handle hasSum mismatch and do independent test setups

exporter/prometheusexporter/accumulator.go

@@ -230,13 +230,13 @@ func (a *lastValueAccumulator) accumulateHistogram(metric pmetric.Metric, il pco
 	for i := 0; i < dps.Len(); i++ {
 		ip := dps.At(i)
 
-		signature := timeseriesSignature(il.Name(), metric, ip.Attributes(), resourceAttrs) // uniquely idenity this time series you are accumulating for
+		signature := timeseriesSignature(il.Name(), metric, ip.Attributes(), resourceAttrs)
 		if ip.Flags().NoRecordedValue() {
 			a.registeredMetrics.Delete(signature)
 			return 0
 		}
 
-		v, ok := a.registeredMetrics.Load(signature) // a accumulates metric values for all times series. Get value for particular time series
+		v, ok := a.registeredMetrics.Load(signature)
 		if !ok {
 			// first data point
 			m := copyMetricMetadata(metric)
@@ -253,18 +253,24 @@ func (a *lastValueAccumulator) accumulateHistogram(metric pmetric.Metric, il pco
 
 		switch histogram.AggregationTemporality() {
 		case pmetric.AggregationTemporalityDelta:
-			if ip.StartTimestamp().AsTime() != mv.value.Histogram().DataPoints().At(0).StartTimestamp().AsTime() {
-				// treat misalgnment as restart and reset or violation of single-writer principle and drop
-				if ip.StartTimestamp().AsTime().After(mv.value.Histogram().DataPoints().At(0).Timestamp().AsTime()) {
+			pp := mv.value.Histogram().DataPoints().At(0) // previous aggregated value for time range
+			if ip.StartTimestamp().AsTime() != pp.StartTimestamp().AsTime() {
+				// treat misalgnment as restart and reset, or violation of single-writer principle and drop
+				if ip.StartTimestamp().AsTime().After(pp.Timestamp().AsTime()) {
 					ip.CopyTo(m.Histogram().DataPoints().AppendEmpty())
 				} else {
 					a.logger.With(
-						zap.String("time_series", signature),
+						zap.String("metric_name", metric.Name()),
 					).Warn("Dropped misaligned histogram datapoint")
 					continue
 				}
+			} else if ip.HasSum() != pp.HasSum() {
+				a.logger.With(
+					zap.String("metric_name", metric.Name()),
+				).Warn("Dropped histogram data point due to disagreement on sum tracking")
+				continue
 			} else {
-				accumulateHistogramValues(mv.value.Histogram().DataPoints().At(0), ip, m.Histogram().DataPoints().AppendEmpty())
+				accumulateHistogramValues(pp, ip, m.Histogram().DataPoints().AppendEmpty())
 			}
 		case pmetric.AggregationTemporalityCumulative:
 			if ip.Timestamp().AsTime().Before(mv.value.Histogram().DataPoints().At(0).Timestamp().AsTime()) {
@@ -351,21 +357,14 @@ func accumulateHistogramValues(prev, current, dest pmetric.HistogramDataPoint) {
 	dest.SetTimestamp(newer.Timestamp())
 
 	// checking for bucket boundary alignment, optionally re-aggregate on newer boundaries
-	match := true
-	if older.ExplicitBounds().Len() == newer.ExplicitBounds().Len() {
-		for i := 0; i < newer.ExplicitBounds().Len(); i++ {
-			if older.ExplicitBounds().At(i) != newer.ExplicitBounds().At(i) {
-				match = false
-				break
-			}
-		}
-	} else {
-		match = false
+	match := older.ExplicitBounds().Len() == newer.ExplicitBounds().Len()
+	for i := 0; match && i < newer.ExplicitBounds().Len(); i++ {
+		match = older.ExplicitBounds().At(i) == newer.ExplicitBounds().At(i)
 	}
 
 	if match {
 		dest.SetCount(newer.Count() + older.Count())
-		if newer.HasSum() && older.HasSum() {
+		if newer.HasSum() {
 			dest.SetSum(newer.Sum() + older.Sum())
 		}