Replace some global Hash usages with the new thread safe cache.

Summary of the changes:
 * Add thread_safe gem.
 * Use thread safe cache for digestor caching.
 * Replace manual synchronization with ThreadSafe::Cache in Relation::Delegation.
 * Replace @attribute_method_matchers_cache Hash with ThreadSafe::Cache.
 * Use TS::Cache to avoid the synchronisation overhead on listener retrieval.
 * Replace synchronisation with TS::Cache usage.
 * Use a preallocated array for performance/memory reasons.
 * Update the controllers cache to the new AS::Dependencies::ClassCache API.
   The original @controllers cache no longer makes much sense after @tenderlove's
   changes in 7b6bfe84f3 and f345e2380c.
 * Use TS::Cache in the connection pool to avoid locking overhead.
 * Use TS::Cache in ConnectionHandler.

1 files changed, 1 insertions, 0 deletions

diff --git a/Gemfile b/Gemfile
index 35bcb68fb2..8be17a841f 100644
--- a/Gemfile
+++ b/Gemfile
@@ -12,6 +12,7 @@ gem 'jquery-rails', '~> 2.1.4', github: 'rails/jquery-rails'
 gem 'turbolinks'
 gem 'coffee-rails', github: 'rails/coffee-rails'
 
+gem 'thread_safe', '~> 0.1'
 gem 'journey', github: 'rails/journey', branch: 'master'
 
 gem 'activerecord-deprecated_finders', github: 'rails/activerecord-deprecated_finders', branch: 'master'