Fix populateWithDelChunkSeriesIterator and gauge histograms (#12330)

Use AppendableGauge to detect corrupt chunk with gauge histograms.
Detect if first sample is a gauge but the chunk is not set up to contain
gauge histograms.

Signed-off-by: György Krajcsovits <gyorgy.krajcsovits@grafana.com>
Signed-off-by: George Krajcsovits <krajorama@users.noreply.github.com>

tsdb/head_read.go

@@ -331,7 +331,7 @@ func (h *headChunkReader) chunk(meta chunks.Meta, copyLastChunk bool) (chunkenc.
 	}
 	s.Unlock()
 
-	return &safeChunk{
+	return &safeHeadChunk{
 		Chunk:    chk,
 		s:        s,
 		cid:      cid,
@@ -627,15 +627,15 @@ func (b boundedIterator) Seek(t int64) chunkenc.ValueType {
 	return b.Iterator.Seek(t)
 }
 
-// safeChunk makes sure that the chunk can be accessed without a race condition
-type safeChunk struct {
+// safeHeadChunk makes sure that the chunk can be accessed without a race condition
+type safeHeadChunk struct {
 	chunkenc.Chunk
 	s        *memSeries
 	cid      chunks.HeadChunkID
 	isoState *isolationState
 }
 
-func (c *safeChunk) Iterator(reuseIter chunkenc.Iterator) chunkenc.Iterator {
+func (c *safeHeadChunk) Iterator(reuseIter chunkenc.Iterator) chunkenc.Iterator {
 	c.s.Lock()
 	it := c.s.iterator(c.cid, c.Chunk, c.isoState, reuseIter)
 	c.s.Unlock()

tsdb/querier.go

@@ -785,14 +785,35 @@ func (p *populateWithDelChunkSeriesIterator) Next() bool {
 		if app, err = newChunk.Appender(); err != nil {
 			break
 		}
-		if hc, ok := p.currChkMeta.Chunk.(*chunkenc.HistogramChunk); ok {
+
+		switch hc := p.currChkMeta.Chunk.(type) {
+		case *chunkenc.HistogramChunk:
 			newChunk.(*chunkenc.HistogramChunk).SetCounterResetHeader(hc.GetCounterResetHeader())
+		case *safeHeadChunk:
+			if unwrapped, ok := hc.Chunk.(*chunkenc.HistogramChunk); ok {
+				newChunk.(*chunkenc.HistogramChunk).SetCounterResetHeader(unwrapped.GetCounterResetHeader())
+			} else {
+				err = fmt.Errorf("internal error, could not unwrap safeHeadChunk to histogram chunk: %T", hc.Chunk)
 			}
+		default:
+			err = fmt.Errorf("internal error, unknown chunk type %T when expecting histogram", p.currChkMeta.Chunk)
+		}
+		if err != nil {
+			break
+		}
+
 		var h *histogram.Histogram
 		t, h = p.currDelIter.AtHistogram()
 		p.curr.MinTime = t
 
+		// Detect missing gauge reset hint.
+		if h.CounterResetHint == histogram.GaugeType && newChunk.(*chunkenc.HistogramChunk).GetCounterResetHeader() != chunkenc.GaugeType {
+			err = fmt.Errorf("found gauge histogram in non gauge chunk")
+			break
+		}
+
 		app.AppendHistogram(t, h)
+
 		for vt := p.currDelIter.Next(); vt != chunkenc.ValNone; vt = p.currDelIter.Next() {
 			if vt != chunkenc.ValHistogram {
 				err = fmt.Errorf("found value type %v in histogram chunk", vt)
@@ -801,6 +822,20 @@ func (p *populateWithDelChunkSeriesIterator) Next() bool {
 			t, h = p.currDelIter.AtHistogram()
 
