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require 'fileutils'
require 'active_support/core_ext/class/attribute_accessors'
module ActionController #:nodoc:
module Caching
# 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 <tt>caches_page</tt> class method:
# class WeblogController < ActionController::Base
# caches_page :show, :new
# end
# This will generate cache files such as <tt>weblog/show/5.html</tt> and <tt>weblog/new.html</tt>, 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.
module Pages
extend ActiveSupport::Concern
included do
# :singleton-method:
# The cache directory should be the document root for the web server and is set using <tt>Base.page_cache_directory = "/document/root"</tt>.
# For Rails, this directory has already been set to Rails.public_path (which is usually set to <tt>Rails.root + "/public"</tt>). Changing
# this setting can be useful to avoid naming conflicts with files in <tt>public/</tt>, but doing so will likely require configuring your
# web server to look in the new location for cached files.
config_accessor :page_cache_directory
self.page_cache_directory ||= ''
# :singleton-method:
# Most Rails requests do not have an extension, such as <tt>/weblog/new</tt>. In these cases, the page caching mechanism will add one in
# order to make it easy for the cached files to be picked up properly by the web server. By default, this cache extension is <tt>.html</tt>.
# If you want something else, like <tt>.php</tt> or <tt>.shtml</tt>, just set Base.page_cache_extension. In cases where a request already has an
# extension, such as <tt>.xml</tt> or <tt>.rss</tt>, page caching will not add an extension. This allows it to work well with RESTful apps.
config_accessor :page_cache_extension
self.page_cache_extension ||= '.html'
module ClassMethods
# Expires the page that was cached with the +path+ as a key. Example:
# expire_page "/lists/show"
def expire_page(path)
return unless perform_caching
path = page_cache_path(path)
instrument_page_cache :expire_page, path do
File.delete(path) if File.exist?(path)
# Manually cache the +content+ in the key determined by +path+. Example:
# cache_page "I'm the cached content", "/lists/show"
def cache_page(content, path, extension = nil)
return unless perform_caching
path = page_cache_path(path, extension)
instrument_page_cache :write_page, path do
FileUtils.makedirs(File.dirname(path)), "wb+") { |f| f.write(content) }
# Caches the +actions+ using the page-caching approach that'll store the cache in a path within the page_cache_directory that
# matches the triggering url.
# Usage:
# # cache the index action
# caches_page :index
# # cache the index action except for JSON requests
# caches_page :index, :if => { |c| !c.request.format.json? }
def caches_page(*actions)
return unless perform_caching
options = actions.extract_options!
after_filter({:only => actions}.merge(options)) { |c| c.cache_page }
def page_cache_file(path, extension)
name = (path.empty? || path == "/") ? "/index" : URI.parser.unescape(path.chomp('/'))
unless (name.split('/').last || name).include? '.'
name << (extension || self.page_cache_extension)
return name
def page_cache_path(path, extension = nil)
page_cache_directory.to_s + page_cache_file(path, extension)
def instrument_page_cache(name, path)
ActiveSupport::Notifications.instrument("#{name}.action_controller", :path => path){ yield }
# Expires the page that was cached with the +options+ as a key. Example:
# expire_page :controller => "lists", :action => "show"
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)))
self.class.expire_page(url_for(options.merge(:only_path => true)))
# 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. Example:
# cache_page "I'm the cached content", :controller => "lists", :action => "show"
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
if (type = Mime::LOOKUP[self.content_type]) && (type_symbol = type.symbol).present?
extension = ".#{type_symbol}"
self.class.cache_page(content || response.body, path, extension)
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