Repository: census-ecosystem/opencensus-go-exporter-stackdriver (go)

Issue:
Add support to convert summary metrics 
SD currently doesn't support Summary metrics. In order to support summary metrics from sources like Prometheus it is desirable to convert summary metrics to following as done for [Java SD exporter.](https://github.com/census-instrumentation/opencensus-java/issues/1514)
Summary.Sum to CUMULATIVE_DOUBLE
Summary.Count to CUMULATIVE_INT64
Summary.Percentiles to CUMULATIVE_GAUGE for the value and percentile as value for Label "percentile"


Pull request description:
convert summary metrics to cumulatives and gauges.
- convert summary.sum to cumulative_int64
- convert summary.count to cumulative_double
- convert summary.percentile to gauge with label "percentile"

fixes #151 

Patch:
diff --git a/metrics_proto.go b/metrics_proto.go
index a48c4c8..0969321 100644
--- a/metrics_proto.go
+++ b/metrics_proto.go
@@ -45,6 +45,10 @@ import (
 
 var errNilMetric = errors.New("expecting a non-nil metric")
 var errNilMetricDescriptor = errors.New("expecting a non-nil metric descriptor")
+var percentileLabelKey = &metricspb.LabelKey{
+	Key:         "percentile",
+	Description: "the value at a given percentile of a distribution",
+}
 
 type metricProtoPayload struct {
 	node             *commonpb.Node
@@ -53,6 +57,18 @@ type metricProtoPayload struct {
 	additionalLabels map[string]labelValue
 }
 
+func (se *statsExporter) addPayload(node *commonpb.Node, rsc *resourcepb.Resource, labels map[string]labelValue, metrics ...*metricspb.Metric) {
+	for _, metric := range metrics {
+		payload := &metricProtoPayload{
+			metric:           metric,
+			resource:         rsc,
+			node:             node,
+			additionalLabels: labels,
+		}
+		se.protoMetricsBundler.Add(payload, 1)
+	}
+}
+
 // ExportMetricsProto exports OpenCensus Metrics Proto to Stackdriver Monitoring.
 func (se *statsExporter) ExportMetricsProto(ctx context.Context, node *commonpb.Node, rsc *resourcepb.Resource, metrics []*metricspb.Metric) error {
 	if len(metrics) == 0 {
@@ -66,18 +82,128 @@ func (se *statsExporter) ExportMetricsProto(ctx context.Context, node *commonpb.
 	}
 
 	for _, metric := range metrics {
-		payload := &metricProtoPayload{
-			metric:           metric,
-			resource:         rsc,
-			node:             node,
-			additionalLabels: additionalLabels,
+		if metric.GetMetricDescriptor().GetType() == metricspb.MetricDescriptor_SUMMARY {
+			se.addPayload(node, rsc, additionalLabels, se.convertSummaryMetrics(metric)...)
+		} else {
+			se.addPayload(node, rsc, additionalLabels, metric)
 		}
-		se.protoMetricsBundler.Add(payload, 1)
 	}
 