 			// Defend against corrupted chunks.
+			if h.CounterResetHint == histogram.GaugeType {
+				pI, nI, bpI, bnI, _, _, okToAppend := app.(*chunkenc.HistogramAppender).AppendableGauge(h)
+				if !okToAppend {
+					err = errors.New("unable to append histogram due to unexpected schema change")
+					break
+				}
+				if len(pI)+len(nI)+len(bpI)+len(bnI) > 0 {
+					err = fmt.Errorf(
+						"bucket layout has changed unexpectedly: forward %d positive, %d negative, backward %d positive %d negative bucket interjections required",
+						len(pI), len(nI), len(bpI), len(bnI),
+					)
+					break
+				}
+			} else {
 				pI, nI, okToAppend, counterReset := app.(*chunkenc.HistogramAppender).Appendable(h)
 				if len(pI)+len(nI) > 0 {
 					err = fmt.Errorf(
@@ -817,7 +852,7 @@ func (p *populateWithDelChunkSeriesIterator) Next() bool {
 					err = errors.New("unable to append histogram due to unexpected schema change")
 					break
 				}
-
+			}
 			app.AppendHistogram(t, h)
 		}
 	case chunkenc.ValFloat:
@@ -842,14 +877,35 @@ func (p *populateWithDelChunkSeriesIterator) Next() bool {
 		if app, err = newChunk.Appender(); err != nil {
 			break
 		}
-		if hc, ok := p.currChkMeta.Chunk.(*chunkenc.FloatHistogramChunk); ok {
+
+		switch hc := p.currChkMeta.Chunk.(type) {
+		case *chunkenc.FloatHistogramChunk:
 			newChunk.(*chunkenc.FloatHistogramChunk).SetCounterResetHeader(hc.GetCounterResetHeader())
+		case *safeHeadChunk:
+			if unwrapped, ok := hc.Chunk.(*chunkenc.FloatHistogramChunk); ok {
+				newChunk.(*chunkenc.FloatHistogramChunk).SetCounterResetHeader(unwrapped.GetCounterResetHeader())
+			} else {
+				err = fmt.Errorf("internal error, could not unwrap safeHeadChunk to float histogram chunk: %T", hc.Chunk)
 			}
+		default:
+			err = fmt.Errorf("internal error, unknown chunk type %T when expecting float histogram", p.currChkMeta.Chunk)
+		}
+		if err != nil {
+			break
+		}
+
 		var h *histogram.FloatHistogram
 		t, h = p.currDelIter.AtFloatHistogram()
 		p.curr.MinTime = t
 
+		// Detect missing gauge reset hint.
+		if h.CounterResetHint == histogram.GaugeType && newChunk.(*chunkenc.FloatHistogramChunk).GetCounterResetHeader() != chunkenc.GaugeType {
+			err = fmt.Errorf("found float gauge histogram in non gauge chunk")
+			break
+		}
+
 		app.AppendFloatHistogram(t, h)
+
 		for vt := p.currDelIter.Next(); vt != chunkenc.ValNone; vt = p.currDelIter.Next() {
 			if vt != chunkenc.ValFloatHistogram {
 				err = fmt.Errorf("found value type %v in histogram chunk", vt)
@@ -858,6 +914,20 @@ func (p *populateWithDelChunkSeriesIterator) Next() bool {
 			t, h = p.currDelIter.AtFloatHistogram()
 
 			// Defend against corrupted chunks.
+			if h.CounterResetHint == histogram.GaugeType {
+				pI, nI, bpI, bnI, _, _, okToAppend := app.(*chunkenc.FloatHistogramAppender).AppendableGauge(h)
+				if !okToAppend {
+					err = errors.New("unable to append histogram due to unexpected schema change")
+					break
+				}
+				if len(pI)+len(nI)+len(bpI)+len(bnI) > 0 {
+					err = fmt.Errorf(
+						"bucket layout has changed unexpectedly: forward %d positive, %d negative, backward %d positive %d negative bucket interjections required",
+						len(pI), len(nI), len(bpI), len(bnI),
+					)
+					break
+				}
+			} else {
 				pI, nI, okToAppend, counterReset := app.(*chunkenc.FloatHistogramAppender).Appendable(h)
 				if len(pI)+len(nI) > 0 {
 					err = fmt.Errorf(
@@ -874,6 +944,7 @@ func (p *populateWithDelChunkSeriesIterator) Next() bool {
 					err = errors.New("unable to append histogram due to unexpected schema change")
 					break
 				}
+			}
 
 			app.AppendFloatHistogram(t, h)
 		}

tsdb/querier_test.go

@@ -29,6 +29,7 @@ import (
 	"github.com/pkg/errors"
 	"github.com/stretchr/testify/require"
 
