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 to trigger the
dynamic generation. This is how the web server is able pick up a cache file
when it exists and otherwise let the request pass on to Action Pack to
generate it.
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.
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 requested url is
used. Example:
cache_page "I'm the cached content", :controller => "lists", :action => "show"
# File lib/action_controller/caching/pages.rb, line 139 def cache_page(content = nil, options = nil) return unless self.class.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 if (type = Mime::LOOKUP[self.content_type]) && (type_symbol = type.symbol).present? extension = ".#{type_symbol}" end self.class.cache_page(content || response.body, path, extension) end
Expires the page that was cached with the options
as a key.
Example:
expire_page :controller => "lists", :action => "show"
# File lib/action_controller/caching/pages.rb, line 120 def expire_page(options = {}) return unless self.class.perform_caching if options.is_a?(Hash) if options[:action].is_a?(Array) options[:action].dup.each do |action| self.class.expire_page(url_for(options.merge(:only_path => true, :action => action))) end else self.class.expire_page(url_for(options.merge(:only_path => true))) end else self.class.expire_page(options) end end