def test_export_histogram(self):
        client = mock.Mock()

        with mock.patch(
                "opentelemetry.exporter.cloud_monitoring.time_ns",
                lambda: NANOS_PER_SECOND,
        ):
            exporter = CloudMonitoringMetricsExporter(
                project_id=self.project_id, client=client)

        exporter.project_name = self.project_name

        client.create_metric_descriptor.return_value = MetricDescriptor(
            **{
                "name": None,
                "type": "custom.googleapis.com/OpenTelemetry/name",
                "display_name": "name",
                "description": "description",
                "labels": [],
                "metric_kind": "CUMULATIVE",
                "value_type": "DISTRIBUTION",
            })

        aggregator = HistogramAggregator(config={"bounds": [2, 4, 6]})
        aggregator.checkpoint = OrderedDict([(2, 1), (4, 2), (6, 4), (">", 3)])
        aggregator.last_update_timestamp = (WRITE_INTERVAL +
                                            1) * NANOS_PER_SECOND
        exporter.export(
            [MetricRecord(
                MockMetric(meter=MockMeter()),
                (),
                aggregator,
            )])

        series = TimeSeries()
        series.metric.type = "custom.googleapis.com/OpenTelemetry/name"
        point = {
            "interval": {
                "start_time": {
                    "seconds": 1
                },
                "end_time": {
                    "seconds": 11
                },
            },
            "value": {
                "distribution_value": {
                    "count": 10,
                    "bucket_options": {
                        "explicit_buckets": {
                            "bounds": [2.0, 4.0, 6.0]
                        }
                    },
                    "bucket_counts": [1, 2, 4, 3],
                }
            },
        }
        series.points.add(**point)
        client.create_time_series.assert_has_calls(
            [mock.call(self.project_name, [series])])
 def test_get_value_observer_metric_descriptor(self):
     client = mock.Mock()
     exporter = CloudMonitoringMetricsExporter(project_id=self.project_id,
                                               client=client)
     exporter.project_name = self.project_name
     record = ExportRecord(
         MockMetric(),
         (),
         ValueObserverAggregator(),
         Resource.create_empty(),
     )
     exporter._get_metric_descriptor(record)
     client.create_metric_descriptor.assert_called_with(
         self.project_name,
         MetricDescriptor(
             **{
                 "name": None,
                 "type": "custom.googleapis.com/OpenTelemetry/name",
                 "display_name": "name",
                 "description": "description",
                 "labels": [],
                 "metric_kind": "GAUGE",
                 "value_type": "INT64",
             }),
     )
    def test_unique_identifier(self):
        client = mock.Mock()
        exporter1 = CloudMonitoringMetricsExporter(
            project_id=self.project_id,
            client=client,
            add_unique_identifier=True,
        )
        exporter2 = CloudMonitoringMetricsExporter(
            project_id=self.project_id,
            client=client,
            add_unique_identifier=True,
        )
        exporter1.project_name = self.project_name
        exporter2.project_name = self.project_name

        client.create_metric_descriptor.return_value = MetricDescriptor(
            **{
                "name":
                None,
                "type":
                "custom.googleapis.com/OpenTelemetry/name",
                "display_name":
                "name",
                "description":
                "description",
                "labels": [
                    LabelDescriptor(key=UNIQUE_IDENTIFIER_KEY,
                                    value_type="STRING"),
                ],
                "metric_kind":
                "CUMULATIVE",
                "value_type":
                "DOUBLE",
            })

        sum_agg_one = SumAggregator()
        sum_agg_one.update(1)
        metric_record = MetricRecord(
            MockMetric(),
            (),
            sum_agg_one,
        )
        exporter1.export([metric_record])
        exporter2.export([metric_record])

