require 'fileutils'
require 'uri'
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 the Action Pack. This can be as much as 100 times faster than going through 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".
#
# == Setting the cache extension
#
# By default, the cache extension is .html, which makes it easy for the cached files to be picked up by the web server. If you want
# something else, like .php or .shtml, just set Base.page_cache_extension.
module Pages
def self.included(base) #:nodoc:
base.extend(ClassMethods)
base.class_eval do
@@page_cache_directory = defined?(RAILS_ROOT) ? "#{RAILS_ROOT}/public" : ""
cattr_accessor :page_cache_directory
@@page_cache_extension = '.html'
cattr_accessor :page_cache_extension
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
benchmark "Expired page: #{page_cache_file(path)}" do
File.delete(page_cache_path(path)) if File.exist?(page_cache_path(path))
end
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
benchmark "Cached page: #{page_cache_file(path)}" do
FileUtils.makedirs(File.dirname(page_cache_path(path)))
File.open(page_cache_path(path), "wb+") { |f| f.write(content) }
end
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 = actions.map(&:to_s)
after_filter { |c| c.cache_page if actions.include?(c.action_name) }
end
private
def page_cache_file(path)
name = (path.empty? || path == "/") ? "/index" : URI.unescape(path.chomp('/'))
name << page_cache_extension unless (name.split('/').last || name).include? '.'
return name
end
def page_cache_path(path)
page_cache_directory + page_cache_file(path)
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.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, :skip_relative_url_root => true, :action => action)))
end
else
self.class.expire_page(url_for(options.merge(:only_path => true, :skip_relative_url_root => true)))
end
else
self.class.expire_page(options)
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 requested url is used. Example:
# cache_page "I'm the cached content", :controller => "lists", :action => "show"
def cache_page(content = nil, options = nil)
return unless perform_caching && caching_allowed
path = case options
when Hash
url_for(options.merge(:only_path => true, :skip_relative_url_root => true, :format => params[:format]))
when String
options
else
request.path
end
self.class.cache_page(content || response.body, path)
end
private
def caching_allowed
request.get? && response.headers['Status'].to_i == 200
end
end
end
end
