Wrapping a fiber in an Async Task

[cramt]

Is it possible to easily take an existing fiber i got from a library and basically just turn it into a task so i can await it, or await it by it self?

Its obviously a "finite" fiber that fits into what an async task expects, aka it yields nil until it at some point yields something truthy and then closes

[ioquatix]

There are specific requirements around the life cycle of a fiber:

async/lib/async/task.rb

Lines 451 to 465 in a093f3a

	begin
	completed!(yield)
	rescue Stop
	stopped!
	rescue StandardError => error
	failed!(error)
	rescue Exception => exception
	failed!(exception)
	# This is a critical failure, we should stop the reactor:
	raise
	ensure
	# Console.info(self) {"Task ensure $! = #{$!} with #{@children&.size.inspect} children!"}
	finish!
	end

Therefore, it's not possible to wrap an existing fiber as it won't emit those events.

However, fibers are pretty cheap and will get scheduled even if not wrapped in tasks:

Async do |parent|
  3.times do
    parent.async do
      Fiber.new do
        sleep 1
        puts "#{Fiber.current} done."
      end.resume
    end
  end
end

# All done at the same time:
#<Fiber:0x00007fdd70f269d0 (irb):5 (resumed)> done.
#<Fiber:0x00007fdd70f226a0 (irb):5 (resumed)> done.
#<Fiber:0x00007fdd70f21ae8 (irb):5 (resumed)> done.
# => #<Async::Task:0x0000000000002290>

So I suggest something like this:

Async do
  # Resume it once:
  existing_fiber.resume
  
  # Or if it can yield values:
  while value = existing_fiber.resume
    process(value)
  end

  # Or if you just want to resume it until completion:
  while existing_fiber.alive?
    existing_fiber.resume
  end
end

Hope that helps!

[cramt]

Thanks, but doesnt busy waiting like this block the async scheduler? if my fiber basically equivilant to

start = Time.now.to_i
Fiber.new do
	loop do
		if start + 5 > Time.now.to_i
			Fiber.yield nil
		elsif
			return "some value"
		end
	end
end

should i throw a sleep in there somewhere? or some other way to tell the scheduler "hey this async task here, you can just schedule it at the end of whatever event queue you have"

[ioquatix]

At present, it's not a bad idea to have sleep(0) as scheduling points if you have CPU bound work. But that is not changed whether you run directly in Async{} or Async{Fiber.new{}.resume} as both are scheduled the same. The only difference is one extra Fiber allocation.