fix bug where an empty exemplar was added to counters

open-telemetry · Apr 15, 2024 · ae18928 · ae18928
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commit ae18928
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Showing 3 changed files with 81 additions and 4 deletions.
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -24,6 +24,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 ### Fixed
 
 - Update all dependencies to address [GO-2024-2687]. (#5359)
+- Fix bug where an empty exemplar was added to counters in `go.opentelemetry.io/contrib/bridges/prometheus`. (#TODO)
 
 ### Removed
 

diff --git a/bridges/prometheus/producer.go b/bridges/prometheus/producer.go
@@ -150,7 +150,9 @@ func convertCounter(metrics []*dto.Metric, now time.Time) metricdata.Sum[float64
 			StartTime:  processStartTime,
 			Time:       now,
 			Value:      m.GetCounter().GetValue(),
-			Exemplars:  []metricdata.Exemplar[float64]{convertExemplar(m.GetCounter().GetExemplar())},
+		}
+		if ex := m.GetCounter().GetExemplar(); ex != nil {
+			dp.Exemplars = []metricdata.Exemplar[float64]{convertExemplar(ex)}
 		}
 		createdTs := m.GetCounter().GetCreatedTimestamp()
 		if createdTs.IsValid() {
@@ -290,8 +292,8 @@ func convertBuckets(buckets []*dto.Bucket) ([]float64, []uint64, []metricdata.Ex
 			bounds[i] = bucket.GetUpperBound()
 		}
 		bucketCounts[i] = bucket.GetCumulativeCount()
-		if bucket.GetExemplar() != nil {
-			exemplars = append(exemplars, convertExemplar(bucket.GetExemplar()))
+		if ex := bucket.GetExemplar(); ex != nil {
+			exemplars = append(exemplars, convertExemplar(ex))
 		}
 	}
 	return bounds, bucketCounts, exemplars

diff --git a/bridges/prometheus/producer_test.go b/bridges/prometheus/producer_test.go
@@ -69,6 +69,41 @@ func TestProduce(t *testing.T) {
 		},
 		{
 			name: "counter",
+			testFn: func(reg *prometheus.Registry) {
+				metric := prometheus.NewCounter(prometheus.CounterOpts{
+					Name: "test_counter_metric",
+					Help: "A counter metric for testing",
+					ConstLabels: prometheus.Labels(map[string]string{
+						"foo": "bar",
+					}),
+				})
+				reg.MustRegister(metric)
+				metric.Add(245.3)
+			},
+			expected: []metricdata.ScopeMetrics{{
+				Scope: instrumentation.Scope{
+					Name: scopeName,
+				},
+				Metrics: []metricdata.Metrics{
+					{
+						Name:        "test_counter_metric",
+						Description: "A counter metric for testing",
+						Data: metricdata.Sum[float64]{
+							Temporality: metricdata.CumulativeTemporality,
+							IsMonotonic: true,
+							DataPoints: []metricdata.DataPoint[float64]{
+								{
+									Attributes: attribute.NewSet(attribute.String("foo", "bar")),
+									Value:      245.3,
+								},
+							},
+						},
+					},
+				},
+			}},
+		},
+		{
+			name: "counter with exemplar",
 			testFn: func(reg *prometheus.Registry) {
 				metric := prometheus.NewCounter(prometheus.CounterOpts{
 					Name: "test_counter_metric",
@@ -158,6 +193,45 @@ func TestProduce(t *testing.T) {
 		},
 		{
 			name: "histogram",
+			testFn: func(reg *prometheus.Registry) {
+				metric := prometheus.NewHistogram(prometheus.HistogramOpts{
+					Name: "test_histogram_metric",
+					Help: "A histogram metric for testing",
+					ConstLabels: prometheus.Labels(map[string]string{
+						"foo": "bar",
+					}),
+				})
+				reg.MustRegister(metric)
+				metric.Observe(578.3)
+			},
+			expected: []metricdata.ScopeMetrics{{
+				Scope: instrumentation.Scope{
+					Name: scopeName,
+				},
+				Metrics: []metricdata.Metrics{
+					{
+						Name:        "test_histogram_metric",
+						Description: "A histogram metric for testing",
+						Data: metricdata.Histogram[float64]{
+							Temporality: metricdata.CumulativeTemporality,
+							DataPoints: []metricdata.HistogramDataPoint[float64]{
+								{
+									Count: 1,
+									Sum:   578.3,
+									// TODO: This appears to be missing the last bucket
+									Bounds:       []float64{0.005, 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1, 2.5, 5},
+									BucketCounts: []uint64{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
+									Attributes:   attribute.NewSet(attribute.String("foo", "bar")),
+									Exemplars:    []metricdata.Exemplar[float64]{},
+								},
+							},
+						},
+					},
+				},
+			}},
+		},
+		{
+			name: "histogram with exemplar",
 			testFn: func(reg *prometheus.Registry) {
 				metric := prometheus.NewHistogram(prometheus.HistogramOpts{
 					Name: "test_histogram_metric",
@@ -189,7 +263,7 @@ func TestProduce(t *testing.T) {
 								{
 									Count:        1,
 									Sum:          578.3,
-									Bounds:       []float64{0.005, 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1, 2.5, 5, 10},
+									Bounds:       prometheus.DefBuckets,
 									BucketCounts: []uint64{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1},
 									Attributes:   attribute.NewSet(attribute.String("foo", "bar")),
 									Exemplars: []metricdata.Exemplar[float64]{