OpenCensus agent exporter fixes

- Pass start_timestamp to the timeseries in OC exporter for stateful
metrics
- Convert label values to strings, just in case

ext/opentelemetry-ext-opencensusexporter/CHANGELOG.md

@@ -2,6 +2,9 @@
 
 ## Unreleased
 
+- Send start_timestamp and convert labels to strings
+  ([#937](https://github.com/open-telemetry/opentelemetry-python/pull/937))
+
 ## 0.8b0
 
 Released 2020-05-27

ext/opentelemetry-ext-opencensusexporter/src/opentelemetry/ext/opencensusexporter/metrics_exporter/__init__.py

@@ -18,6 +18,7 @@
 from typing import Sequence
 
 import grpc
+from google.protobuf.timestamp_pb2 import Timestamp
 from opencensus.proto.agent.metrics.v1 import (
     metrics_service_pb2,
     metrics_service_pb2_grpc,
@@ -65,6 +66,8 @@ def __init__(
             self.client = client
 
         self.node = utils.get_node(service_name, host_name)
+        self.exporter_start_timestamp = Timestamp()
+        self.exporter_start_timestamp.GetCurrentTime()
 
     def export(
         self, metric_records: Sequence[MetricRecord]
@@ -89,7 +92,9 @@ def shutdown(self) -> None:
     def generate_metrics_requests(
         self, metrics: Sequence[MetricRecord]
     ) -> metrics_service_pb2.ExportMetricsServiceRequest:
-        collector_metrics = translate_to_collector(metrics)
+        collector_metrics = translate_to_collector(
+            metrics, self.exporter_start_timestamp
+        )
         service_request = metrics_service_pb2.ExportMetricsServiceRequest(
             node=self.node, metrics=collector_metrics
         )
@@ -99,6 +104,7 @@ def generate_metrics_requests(
 # pylint: disable=too-many-branches
 def translate_to_collector(
     metric_records: Sequence[MetricRecord],
+    exporter_start_timestamp: Timestamp,
 ) -> Sequence[metrics_pb2.Metric]:
     collector_metrics = []
     for metric_record in metric_records:
@@ -109,7 +115,8 @@ def translate_to_collector(
             label_keys.append(metrics_pb2.LabelKey(key=label_tuple[0]))
             label_values.append(
                 metrics_pb2.LabelValue(
-                    has_value=label_tuple[1] is not None, value=label_tuple[1]
+                    has_value=label_tuple[1] is not None,
+                    value=str(label_tuple[1]),
                 )
             )
 
@@ -121,9 +128,17 @@ def translate_to_collector(
             label_keys=label_keys,
         )
 
+        # If cumulative and stateful, explicitly set the start_timestamp to
+        # exporter start time.
+        if metric_record.instrument.meter.batcher.stateful:
+            start_timestamp = exporter_start_timestamp
+        else:
+            start_timestamp = None
+
         timeseries = metrics_pb2.TimeSeries(
             label_values=label_values,
             points=[get_collector_point(metric_record)],
+            start_timestamp=start_timestamp,
         )
         collector_metrics.append(
             metrics_pb2.Metric(

ext/opentelemetry-ext-opencensusexporter/tests/test_otcollector_metrics_exporter.py

@@ -41,7 +41,7 @@ def setUpClass(cls):
         # pylint: disable=protected-access
         metrics.set_meter_provider(MeterProvider())
         cls._meter = metrics.get_meter(__name__)
-        cls._labels = {"environment": "staging"}
+        cls._labels = {"environment": "staging", "number": 321}
         cls._key_labels = get_labels_as_key(cls._labels)
 
     def test_constructor(self):
@@ -119,7 +119,7 @@ def test_export(self):
             client=mock_client, host_name=host_name
         )
         test_metric = self._meter.create_metric(
-            "testname", "testdesc", "unit", int, Counter, ["environment"]
+            "testname", "testdesc", "unit", int, Counter, self._labels.keys(),
         )
         record = MetricRecord(
             test_metric, self._key_labels, aggregate.SumAggregator(),
@@ -142,13 +142,16 @@ def test_export(self):
 
     def test_translate_to_collector(self):
         test_metric = self._meter.create_metric(
-            "testname", "testdesc", "unit", int, Counter, ["environment"]
+            "testname", "testdesc", "unit", int, Counter, self._labels.keys()
         )
         aggregator = aggregate.SumAggregator()
         aggregator.update(123)
         aggregator.take_checkpoint()
         record = MetricRecord(test_metric, self._key_labels, aggregator,)
-        output_metrics = metrics_exporter.translate_to_collector([record])
+        start_timestamp = Timestamp()
+        output_metrics = metrics_exporter.translate_to_collector(
+            [record], start_timestamp,
+        )
         self.assertEqual(len(output_metrics), 1)
         self.assertIsInstance(output_metrics[0], metrics_pb2.Metric)
         self.assertEqual(output_metrics[0].metric_descriptor.name, "testname")
@@ -161,14 +164,20 @@ def test_translate_to_collector(self):
             metrics_pb2.MetricDescriptor.CUMULATIVE_INT64,
         )
         self.assertEqual(
-            len(output_metrics[0].metric_descriptor.label_keys), 1
+            len(output_metrics[0].metric_descriptor.label_keys), 2
         )
         self.assertEqual(
             output_metrics[0].metric_descriptor.label_keys[0].key,
             "environment",
         )
+        self.assertEqual(
+            output_metrics[0].metric_descriptor.label_keys[1].key, "number",
+        )
         self.assertEqual(len(output_metrics[0].timeseries), 1)
-        self.assertEqual(len(output_metrics[0].timeseries[0].label_values), 1)
+        self.assertEqual(len(output_metrics[0].timeseries[0].label_values), 2)
+        self.assertEqual(
+            output_metrics[0].timeseries[0].start_timestamp, start_timestamp
+        )
         self.assertEqual(
             output_metrics[0].timeseries[0].label_values[0].has_value, True
         )