 	return nil
 }
 
+func (se *statsExporter) convertSummaryMetrics(summary *metricspb.Metric) []*metricspb.Metric {
+	var metrics []*metricspb.Metric
+	var percentileTss []*metricspb.TimeSeries
+	var countTss []*metricspb.TimeSeries
+	var sumTss []*metricspb.TimeSeries
+
+	for _, ts := range summary.Timeseries {
+		lvs := ts.GetLabelValues()
+
+		startTime := ts.StartTimestamp
+		for _, pt := range ts.GetPoints() {
+			ptTimestamp := pt.GetTimestamp()
+			summaryValue := pt.GetSummaryValue()
+			if summaryValue.Sum != nil {
+				sumTs := &metricspb.TimeSeries{
+					LabelValues:    lvs,
+					StartTimestamp: startTime,
+					Points: []*metricspb.Point{
+						{
+							Value: &metricspb.Point_DoubleValue{
+								DoubleValue: summaryValue.Sum.Value,
+							},
+							Timestamp: ptTimestamp,
+						},
+					},
+				}
+				sumTss = append(sumTss, sumTs)
+			}
+
+			if summaryValue.Count != nil {
+				countTs := &metricspb.TimeSeries{
+					LabelValues:    lvs,
+					StartTimestamp: startTime,
+					Points: []*metricspb.Point{
+						{
+							Value: &metricspb.Point_Int64Value{
+								Int64Value: summaryValue.Count.Value,
+							},
+							Timestamp: ptTimestamp,
+						},
+					},
+				}
+				countTss = append(countTss, countTs)
+			}
+
+			snapshot := summaryValue.GetSnapshot()
+			for _, percentileValue := range snapshot.GetPercentileValues() {
+				lvsWithPercentile := lvs[0:]
+				lvsWithPercentile = append(lvsWithPercentile, &metricspb.LabelValue{
+					Value: fmt.Sprintf("%f", percentileValue.Percentile),
+				})
+				percentileTs := &metricspb.TimeSeries{
+					LabelValues:    lvsWithPercentile,
+					StartTimestamp: nil,
+					Points: []*metricspb.Point{
+						{
+							Value: &metricspb.Point_DoubleValue{
+								DoubleValue: percentileValue.Value,
+							},
+							Timestamp: ptTimestamp,
+						},
+					},
+				}
+				percentileTss = append(percentileTss, percentileTs)
+			}
+		}
+
+		if len(sumTss) > 0 {
+			metric := &metricspb.Metric{
+				MetricDescriptor: &metricspb.MetricDescriptor{
+					Name:        fmt.Sprintf("%s_summary_sum", summary.GetMetricDescriptor().GetName()),
+					Description: summary.GetMetricDescriptor().GetDescription(),
+					Type:        metricspb.MetricDescriptor_CUMULATIVE_DOUBLE,
+					Unit:        summary.GetMetricDescriptor().GetUnit(),
+					LabelKeys:   summary.GetMetricDescriptor().GetLabelKeys(),
+				},
+				Timeseries: sumTss,
+			}
+			metrics = append(metrics, metric)
+		}
+		if len(countTss) > 0 {
+			metric := &metricspb.Metric{
+				MetricDescriptor: &metricspb.MetricDescriptor{
+					Name:        fmt.Sprintf("%s_summary_count", summary.GetMetricDescriptor().GetName()),
+					Description: summary.GetMetricDescriptor().GetDescription(),
+					Type:        metricspb.MetricDescriptor_CUMULATIVE_INT64,
+					Unit:        "1",
+					LabelKeys:   summary.GetMetricDescriptor().GetLabelKeys(),
+				},
+				Timeseries: countTss,
+			}
+			metrics = append(metrics, metric)
+		}
+		if len(percentileTss) > 0 {
+			lks := summary.GetMetricDescriptor().GetLabelKeys()[0:]
+			lks = append(lks, percentileLabelKey)
+			metric := &metricspb.Metric{
+				MetricDescriptor: &metricspb.MetricDescriptor{
+					Name:        fmt.Sprintf("%s_summary_percentile", summary.GetMetricDescriptor().GetName()),
+					Description: summary.GetMetricDescriptor().GetDescription(),
+					Type:        metricspb.MetricDescriptor_GAUGE_DOUBLE,
+					Unit:        summary.GetMetricDescriptor().GetUnit(),
+					LabelKeys:   lks,
+				},
+				Timeseries: percentileTss,
+			}
+			metrics = append(metrics, metric)
+		}
+	}
+	return metrics
+}
+
 func (se *statsExporter) handleMetricsProtoUpload(payloads []*metricProtoPayload) error {
 	ctx, cancel := se.o.newContextWithTimeout()
 	defer cancel()


Test patch:
diff --git a/metrics_proto_test.go b/metrics_proto_test.go
index 4267b09..d392acd 100644
--- a/metrics_proto_test.go
+++ b/metrics_proto_test.go
@@ -20,7 +20,7 @@ import (
 	"strings"
 	"testing"
 
-	monitoring "cloud.google.com/go/monitoring/apiv3"
+	"cloud.google.com/go/monitoring/apiv3"
 	"github.com/golang/protobuf/ptypes/timestamp"
 	distributionpb "google.golang.org/genproto/googleapis/api/distribution"
 	labelpb "google.golang.org/genproto/googleapis/api/label"
@@ -31,6 +31,8 @@ import (
 	commonpb "github.com/census-instrumentation/opencensus-proto/gen-go/agent/common/v1"
 	metricspb "github.com/census-instrumentation/opencensus-proto/gen-go/metrics/v1"
 	resourcepb "github.com/census-instrumentation/opencensus-proto/gen-go/resource/v1"
+	"github.com/golang/protobuf/ptypes/wrappers"
+	"github.com/google/go-cmp/cmp"
 )
 
