Created a runtime registry for thread local variables in active record.

activerecord/lib/active_record.rb

@@ -50,6 +50,7 @@ module ActiveRecord
   autoload :Querying
   autoload :ReadonlyAttributes
   autoload :Reflection
+  autoload :RuntimeRegistry
   autoload :Sanitization
   autoload :Schema
   autoload :SchemaDumper

activerecord/lib/active_record/connection_handling.rb

@@ -54,11 +54,11 @@ def connection
     end
 
     def connection_id
-      Thread.current['ActiveRecord::Base.connection_id']
+      ActiveRecord::RuntimeRegistry.instance.connection_id
     end
 
     def connection_id=(connection_id)
-      Thread.current['ActiveRecord::Base.connection_id'] = connection_id
+      ActiveRecord::RuntimeRegistry.instance.connection_id = connection_id
     end
 
     # Returns the configuration of the associated connection as a hash:

activerecord/lib/active_record/core.rb

@@ -80,11 +80,11 @@ module Core
       class_attribute :default_connection_handler, instance_writer: false
 
       def self.connection_handler
-        Thread.current[:active_record_connection_handler] || self.default_connection_handler
+        ActiveRecord::RuntimeRegistry.instance.connection_handler || self.default_connection_handler
       end
 
       def self.connection_handler=(handler)
-        Thread.current[:active_record_connection_handler] = handler
+        ActiveRecord::RuntimeRegistry.instance.connection_handler = handler
       end
 
       self.default_connection_handler = ConnectionAdapters::ConnectionHandler.new

activerecord/lib/active_record/log_subscriber.rb

@@ -3,11 +3,11 @@ class LogSubscriber < ActiveSupport::LogSubscriber
     IGNORE_PAYLOAD_NAMES = ["SCHEMA", "EXPLAIN"]
 
     def self.runtime=(value)
-      Thread.current[:active_record_sql_runtime] = value
+      ActiveRecord::RuntimeRegistry.instance.sql_runtime = value
     end
 
     def self.runtime
-      Thread.current[:active_record_sql_runtime] ||= 0
+      ActiveRecord::RuntimeRegistry.instance.sql_runtime ||= 0
     end
 
     def self.reset_runtime

activerecord/lib/active_record/runtime_registry.rb

@@ -0,0 +1,32 @@
+require 'active_support/per_thread_registry'
+
+module ActiveRecord
+  # This is a registry class for storing local variables in active record. The
+  # class allows you to access variables that are local to the current thread.
+  # These thread local variables are stored as attributes in the
+  # +RuntimeRegistry+ class.
+  #
+  # You can access the thread local variables by calling a variable's name on
+  # the +RuntimeRegistry+ class. For example, if you wanted to obtain the
+  # connection handler for the current thread, you would invoke:
+  #
+  #   ActiveRecord::RuntimeRegistry.instance.connection_handler
+  #
+  # The +PerThreadRegistry+ module will make a new +RuntimeRegistry+ instance
+  # and store it in +Thread.current+. Whenever you make a call for an attribute
+  # on the +RuntimeRegistry+ class, the call will be sent to the instance that
+  # is stored in +Thread.current+.
+  #
+  # Note that you can also make the following call which would provide an
+  # equivalent result as the previous code:
+  #
+  #   ActiveRecord::RuntimeRegistry.connection_handler
+  #
+  # However, this is less performant because it makes a call to +method_missing+
+  # before it sends the method call to the +instance+.
+  class RuntimeRegistry
+    extend ActiveSupport::PerThreadRegistry
+
+    attr_accessor :connection_handler, :sql_runtime, :connection_id
+  end
+end