From c52809278bd7e01672706bb25f95b5c04f2fe0c2 Mon Sep 17 00:00:00 2001
From: David Ashpole <dashpole@google.com>
Date: Tue, 25 Jul 2023 20:31:25 +0000
Subject: [PATCH] fix timestamps from prometheus instruments

---
 bridge/prometheus/producer.go | 41 +++++++++++++++++++++++------------
 1 file changed, 27 insertions(+), 14 deletions(-)

diff --git a/bridge/prometheus/producer.go b/bridge/prometheus/producer.go
index 5323bc17af1..304b6148223 100644
--- a/bridge/prometheus/producer.go
+++ b/bridge/prometheus/producer.go
@@ -54,6 +54,7 @@ func NewMetricProducer(opts ...Option) metric.Producer {
 }
 
 func (p *producer) Produce(context.Context) ([]metricdata.ScopeMetrics, error) {
+	now := time.Now()
 	var errs multierr
 	otelMetrics := make([]metricdata.Metrics, 0)
 	for _, gatherer := range p.gatherers {
@@ -62,7 +63,7 @@ func (p *producer) Produce(context.Context) ([]metricdata.ScopeMetrics, error) {
 			errs = append(errs, err)
 			continue
 		}
-		m, err := convertPrometheusMetricsInto(promMetrics)
+		m, err := convertPrometheusMetricsInto(promMetrics, now)
 		otelMetrics = append(otelMetrics, m...)
 		if err != nil {
 			errs = append(errs, err)
@@ -82,7 +83,7 @@ func (p *producer) Produce(context.Context) ([]metricdata.ScopeMetrics, error) {
 	}}, nil
 }
 
-func convertPrometheusMetricsInto(promMetrics []*dto.MetricFamily) ([]metricdata.Metrics, error) {
+func convertPrometheusMetricsInto(promMetrics []*dto.MetricFamily, now time.Time) ([]metricdata.Metrics, error) {
 	var errs multierr
 	otelMetrics := make([]metricdata.Metrics, 0)
 	for _, pm := range promMetrics {
@@ -92,11 +93,11 @@ func convertPrometheusMetricsInto(promMetrics []*dto.MetricFamily) ([]metricdata
 		}
 		switch pm.GetType() {
 		case dto.MetricType_GAUGE:
-			newMetric.Data = convertGauge(pm.GetMetric())
+			newMetric.Data = convertGauge(pm.GetMetric(), now)
 		case dto.MetricType_COUNTER:
-			newMetric.Data = convertCounter(pm.GetMetric())
+			newMetric.Data = convertCounter(pm.GetMetric(), now)
 		case dto.MetricType_HISTOGRAM:
-			newMetric.Data = convertHistogram(pm.GetMetric())
+			newMetric.Data = convertHistogram(pm.GetMetric(), now)
 		default:
 			// MetricType_GAUGE_HISTOGRAM, MetricType_SUMMARY, MetricType_UNTYPED
 			errs = append(errs, fmt.Errorf("%w: %v for metric %v", errUnsupportedType, pm.GetType(), pm.GetName()))
@@ -107,55 +108,67 @@ func convertPrometheusMetricsInto(promMetrics []*dto.MetricFamily) ([]metricdata
 	return otelMetrics, errs.errOrNil()
 }
 
-func convertGauge(metrics []*dto.Metric) metricdata.Gauge[float64] {
+func convertGauge(metrics []*dto.Metric, now time.Time) metricdata.Gauge[float64] {
 	otelGauge := metricdata.Gauge[float64]{
 		DataPoints: make([]metricdata.DataPoint[float64], len(metrics)),
 	}
 	for i, m := range metrics {
-		otelGauge.DataPoints[i] = metricdata.DataPoint[float64]{
+		dp := metricdata.DataPoint[float64]{
 			Attributes: convertLabels(m.GetLabel()),
-			Time:       time.UnixMilli(m.GetTimestampMs()),
+			Time:       now,
 			Value:      m.GetGauge().GetValue(),
 		}
+		if m.GetTimestampMs() != 0 {
+			dp.Time = time.UnixMilli(m.GetTimestampMs())
+		}
+		otelGauge.DataPoints[i] = dp
 	}
 	return otelGauge
 }
 
-func convertCounter(metrics []*dto.Metric) metricdata.Sum[float64] {
+func convertCounter(metrics []*dto.Metric, now time.Time) metricdata.Sum[float64] {
 	otelCounter := metricdata.Sum[float64]{
 		DataPoints:  make([]metricdata.DataPoint[float64], len(metrics)),
 		Temporality: metricdata.CumulativeTemporality,
 		IsMonotonic: true,
 	}
 	for i, m := range metrics {
-		otelCounter.DataPoints[i] = metricdata.DataPoint[float64]{
+		dp := metricdata.DataPoint[float64]{
 			Attributes: convertLabels(m.GetLabel()),
 			StartTime:  m.GetCounter().GetCreatedTimestamp().AsTime(),
-			Time:       time.UnixMilli(m.GetTimestampMs()),
+			Time:       now,
 			Value:      m.GetCounter().GetValue(),
 			Exemplars:  []metricdata.Exemplar[float64]{convertExemplar(m.GetCounter().GetExemplar())},
 		}
+		if m.GetTimestampMs() != 0 {
+			dp.Time = time.UnixMilli(m.GetTimestampMs())
+		}
+		otelCounter.DataPoints[i] = dp
 	}
 	return otelCounter
 }
 
-func convertHistogram(metrics []*dto.Metric) metricdata.Histogram[float64] {
+func convertHistogram(metrics []*dto.Metric, now time.Time) metricdata.Histogram[float64] {
 	otelHistogram := metricdata.Histogram[float64]{
 		DataPoints:  make([]metricdata.HistogramDataPoint[float64], len(metrics)),
 		Temporality: metricdata.CumulativeTemporality,
 	}
 	for i, m := range metrics {
 		bounds, bucketCounts, exemplars := convertBuckets(m.GetHistogram().GetBucket())
-		otelHistogram.DataPoints[i] = metricdata.HistogramDataPoint[float64]{
+		dp := metricdata.HistogramDataPoint[float64]{
 			Attributes:   convertLabels(m.GetLabel()),
 			StartTime:    m.GetHistogram().GetCreatedTimestamp().AsTime(),
-			Time:         time.UnixMilli(m.GetTimestampMs()),
+			Time:         now,
 			Count:        m.GetHistogram().GetSampleCount(),
 			Sum:          m.GetHistogram().GetSampleSum(),
 			Bounds:       bounds,
 			BucketCounts: bucketCounts,
 			Exemplars:    exemplars,
 		}
+		if m.GetTimestampMs() != 0 {
+			dp.Time = time.UnixMilli(m.GetTimestampMs())
+		}
+		otelHistogram.DataPoints[i] = dp
 	}
 	return otelHistogram
 }