while is_running():
    task = get_next_task_from_queue()
    if task:
        submit_task_for_processing(task)
    else:
        sleep_for_a_moment()

class ExampleApp(ConsumerAppBase):

    def _get_next_task(self):

        # Get next task from the queue.
        return self._queue.next()

    def _run_task(self, task):

        # This code's being executed in separate worker thread of
        # ThreadPoolExecutor
        return task / 2

    def _on_task_done(self, task, future):

        # Once worker thread finished - task results are available
        # in _on_task_done() callback as a concurrent.futures.Future object.
        self._log.info('Task done. Result: %s', future.result())