Module: ActiveSupport::PerThreadRegistry

Included in:

ActiveRecord::ExplainRegistry, ActiveRecord::RuntimeRegistry, ActiveRecord::Scoping::ScopeRegistry, Cache::Strategy::LocalCache::LocalCacheRegistry, Notifications::InstrumentationRegistry, SubscriberQueueRegistry

Defined in:

activesupport/lib/active_support/per_thread_registry.rb

Overview

This module is used to encapsulate access to thread local variables.

Instead of polluting the thread locals namespace:

Thread.current[:connection_handler]

you define a class that extends this module:

module ActiveRecord
  class RuntimeRegistry
    extend ActiveSupport::PerThreadRegistry

    attr_accessor :connection_handler
  end
end

and invoke the declared instance accessors as class methods. So

ActiveRecord::RuntimeRegistry.connection_handler = connection_handler

sets a connection handler local to the current thread, and

ActiveRecord::RuntimeRegistry.connection_handler

returns a connection handler local to the current thread.

This feature is accomplished by instantiating the class and storing the instance as a thread local keyed by the class name. In the example above a key “ActiveRecord::RuntimeRegistry” is stored in Thread.current. The class methods proxy to said thread local instance.

If the class has an initializer, it must accept no arguments.

Dynamic Method Handling

This class handles dynamic methods through the method_missing method

#method_missing(name, *args, &block) ⇒ Object (protected)

:nodoc:

# File 'activesupport/lib/active_support/per_thread_registry.rb', line 37

def method_missing(name, *args, &block) # :nodoc:
  # Caches the method definition as a singleton method of the receiver.
  define_singleton_method(name) do |*a, &b|
    per_thread_registry_instance.public_send(name, *a, &b)
  end

  send(name, *args, &block)
end