require 'fileutils' module ActionController #:nodoc: # Caching is a cheap way of speeding up slow applications by keeping the result of calculations, renderings, and database calls # around for subsequent requests. Action Controller affords you three approaches in varying levels of granularity: Page, Action, Fragment. # # You can read more about each approach and the sweeping assistance by clicking the modules below. # # Note: To turn off all caching and sweeping, set Base.perform_caching = false. module Caching def self.append_features(base) #:nodoc: super base.send(:include, Pages, Actions, Fragments, Sweeping) base.class_eval do @@perform_caching = true cattr_accessor :perform_caching end end # 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 the Action Pack. This can be as much as 100 times faster than going the process of dynamically # 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 cach is done through the caches class method: # # class WeblogController < ActionController::Base # caches_page :show, :new # end # # This will generate cache files such as weblog/show/5 and weblog/new, 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 # the 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. # # == Setting the cache directory # # The cache directory should be the document root for the web server and is set using Base.page_cache_directory = "/document/root". # For Rails, this directory has already been set to RAILS_ROOT + "/public". module Pages def self.append_features(base) #:nodoc: super base.extend(ClassMethods) base.class_eval do @@page_cache_directory = defined?(RAILS_ROOT) ? "#{RAILS_ROOT}/public" : "" cattr_accessor :page_cache_directory end end 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 File.delete(page_cache_path(path)) if File.exists?(page_cache_path(path)) logger.info "Expired page: #{path}" unless logger.nil? end # 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) return unless perform_caching FileUtils.makedirs(File.dirname(page_cache_path(path))) File.open(page_cache_path(path), "w+") { |f| f.write(content) } logger.info "Cached page: #{path}" unless logger.nil? end # 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. def caches_page(*actions) return unless perform_caching actions.each do |action| class_eval "after_filter { |c| c.cache_page if c.action_name == '#{action}' }" end end private def page_cache_path(path) if path[-1,1] == '/' page_cache_directory + path + '/index' else page_cache_directory + path end end end # 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 perform_caching 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 end # 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 current +options+ for this action is used. Example: # cache_page "I'm the cached content", :controller => "lists", :action => "show" def cache_page(content = nil, options = {}) return unless perform_caching && caching_allowed self.class.cache_page(content || @response.body, url_for(options.merge({ :only_path => true }))) end private def caching_allowed !@request.post? && (@request.parameters.reject { |k, v| %w( id action controller ).include?(k) }).empty? end end # Action caching is similar to page caching by the fact that the entire output of the response is cached, but unlike page caching, # every request still goes through the Action Pack. The key benefit of this is that filters are run before the cache is served, which # allows for authentication and other restrictions on whether someone are supposed to see the cache. Example: # # class ListsController < ApplicationController # before_filter :authenticate, :except => :public # caches_page :public # caches_action :show, :feed # end # # In this example, the public action doesn't require authentication, so it's possible to use the faster page caching method. But both the # show and feed action are to be shielded behind the authenticate filter, so we need to implement those as action caches. # # Action caching internally uses the fragment caching and an around filter to do the job. The fragment cache is named according to both # the current host and the path. So a page that is accessed at http://david.somewhere.com/lists/show/1 will result in a fragment named # "david.somewhere.com/lists/show/1". This allows the cacher to differentiate between "david.somewhere.com/lists/" and # "jamis.somewhere.com/lists/" -- which is a helpful way of assisting the subdomain-as-account-key pattern. module Actions def self.append_features(base) #:nodoc: super base.extend(ClassMethods) base.send(:attr_accessor, :rendered_action_cache) end module ClassMethods #:nodoc: def caches_action(*actions) return unless perform_caching around_filter(ActionCacheFilter.new(*actions)) end end def expire_action(options = {}) return unless perform_caching if options[:action].is_a?(Array) options[:action].dup.each do |action| expire_fragment(url_for(options.merge({ :action => action })).split("://").last) end else expire_fragment(url_for(options).split("://").last) end end class ActionCacheFilter #:nodoc: def initialize(*actions) @actions = actions end def before(controller) return unless @actions.include?(controller.action_name.intern) if cache = controller.read_fragment(controller.url_for.split("://").last) controller.rendered_action_cache = true controller.send(:render_text, cache) false end end def after(controller) return if !@actions.include?(controller.action_name.intern) || controller.rendered_action_cache controller.write_fragment(controller.url_for.split("://").last, controller.response.body) end end end # Fragment caching is used for caching various blocks within templates without caching the entire action as a whole. This is useful when # certain elements of an action change frequently or depend on complicated state while other parts rarely change or can be shared amongst multiple # parties. The caching is doing using the cache helper available in the Action View. A template with caching might look something like: # # Hello <%= @name %> # <% cache(binding) do %> # All the topics in the system: # <%= render_collection_of_partials "topic", Topic.find_all %> # <% end %> # # This cache will bind to the name of action that called it. So you would be able to invalidate it using # expire_fragment(:controller => "topics", :action => "list") -- if that was the controller/action used. This is not