def create_worker_thread
      wrkr = ThreadPoolWorker.new(@queue, self)
      Thread.new(wrkr, self) do |worker, parent|
        Thread.current.abort_on_exception = false
        worker.run
        parent.on_worker_exit(worker)
      end
      return wrkr
    end
def create_worker_thread
      wrkr = ThreadPoolWorker.new(@queue, self)
      Thread.new(wrkr, self) do |worker, parent|
        Thread.current.abort_on_exception = false
        worker.run
        parent.on_worker_exit(worker)
      end
      return wrkr
    end
Create a single worker thread to be added to the pool.

 @return [Thread] the new thread.

 @!visibility private