fix native histogram empty bucket marshal panic

CHANGELOG.md

@@ -11,6 +11,7 @@
 * [BUGFIX] Ingester: Fix labelset data race condition. #6573
 * [BUGFIX] Compactor: Cleaner should not put deletion marker for blocks with no-compact marker. #6576
 * [BUGFIX] Compactor: Cleaner would delete bucket index when there is no block in bucket store. #6577
+* [BUGFIX] Querier: Fix marshal native histogram with empty bucket when protobuf codec is enabled. #6595
 
 ## 1.19.0 in progress
 

pkg/querier/codec/protobuf_codec.go

@@ -134,15 +134,13 @@ func getMatrixSampleStreams(data *v1.QueryData) *[]tripperware.SampleStream {
 				if sampleStream.Histograms[j].H.ZeroCount > 0 {
 					bucketsLen = len(sampleStream.Histograms[j].H.NegativeBuckets) + len(sampleStream.Histograms[j].H.PositiveBuckets) + 1
 				}
-				buckets := make([]*tripperware.HistogramBucket, bucketsLen)
 				it := sampleStream.Histograms[j].H.AllBucketIterator()
-				getBuckets(buckets, it)
 				histograms[j] = tripperware.SampleHistogramPair{
 					TimestampMs: sampleStream.Histograms[j].T,
 					Histogram: tripperware.SampleHistogram{
 						Count:   sampleStream.Histograms[j].H.Count,
 						Sum:     sampleStream.Histograms[j].H.Sum,
-						Buckets: buckets,
+						Buckets: getBuckets(bucketsLen, it),
 					},
 				}
 			}
@@ -192,22 +190,21 @@ func getVectorSamples(data *v1.QueryData, cortexInternal bool) *[]tripperware.Sa
 		if sample.H.ZeroCount > 0 {
 			bucketsLen = len(sample.H.NegativeBuckets) + len(sample.H.PositiveBuckets) + 1
 		}
-		buckets := make([]*tripperware.HistogramBucket, bucketsLen)
 		it := sample.H.AllBucketIterator()
-		getBuckets(buckets, it)
 		vectorSamples[i].Histogram = &tripperware.SampleHistogramPair{
 			TimestampMs: sample.T,
 			Histogram: tripperware.SampleHistogram{
 				Count:   sample.H.Count,
 				Sum:     sample.H.Sum,
-				Buckets: buckets,
+				Buckets: getBuckets(bucketsLen, it),
 			},
 		}
 	}
 	return &vectorSamples
 }
 
-func getBuckets(bucketsList []*tripperware.HistogramBucket, it histogram.BucketIterator[float64]) {
+func getBuckets(bucketsLen int, it histogram.BucketIterator[float64]) []*tripperware.HistogramBucket {
+	buckets := make([]*tripperware.HistogramBucket, bucketsLen)
 	bucketIdx := 0
 	for it.Next() {
 		bucket := it.At()
@@ -226,14 +223,16 @@ func getBuckets(bucketsList []*tripperware.HistogramBucket, it histogram.BucketI
 				boundaries = 0 // Inclusive only on upper end AKA left open.
 			}
 		}
-		bucketsList[bucketIdx] = &tripperware.HistogramBucket{
+		buckets[bucketIdx] = &tripperware.HistogramBucket{
 			Boundaries: int32(boundaries),
 			Lower:      bucket.Lower,
 			Upper:      bucket.Upper,
 			Count:      bucket.Count,
 		}
 		bucketIdx += 1
 	}
+	buckets = buckets[:bucketIdx]
+	return buckets
 }
 
 func getStats(builtin *stats.BuiltinStats) *tripperware.PrometheusResponseSamplesStats {

pkg/querier/codec/protobuf_codec_test.go

@@ -39,6 +39,17 @@ func TestProtobufCodec_Encode(t *testing.T) {
 	}
 	testProtoHistogram := cortexpb.FloatHistogramToHistogramProto(1000, testFloatHistogram)
 
+	floatHistogramWithEmptyBucket := &histogram.FloatHistogram{
+		CounterResetHint: 0,
+		Schema:           1,
+		ZeroThreshold:    0.01,
+		ZeroCount:        0,
+		Count:            0,
+		Sum:              1,
+		PositiveSpans:    []histogram.Span{{Offset: 0, Length: 1}},
+		PositiveBuckets:  []float64{0},
+	}
+
 	tests := []struct {
 		name           string
 		data           *v1.QueryData
@@ -287,6 +298,47 @@ func TestProtobufCodec_Encode(t *testing.T) {
 				},
 			},
 		},
+		{
+			name: "matrix with histogram and not cortex internal, empty bucket",
+			data: &v1.QueryData{
+				ResultType: parser.ValueTypeMatrix,
+				Result: promql.Matrix{
+					promql.Series{
+						Histograms: []promql.HPoint{{H: floatHistogramWithEmptyBucket, T: 1000}},
+						Metric:     labels.FromStrings("__name__", "foo"),
+					},
+				},
+			},
+			expected: &tripperware.PrometheusResponse{
+				Status: tripperware.StatusSuccess,
+				Data: tripperware.PrometheusData{
+					ResultType: model.ValMatrix.String(),
+					Result: tripperware.PrometheusQueryResult{
+						Result: &tripperware.PrometheusQueryResult_Matrix{
+							Matrix: &tripperware.Matrix{
+								SampleStreams: []tripperware.SampleStream{
+									{
+										Labels: []cortexpb.LabelAdapter{
+											{Name: "__name__", Value: "foo"},
+										},
+										Histograms: []tripperware.SampleHistogramPair{
+											{
+												TimestampMs: 1000,
+												Histogram: tripperware.SampleHistogram{
+													Count:   0,
+													Sum:     1,
+													Buckets: []*tripperware.HistogramBucket{},
+												},
+											},
+										},
+									},
+								},
+							},
+						},
+					},
+				},
+			},
+		},
 		{
 			name: "vector with histogram and not cortex internal",
 			data: &v1.QueryData{
@@ -376,6 +428,46 @@ func TestProtobufCodec_Encode(t *testing.T) {
 				},
 			},
 		},
+		{
+			name: "vector with histogram with and not cortex internal, empty bucket",
+			data: &v1.QueryData{
+				ResultType: parser.ValueTypeVector,
+				Result: promql.Vector{
+					promql.Sample{
+						Metric: labels.FromStrings("__name__", "foo"),
+						T:      1000,
+						H:      floatHistogramWithEmptyBucket,
+					},
+				},
+			},
+			expected: &tripperware.PrometheusResponse{
+				Status: tripperware.StatusSuccess,
+				Data: tripperware.PrometheusData{
+					ResultType: model.ValVector.String(),
+					Result: tripperware.PrometheusQueryResult{
+						Result: &tripperware.PrometheusQueryResult_Vector{
+							Vector: &tripperware.Vector{
+								Samples: []tripperware.Sample{
+									{
+										Labels: []cortexpb.LabelAdapter{
+											{Name: "__name__", Value: "foo"},
+										},
+										Histogram: &tripperware.SampleHistogramPair{
+											TimestampMs: 1000,
+											Histogram: tripperware.SampleHistogram{
+												Count:   0,
+												Sum:     1,
+												Buckets: []*tripperware.HistogramBucket{},
+											},
+										},
+									},
+								},
+							},
+						},
+					},
+				},
+			},
+		},
 		{
 			name:           "vector with histogram and cortex internal",
 			cortexInternal: true,