Module | ActionController::Caching::Fragments |
In: |
vendor/rails/actionpack/lib/action_controller/caching.rb
|
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 :partial => "topic", :collection => Topic.find(:all) %> <% end %>
This cache will bind to the name of the action that called it, so if this code was part of the view for the topics/list action, you would be able to invalidate it using expire_fragment(:controller => "topics", :action => "list").
This default behavior is of limited use if you need to cache multiple fragments per action or if the action itself is cached using caches_action, so we also have the option to qualify the name of the cached fragment with something like:
<% cache(:action => "list", :action_suffix => "all_topics") do %>
That would result in a name such as "/topics/list/all_topics", avoiding conflicts with the action cache and with any fragments that use a different suffix. Note that the URL doesn‘t have to really exist or be callable - the url_for system is just used to generate unique cache names that we can refer to when we need to expire the cache.
The expiration call for this example is:
expire_fragment(:controller => "topics", :action => "list", :action_suffix => "all_topics")
By default, cached fragments are stored in memory. The available store options are:
Configuration examples (MemoryStore is the default):
ActionController::Base.fragment_cache_store = :memory_store ActionController::Base.fragment_cache_store = :file_store, "/path/to/cache/directory" ActionController::Base.fragment_cache_store = :drb_store, "druby://localhost:9192" ActionController::Base.fragment_cache_store = :mem_cache_store, "localhost" ActionController::Base.fragment_cache_store = MyOwnStore.new("parameter")
Defines the storage option for cached fragments
# File vendor/rails/actionpack/lib/action_controller/caching.rb, line 354 354: def self.fragment_cache_store=(store_option) 355: store, *parameters = *([ store_option ].flatten) 356: @@fragment_cache_store = if store.is_a?(Symbol) 357: store_class_name = (store == :drb_store ? "DRbStore" : store.to_s.camelize) 358: store_class = ActionController::Caching::Fragments.const_get(store_class_name) 359: store_class.new(*parameters) 360: else 361: store 362: end 363: end
Called by CacheHelper#cache
# File vendor/rails/actionpack/lib/action_controller/caching.rb, line 375 375: def cache_erb_fragment(block, name = {}, options = nil) 376: unless perform_caching then block.call; return end 377: 378: buffer = eval(ActionView::Base.erb_variable, block.binding) 379: 380: if cache = read_fragment(name, options) 381: buffer.concat(cache) 382: else 383: pos = buffer.length 384: block.call 385: write_fragment(name, buffer[pos..-1], options) 386: end 387: end
Name can take one of three forms:
%r{pages/\d*/notes}
Ensure you do not specify start and finish in the regex (^$) because the actual filename matched looks like ./cache/filename/path.cache Regexp expiration is only supported on caches that can iterate over all keys (unlike memcached).
# File vendor/rails/actionpack/lib/action_controller/caching.rb, line 419 419: def expire_fragment(name, options = nil) 420: return unless perform_caching 421: 422: key = fragment_cache_key(name) 423: 424: if key.is_a?(Regexp) 425: self.class.benchmark "Expired fragments matching: #{key.source}" do 426: fragment_cache_store.delete_matched(key, options) 427: end 428: else 429: self.class.benchmark "Expired fragment: #{key}" do 430: fragment_cache_store.delete(key, options) 431: end 432: end 433: end
Given a name (as described in expire_fragment), returns a key suitable for use in reading, writing, or expiring a cached fragment. If the name is a hash, the generated name is the return value of url_for on that hash (without the protocol).
# File vendor/rails/actionpack/lib/action_controller/caching.rb, line 370 370: def fragment_cache_key(name) 371: name.is_a?(Hash) ? url_for(name).split("://").last : name 372: end
Reads a cached fragment from the location signified by name (see expire_fragment for acceptable formats)
# File vendor/rails/actionpack/lib/action_controller/caching.rb, line 401 401: def read_fragment(name, options = nil) 402: return unless perform_caching 403: 404: key = fragment_cache_key(name) 405: self.class.benchmark "Fragment read: #{key}" do 406: fragment_cache_store.read(key, options) 407: end 408: end
Writes content to the location signified by name (see expire_fragment for acceptable formats)
# File vendor/rails/actionpack/lib/action_controller/caching.rb, line 390 390: def write_fragment(name, content, options = nil) 391: return unless perform_caching 392: 393: key = fragment_cache_key(name) 394: self.class.benchmark "Cached fragment: #{key}" do 395: fragment_cache_store.write(key, content, options) 396: end 397: content 398: end