+	"github.com/prometheus/prometheus/model/histogram"
 	"github.com/prometheus/prometheus/model/labels"
 	"github.com/prometheus/prometheus/storage"
 	"github.com/prometheus/prometheus/tsdb/chunkenc"
@@ -907,6 +908,202 @@ func TestPopulateWithTombSeriesIterators(t *testing.T) {
 				sample{3, 5, nil, nil}, sample{6, 1, nil, nil}, sample{7, 89, nil, nil},
 			},
 		},
+		{
+			name: "one histogram chunk",
+			chks: [][]tsdbutil.Sample{
+				{
+					sample{1, 0, tsdbutil.GenerateTestHistogram(1), nil},
+					sample{2, 0, tsdbutil.GenerateTestHistogram(2), nil},
+					sample{3, 0, tsdbutil.GenerateTestHistogram(3), nil},
+					sample{6, 0, tsdbutil.GenerateTestHistogram(6), nil},
+				},
+			},
+			expected: []tsdbutil.Sample{
+				sample{1, 0, tsdbutil.GenerateTestHistogram(1), nil},
+				sample{2, 0, tsdbutil.SetHistogramNotCounterReset(tsdbutil.GenerateTestHistogram(2)), nil},
+				sample{3, 0, tsdbutil.SetHistogramNotCounterReset(tsdbutil.GenerateTestHistogram(3)), nil},
+				sample{6, 0, tsdbutil.SetHistogramNotCounterReset(tsdbutil.GenerateTestHistogram(6)), nil},
+			},
+			expectedChks: []chunks.Meta{
+				tsdbutil.ChunkFromSamples([]tsdbutil.Sample{
+					sample{1, 0, tsdbutil.GenerateTestHistogram(1), nil},
+					sample{2, 0, tsdbutil.SetHistogramNotCounterReset(tsdbutil.GenerateTestHistogram(2)), nil},
+					sample{3, 0, tsdbutil.SetHistogramNotCounterReset(tsdbutil.GenerateTestHistogram(3)), nil},
+					sample{6, 0, tsdbutil.SetHistogramNotCounterReset(tsdbutil.GenerateTestHistogram(6)), nil},
+				}),
+			},
+		},
+		{
+			name: "one histogram chunk intersect with deletion interval",
+			chks: [][]tsdbutil.Sample{
+				{
+					sample{1, 0, tsdbutil.GenerateTestHistogram(1), nil},
+					sample{2, 0, tsdbutil.GenerateTestHistogram(2), nil},
+					sample{3, 0, tsdbutil.GenerateTestHistogram(3), nil},
+					sample{6, 0, tsdbutil.GenerateTestHistogram(6), nil},
+				},
+			},
+			intervals: tombstones.Intervals{{Mint: 5, Maxt: 20}},
+			expected: []tsdbutil.Sample{
+				sample{1, 0, tsdbutil.GenerateTestHistogram(1), nil},
+				sample{2, 0, tsdbutil.SetHistogramNotCounterReset(tsdbutil.GenerateTestHistogram(2)), nil},
+				sample{3, 0, tsdbutil.SetHistogramNotCounterReset(tsdbutil.GenerateTestHistogram(3)), nil},
+			},
+			expectedChks: []chunks.Meta{
+				tsdbutil.ChunkFromSamples([]tsdbutil.Sample{
+					sample{1, 0, tsdbutil.GenerateTestHistogram(1), nil},
+					sample{2, 0, tsdbutil.SetHistogramNotCounterReset(tsdbutil.GenerateTestHistogram(2)), nil},
+					sample{3, 0, tsdbutil.SetHistogramNotCounterReset(tsdbutil.GenerateTestHistogram(3)), nil},
+				}),
+			},
+		},
+		{
+			name: "one float histogram chunk",
+			chks: [][]tsdbutil.Sample{
+				{
+					sample{1, 0, nil, tsdbutil.GenerateTestFloatHistogram(1)},
+					sample{2, 0, nil, tsdbutil.GenerateTestFloatHistogram(2)},
+					sample{3, 0, nil, tsdbutil.GenerateTestFloatHistogram(3)},
+					sample{6, 0, nil, tsdbutil.GenerateTestFloatHistogram(6)},
+				},
+			},
+			expected: []tsdbutil.Sample{
+				sample{1, 0, nil, tsdbutil.GenerateTestFloatHistogram(1)},
+				sample{2, 0, nil, tsdbutil.SetFloatHistogramNotCounterReset(tsdbutil.GenerateTestFloatHistogram(2))},
