docs: private void sendRegisterRequest() {
      Metrics.MetricPublisher publisher = Metrics.MetricPublisher.newBuilder().
          setHostname(hostname).
          setPort(instance.getInfo().getTaskId()).
          setComponentName(instance.getInfo().getComponentName()).
          setInstanceId(instance.getInstanceId()).
          setInstanceIndex(instance.getInfo().getComponentIndex()).
          build();
      Metrics.MetricPublisherRegisterRequest request =
          Metrics.MetricPublisherRegisterRequest.newBuilder().
              setPublisher(publisher).
              build();
  
      // The timeout would be the reconnect-interval-seconds
      sendRequest(request, null,
          Metrics.MetricPublisherRegisterResponse.newBuilder(),
          systemConfig.getInstanceReconnectMetricsmgrInterval());
    }