diff options
Diffstat (limited to 'actionview')
| -rw-r--r-- | actionview/lib/action_view/digestor.rb | 38 |
1 files changed, 29 insertions, 9 deletions
diff --git a/actionview/lib/action_view/digestor.rb b/actionview/lib/action_view/digestor.rb index a674e4d7ea..64239c81b2 100644 --- a/actionview/lib/action_view/digestor.rb +++ b/actionview/lib/action_view/digestor.rb @@ -1,20 +1,40 @@ require 'thread_safe' require 'action_view/dependency_tracker' +require 'monitor' module ActionView class Digestor cattr_reader(:cache) - @@cache = ThreadSafe::Cache.new - - def self.digest(name, format, finder, options = {}) - cache_key = ([name, format] + Array.wrap(options[:dependencies])).join('.') - @@cache.fetch(cache_key) do - @@cache[cache_key] ||= nil if options[:partial] # Prevent re-entry + @@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 - klass = options[:partial] || name.include?("/_") ? PartialDigestor : Digestor - digest = klass.new(name, format, finder, options).digest + 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 # Store the value + @@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 |