too helpful # if you need to cache multiple fragments per action or if the action itself is cached using caches_action. So instead we should # qualify the name of the action used with something like: # # <% cache(binding, :action => "list", :action_suffix => "all_topics") do %> # # That would result in a name such as "/topics/list/all_topics", which wouldn't conflict with any action cache and neither with another # fragment using a different suffix. Note that the URL doesn't have to really exist or be callable. We're just using the url_for system # to generate unique cache names that we can refer to later for expirations. The expiration call for this example would be # expire_fragment(:controller => "topics", :action => "list", :action_suffix => "all_topics"). # # == Fragment stores # # In order to use the fragment caching, you need to designate where the caches should be stored. This is done by assigning a fragment store # of which there are four different kinds: # # * FileStore: Keeps the fragments on disk in the +cache_path+, which works well for all types of environments and share the fragments for # all the web server processes running off the same application directory. # * MemoryStore: Keeps the fragments in memory, which is fine for WEBrick and for FCGI (if you don't care that each FCGI process holds its # own fragment store). It's not suitable for CGI as the process is thrown away at the end of each request. It can potentially also take # up a lot of memory since each process keeps all the caches in memory. # * DRbStore: Keeps the fragments in the memory of a separate, shared DRb process. This works for all environments and only keeps one cache # around for all processes, but requires that you run and manage a separate DRb process. # * MemCachedStore: Works like DRbStore, but uses Danga's MemCached instead. # # Configuration examples (MemoryStore is the default): # # ActionController::Base.fragment_cache_store = # ActionController::Caching::Fragments::MemoryStore.new # # ActionController::Base.fragment_cache_store = # ActionController::Caching::Fragments::FileStore.new("/path/to/cache/directory") # # ActionController::Base.fragment_cache_store = # ActionController::Caching::Fragments::DRbStore.new("druby://localhost:9192") # # ActionController::Base.fragment_cache_store = # ActionController::Caching::Fragments::FileStore.new("localhost") module Fragments def self.append_features(base) #:nodoc: super base.class_eval do @@cache_store = MemoryStore.new cattr_accessor :fragment_cache_store end end # Called by CacheHelper#cache def cache_erb_fragment(binding, name = {}, options = {}) unless perform_caching then yield; return end buffer = eval("_erbout", binding) if cache = read_fragment(name, options) buffer.concat(cache) else pos = buffer.length yield write_fragment(name, buffer[pos..-1], options) end end def write_fragment(name, content, options = {}) name = url_for(name).split("://").last if name.is_a?(Hash) fragment_cache_store.write(name, content, options) logger.info "Cached fragment: #{name}" unless logger.nil? content end def read_fragment(name, options = {}) name = url_for(name).split("://").last if name.is_a?(Hash) if cache = fragment_cache_store.read(name, options) logger.info "Fragment hit: #{name}" unless logger.nil? cache else false end end def expire_fragment(name, options = {}) name = url_for(name).split("://").last if name.is_a?(Hash) fragment_cache_store.delete(name, options) logger.info "Expired fragment: #{name}" unless logger.nil? end class MemoryStore #:nodoc: def initialize @data, @mutex = { }, Mutex.new end def read(name, options = {}) #:nodoc: begin @mutex.synchronize { @data[name] } rescue nil end end def write(name, value, options = {}) #:nodoc: @mutex.synchronize { @data[name] = value } end def delete(name, options = {}) #:nodoc: @mutex.synchronize { @data.delete(name) } end end class DRbStore < MemoryStore #:nodoc: def initialize(address = 'druby://localhost:9192') @data = DRbObject.new(nil, address) end end class MemCacheStore < MemoryStore #:nodoc: def initialize(address = 'localhost') @data = MemCache.new(address) end end class FileStore #:nodoc: def initialize(cache_path) @cache_path = cache_path end def write(name, value, options = {}) #:nodoc: begin ensure_cache_path(File.dirname(real_file_path(name))) File.open(real_file_path(name), "w+") { |f| f.write(value) } rescue => e Base.logger.info "Couldn't create cache directory: #{name} (#{e.message})" unless Base.logger.nil? end end def read(name, options = {}) #:nodoc: begin IO.read(real_file_path(name)) rescue nil end end def delete(name, options) #:nodoc: File.delete(real_file_path(name)) if File.exist?(real_file_path(name)) end private def real_file_path(name) "#{@cache_path}/#{name}" end def ensure_cache_path(path) FileUtils.makedirs(path) unless File.exists?(path) end end end # Sweepers are the terminators of the caching world and responsible for expiring caches when model objects change. # They do this by being half-observers, half-filters and implementing callbacks for both roles. A Sweeper example: # # class ListSweeper < ActiveRecord::Observer # observe List, Item # # def after_save(record) # @list = record.is_a?(List) ? record : record.list # end # # def filter(controller) # controller.expire_page(:controller => "lists", :action => %w( show public feed ), :id => @list.id) # controller.expire_action(:controller => "lists", :action => "all") # @list.shares.each { |share| controller.expire_page(:controller => "lists", :action => "show", :id => share.url_key) } # end # end # # The sweeper is assigned on the controllers that wish to have its job performed using the cache_sweeper class method: # # class ListsController < ApplicationController # caches_action :index, :show, :public, :feed # cache_sweeper :list_sweeper, :only => [ :edit, :destroy, :share ] # end # # In the example above, four actions are cached and three actions are responsible of expiring those caches. module Sweeping def self.append_features(base) #:nodoc: super base.extend(ClassMethods) end module ClassMethods #:nodoc: def cache_sweeper(*sweepers) return unless perform_caching configuration = sweepers.last.is_a?(Hash) ? sweepers.pop : {} sweepers.each do |sweeper| observer(sweeper) after_filter(Object.const_get(Inflector.classify(sweeper)).instance, :only => configuration[:only]) end end end end end end