EMF: Store the initial value for cumulative metrics and skip sending to backend

Author: bjrara

exporter/awsemfexporter/datapoint.go

@@ -32,8 +32,10 @@ func calculateSummaryDelta(prev *aws.MetricValue, val interface{}, timestampMs t
 	countDelta := metricEntry.count
 	if prev != nil {
 		prevSummaryEntry := prev.RawValue.(summaryMetricEntry)
-		summaryDelta = summaryDelta - prevSummaryEntry.sum
-		countDelta = countDelta - prevSummaryEntry.count
+		summaryDelta = metricEntry.sum - prevSummaryEntry.sum
+		countDelta = metricEntry.count - prevSummaryEntry.count
+	} else {
+		return summaryMetricEntry{summaryDelta, countDelta}, false
 	}
 	return summaryMetricEntry{summaryDelta, countDelta}, true
 }
@@ -53,8 +55,11 @@ type DataPoint struct {
 //  - pdata.SummaryDataPointSlice
 type DataPoints interface {
 	Len() int
-	// NOTE: At() is an expensive call as it calculates the metric's value
-	At(i int) DataPoint
+	// At gets the adjusted datapoint from the DataPointSlice at i-th index.
+	// dataPoint: the adjusted data point
+	// retained: indicates whether the data point is valid for further process
+	// NOTE: It is an expensive call as it calculates the metric value.
+	At(i int) (dataPoint DataPoint, retained bool)
 }
 
 // deltaMetricMetadata contains the metadata required to perform rate/delta calculation
@@ -112,49 +117,67 @@ type summaryMetricEntry struct {
 }
 
 // At retrieves the IntDataPoint at the given index and performs rate/delta calculation if necessary.
-func (dps IntDataPointSlice) At(i int) DataPoint {
+func (dps IntDataPointSlice) At(i int) (DataPoint, bool) {
 	metric := dps.IntDataPointSlice.At(i)
 	timestampMs := unixNanoToMilliseconds(metric.Timestamp())
 	labels := createLabels(metric.LabelsMap(), dps.instrumentationLibraryName)
 
 	var metricVal float64
 	metricVal = float64(metric.Value())
+	retained := true
 	if dps.adjustToDelta {
-		deltaVal, _ := deltaMetricCalculator.Calculate(dps.metricName, mergeLabels(dps.deltaMetricMetadata, labels),
+		var deltaVal interface{}
+		deltaVal, retained = deltaMetricCalculator.Calculate(dps.metricName, mergeLabels(dps.deltaMetricMetadata, labels),
 			metricVal, metric.Timestamp().AsTime())
-		metricVal = deltaVal.(float64)
+		if !retained {
+			return DataPoint{}, retained
+		}
+		// It should not happen in practice that the previous metric value is smaller than the current one.
+		// If it happens, we assume that the metric is reset for some reason.
+		if deltaVal.(float64) >= 0 {
+			metricVal = deltaVal.(float64)
+		}
 	}
 
 	return DataPoint{
 		Value:       metricVal,
 		Labels:      labels,
 		TimestampMs: timestampMs,
-	}
+	}, retained
 }
 
 // At retrieves the DoubleDataPoint at the given index and performs rate/delta calculation if necessary.
-func (dps DoubleDataPointSlice) At(i int) DataPoint {
+func (dps DoubleDataPointSlice) At(i int) (DataPoint, bool) {
 	metric := dps.DoubleDataPointSlice.At(i)
 	labels := createLabels(metric.LabelsMap(), dps.instrumentationLibraryName)
 	timestampMs := unixNanoToMilliseconds(metric.Timestamp())
 
 	var metricVal float64
 	metricVal = metric.Value()
+	retained := true
 	if dps.adjustToDelta {
-		deltaVal, _ := deltaMetricCalculator.Calculate(dps.metricName, mergeLabels(dps.deltaMetricMetadata, labels),
+		var deltaVal interface{}
+		deltaVal, retained = deltaMetricCalculator.Calculate(dps.metricName, mergeLabels(dps.deltaMetricMetadata, labels),
 			metricVal, metric.Timestamp().AsTime())
-		metricVal = deltaVal.(float64)
+		if !retained {
+			return DataPoint{}, retained
+		}
+		// It should not happen in practice that the previous metric value is smaller than the current one.
+		// If it happens, we assume that the metric is reset for some reason.
+		if deltaVal.(float64) >= 0 {
+			metricVal = deltaVal.(float64)
+		}
 	}
 
 	return DataPoint{
 		Value:       metricVal,
 		Labels:      labels,
 		TimestampMs: timestampMs,
-	}
+	}, retained
 }
 
 // At retrieves the HistogramDataPoint at the given index.
-func (dps HistogramDataPointSlice) At(i int) DataPoint {
+func (dps HistogramDataPointSlice) At(i int) (DataPoint, bool) {
 	metric := dps.HistogramDataPointSlice.At(i)
 	labels := createLabels(metric.LabelsMap(), dps.instrumentationLibraryName)
 	timestamp := unixNanoToMilliseconds(metric.Timestamp())
@@ -166,20 +189,25 @@ func (dps HistogramDataPointSlice) At(i int) DataPoint {
 		},
 		Labels:      labels,
 		TimestampMs: timestamp,
-	}
+	}, true
 }
 
 // At retrieves the SummaryDataPoint at the given index.
-func (dps SummaryDataPointSlice) At(i int) DataPoint {
+func (dps SummaryDataPointSlice) At(i int) (DataPoint, bool) {
 	metric := dps.SummaryDataPointSlice.At(i)
 	labels := createLabels(metric.LabelsMap(), dps.instrumentationLibraryName)
 	timestampMs := unixNanoToMilliseconds(metric.Timestamp())
 
 	sum := metric.Sum()
 	count := metric.Count()
+	retained := true
 	if dps.adjustToDelta {
-		delta, _ := summaryMetricCalculator.Calculate(dps.metricName, mergeLabels(dps.deltaMetricMetadata, labels),
+		var delta interface{}
+		delta, retained = summaryMetricCalculator.Calculate(dps.metricName, mergeLabels(dps.deltaMetricMetadata, labels),
 			summaryMetricEntry{metric.Sum(), metric.Count()}, metric.Timestamp().AsTime())
+		if !retained {
+			return DataPoint{}, retained
+		}
 		summaryMetricDelta := delta.(summaryMetricEntry)
 		sum = summaryMetricDelta.sum
 		count = summaryMetricDelta.count
@@ -198,7 +226,7 @@ func (dps SummaryDataPointSlice) At(i int) DataPoint {
 		Value:       metricVal,
 		Labels:      labels,
 		TimestampMs: timestampMs,
-	}
+	}, retained
 }
 
 // createLabels converts OTel StringMap labels to a map