+				sample{3, 0, nil, tsdbutil.SetFloatHistogramNotCounterReset(tsdbutil.GenerateTestFloatHistogram(3))},
+				sample{6, 0, nil, tsdbutil.SetFloatHistogramNotCounterReset(tsdbutil.GenerateTestFloatHistogram(6))},
+			},
+			expectedChks: []chunks.Meta{
+				tsdbutil.ChunkFromSamples([]tsdbutil.Sample{
+					sample{1, 0, nil, tsdbutil.GenerateTestFloatHistogram(1)},
+					sample{2, 0, nil, tsdbutil.SetFloatHistogramNotCounterReset(tsdbutil.GenerateTestFloatHistogram(2))},
+					sample{3, 0, nil, tsdbutil.SetFloatHistogramNotCounterReset(tsdbutil.GenerateTestFloatHistogram(3))},
+					sample{6, 0, nil, tsdbutil.SetFloatHistogramNotCounterReset(tsdbutil.GenerateTestFloatHistogram(6))},
+				}),
+			},
+		},
+		{
+			name: "one float histogram chunk intersect with deletion interval",
+			chks: [][]tsdbutil.Sample{
+				{
+					sample{1, 0, nil, tsdbutil.GenerateTestFloatHistogram(1)},
+					sample{2, 0, nil, tsdbutil.GenerateTestFloatHistogram(2)},
+					sample{3, 0, nil, tsdbutil.GenerateTestFloatHistogram(3)},
+					sample{6, 0, nil, tsdbutil.GenerateTestFloatHistogram(6)},
+				},
+			},
+			intervals: tombstones.Intervals{{Mint: 5, Maxt: 20}},
+			expected: []tsdbutil.Sample{
+				sample{1, 0, nil, tsdbutil.GenerateTestFloatHistogram(1)},
+				sample{2, 0, nil, tsdbutil.SetFloatHistogramNotCounterReset(tsdbutil.GenerateTestFloatHistogram(2))},
+				sample{3, 0, nil, tsdbutil.SetFloatHistogramNotCounterReset(tsdbutil.GenerateTestFloatHistogram(3))},
+			},
+			expectedChks: []chunks.Meta{
+				tsdbutil.ChunkFromSamples([]tsdbutil.Sample{
+					sample{1, 0, nil, tsdbutil.GenerateTestFloatHistogram(1)},
+					sample{2, 0, nil, tsdbutil.SetFloatHistogramNotCounterReset(tsdbutil.GenerateTestFloatHistogram(2))},
+					sample{3, 0, nil, tsdbutil.SetFloatHistogramNotCounterReset(tsdbutil.GenerateTestFloatHistogram(3))},
+				}),
+			},
+		},
+		{
+			name: "one gauge histogram chunk",
+			chks: [][]tsdbutil.Sample{
+				{
+					sample{1, 0, tsdbutil.GenerateTestGaugeHistogram(1), nil},
+					sample{2, 0, tsdbutil.GenerateTestGaugeHistogram(2), nil},
+					sample{3, 0, tsdbutil.GenerateTestGaugeHistogram(3), nil},
+					sample{6, 0, tsdbutil.GenerateTestGaugeHistogram(6), nil},
+				},
+			},
+			expected: []tsdbutil.Sample{
+				sample{1, 0, tsdbutil.GenerateTestGaugeHistogram(1), nil},
+				sample{2, 0, tsdbutil.GenerateTestGaugeHistogram(2), nil},
+				sample{3, 0, tsdbutil.GenerateTestGaugeHistogram(3), nil},
+				sample{6, 0, tsdbutil.GenerateTestGaugeHistogram(6), nil},
+			},
+			expectedChks: []chunks.Meta{
+				tsdbutil.ChunkFromSamples([]tsdbutil.Sample{
+					sample{1, 0, tsdbutil.GenerateTestGaugeHistogram(1), nil},
+					sample{2, 0, tsdbutil.GenerateTestGaugeHistogram(2), nil},
+					sample{3, 0, tsdbutil.GenerateTestGaugeHistogram(3), nil},
+					sample{6, 0, tsdbutil.GenerateTestGaugeHistogram(6), nil},
+				}),
+			},
+		},
+		{
+			name: "one gauge histogram chunk intersect with deletion interval",
+			chks: [][]tsdbutil.Sample{
+				{
+					sample{1, 0, tsdbutil.GenerateTestGaugeHistogram(1), nil},
+					sample{2, 0, tsdbutil.GenerateTestGaugeHistogram(2), nil},
