def _submit_gauge(self, metric_name, val, metric, custom_tags=None, hostname=None):
        """
        Submit a metric as a gauge, additional tags provided will be added to
        the ones from the label provided via the metrics object.

        `custom_tags` is an array of 'tag:value' that will be added to the
        metric when sending the gauge to Datadog.
        """
        _tags = self._metric_tags(metric_name, val, metric, custom_tags, hostname)
        self.check.gauge('{}.{}'.format(self.NAMESPACE, metric_name), val, _tags, hostname=hostname)