        (
            first_call,
            second_call,
        ) = client.create_metric_descriptor.call_args_list
        self.assertEqual(first_call[0][1].labels[0].key, UNIQUE_IDENTIFIER_KEY)
        self.assertEqual(second_call[0][1].labels[0].key,
                         UNIQUE_IDENTIFIER_KEY)

        first_call, second_call = client.create_time_series.call_args_list
        self.assertNotEqual(
            first_call[0][1][0].metric.labels[UNIQUE_IDENTIFIER_KEY],
            second_call[0][1][0].metric.labels[UNIQUE_IDENTIFIER_KEY],
        )
    def test_export_value_observer(self):
        client = mock.Mock()

        with mock.patch(
                "opentelemetry.exporter.cloud_monitoring.time_ns",
                lambda: NANOS_PER_SECOND,
        ):
            exporter = CloudMonitoringMetricsExporter(
                project_id=self.project_id, client=client)

        exporter.project_name = self.project_name

        client.create_metric_descriptor.return_value = MetricDescriptor(
            **{
                "name": None,
                "type": "custom.googleapis.com/OpenTelemetry/name",
                "display_name": "name",
                "description": "description",
                "labels": [],
                "metric_kind": "GAUGE",
                "value_type": "INT64",
            })

        aggregator = ValueObserverAggregator()
        aggregator.checkpoint = aggregator._TYPE(1, 2, 3, 4, 5)
        aggregator.last_update_timestamp = (WRITE_INTERVAL +
                                            1) * NANOS_PER_SECOND
        exporter.export([
            ExportRecord(
                MockMetric(meter=mock_meter()),
                (),
                aggregator,
                Resource.create_empty(),
            )
        ])

        series = TimeSeries()
        series.metric_kind = MetricDescriptor.MetricKind.GAUGE
        series.metric.type = "custom.googleapis.com/OpenTelemetry/name"
        point = series.points.add()
        point.value.int64_value = 5
        point.interval.end_time.seconds = WRITE_INTERVAL + 1
        point.interval.end_time.nanos = 0
        point.interval.start_time.seconds = WRITE_INTERVAL + 1
        point.interval.start_time.nanos = 0
        client.create_time_series.assert_has_calls(
            [mock.call(self.project_name, [series])])
    def initialize_base_metrics_message(
        self,
        metric_name: str,
        labels: dict,
        metric_kind=MetricDescriptor.GAUGE,
        value_type=MetricDescriptor.INT64,
        unit=None,
    ) -> TimeSeries:
        """
        creates an TimeSeries metrics object called metric_name and with labels
        :param metric_name: name to call custom metric. As in custom.googleapis.com/ + metric_name
        :param labels: metric labels to add
        :param metric_kind: the kind of measurement. It describes how the data is reported
        :param value_type: Type of metric value
        :param unit: The unit in which the metric value is reported.
        :return: ::google.cloud.monitoring_v3.types.TimeSeries::
        """
        metric_descriptor_values = {
            "metric_kind": metric_kind,
            "value_type": value_type,
            "type": f"custom.googleapis.com/{metric_name}",
        }
        if unit is not None:
            metric_descriptor_values["unit"] = unit

        self.metrics_client.create_metric_descriptor(
            name=self.monitoring_project_path,
            metric_descriptor=MetricDescriptor(**metric_descriptor_values),
        )

        # if we send requests through metrics_client one after another, we receive unclear error 500,
        # probably due to google's requests throttling
        sleep(1)

        series = self.metrics_type(metric_kind=metric_kind,
                                   value_type=value_type)

        series.resource.type = "global"
        series.metric.type = f"custom.googleapis.com/{metric_name}"
        series.metric.labels.update(labels)
        return series
    def _get_metric_descriptor(
        self, record: MetricRecord
    ) -> Optional[MetricDescriptor]:
        """ We can map Metric to MetricDescriptor using Metric.name or
        MetricDescriptor.type. We create the MetricDescriptor if it doesn't
        exist already and cache it. Note that recreating MetricDescriptors is
        a no-op if it already exists.

        :param record:
        :return:
        """
        instrument = record.instrument
        descriptor_type = "custom.googleapis.com/OpenTelemetry/{}".format(
            instrument.name
        )
        if descriptor_type in self._metric_descriptors:
            return self._metric_descriptors[descriptor_type]
        descriptor = {
            "name": None,
            "type": descriptor_type,
            "display_name": instrument.name,
            "description": instrument.description,
            "labels": [],
        }
        for key, value in record.labels:
            if isinstance(value, str):
                descriptor["labels"].append(
                    LabelDescriptor(key=key, value_type="STRING")
                )
            elif isinstance(value, bool):
                descriptor["labels"].append(
                    LabelDescriptor(key=key, value_type="BOOL")
                )
            elif isinstance(value, int):
                descriptor["labels"].append(
                    LabelDescriptor(key=key, value_type="INT64")
                )
            else:
                logger.warning(
                    "Label value %s is not a string, bool or integer, ignoring it",
                    value,
                )

        if self.unique_identifier:
            descriptor["labels"].append(
                LabelDescriptor(key=UNIQUE_IDENTIFIER_KEY, value_type="STRING")
            )

