require 'thread_safe' require 'action_view/dependency_tracker' require 'monitor' module ActionView class Digestor cattr_reader(:cache) @@cache = ThreadSafe::Cache.new @@digest_monitor = Monitor.new class << self def digest(name, format, finder, options = {}) cache_key = ([name, format] + Array.wrap(options[:dependencies])).join('.') # this is a correctly done double-checked locking idiom # (ThreadSafe::Cache's lookups have volatile semantics) @@cache[cache_key] || @@digest_monitor.synchronize do @@cache.fetch(cache_key) do # re-check under lock compute_and_store_digest(cache_key, name, format, finder, options) end end end private def compute_and_store_digest(cache_key, name, format, finder, options) # called under @@digest_monitor lock klass = if options[:partial] || name.include?("/_") # Prevent re-entry or else recursive templates will blow the stack. # There is no need to worry about other threads seeing the +false+ value, # as they will then have to wait for this thread to let go of the @@digest_monitor lock. pre_stored = @@cache.put_if_absent(cache_key, false).nil? # put_if_absent returns nil on insertion PartialDigestor else Digestor end @@cache[cache_key] = digest = klass.new(name, format, finder, options).digest # Store the actual digest ensure @@cache.delete_pair(cache_key, false) if pre_stored && !digest # something went wrong, make sure not to corrupt the @@cache end end attr_reader :name, :format, :finder, :options def initialize(name, format, finder, options={}) @name, @format, @finder, @options = name, format, finder, options end def digest Digest::MD5.hexdigest("#{source}-#{dependency_digest}").tap do |digest| logger.try :info, "Cache digest for #{name}.#{format}: #{digest}" end rescue ActionView::MissingTemplate logger.try :error, "Couldn't find template for digesting: #{name}.#{format}" '' end def dependencies DependencyTracker.find_dependencies(name, template) rescue ActionView::MissingTemplate [] # File doesn't exist, so no dependencies end def nested_dependencies dependencies.collect do |dependency| dependencies = PartialDigestor.new(dependency, format, finder).nested_dependencies dependencies.any? ? { dependency => dependencies } : dependency end end private def logger ActionView::Base.logger end def logical_name name.gsub(%r|/_|, "/") end def partial? false end def template @template ||= finder.find(logical_name, [], partial?, formats: [ format ]) end def source template.source end def dependency_digest template_digests = dependencies.collect do |template_name| Digestor.digest(template_name, format, finder, partial: true) end (template_digests + injected_dependencies).join("-") end def injected_dependencies Array.wrap(options[:dependencies]) end end class PartialDigestor < Digestor # :nodoc: def partial? true end end end