This Ruby Gem offers a duck type for Fiber that will reuse old native fibers for a small performance gain. It will work as a drop in replacment for Ruby's natve Fiber, offering a small performance gain.

gem install fiber_recycling

Then simply require 'fiber_recycling' in your project.

FiberRecycling::Fiber can be used just like ::Fiber.

fiber = FiberRecycling::Fiber.new do |a, b|
  c = FiberRecycling::Fiber.yield(a)
  d = FiberRecycling::Fiber.yield(c + 1)
  d
end

fiber.resume(1, 2) # => 1
fiber.resume(3) # => 4
fiber.resume(5) # => 5

fiber = FiberRecycling::Fiber.new do
  FiberRecycling::Fiber.yield
end

fiber.resume # => nil
fiber.resume # => nil
fiber.resume # => FiberRecycling::FiberError, dead fiber called

To integrate FiberRecycling into an existing project that relies on Fiber you can include FiberRecycling::DuckTypes.

module A
  include FiberRecycling::DuckTypes
  
  def self.a
    fiber = Fiber.new do
      Fiber.yield
    end
    
    fiber # => FiberRecycling::Fiber
    fiber.resume # => nil
    fiber.resume # => nil
    fiber.resume # => FiberRecycling::FiberError, dead fiber called
  end
  
end

A.a

As fibers can only be resumed in the thread that they were created, a native fiber pool will be created on demand for each thread that a pool is needed. The native fibers in each pool also only be created on demand. When a new FiberRecycling::Fiber is created, it will create a new native fiber if none are available in thread's pool. The native fiber will only be returned to the pool when the FiberRecycling::Fiber has completed executing it's block (is in a dead state) or has been collected by the garbage collector. As each pool is shared globally, possibly being accessed by multiple code bases that have no knowledge of each other, it is impossible to allow a code base to set a maximum pool size limit. One project may want a maximum size of 5 native fibers per thread while another may want 10, there is no way to satisfy both requests. As such FiberRecycling will put no constraint on the number of native fibers that can be created. Therefore, it is important to keep in mind that FiberRecycling will create as many native fibers as is simoustanly demanded and will not delete them until the thread gets garbage collected (if you are creating fibers in the main thread, this will obviously never happen). It is up to the developer of the code base to ensure that only a reasonable amount of FiberRecycling::Fiber will ever be alive simoustanly.