        # SumAggregator is best represented as a cumulative, but it can't be
        # represented that way if it can decrement. So we need to make sure
        # that the instrument is not an UpDownCounter
        if isinstance(record.aggregator, SumAggregator) and not isinstance(
            record.instrument, UpDownCounter
        ):
            descriptor["metric_kind"] = MetricDescriptor.MetricKind.CUMULATIVE
        elif isinstance(record.aggregator, ValueObserverAggregator):
            descriptor["metric_kind"] = MetricDescriptor.MetricKind.GAUGE
        elif isinstance(record.aggregator, HistogramAggregator):
            descriptor["metric_kind"] = MetricDescriptor.MetricKind.CUMULATIVE
        else:
            logger.warning(
                "Unsupported instrument/aggregator combo, types %s and %s, ignoring it",
                type(record.instrument).__name__,
                type(record.aggregator).__name__,
            )
            return None

        if isinstance(record.aggregator, HistogramAggregator):
            descriptor["value_type"] = MetricDescriptor.ValueType.DISTRIBUTION
        elif instrument.value_type == int:
            descriptor["value_type"] = MetricDescriptor.ValueType.INT64
        elif instrument.value_type == float:
            descriptor["value_type"] = MetricDescriptor.ValueType.DOUBLE

        proto_descriptor = MetricDescriptor(**descriptor)
        try:
            descriptor = self.client.create_metric_descriptor(
                self.project_name, proto_descriptor
            )
        # pylint: disable=broad-except
        except Exception as ex:
            logger.error(
                "Failed to create metric descriptor %s",
                proto_descriptor,
                exc_info=ex,
            )
            return None
        self._metric_descriptors[descriptor_type] = descriptor
        return descriptor
Example #7
0
    def test_stateless_times(self):
        client = mock.Mock()
        with mock.patch(
            "opentelemetry.exporter.cloud_monitoring.time_ns",
            lambda: NANOS_PER_SECOND,
        ):
            exporter = CloudMonitoringMetricsExporter(
                project_id=self.project_id, client=client,
            )

        client.create_metric_descriptor.return_value = MetricDescriptor(
            **{
                "name": None,
                "type": "custom.googleapis.com/OpenTelemetry/name",
                "display_name": "name",
                "description": "description",
                "labels": [
                    LabelDescriptor(
                        key=UNIQUE_IDENTIFIER_KEY, value_type="STRING"
                    ),
                ],
                "metric_kind": "CUMULATIVE",
                "value_type": "DOUBLE",
            }
        )

        agg = SumAggregator()
        agg.checkpoint = 1
        agg.last_update_timestamp = (WRITE_INTERVAL + 1) * NANOS_PER_SECOND

        metric_record = MetricRecord(MockMetric(stateful=False), (), agg)

        exporter.export([metric_record])

        exports_1 = client.create_time_series.call_args_list[0]

        # verify the first metric started at exporter start time
        self.assertEqual(
            exports_1[0][1][0].points[0].interval.start_time.seconds, 1
        )
        self.assertEqual(
            exports_1[0][1][0].points[0].interval.start_time.nanos, 0
        )

        self.assertEqual(
            exports_1[0][1][0].points[0].interval.end_time.seconds,
            WRITE_INTERVAL + 1,
        )

        agg.last_update_timestamp = (WRITE_INTERVAL * 2 + 2) * NANOS_PER_SECOND

        metric_record = MetricRecord(MockMetric(stateful=False), (), agg)

        exporter.export([metric_record])

        exports_2 = client.create_time_series.call_args_list[1]

