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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 cache is done through the <tt>caches</tt> 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:
#
# <b>Hello <%= @name %></b>
# <% cache 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
# <tt>expire_fragment(:controller => "topics", :action => "list")</tt> -- 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 <tt>caches_action</tt>. So instead we should
# qualify the name of the action used with something like:
#
# <% cache(: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
# <tt>expire_fragment(:controller => "topics", :action => "list", :action_suffix => "all_topics")</tt>.
#
# == 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
@@fragment_cache_store = MemoryStore.new
cattr_accessor :fragment_cache_store
end
end
# Called by CacheHelper#cache
def cache_erb_fragment(block, name = {}, options = {})
unless perform_caching then block.call; return end
buffer = eval("_erbout", block.binding)
if cache = read_fragment(name, options)
buffer.concat(cache)
else
pos = buffer.length
block.call
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 <tt>cache_sweeper</tt> 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
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