer of OpenX, PHPCompatibility, ... Speaker at PHP and Open Source conferences
  4. 4. Who are you ? Developers ? System/network engineers ? Managers ?
  5. 5. To understand the present Understand the past
  6. 6. The Stone Age New blog post by : caveman003
  7. 7. Pre-PHP : draw it and make html
  8. 8. The Egyptian Era
  9. 9. Old-school PHP : 'rebuild-every-time'
  10. 10. The Industrial Revolution
  11. 11. PHP : let's cache
  12. 12. Extra ! Extra !
  13. 13. PHP : dynamic content in static content
  14. 14. The Modern Era
  15. 15. PHP : multiple webservers
  16. 16. PHP : push updates to cache
  17. 17. Today
  18. 18. Adding reverse proxy caching
  19. 19. Website X with ESI Header Latest news Article content page Navigation Page content
  20. 20. Website X with ESI Top header (TTL = 2h) Latest news Article content page Navigation (TTL = 1h) Page content
  21. 21. Website X with ESI Top header (TTL = 2h) Latest news (TTL = 2m) Article content page Navigation (TTL = 1h) Page content (TTL = 30m)
  22. 22. Going to /page/id/732 <esi:include src="/top"/> <esi:include src="/nav"/> <esi:include src="/latest-news"/> <esi:include src="/article/id/732"/>
  23. 23. Varnish - ESI <esi:include src="/top"/> <esi:include src="/news"/> Article content page <esi:include src="/nav"/> <esi:include src="/article/732"/>
  24. 24. A simple benchmark – 2KByte JPEG Apache 2.2 4210 IIS 7.5 3960 Varnish 3.0 11400
  25. 25. A dynamically generated, but static page Apache 2.2 + PHP (3 DB queries) 18 IIS 7.5 + .Net (3 DB queries) 16 Varnish 3.0 11400
  26. 26. Varnish - what can/can't be cached ? Can : Static pages Images, js, css Static 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
  27. 27. ESI → no caching on user-specific content ? Logged in as : Wim Godden TTL = 0s ? TTL=1h 5 messages TTL = 5min
  28. 28. Nginx Web server Reverse proxy Lightweight, fast 12.81% of all Websites
  29. 29. Nginx No threads, event-driven Uses epoll / kqueue Low memory footprint 10000 active connections = normal
  30. 30. ESI on Nginx Logged in as : Wim Godden 5 messages Menu NEWS
  31. 31. ESI SCL on Nginx <scl:include key="top" src="/top" session="true" ttl="1h" /> <scl:include key="menu" src="/menu" ttl="1h" /> <scl:include key="news" src="/news" ttl="5m" />
  32. 32. Requesting /page (1st time) Nginx 1 Shared memory /page 4 /page 3 2
  33. 33. Requesting /page ESI subrequests (1st time) Nginx 1 2 3 /menu /news /top (in SCL session)
  34. 34. Requesting /page (next time) Nginx Shared memory 1 /page 2 /page /menu /news /top (in SCL session)
  35. 35. New message is sent... POST /send o i nt rt e ins ... se t (.. .) DB top (in SCL session)
  36. 36. 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
  37. 37. News added addnews() method o i nt rt e ins ... se t (.. .) DB Memcache key /news
  38. 38. 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 No TTLs for non-specific content
  39. 39. How many Memcache requests ? Logged in as : Wim Godden <scl:include key="top" src="/top" session="true" ttl="1h" /> 5 messages <scl:include key="menu" src="/menu" ttl="1h" /> <scl:include key="news" src="/news" ttl="5m" />
  40. 40. First release : ESI Part of the ESI 1.0 spec Only relevant features implemented Extension for dynamic session support But : unavailable for copyright reasons
  41. 41. Rebuilt from scratch : SCL Session-specific Caching Language Language details : Control structures : if/else, switch/case, foreach Variable handling Strings : concatenation, substring, … Exception handling, header manipulation, ...
  42. 42. SCL code samples You are logged in as : <scl:session_var("person_name") /> You are logged in as : <@s("person_name") />
  43. 43. SCL code samples <scl:switch var="session_var('isAdmin')"> <scl:case value="1"> <scl:include key="admin-buttons" src="/admin-buttons.php" /> </scl:case> <scl:default> <div id="just-a-user"> <scl:include key="user-buttons" src="/user-buttons.php" /> </div> </scl:default> </scl:switch>
  44. 44. SCL code samples <scl:foreach item="messageId" src="global_var('thread' + query_var('threadId'))"> <scl:include key="'thread-message_' + messageId" src="'/thread/message.php?id=' + messageId" /> </scl:foreach>
  45. 45. Identifying the user In Nginx configuration : scl_session_cookie <name> → Defined by language (or configurable) scl_session_identifier <string> → Defined by you Example for PHP : scl_session_cookie PHPSESSID scl_session_identifier UID
  46. 46. Identifying the user Cookie : PHPSESSID = jpsidc1po35sq9q3og4f3hi6e2 Nginx + SCL 432 get UID_jpsidc1po35sq9q3og4f3hi6e2
  47. 47. Retrieving user specific content Cookie : PHPSESSID = jpsidc1po35sq9q3og4f3hi6e2 Nginx + SCL get top_432
  48. 48. Why Nginx ? Native Memcached support Excellent and superfast subrequest system Including parallel subrequests Handles thousands of connections per worker With minimal memory footprint Integrates with php-fpm Additional features (chroot, slow request log, offline processing, ...) Graceful rolling upgrades
  49. 49. What's the result ?
  50. 50. Figures 2nd customer : No. of web servers : 72 → 8 No. of db servers : 15 → 4 Total : 87 → 12 (86% reduction !) Last customer : No. of total servers : +/- 1350 Expected reduction : 1350 → 300 Expected savings : €1.6 Million per year
  51. 51. Why is it so much faster ?
  52. 52. A real example : vBulletin
  53. 53. A real example : vBulletin isAdmin session variable Post isModerator session variable
  54. 54. A real example : vBulletin 35 30 25 20 Standard install With Memcached Nginx + SCL + memcached 15 10 5 0 DB Server Load Web Server Load Max Requests/sec (1 = 282)
  55. 55. Availability Good news : It will become Open Source It's solid : ESI version stable at 4 customers Bad news : First customer holds copyrights Total rebuild → Open Source release No current projects, so spare time Beta : Jan-Feb Stable : Q2 (on Github)
  56. 56. So...
  57. 57. Questions ?
  58. 58. Questions ?
  59. 59. Contact Twitter Web Slides E-mail @wimgtr http://techblog.wimgodden.be http://www.slideshare.net/wimg wim.godden@cu.be Please provide feedback : http://go.cu.be/velocity2013

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