        # 1ms ahead of end time of last export
        self.assertEqual(
            exports_2[0][1][0].points[0].interval.start_time.seconds,
            WRITE_INTERVAL + 1,
        )
        self.assertEqual(
            exports_2[0][1][0].points[0].interval.start_time.nanos, 1e6
        )

        self.assertEqual(
            exports_2[0][1][0].points[0].interval.end_time.seconds,
            WRITE_INTERVAL * 2 + 2,
        )
Example #8
0
    def test_export(self):
        client = mock.Mock()

        with mock.patch(
            "opentelemetry.exporter.cloud_monitoring.time_ns",
            lambda: NANOS_PER_SECOND,
        ):
            exporter = CloudMonitoringMetricsExporter(
                project_id=self.project_id, client=client
            )

        exporter.project_name = self.project_name

        exporter.export(
            [
                MetricRecord(
                    MockMetric(),
                    (("label1", "value1"),),
                    UnsupportedAggregator(),
                )
            ]
        )
        client.create_time_series.assert_not_called()

        client.create_metric_descriptor.return_value = MetricDescriptor(
            **{
                "name": None,
                "type": "custom.googleapis.com/OpenTelemetry/name",
                "display_name": "name",
                "description": "description",
                "labels": [
                    LabelDescriptor(key="label1", value_type="STRING"),
                    LabelDescriptor(key="label2", value_type="INT64"),
                ],
                "metric_kind": "CUMULATIVE",
                "value_type": "DOUBLE",
            }
        )

        resource = Resource(
            labels={
                "cloud.account.id": 123,
                "host.id": "host",
                "cloud.zone": "US",
                "cloud.provider": "gcp",
                "extra_info": "extra",
                "gcp.resource_type": "gce_instance",
                "not_gcp_resource": "value",
            }
        )

        sum_agg_one = SumAggregator()
        sum_agg_one.checkpoint = 1
        sum_agg_one.last_update_timestamp = (
            WRITE_INTERVAL + 1
        ) * NANOS_PER_SECOND
        exporter.export(
            [
                MetricRecord(
                    MockMetric(meter=MockMeter(resource=resource)),
                    (("label1", "value1"), ("label2", 1),),
                    sum_agg_one,
                ),
                MetricRecord(
                    MockMetric(meter=MockMeter(resource=resource)),
                    (("label1", "value2"), ("label2", 2),),
                    sum_agg_one,
                ),
            ]
        )
        expected_resource = MonitoredResource(
            type="gce_instance",
            labels={"project_id": "123", "instance_id": "host", "zone": "US"},
        )

        series1 = TimeSeries(resource=expected_resource)
        series1.metric.type = "custom.googleapis.com/OpenTelemetry/name"
        series1.metric.labels["label1"] = "value1"
        series1.metric.labels["label2"] = "1"
        point = series1.points.add()
        point.value.int64_value = 1
        point.interval.end_time.seconds = WRITE_INTERVAL + 1
        point.interval.end_time.nanos = 0
        point.interval.start_time.seconds = 1
        point.interval.start_time.nanos = 0

        series2 = TimeSeries(resource=expected_resource)
        series2.metric.type = "custom.googleapis.com/OpenTelemetry/name"
        series2.metric.labels["label1"] = "value2"
        series2.metric.labels["label2"] = "2"
        point = series2.points.add()
        point.value.int64_value = 1
        point.interval.end_time.seconds = WRITE_INTERVAL + 1
        point.interval.end_time.nanos = 0
        point.interval.start_time.seconds = 1
        point.interval.start_time.nanos = 0

        client.create_time_series.assert_has_calls(
            [mock.call(self.project_name, [series1, series2])]
        )

        # Attempting to export too soon after another export with the exact
        # same labels leads to it being dropped

        sum_agg_two = SumAggregator()
        sum_agg_two.checkpoint = 1
        sum_agg_two.last_update_timestamp = (
            WRITE_INTERVAL + 2
        ) * NANOS_PER_SECOND
        exporter.export(
            [
                MetricRecord(
                    MockMetric(),
                    (("label1", "value1"), ("label2", 1),),
                    sum_agg_two,
                ),
                MetricRecord(
                    MockMetric(),
                    (("label1", "value2"), ("label2", 2),),
                    sum_agg_two,
                ),
            ]
        )
        self.assertEqual(client.create_time_series.call_count, 1)