 func TestProtoResourceToMonitoringResource(t *testing.T) {
@@ -515,3 +517,169 @@ func TestNodeToDefaultLabels(t *testing.T) {
 		}
 	}
 }
+
+func TestConvertSummaryMetrics(t *testing.T) {
+	startTimestamp := &timestamp.Timestamp{
+		Seconds: 1543160298,
+		Nanos:   100000090,
+	}
+	endTimestamp := &timestamp.Timestamp{
+		Seconds: 1543160298,
+		Nanos:   100000997,
+	}
+
+	tests := []struct {
+		in            *metricspb.Metric
+		want          []*metricspb.Metric
+		statsExporter *statsExporter
+	}{
+		{
+			in: &metricspb.Metric{
+				MetricDescriptor: &metricspb.MetricDescriptor{
+					Name:        "summary_metric_descriptor",
+					Description: "This is a test",
+					Unit:        "ms",
+					Type:        metricspb.MetricDescriptor_SUMMARY,
+				},
+				Timeseries: []*metricspb.TimeSeries{
+					{
+						StartTimestamp: startTimestamp,
+						Points: []*metricspb.Point{
+							{
+								Timestamp: endTimestamp,
+								Value: &metricspb.Point_SummaryValue{
+									SummaryValue: &metricspb.SummaryValue{
+										Count: &wrappers.Int64Value{Value: 10},
+										Sum:   &wrappers.DoubleValue{Value: 119.0},
+										Snapshot: &metricspb.SummaryValue_Snapshot{
+											PercentileValues: []*metricspb.SummaryValue_Snapshot_ValueAtPercentile{
+												makePercentileValue(5.6, 10.0),
+												makePercentileValue(9.6, 50.0),
+												makePercentileValue(12.6, 90.0),
+												makePercentileValue(19.6, 99.0),
+											},
+										},
+									},
+								},
+							},
+						},
+					},
+				},
+			},
+			statsExporter: &statsExporter{
+				o: Options{ProjectID: "foo"},
+			},
+			want: []*metricspb.Metric{
+				{
+					MetricDescriptor: &metricspb.MetricDescriptor{
+						Name:        "summary_metric_descriptor_summary_sum",
+						Description: "This is a test",
+						Unit:        "ms",
+						Type:        metricspb.MetricDescriptor_CUMULATIVE_DOUBLE,
+					},
+					Timeseries: []*metricspb.TimeSeries{
+						makeDoubleTs(119.0, "", startTimestamp, endTimestamp),
+					},
+				},
+				{
+					MetricDescriptor: &metricspb.MetricDescriptor{
+						Name:        "summary_metric_descriptor_summary_count",
+						Description: "This is a test",
+						Unit:        "1",
+						Type:        metricspb.MetricDescriptor_CUMULATIVE_INT64,
+					},
+					Timeseries: []*metricspb.TimeSeries{
+						makeInt64Ts(10, "", startTimestamp, endTimestamp),
+					},
+				},
+				{
+					MetricDescriptor: &metricspb.MetricDescriptor{
+						Name:        "summary_metric_descriptor_summary_percentile",
+						Description: "This is a test",
+						Unit:        "ms",
+						Type:        metricspb.MetricDescriptor_GAUGE_DOUBLE,
+						LabelKeys: []*metricspb.LabelKey{
+							percentileLabelKey,
+						},
+					},
+					Timeseries: []*metricspb.TimeSeries{
+						makeDoubleTs(5.6, "10.000000", nil, endTimestamp),
+						makeDoubleTs(9.6, "50.000000", nil, endTimestamp),
+						makeDoubleTs(12.6, "90.000000", nil, endTimestamp),
+						makeDoubleTs(19.6, "99.000000", nil, endTimestamp),
+					},
+				},
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		se := tt.statsExporter
+		if se == nil {
+			se = new(statsExporter)
+		}
+		got := se.convertSummaryMetrics(tt.in)
+		if !cmp.Equal(got, tt.want) {
+			t.Fatalf("conversion failed:\n  got=%v\n want=%v\n", got, tt.want)
+		}
+	}
+}
+
+func makeInt64Ts(val int64, label string, start, end *timestamp.Timestamp) *metricspb.TimeSeries {
+	ts := &metricspb.TimeSeries{
+		StartTimestamp: start,
+		Points:         makeInt64Point(val, end),
+	}
+	if label != "" {
+		ts.LabelValues = makeLabelValue(label)
+	}
+	return ts
+}
+
+func makeInt64Point(val int64, end *timestamp.Timestamp) []*metricspb.Point {
+	return []*metricspb.Point{
+		{
+			Timestamp: end,
+			Value: &metricspb.Point_Int64Value{
+				Int64Value: val,
+			},
+		},
+	}
+}
+
+func makeDoubleTs(val float64, label string, start, end *timestamp.Timestamp) *metricspb.TimeSeries {
+	ts := &metricspb.TimeSeries{
+		StartTimestamp: start,
+		Points:         makeDoublePoint(val, end),
+	}
+	if label != "" {
+		ts.LabelValues = makeLabelValue(label)
+	}
+	return ts
+}
+
+func makeDoublePoint(val float64, end *timestamp.Timestamp) []*metricspb.Point {
+	return []*metricspb.Point{
+		{
+			Timestamp: end,
+			Value: &metricspb.Point_DoubleValue{
+				DoubleValue: val,
+			},
+		},
+	}
+}
+
+func makeLabelValue(value string) []*metricspb.LabelValue {
+	return []*metricspb.LabelValue{
+		{
+			Value: value,
+		},
+	}
+}
+
+func makePercentileValue(val, percentile float64) *metricspb.SummaryValue_Snapshot_ValueAtPercentile {
+	return &metricspb.SummaryValue_Snapshot_ValueAtPercentile{
+		Value:      val,
+		Percentile: percentile,
+	}
+}