Creating a module so that per thread registries can be easily created as

thread local variables.

activesupport/lib/active_support/per_thread_registry.rb

@@ -0,0 +1,41 @@
+module ActiveSupport
+  # This module creates a local registry class inside each thread. It provides
+  # basic methods which will store thread locals in a single class. This
+  # prevents the proliferation of too many thread locals and allows you to
+  # explicitly keep track of each of the variables you're using as thread
+  # locals in a class which includes this module.
+  #
+  # For example, instead of using a bunch of different thread locals to keep
+  # track of some variables like so:
+  #
+  #   Thread.current[:active_record_connection_handler] = connection_handler
+  #   Thread.current[:active_record_sql_runtime]        = sql_runtime
+  #
+  # You could use the following class which implements the +PerThreadRegistry+
+  # module:
+  #
+  #   class NewRegistry
+  #     extend ActiveSupport::PerThreadRegistry
+  #
+  #     attr_accessor :connection_handler, :sql_runtime
+  #   end
+  #
+  #   NewRegistry.instance.connection_handler = connection_handler
+  #   NewRegistry.instance.sql_runtime        = sql_runtime
+  #
+  # The new way of keeping track of the thread locals will create a new local
+  # inside of +Thread.current+ with a key which is the name of the extended
+  # class. Now you can easily access per thread variables by just calling the
+  # variable name on the registry.
+  module PerThreadRegistry
+    def instance
+      Thread.current[self.name] ||= new
+    end
+
+    protected
+
+      def method_missing(*args, &block)
+        instance.send(*args, &block)
+      end
+  end
+end