Caching your rails application
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Caching your rails application

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Bernard from Openminds talks about caching your Rails appication.

Bernard from Openminds talks about caching your Rails appication.

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Caching your rails application Caching your rails application Presentation Transcript

  • Rails Need short bursts of speed?
  • I’m a thief • http://railslab.newrelic.com/
  • Perception
  • Communication: Two parts • Server speed • Browser speed
  • Browser speed • Firebug / Safari developer • YSlow • Different parts of a site
  • Webpage parts • Page itself (<html> ... ) • Additional files (CSS, JavaScript) • Images • ... generating dynamic content
  • Siteparts • 10 requests:10 times slower as one request • stylesheet_tag :defaults, ‘screen’, :cache => ‘all’
  • images • asset hosts • Content Delivery Network
  • Page Caching
  • 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)...
  • implementation
  • result
  • expire_page
  • expires-result
  • conclusion: page cache • very simple • limited scope to apply • cache invalidation! Important!
  • Cache Expiry
  • Why not expire_page in the action? • Not DRY (update, create, destroy,...) • after_filter possible, but other controllers might need to expire the cache
  • after_filter • PostsController (clear_posts_cache) • CommentsController (clear_posts_cache)
  • sweeper • observer on controller and model • if saved, call clear_posts_cache • if deleted, call clear_posts_cache
  • how
  • Page caching - part 2 • Ajax Callbacks for dynamic data
  • login/logout • pain!
  • Action Caching
  • Action cache • Cached output stored • Filters are processed before the cached version is returned to the browser • Example: authenticatie
  • caches_action
  • action cache • Filter is executed before sending the reply • Output is the same for everyone!
  • Welcome <username> • content is cached • layout is rendered
  • Warning! Attention! • fetch needed data with a before_filter • action is not executed!
  • Conditional AC • caching only on certain conditions
  • Action Caching • when? • execute code on each hit (authentication) • result remains the same • very easy to implement
  • Fragment Caching
  • Fragment caching • Cache part of a page • Logical blocks are candidates
  • Example
  • Fragment Caching
  • No useless actions
  • Fragment Cache expiry • expire_fragment
  • PC/AC Storage
  • Page cache storage • on disk
  • Storage: action / fragment cache • memory (default) or syncronised memory • file on disk • drb • memcache (normal or compressed) • custom_store (not hard to impelement!)
  • DYI
  • DYI caching • Caching hard parts in the code • Only spend cycles when really needed
  • Client-side caching • The cloud is there, use it
  • Three tags • max-age • etag • last_modified
  • max-age
  • etag • rails has this embedded • MD5(body) => etag • 304 Not Modified
  • etag • Beware, the complete parsing is done! • Less bandwidth / traffic • Client load time faster
  • etag
  • last_modified
  • Scary technology? • memcached • reverse proxy’s
  • Memcached • Daemon • Is a big hash in memory • Rails has default routines for this • Hoster / setup should support this
  • Reverse Proxy’s • a proxy, but on the server side • controle over expiry: max_age + etag • expiry remains a pain
  • Rack::Cache • gem install rack-cache • rails 2.3 needed!
  • Need for speed? • Database (n+1, joins / includes) • Disk IO • Implementing caching • Browser caching • External components (CDN, memcached, ...)