This document discusses how to cache pages in Rails to improve performance. It covers: 1. Enabling caching in the development environment configuration and indicating which actions to cache. 2. Using sweepers to expire cached pages when content changes, ensuring users see updated content. 3. Implementing a sweeper class to observe models and expire related cached pages on save/destroy events. 4. Configuring the controller to call the sweeper on relevant actions. 5. Configuring Apache rewrite rules to serve cached pages when available.

1. Rails Page Caching Travis Roberts http://travisonrails.com http://twitter.com/travisroberts

2. Why Cache? Significantly speed up page load. Reduce resource usage on server.

3. But, How Do We Do It? in config/environments/development.rb in app/controllers/[controller_name].rb in config/environment.rb config.action_controller.perform_caching = true caches_page :index, :show, :feed # Move the cached files into their own directory config.action_controller.page_cache_directory = RAILS_ROOT + "/public/cache/"

4. What About New Content? New content won’t show, so we have to expire the cache in config/environment.rb This tells the application to load our “sweepers” dir We put the expire logic in the sweepers config.load_paths += %W( #{RAILS_ROOT}/app/sweepers )

5. Quick and Dirty Sweeper class SiteSweeper < ActionController::Caching::Sweeper observe Post, Comment def after_save (record) self.class::sweep end def after_destroy (record) self.class::sweep end def self.sweep cache_dir = ActionController :: Base .page_cache_directory unless cache_dir == RAILS_ROOT + &quot;/public&quot; FileUtils .rm_r( Dir .glob(cache_dir + &quot;/*&quot; )) rescue Errno ::ENOENT RAILS_DEFAULT_LOGGER .info( &quot;Cache directory fully swept.&quot; ) end end end

6. We Can Do Better in app/sweepers/post_sweeper.rb class PostSweeper < ActionController::Caching::Sweeper observe Post def after_save (post) expire_pages(post) end def after_destroy (post) expire_pages(post) end def expire_pages (post) expire_page(blog_path(:page => nil )) # expire blog index (/blog/list) expire_page(blog_path(post)) # expire detail page (/blog/12) # if we need to remove an entire directory in the cache cache_dir = ActionController :: Base .page_cache_directory FileUtils .rm_r( Dir .glob(cache_dir + &quot;/blog/list/*&quot; )) rescue Errno ::ENOENT # expire list RAILS_DEFAULT_LOGGER .info( &quot;Cache directory for blog successfully swept.&quot; ) end end

7. Calling the Sweeper We need to tell our controller when to invoke the sweeper in app/controllers/post_controller.rb class Manage::PostsController < ApplicationController cache_sweeper :post_sweeper, :only => [:create, :update, :destroy] # other code... end

8. Tell the Server to Use Cache Add the following lines to your .conf file # Rewrite index to check for static index RewriteRule ^/$ /cache/index.html [QSA] # Rewrite to check for cached pages RewriteRule ^([^.]+)$ /cache/$1.html [QSA]

9. What about pagination? With default pagination, caching won’t work (site.com/blog?page=2) We need to add a route for caching map.blog_list 'blog/list/:page' , :controller => 'blog' , :action => 'index' , :requirements => { :page => / \d +/ }, :page => nil # This will add the following routes # blog_list_path => site.com/blog/list # blog_list_path(:page => 3) => site.com/blog/list/3

10. The End! Questions? Comments?