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