diff options
Diffstat (limited to 'actionpack/lib/action_view/helpers/asset_id_helper.rb')
| -rw-r--r-- | actionpack/lib/action_view/helpers/asset_id_helper.rb | 154 |
1 files changed, 154 insertions, 0 deletions
diff --git a/actionpack/lib/action_view/helpers/asset_id_helper.rb b/actionpack/lib/action_view/helpers/asset_id_helper.rb new file mode 100644 index 0000000000..ba8e5e9050 --- /dev/null +++ b/actionpack/lib/action_view/helpers/asset_id_helper.rb @@ -0,0 +1,154 @@ +require 'thread' +require 'active_support/core_ext/file' +require 'active_support/core_ext/module/attribute_accessors' + +module ActionView + # = Action View Asset Cache ID Helpers + # + # Rails appends asset's timestamps to public asset paths. This allows + # you to set a cache-expiration date for the asset far into the future, but + # still be able to instantly invalidate it by simply updating the file (and + # hence updating the timestamp, which then updates the URL as the timestamp + # is part of that, which in turn busts the cache). + # + # It's the responsibility of the web server you use to set the far-future + # expiration date on cache assets that you need to take advantage of this + # feature. Here's an example for Apache: + # + # # Asset Expiration + # ExpiresActive On + # <FilesMatch "\.(ico|gif|jpe?g|png|js|css)$"> + # ExpiresDefault "access plus 1 year" + # </FilesMatch> + # + # Also note that in order for this to work, all your application servers must + # return the same timestamps. This means that they must have their clocks + # synchronized. If one of them drifts out of sync, you'll see different + # timestamps at random and the cache won't work. In that case the browser + # will request the same assets over and over again even thought they didn't + # change. You can use something like Live HTTP Headers for Firefox to verify + # that the cache is indeed working. + # + # This strategy works well enough for most server setups and requires the + # least configuration, but if you deploy several application servers at + # different times - say to handle a temporary spike in load - then the + # asset time stamps will be out of sync. In a setup like this you may want + # to set the way that asset paths are generated yourself. + # + # Altering the asset paths that Rails generates can be done in two ways. + # The easiest is to define the RAILS_ASSET_ID environment variable. The + # contents of this variable will always be used in preference to + # calculated timestamps. A more complex but flexible way is to set + # <tt>ActionController::Base.config.asset_path</tt> to a proc + # that takes the unmodified asset path and returns the path needed for + # your asset caching to work. Typically you'd do something like this in + # <tt>config/environments/production.rb</tt>: + # + # # Normally you'd calculate RELEASE_NUMBER at startup. + # RELEASE_NUMBER = 12345 + # config.action_controller.asset_path = proc { |asset_path| + # "/release-#{RELEASE_NUMBER}#{asset_path}" + # } + # + # This example would cause the following behavior on all servers no + # matter when they were deployed: + # + # image_tag("rails.png") + # # => <img alt="Rails" src="/release-12345/images/rails.png" /> + # stylesheet_link_tag("application") + # # => <link href="/release-12345/stylesheets/application.css?1232285206" media="screen" rel="stylesheet" /> + # + # Changing the asset_path does require that your web servers have + # knowledge of the asset template paths that you rewrite to so it's not + # suitable for out-of-the-box use. To use the example given above you + # could use something like this in your Apache VirtualHost configuration: + # + # <LocationMatch "^/release-\d+/(images|javascripts|stylesheets)/.*$"> + # # Some browsers still send conditional-GET requests if there's a + # # Last-Modified header or an ETag header even if they haven't + # # reached the expiry date sent in the Expires header. + # Header unset Last-Modified + # Header unset ETag + # FileETag None + # + # # Assets requested using a cache-busting filename should be served + # # only once and then cached for a really long time. The HTTP/1.1 + # # spec frowns on hugely-long expiration times though and suggests + # # that assets which never expire be served with an expiration date + # # 1 year from access. + # ExpiresActive On + # ExpiresDefault "access plus 1 year" + # </LocationMatch> + # + # # We use cached-busting location names with the far-future expires + # # headers to ensure that if a file does change it can force a new + # # request. The actual asset filenames are still the same though so we + # # need to rewrite the location from the cache-busting location to the + # # real asset location so that we can serve it. + # RewriteEngine On + # RewriteRule ^/release-\d+/(images|javascripts|stylesheets)/(.*)$ /$1/$2 [L] + # + module Helpers #:nodoc: + module AssetIdHelper + # You can enable or disable the asset tag ids cache. + # With the cache enabled, the asset tag helper methods will make fewer + # expensive file system calls (the default implementation checks the file + # system timestamp). However this prevents you from modifying any asset + # files while the server is running. + # + # ActionView::Helpers::AssetIdHelper.cache_asset_ids = false + mattr_accessor :cache_asset_ids + + # Add or change an asset id in the asset id cache. This can be used + # for SASS on Heroku. + # :api: public + def add_to_asset_ids_cache(source, asset_id) + self.asset_ids_cache_guard.synchronize do + self.asset_ids_cache[source] = asset_id + end + end + + mattr_accessor :asset_ids_cache + self.asset_ids_cache = {} + + mattr_accessor :asset_ids_cache_guard + self.asset_ids_cache_guard = Mutex.new + + # Use the RAILS_ASSET_ID environment variable or the source's + # modification time as its cache-busting asset id. + def rails_asset_id(source) + if asset_id = ENV["RAILS_ASSET_ID"] + asset_id + else + if self.cache_asset_ids && (asset_id = self.asset_ids_cache[source]) + asset_id + else + path = File.join(config.assets_dir, source) + asset_id = File.exist?(path) ? File.mtime(path).to_i.to_s : '' + + if self.cache_asset_ids + add_to_asset_ids_cache(source, asset_id) + end + + asset_id + end + end + end + + # Override +compute_asset_path+ to add asset id query strings to + # generated urls. See +compute_asset_path+ in AssetUrlHelper. + def compute_asset_path(source, options = {}) + source = super(source, options) + path = config.asset_path + + if path && path.respond_to?(:call) + path.call(source) + elsif path && path.is_a?(String) + path % [source] + elsif asset_id = rails_asset_id(source) + asset_id.empty? ? source : "#{source}?#{asset_id}" + end + end + end + end +end |