Ruby: Get Fiber parent

Question

Is it possible to retrieve the fiber which created the current fiber? It would suffice if I could get this information upon creation of a new Fiber.

Monkey-patching Fiber#new doesn't work, as calling Fiber#current results in "uninitialized fiber" error.

Answer 1

I finally found a way to get it working. If we redefine initialize it would fail as the internals won't initialize the fiber. It is however possible to alias it, create a new one, and then run the old one:

  class Fiber
    alias_method :old_init, :initialize

    def initialize
      old_init
      @parent = Fiber.current
    end

    def parent
      @parent
    end
  end

Since the Fiber.current doesn't change until we execute resume on the fiber, we can safely copy a reference in the initializer.

Now we can ask the system "Who's your grandpa?" Fiber.current.parent.parent.