std::unique_ptr<MockQueueRunner> qr1(new MockQueueRunner(&coord));
  qr1->StartCounting(&counter, 100);
  TF_ASSERT_OK(coord.RegisterRunner(std::move(qr1)));

  std::unique_ptr<MockQueueRunner> qr2(new MockQueueRunner(&coord));
  qr2->StartCounting(&counter, 100);
  TF_ASSERT_OK(coord.RegisterRunner(std::move(qr2)));

  // Wait until the counting has started
  while (counter.load() == 0)
    ;

/// thread or any client.
/// Usage, in the client:
///   Coordinator coord;
///   std::unique_ptr<QueueRunner> qr(&coord, ...);
///   qr.Start(session);
///   coord.RegisterRunner(std::move(qr));
///   /// do some work
///   TF_CHECK_OK(coord.Join());
/// In each thread of QueueRunner, the coordinator needs to be used as:
///   void Run() {
///     while (!coord->ShouldStop()) {

      clean_stop_errors_.insert(static_cast<int>(code));
    }
  }
}

Coordinator::~Coordinator() {
  RequestStop().IgnoreError();
  Join().IgnoreError();
}

Status Coordinator::RegisterRunner(std::unique_ptr<RunnerInterface> runner) {
  {
    mutex_lock l(mu_);
    if (should_stop_) {
      return Status(absl::StatusCode::kFailedPrecondition,
                    "The coordinator has been stopped.");
    }

  std::unique_ptr<QueueRunner> qr1;
  TF_EXPECT_OK(QueueRunner::New(queue_runner1, &coord, &qr1));
  TF_CHECK_OK(qr1->Start(session.get()));

  TF_EXPECT_OK(coord.RegisterRunner(std::move(qr0)));
  TF_EXPECT_OK(coord.RegisterRunner(std::move(qr1)));

  std::vector<Tensor> dq;
  TF_EXPECT_OK(session->Run({}, {kDequeueOp1}, {}, &dq));
  EXPECT_EQ(*dq[0].scalar<int>().data(), 10);