Method request_shutdown

include/dmlc/thread_group.h:562–569

! * \brief Signal the thread that a shutdown is desired * \note Since consumer doesn't necessarily get items in order, we must wait for * the queue to empty. * This is generally a shutdown procedure and should not be called from * a performance-sensitive area */

   *       a performance-sensitive area
   */
  void request_shutdown() override {
    shutdown_in_progress_ = true;
    while (queue_->size_approx() > 0 && !ThreadGroup::Thread::is_shutdown_requested()) {
      std::this_thread::sleep_for(std::chrono::milliseconds(1));
    }
    ThreadGroup::Thread::request_shutdown();
    queue_->enqueue(quit_item);
  }

  /*!
   * \brief Enqueue and item