Record a Start Time Per Time Series within a View (#1220)

plugin/ocgrpc/client_stats_handler_test.go

@@ -318,6 +318,9 @@ func TestClientDefaultCollections(t *testing.T) {
 				t.Errorf("%q: RetrieveData(%q) = %v", tc.label, wantData.v().Name, err)
 				continue
 			}
+			for i := range gotRows {
+				view.ClearStart(gotRows[i].Data)
+			}
 
 			for _, gotRow := range gotRows {
 				if !containsRow(wantData.rows, gotRow) {

plugin/ocgrpc/server_stats_handler_test.go

@@ -305,6 +305,10 @@ func TestServerDefaultCollections(t *testing.T) {
 				continue
 			}
 
+			for i := range gotRows {
+				view.ClearStart(gotRows[i].Data)
+			}
+
 			for _, gotRow := range gotRows {
 				if !containsRow(wantData.rows, gotRow) {
 					t.Errorf("%q: unwanted row for view %q: %v", tc.label, wantData.v().Name, gotRow)

plugin/ochttp/route_test.go

@@ -53,6 +53,9 @@ func TestWithRouteTag(t *testing.T) {
 	view.Unregister(v) // trigger exporting
 
 	got := e.rowsForView("request_total")
+	for i := range got {
+		view.ClearStart(got[i].Data)
+	}
 	want := []*view.Row{
 		{Data: &view.CountData{Value: 1}, Tags: []tag.Tag{{Key: ochttp.KeyServerRoute, Value: "/a/"}}},
 	}
@@ -90,6 +93,9 @@ func TestSetRoute(t *testing.T) {
 	view.Unregister(v) // trigger exporting
 
 	got := e.rowsForView("request_total")
+	for i := range got {
+		view.ClearStart(got[i].Data)
+	}
 	want := []*view.Row{
 		{Data: &view.CountData{Value: 1}, Tags: []tag.Tag{{Key: ochttp.KeyServerRoute, Value: "/a/"}}},
 	}

stats/view/aggregation.go

@@ -15,6 +15,8 @@
 
 package view
 
+import "time"
+
 // AggType represents the type of aggregation function used on a View.
 type AggType int
 
@@ -45,20 +47,20 @@ type Aggregation struct {
 	Type    AggType   // Type is the AggType of this Aggregation.
 	Buckets []float64 // Buckets are the bucket endpoints if this Aggregation represents a distribution, see Distribution.
 
-	newData func() AggregationData
+	newData func(time.Time) AggregationData
 }
 
 var (
 	aggCount = &Aggregation{
 		Type: AggTypeCount,
-		newData: func() AggregationData {
-			return &CountData{}
+		newData: func(t time.Time) AggregationData {
+			return &CountData{Start: t}
 		},
 	}
 	aggSum = &Aggregation{
 		Type: AggTypeSum,
-		newData: func() AggregationData {
-			return &SumData{}
+		newData: func(t time.Time) AggregationData {
+			return &SumData{Start: t}
 		},
 	}
 )
@@ -103,8 +105,8 @@ func Distribution(bounds ...float64) *Aggregation {
 		Type:    AggTypeDistribution,
 		Buckets: bounds,
 	}
-	agg.newData = func() AggregationData {
-		return newDistributionData(agg)
+	agg.newData = func(t time.Time) AggregationData {
+		return newDistributionData(agg, t)
 	}
 	return agg
 }
@@ -114,7 +116,7 @@ func Distribution(bounds ...float64) *Aggregation {
 func LastValue() *Aggregation {
 	return &Aggregation{
 		Type: AggTypeLastValue,
-		newData: func() AggregationData {
+		newData: func(_ time.Time) AggregationData {
 			return &LastValueData{}
 		},
 	}

stats/view/aggregation_data.go

@@ -31,6 +31,7 @@ type AggregationData interface {
 	clone() AggregationData
 	equal(other AggregationData) bool
 	toPoint(t metricdata.Type, time time.Time) metricdata.Point
+	StartTime() time.Time
 }
 
 const epsilon = 1e-9
@@ -40,6 +41,7 @@ const epsilon = 1e-9
 //
 // Most users won't directly access count data.
 type CountData struct {
+	Start time.Time
 	Value int64
 }
 
@@ -50,7 +52,7 @@ func (a *CountData) addSample(_ float64, _ map[string]interface{}, _ time.Time)
 }
 
 func (a *CountData) clone() AggregationData {
-	return &CountData{Value: a.Value}
+	return &CountData{Value: a.Value, Start: a.Start}
 }
 
 func (a *CountData) equal(other AggregationData) bool {
@@ -59,7 +61,7 @@ func (a *CountData) equal(other AggregationData) bool {
 		return false
 	}
 
-	return a.Value == a2.Value
+	return a.Start.Equal(a2.Start) && a.Value == a2.Value
 }
 
 func (a *CountData) toPoint(metricType metricdata.Type, t time.Time) metricdata.Point {
@@ -71,11 +73,17 @@ func (a *CountData) toPoint(metricType metricdata.Type, t time.Time) metricdata.
 	}
 }
 
+// StartTime returns the start time of the data being aggregated by CountData.
+func (a *CountData) StartTime() time.Time {
+	return a.Start
+}
+
 // SumData is the aggregated data for the Sum aggregation.
 // A sum aggregation processes data and sums up the recordings.
 //
 // Most users won't directly access sum data.
 type SumData struct {
+	Start time.Time
 	Value float64
 }
 
