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

cache_page(content = nil, options = nil, gzip = Zlib::BEST_COMPRESSION) click to toggle source

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
caching_allowed?() click to toggle source
# File lib/action_controller/caching/pages.rb, line 292
def caching_allowed?
  (request.get? || request.head?) && response.status == 200
end
expire_page(options = {}) click to toggle source

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
perform_caching?() click to toggle source
# File lib/action_controller/caching/pages.rb, line 296
def perform_caching?
  self.class.perform_caching
end

Private Instance Methods

page_cache() click to toggle source
# File lib/action_controller/caching/pages.rb, line 301
def page_cache
  PageCache.new(page_cache_directory, default_static_extension, self)
end