Wrapping a fiber in an Async Task #429

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1. ioquatix commented on Nov 11, 2025

   

   ioquatix

   on Nov 11, 2025

   Member

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   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!
2. cramt commented on Nov 13, 2025

   

   cramt

   on Nov 13, 2025

   Author

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   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"
3. socketry

   locked and limited conversation to collaborators on Nov 13, 2025
4. ioquatix

   converted this issue into a discussion #430 on Nov 13, 2025