@@ -86,15 +94,15 @@ func (a *SumData) addSample(v float64, _ map[string]interface{}, _ time.Time) {
 }
 
 func (a *SumData) clone() AggregationData {
-	return &SumData{Value: a.Value}
+	return &SumData{Value: a.Value, Start: a.Start}
 }
 
 func (a *SumData) equal(other AggregationData) bool {
 	a2, ok := other.(*SumData)
 	if !ok {
 		return false
 	}
-	return math.Pow(a.Value-a2.Value, 2) < epsilon
+	return a.Start.Equal(a2.Start) && math.Pow(a.Value-a2.Value, 2) < epsilon
 }
 
 func (a *SumData) toPoint(metricType metricdata.Type, t time.Time) metricdata.Point {
@@ -108,6 +116,11 @@ func (a *SumData) toPoint(metricType metricdata.Type, t time.Time) metricdata.Po
 	}
 }
 
+// StartTime returns the start time of the data being aggregated by SumData.
+func (a *SumData) StartTime() time.Time {
+	return a.Start
+}
+
 // DistributionData is the aggregated data for the
 // Distribution aggregation.
 //
@@ -126,16 +139,18 @@ type DistributionData struct {
 	// an exemplar for the associated bucket, or nil.
 	ExemplarsPerBucket []*metricdata.Exemplar
 	bounds             []float64 // histogram distribution of the values
+	Start              time.Time
 }
 
-func newDistributionData(agg *Aggregation) *DistributionData {
+func newDistributionData(agg *Aggregation, t time.Time) *DistributionData {
 	bucketCount := len(agg.Buckets) + 1
 	return &DistributionData{
 		CountPerBucket:     make([]int64, bucketCount),
 		ExemplarsPerBucket: make([]*metricdata.Exemplar, bucketCount),
 		bounds:             agg.Buckets,
 		Min:                math.MaxFloat64,
 		Max:                math.SmallestNonzeroFloat64,
+		Start:              t,
 	}
 }
 
@@ -226,7 +241,11 @@ func (a *DistributionData) equal(other AggregationData) bool {
 			return false
 		}
 	}
-	return a.Count == a2.Count && a.Min == a2.Min && a.Max == a2.Max && math.Pow(a.Mean-a2.Mean, 2) < epsilon && math.Pow(a.variance()-a2.variance(), 2) < epsilon
+	return a.Start.Equal(a2.Start) &&
+		a.Count == a2.Count &&
+		a.Min == a2.Min &&
+		a.Max == a2.Max &&
+		math.Pow(a.Mean-a2.Mean, 2) < epsilon && math.Pow(a.variance()-a2.variance(), 2) < epsilon
 }
 
 func (a *DistributionData) toPoint(metricType metricdata.Type, t time.Time) metricdata.Point {
@@ -256,6 +275,11 @@ func (a *DistributionData) toPoint(metricType metricdata.Type, t time.Time) metr
 	}
 }
 
+// StartTime returns the start time of the data being aggregated by DistributionData.
+func (a *DistributionData) StartTime() time.Time {
+	return a.Start
+}
+
 // LastValueData returns the last value recorded for LastValue aggregation.
 type LastValueData struct {
 	Value float64
@@ -291,3 +315,22 @@ func (l *LastValueData) toPoint(metricType metricdata.Type, t time.Time) metricd
 		panic("unsupported metricdata.Type")
 	}
 }
+
+// StartTime returns an empty time value as start time is not recorded when using last value
+// aggregation.
+func (l *LastValueData) StartTime() time.Time {
+	return time.Time{}
+}
+
+// ClearStart clears the Start field from data if present. Useful for testing in cases where the
+// start time will be nondeterministic.
+func ClearStart(data AggregationData) {
+	switch data := data.(type) {
+	case *CountData:
+		data.Start = time.Time{}
+	case *SumData:
+		data.Start = time.Time{}
+	case *DistributionData:
+		data.Start = time.Time{}
+	}
+}

stats/view/aggregation_data_test.go

@@ -29,7 +29,7 @@ func TestDataClone(t *testing.T) {
 	agg := &Aggregation{
 		Buckets: []float64{1, 2, 3, 4},
 	}
-	dist := newDistributionData(agg)
+	dist := newDistributionData(agg, time.Time{})
 	dist.Count = 7
 	dist.Max = 11
 	dist.Min = 1
@@ -72,7 +72,7 @@ func TestDistributionData_addSample(t *testing.T) {
 	agg := &Aggregation{
 		Buckets: []float64{1, 2},
 	}
-	dd := newDistributionData(agg)
+	dd := newDistributionData(agg, time.Time{})
 	attachments1 := map[string]interface{}{"key1": "value1"}
 	t1 := time.Now()
 	dd.addSample(0.5, attachments1, t1)

stats/view/collector.go

@@ -35,7 +35,7 @@ type collector struct {
 func (c *collector) addSample(s string, v float64, attachments map[string]interface{}, t time.Time) {
 	aggregator, ok := c.signatures[s]
 	if !ok {
-		aggregator = c.a.newData()
+		aggregator = c.a.newData(t)
 		c.signatures[s] = aggregator
 	}
 	aggregator.addSample(v, attachments, t)