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Caching your rails application
- 1. Rails Need short bursts of speed?
- 2. I’m a thief • http://railslab.newrelic.com/
- 3. Perception
- 4. Communication: Two parts • Server speed • Browser speed
- 5. Browser speed • Firebug / Safari developer • YSlow • Different parts of a site
- 6. Webpage parts • Page itself (<html> ... ) • Additional files (CSS, JavaScript) • Images • ... generating dynamic content
- 7. Siteparts • 10 requests:10 times slower as one request • stylesheet_tag :defaults, ‘screen’, :cache => ‘all’
- 9. images • asset hosts • Content Delivery Network
- 10. Page Caching
- 11. Why? • Code parsing: 20 to 50 req/second • Webserver: easily > 100 req/sec • Webserver stresses less, less database queries • Why not, it is easy (with rails)...
- 12. implementation
- 13. result
- 14. expire_page
- 15. expires-result
- 16. conclusion: page cache • very simple • limited scope to apply • cache invalidation! Important!
- 17. Cache Expiry
- 18. Why not expire_page in the action? • Not DRY (update, create, destroy,...) • after_filter possible, but other controllers might need to expire the cache
- 19. after_filter • PostsController (clear_posts_cache) • CommentsController (clear_posts_cache)
- 20. sweeper • observer on controller and model • if saved, call clear_posts_cache • if deleted, call clear_posts_cache
- 21. how
- 22. Page caching - part 2 • Ajax Callbacks for dynamic data
- 23. login/logout • pain!
- 24. Action Caching
- 25. Action cache • Cached output stored • Filters are processed before the cached version is returned to the browser • Example: authenticatie
- 26. caches_action
- 27. action cache • Filter is executed before sending the reply • Output is the same for everyone!
- 28. Welcome <username> • content is cached • layout is rendered
- 29. Warning! Attention! • fetch needed data with a before_filter • action is not executed!
- 30. Conditional AC • caching only on certain conditions
- 31. Action Caching • when? • execute code on each hit (authentication) • result remains the same • very easy to implement
- 32. Fragment Caching
- 33. Fragment caching • Cache part of a page • Logical blocks are candidates
- 34. Example
- 35. Fragment Caching
- 37. Fragment Cache expiry • expire_fragment
- 38. PC/AC Storage
- 39. Page cache storage • on disk
- 40. Storage: action / fragment cache • memory (default) or syncronised memory • file on disk • drb • memcache (normal or compressed) • custom_store (not hard to impelement!)
- 41. DYI
- 42. DYI caching • Caching hard parts in the code • Only spend cycles when really needed
- 44. Client-side caching • The cloud is there, use it
- 45. Three tags • max-age • etag • last_modified
- 46. max-age
- 47. etag • rails has this embedded • MD5(body) => etag • 304 Not Modified
- 48. etag • Beware, the complete parsing is done! • Less bandwidth / traffic • Client load time faster
- 49. etag
- 50. last_modified
- 51. Scary technology? • memcached • reverse proxy’s
- 52. Memcached • Daemon • Is a big hash in memory • Rails has default routines for this • Hoster / setup should support this
- 53. Reverse Proxy’s • a proxy, but on the server side • controle over expiry: max_age + etag • expiry remains a pain
- 54. Rack::Cache • gem install rack-cache • rails 2.3 needed!
- 55. Need for speed? • Database (n+1, joins / includes) • Disk IO • Implementing caching • Browser caching • External components (CDN, memcached, ...)