Module: ActiveSupport::PerThreadRegistry

Relationships & Source Files
Extension / Inclusion / Inheritance Descendants
Extended In: ActiveRecord::ExplainRegistry, ActiveRecord::Relation::RecordFetchWarning::QueryRegistry, ActiveRecord::RuntimeRegistry, ActiveRecord::Scoping::ScopeRegistry, ActiveRecord::SuppressorRegistry, ActiveSupport::Cache::Strategy::LocalCache::LocalCacheRegistry, ActiveSupport::Notifications::InstrumentationRegistry, ActiveSupport::SubscriberQueueRegistry
Defined in:	activesupport/lib/active_support/per_thread_registry.rb

Overview

NOTE: This approach has been deprecated for end-user code in favor of thread_mattr_accessor and friends. Please use that approach instead.

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.

Class Method Summary

.extended(object)

Instance Method Summary

#instance

Dynamic Method Handling

This class handles dynamic methods through the method_missing method

#method_missing(name, *args, &block) (private)

[ GitHub ]

# File 'activesupport/lib/active_support/per_thread_registry.rb', line 51


def method_missing(name, *args, &block)
  # Caches the method definition as a singleton method of the receiver.
  #
  # By letting #delegate handle it, we avoid an enclosure that'll capture args.
  singleton_class.delegate name, to: :instance

  send(name, *args, &block)
end

Class Method Details

.extended(object)

[ GitHub ]

# File 'activesupport/lib/active_support/per_thread_registry.rb', line 42


def self.extended(object)
  object.instance_variable_set :@per_thread_registry_key, object.name.freeze
end

Instance Method Details

#instance

[ GitHub ]

# File 'activesupport/lib/active_support/per_thread_registry.rb', line 46


def instance
  Thread.current[@per_thread_registry_key] ||= new
end