        # But exporting with different labels is fine
        sum_agg_two.checkpoint = 2
        exporter.export(
            [
                MetricRecord(
                    MockMetric(),
                    (("label1", "changed_label"), ("label2", 2),),
                    sum_agg_two,
                ),
            ]
        )
        series3 = TimeSeries()
        series3.metric.type = "custom.googleapis.com/OpenTelemetry/name"
        series3.metric.labels["label1"] = "changed_label"
        series3.metric.labels["label2"] = "2"
        point = series3.points.add()
        point.value.int64_value = 2
        point.interval.end_time.seconds = WRITE_INTERVAL + 2
        point.interval.end_time.nanos = 0
        point.interval.start_time.seconds = 1
        point.interval.start_time.nanos = 0

        client.create_time_series.assert_has_calls(
            [
                mock.call(self.project_name, [series1, series2]),
                mock.call(self.project_name, [series3]),
            ]
        )
Example #9
0
    def test_get_metric_descriptor(self):
        client = mock.Mock()
        exporter = CloudMonitoringMetricsExporter(
            project_id=self.project_id, client=client
        )
        exporter.project_name = self.project_name

        self.assertIsNone(
            exporter._get_metric_descriptor(
                MetricRecord(MockMetric(), (), UnsupportedAggregator())
            )
        )

        record = MetricRecord(
            MockMetric(), (("label1", "value1"),), SumAggregator(),
        )
        metric_descriptor = exporter._get_metric_descriptor(record)
        client.create_metric_descriptor.assert_called_with(
            self.project_name,
            MetricDescriptor(
                **{
                    "name": None,
                    "type": "custom.googleapis.com/OpenTelemetry/name",
                    "display_name": "name",
                    "description": "description",
                    "labels": [
                        LabelDescriptor(key="label1", value_type="STRING")
                    ],
                    "metric_kind": "CUMULATIVE",
                    "value_type": "INT64",
                }
            ),
        )

        # Getting a cached metric descriptor shouldn't use another call
        cached_metric_descriptor = exporter._get_metric_descriptor(record)
        self.assertEqual(client.create_metric_descriptor.call_count, 1)
        self.assertEqual(metric_descriptor, cached_metric_descriptor)

        # Drop labels with values that aren't string, int or bool
        exporter._get_metric_descriptor(
            MetricRecord(
                MockMetric(name="name2", value_type=float),
                (
                    ("label1", "value1"),
                    ("label2", dict()),
                    ("label3", 3),
                    ("label4", False),
                ),
                SumAggregator(),
            )
        )
        client.create_metric_descriptor.assert_called_with(
            self.project_name,
            MetricDescriptor(
                **{
                    "name": None,
                    "type": "custom.googleapis.com/OpenTelemetry/name2",
                    "display_name": "name2",
                    "description": "description",
                    "labels": [
                        LabelDescriptor(key="label1", value_type="STRING"),
                        LabelDescriptor(key="label3", value_type="INT64"),
                        LabelDescriptor(key="label4", value_type="BOOL"),
                    ],
                    "metric_kind": "CUMULATIVE",
                    "value_type": "DOUBLE",
                }
            ),
        )
    def test_export(self):
        client = mock.Mock()
        exporter = CloudMonitoringMetricsExporter(
            project_id=self.project_id, client=client
        )
        exporter.project_name = self.project_name

        exporter.export(
            [
                MetricRecord(
                    MockMetric(),
                    (("label1", "value1"),),
                    UnsupportedAggregator(),
                )
            ]
        )
        client.create_time_series.assert_not_called()

        client.create_metric_descriptor.return_value = MetricDescriptor(
            **{
                "name": None,
                "type": "custom.googleapis.com/OpenTelemetry/name",
                "display_name": "name",
                "description": "description",
                "labels": [
                    LabelDescriptor(key="label1", value_type="STRING"),
                    LabelDescriptor(key="label2", value_type="INT64"),
                ],
                "metric_kind": "GAUGE",
                "value_type": "DOUBLE",
            }
        )

        counter_one = CounterAggregator()
        counter_one.checkpoint = 1
        counter_one.last_update_timestamp = (WRITE_INTERVAL + 1) * 1e9
        exporter.export(
            [
                MetricRecord(
                    MockMetric(),
                    (("label1", "value1"), ("label2", 1),),
                    counter_one,
                ),
                MetricRecord(
                    MockMetric(),
                    (("label1", "value2"), ("label2", 2),),
                    counter_one,
                ),
            ]
        )
        series1 = TimeSeries()
        series1.metric.type = "custom.googleapis.com/OpenTelemetry/name"
        series1.metric.labels["label1"] = "value1"
        series1.metric.labels["label2"] = "1"
        point = series1.points.add()
        point.value.int64_value = 1
        point.interval.end_time.seconds = WRITE_INTERVAL + 1
        point.interval.end_time.nanos = 0

        series2 = TimeSeries()
        series2.metric.type = "custom.googleapis.com/OpenTelemetry/name"
        series2.metric.labels["label1"] = "value2"
        series2.metric.labels["label2"] = "2"
        point = series2.points.add()
        point.value.int64_value = 1
        point.interval.end_time.seconds = WRITE_INTERVAL + 1
        point.interval.end_time.nanos = 0
        client.create_time_series.assert_has_calls(
            [mock.call(self.project_name, [series1, series2])]
        )

