Perform integer/float histogram type checking on conversions, and use a consistent method for determining integer vs float histogram

Signed-off-by: Jeanette Tan <jeanette.tan@grafana.com>

prompb/custom.go

@@ -20,6 +20,11 @@ import (
 func (m Sample) T() int64   { return m.Timestamp }
 func (m Sample) V() float64 { return m.Value }
 
+func (h Histogram) IsFloatHistogram() bool {
+	_, ok := h.GetCount().(*Histogram_CountFloat)
+	return ok
+}
+
 func (r *ChunkedReadResponse) PooledMarshal(p *sync.Pool) ([]byte, error) {
 	size := r.Size()
 	data, ok := p.Get().(*[]byte)

storage/remote/codec.go

@@ -455,10 +455,10 @@ func (c *concreteSeriesIterator) Seek(t int64) chunkenc.ValueType {
 }
 
 func getHistogramValType(h *prompb.Histogram) chunkenc.ValueType {
-	if _, isInt := h.GetCount().(*prompb.Histogram_CountInt); isInt {
-		return chunkenc.ValHistogram
+	if h.IsFloatHistogram() {
+		return chunkenc.ValFloatHistogram
 	}
-	return chunkenc.ValFloatHistogram
+	return chunkenc.ValHistogram
 }
 
 // At implements chunkenc.Iterator.
@@ -624,9 +624,11 @@ func exemplarProtoToExemplar(ep prompb.Exemplar) exemplar.Exemplar {
 }
 
 // HistogramProtoToHistogram extracts a (normal integer) Histogram from the
-// provided proto message. The caller has to make sure that the proto message
-// represents an integer histogram and not a float histogram.
+// provided proto message.
 func HistogramProtoToHistogram(hp prompb.Histogram) *histogram.Histogram {
+	if hp.IsFloatHistogram() {
+		panic("don't call HistogramProtoToHistogram on a float histogram")
+	}
 	return &histogram.Histogram{
 		CounterResetHint: histogram.CounterResetHint(hp.ResetHint),
 		Schema:           hp.Schema,
@@ -642,9 +644,11 @@ func HistogramProtoToHistogram(hp prompb.Histogram) *histogram.Histogram {
 }
 
 // FloatHistogramProtoToFloatHistogram extracts a float Histogram from the
-// provided proto message to a Float Histogram. The caller has to make sure that
-// the proto message represents a float histogram and not an integer histogram.
+// provided proto message to a Float Histogram.
 func FloatHistogramProtoToFloatHistogram(hp prompb.Histogram) *histogram.FloatHistogram {
+	if !hp.IsFloatHistogram() {
+		panic("don't call FloatHistogramProtoToFloatHistogram on an integer histogram")
+	}
 	return &histogram.FloatHistogram{
 		CounterResetHint: histogram.CounterResetHint(hp.ResetHint),
 		Schema:           hp.Schema,
@@ -660,9 +664,11 @@ func FloatHistogramProtoToFloatHistogram(hp prompb.Histogram) *histogram.FloatHi
 }
 
 // HistogramProtoToFloatHistogram extracts and converts a (normal integer) histogram from the provided proto message
-// to a float histogram. The caller has to make sure that the proto message represents an integer histogram and not a
-// float histogram.
+// to a float histogram.
 func HistogramProtoToFloatHistogram(hp prompb.Histogram) *histogram.FloatHistogram {
+	if hp.IsFloatHistogram() {
+		panic("don't call HistogramProtoToFloatHistogram on a float histogram")
+	}
 	return &histogram.FloatHistogram{
 		CounterResetHint: histogram.CounterResetHint(hp.ResetHint),
 		Schema:           hp.Schema,

storage/remote/codec_test.go

@@ -528,7 +528,7 @@ func TestNilHistogramProto(*testing.T) {
 	// This function will panic if it impromperly handles nil
 	// values, causing the test to fail.
 	HistogramProtoToHistogram(prompb.Histogram{})
-	FloatHistogramProtoToFloatHistogram(prompb.Histogram{})
+	HistogramProtoToFloatHistogram(prompb.Histogram{})
 }
 
 func exampleHistogram() histogram.Histogram {

storage/remote/queue_manager_test.go

@@ -802,7 +802,7 @@ func (c *TestWriteClient) Store(_ context.Context, req []byte) error {
 
 		for _, histogram := range ts.Histograms {
 			count++
-			if histogram.GetCountFloat() > 0 || histogram.GetZeroCountFloat() > 0 {
+			if histogram.IsFloatHistogram() {
 				c.receivedFloatHistograms[seriesName] = append(c.receivedFloatHistograms[seriesName], histogram)
 			} else {
 				c.receivedHistograms[seriesName] = append(c.receivedHistograms[seriesName], histogram)

storage/remote/write_handler.go

@@ -125,7 +125,7 @@ func (h *writeHandler) write(ctx context.Context, req *prompb.WriteRequest) (err
 		}
 
 		for _, hp := range ts.Histograms {
-			if hp.GetCountFloat() > 0 || hp.GetZeroCountFloat() > 0 { // It is a float histogram.
+			if hp.IsFloatHistogram() {
 				fhs := FloatHistogramProtoToFloatHistogram(hp)
 				_, err = app.AppendHistogram(0, labels, hp.Timestamp, nil, fhs)
 			} else {

storage/remote/write_handler_test.go

@@ -68,7 +68,7 @@ func TestRemoteWriteHandler(t *testing.T) {
 		}
 
 		for _, hp := range ts.Histograms {
-			if hp.GetCountFloat() > 0 || hp.GetZeroCountFloat() > 0 { // It is a float histogram.
+			if hp.IsFloatHistogram() {
 				fh := FloatHistogramProtoToFloatHistogram(hp)
 				require.Equal(t, mockHistogram{labels, hp.Timestamp, nil, fh}, appendable.histograms[k])
 			} else {