def tasks2(self):
        self.running = True

        while self.running:
            self.update_event.clear()

            if not len(self.heap):
                self.update_event.wait()

            timeout = 0
            task = None

            with self.heap_lock:
                runtime, delay, queue = self.heap[0]
                if runtime > time():
                    timeout = runtime - time()
                else :
                    heappop(self, heap)
                    try :
                        task = queue.get_nowait()
                    except Queue.Empty:
                        pass
                    else :
                        queue.task_done()
                        heappush(self.heap, (time() + delay, delay, queue))
            if task:
                yield task

            self.update_event.wait(timeout)