        # Attempting to export too soon after another export with the exact
        # same labels leads to it being dropped

        counter_two = CounterAggregator()
        counter_two.checkpoint = 1
        counter_two.last_update_timestamp = (WRITE_INTERVAL + 2) * 1e9
        exporter.export(
            [
                MetricRecord(
                    MockMetric(),
                    (("label1", "value1"), ("label2", 1),),
                    counter_two,
                ),
                MetricRecord(
                    MockMetric(),
                    (("label1", "value2"), ("label2", 2),),
                    counter_two,
                ),
            ]
        )
        self.assertEqual(client.create_time_series.call_count, 1)

        # But exporting with different labels is fine
        counter_two.checkpoint = 2
        exporter.export(
            [
                MetricRecord(
                    MockMetric(),
                    (("label1", "changed_label"), ("label2", 2),),
                    counter_two,
                ),
            ]
        )
        series3 = TimeSeries()
        series3.metric.type = "custom.googleapis.com/OpenTelemetry/name"
        series3.metric.labels["label1"] = "changed_label"
        series3.metric.labels["label2"] = "2"
        point = series3.points.add()
        point.value.int64_value = 2
        point.interval.end_time.seconds = WRITE_INTERVAL + 2
        point.interval.end_time.nanos = 0
        client.create_time_series.assert_has_calls(
            [
                mock.call(self.project_name, [series1, series2]),
                mock.call(self.project_name, [series3]),
            ]
        )
Example #11
0
    def _get_metric_descriptor(
            self, record: MetricRecord) -> Optional[MetricDescriptor]:
        """ We can map Metric to MetricDescriptor using Metric.name or
        MetricDescriptor.type. We create the MetricDescriptor if it doesn't
        exist already and cache it. Note that recreating MetricDescriptors is
        a no-op if it already exists.

        :param record:
        :return:
        """
        instrument = record.instrument
        descriptor_type = "custom.googleapis.com/OpenTelemetry/{}".format(
            instrument.name)
        if descriptor_type in self._metric_descriptors:
            return self._metric_descriptors[descriptor_type]
        descriptor = {
            "name": None,
            "type": descriptor_type,
            "display_name": instrument.name,
            "description": instrument.description,
            "labels": [],
        }
        for key, value in record.labels:
            if isinstance(value, str):
                descriptor["labels"].append(
                    LabelDescriptor(key=key, value_type="STRING"))
            elif isinstance(value, bool):
                descriptor["labels"].append(
                    LabelDescriptor(key=key, value_type="BOOL"))
            elif isinstance(value, int):
                descriptor["labels"].append(
                    LabelDescriptor(key=key, value_type="INT64"))
            else:
                logger.warning(
                    "Label value %s is not a string, bool or integer", value)
        if isinstance(record.aggregator, SumAggregator):
            descriptor["metric_kind"] = MetricDescriptor.MetricKind.GAUGE
        else:
            logger.warning(
                "Unsupported aggregation type %s, ignoring it",
                type(record.aggregator).__name__,
            )
            return None
        if instrument.value_type == int:
            descriptor["value_type"] = MetricDescriptor.ValueType.INT64
        elif instrument.value_type == float:
            descriptor["value_type"] = MetricDescriptor.ValueType.DOUBLE
        proto_descriptor = MetricDescriptor(**descriptor)
        try:
            descriptor = self.client.create_metric_descriptor(
                self.project_name, proto_descriptor)
        # pylint: disable=broad-except
        except Exception as ex:
            logger.error(
                "Failed to create metric descriptor %s",
                proto_descriptor,
                exc_info=ex,
            )
            return None
        self._metric_descriptors[descriptor_type] = descriptor
        return descriptor