module ActionController::Caching::Pages
Page caching is an approach to caching where the entire action output of is stored as a HTML file that the web server can serve without going through Action Pack. This is the fastest way to cache your content as opposed to going dynamically through the process of generating the content. Unfortunately, this incredible speed-up is only available to stateless pages where all visitors are treated the same. Content management systems – including weblogs and wikis – have many pages that are a great fit for this approach, but account-based systems where people log in and manipulate their own data are often less likely candidates.
Specifying which actions to cache is done through the caches_page
class method:
class WeblogController < ActionController::Base caches_page :show, :new end
This will generate cache files such as weblog/show/5.html
and weblog/new.html
, which match the URLs used that would normally trigger dynamic page generation. Page caching works by configuring a web server to first check for the existence of files on disk, and to serve them directly when found, without passing the request through to Action Pack. This is much faster than handling the full dynamic request in the usual way.
Expiration of the cache is handled by deleting the cached file, which results in a lazy regeneration approach where the cache is not restored before another hit is made against it. The API for doing so mimics the options from url_for
and friends:
class WeblogController < ActionController::Base def update List.update(params[:list][:id], params[:list]) expire_page action: "show", id: params[:list][:id] redirect_to action: "show", id: params[:list][:id] end end
Additionally, you can expire caches using Sweepers that act on changes in the model to determine when a cache is supposed to be expired.
Public Instance Methods
Manually cache the content
in the key determined by options
. If no content is provided, the contents of response.body is used. If no options are provided, the url of the current request being handled is used.
cache_page "I'm the cached content", controller: "lists", action: "show"
# File lib/action_controller/caching/pages.rb, line 266 def cache_page(content = nil, options = nil, gzip = Zlib::BEST_COMPRESSION) if perform_caching? && caching_allowed? path = \ case options when Hash url_for(options.merge(only_path: true, format: params[:format])) when String options else request.path end type = if self.respond_to?(:media_type) Mime::LOOKUP[self.media_type] else Mime::LOOKUP[self.content_type] end if type && (type_symbol = type.symbol).present? extension = ".#{type_symbol}" end page_cache.cache(content || response.body, path, extension, gzip) end end
# File lib/action_controller/caching/pages.rb, line 292 def caching_allowed? (request.get? || request.head?) && response.status == 200 end
Expires the page that was cached with the options
as a key.
expire_page controller: "lists", action: "show"
# File lib/action_controller/caching/pages.rb, line 245 def expire_page(options = {}) if perform_caching? case options when Hash case options[:action] when Array options[:action].each { |action| expire_page(options.merge(action: action)) } else page_cache.expire(url_for(options.merge(only_path: true))) end else page_cache.expire(options) end end end
# File lib/action_controller/caching/pages.rb, line 296 def perform_caching? self.class.perform_caching end
Private Instance Methods
# File lib/action_controller/caching/pages.rb, line 301 def page_cache PageCache.new(page_cache_directory, default_static_extension, self) end