Introduce synchronization around connection pool access

- use new active support Module#synchronize
- allow_concurrency now switches between a null monitor and a
  regular monitor (defaulting to null monitor to avoid overhead)

1 files changed, 4 insertions, 0 deletions

diff --git a/activerecord/test/cases/threaded_connections_test.rb b/activerecord/test/cases/threaded_connections_test.rb
index 9bf7217958..3f88f79189 100644
--- a/activerecord/test/cases/threaded_connections_test.rb
+++ b/activerecord/test/cases/threaded_connections_test.rb
@@ -11,11 +11,15 @@ unless %w(FrontBase).include? ActiveRecord::Base.connection.adapter_name
     def setup
       @connection = ActiveRecord::Base.remove_connection
       @connections = []
+      @allow_concurrency = ActiveRecord::Base.allow_concurrency
+      ActiveRecord::Base.allow_concurrency = true
     end
 
     def teardown
       # clear the connection cache
       ActiveRecord::Base.clear_active_connections!
+      # set allow_concurrency to saved value
+      ActiveRecord::Base.allow_concurrency = @allow_concurrency
       # reestablish old connection
       ActiveRecord::Base.establish_connection(@connection)
     end