Issue #8556 has been updated by naruse (Yui NARUSE).

Status changed from Open to Assigned
Assignee set to ko1 (Koichi Sasada)

ko1 will write objection.
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Feature #8556: MutexedDelegator as a trivial way to make an object thread-safe
https://bugs.ruby-lang.org/issues/8556#change-42136

Author: headius (Charles Nutter)
Status: Assigned
Priority: Normal
Assignee: ko1 (Koichi Sasada)
Category: 
Target version: Ruby 2.1.0


=begin
I propose adding (({MutexedDelegator})) as a simple way to wrap any object with a thread-safe wrapper, via existing delegation logic in ((%delegate.rb%)).

(({Delegator})) provides a way to pass method calls through to a wrapped object. (({SimpleDelegator})) is a trivial implementation that just holds the object in an instance variable. (({MutexedDelegator})) would extend (({SimpleDelegator})) and only override initialize and (({method_missing})) as follows:

  class MutexedDelegator < SimpleDelegator
    def initialize(*)
      super
      @mutex = Mutex.new
    end
    
    def method_missing(m, *args, &block)
      target, mutex = self.__getobj__, @mutex
      begin
        mutex.lock
        target.__send__(m, *args, &block)
      ensure
        mutex.unlock
      end
    end
  end

The only changes here are:

* (({Mutex#lock})) and (({unlock})) logic wrapping the send
* No (({respond_to?})) check; I'm not sure why it's there to begin with, since if we're in (({method_missing})) the (({super()})) call will fail just like a normal (({method_missing})) failure anyway
* No backtrace manipulation. This does not work on JRuby and Rubinius anyway, and in this case I feel that the delegator should not hide itself, since there's real behavior change happening.

This is a trivial addition to stdlib that would make it simple to synchronize all calls to a given object in the same way as the JDK's (({Collections.synchronizedSet}))/(({Map}))/(({List})) calls.
=end



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