+					sample{3, 0, tsdbutil.GenerateTestGaugeHistogram(3), nil},
+					sample{6, 0, tsdbutil.GenerateTestGaugeHistogram(6), nil},
+				},
+			},
+			intervals: tombstones.Intervals{{Mint: 5, Maxt: 20}},
+			expected: []tsdbutil.Sample{
+				sample{1, 0, tsdbutil.GenerateTestGaugeHistogram(1), nil},
+				sample{2, 0, tsdbutil.GenerateTestGaugeHistogram(2), nil},
+				sample{3, 0, tsdbutil.GenerateTestGaugeHistogram(3), nil},
+			},
+			expectedChks: []chunks.Meta{
+				tsdbutil.ChunkFromSamples([]tsdbutil.Sample{
+					sample{1, 0, tsdbutil.GenerateTestGaugeHistogram(1), nil},
+					sample{2, 0, tsdbutil.GenerateTestGaugeHistogram(2), nil},
+					sample{3, 0, tsdbutil.GenerateTestGaugeHistogram(3), nil},
+				}),
+			},
+		},
+		{
+			name: "one gauge float histogram",
+			chks: [][]tsdbutil.Sample{
+				{
+					sample{1, 0, nil, tsdbutil.GenerateTestGaugeFloatHistogram(1)},
+					sample{2, 0, nil, tsdbutil.GenerateTestGaugeFloatHistogram(2)},
+					sample{3, 0, nil, tsdbutil.GenerateTestGaugeFloatHistogram(3)},
+					sample{6, 0, nil, tsdbutil.GenerateTestGaugeFloatHistogram(6)},
+				},
+			},
+			expected: []tsdbutil.Sample{
+				sample{1, 0, nil, tsdbutil.GenerateTestGaugeFloatHistogram(1)},
+				sample{2, 0, nil, tsdbutil.GenerateTestGaugeFloatHistogram(2)},
+				sample{3, 0, nil, tsdbutil.GenerateTestGaugeFloatHistogram(3)},
+				sample{6, 0, nil, tsdbutil.GenerateTestGaugeFloatHistogram(6)},
+			},
+			expectedChks: []chunks.Meta{
+				tsdbutil.ChunkFromSamples([]tsdbutil.Sample{
+					sample{1, 0, nil, tsdbutil.GenerateTestGaugeFloatHistogram(1)},
+					sample{2, 0, nil, tsdbutil.GenerateTestGaugeFloatHistogram(2)},
+					sample{3, 0, nil, tsdbutil.GenerateTestGaugeFloatHistogram(3)},
+					sample{6, 0, nil, tsdbutil.GenerateTestGaugeFloatHistogram(6)},
+				}),
+			},
+		},
+		{
+			name: "one gauge float histogram chunk intersect with deletion interval",
+			chks: [][]tsdbutil.Sample{
+				{
+					sample{1, 0, nil, tsdbutil.GenerateTestGaugeFloatHistogram(1)},
+					sample{2, 0, nil, tsdbutil.GenerateTestGaugeFloatHistogram(2)},
+					sample{3, 0, nil, tsdbutil.GenerateTestGaugeFloatHistogram(3)},
+					sample{6, 0, nil, tsdbutil.GenerateTestGaugeFloatHistogram(6)},
+				},
+			},
+			intervals: tombstones.Intervals{{Mint: 5, Maxt: 20}},
+			expected: []tsdbutil.Sample{
+				sample{1, 0, nil, tsdbutil.GenerateTestGaugeFloatHistogram(1)},
+				sample{2, 0, nil, tsdbutil.GenerateTestGaugeFloatHistogram(2)},
+				sample{3, 0, nil, tsdbutil.GenerateTestGaugeFloatHistogram(3)},
+			},
+			expectedChks: []chunks.Meta{
+				tsdbutil.ChunkFromSamples([]tsdbutil.Sample{
+					sample{1, 0, nil, tsdbutil.GenerateTestGaugeFloatHistogram(1)},
+					sample{2, 0, nil, tsdbutil.GenerateTestGaugeFloatHistogram(2)},
+					sample{3, 0, nil, tsdbutil.GenerateTestGaugeFloatHistogram(3)},
+				}),
+			},
+		},
 	}
 	for _, tc := range cases {
 		t.Run(tc.name, func(t *testing.T) {
@@ -2411,3 +2608,80 @@ func BenchmarkHeadQuerier(b *testing.B) {
 		require.NoError(b, ss.Err())
 	}
 }
+
+// This is a regression test for the case where gauge histograms were not handled by
+// populateWithDelChunkSeriesIterator correctly.
+func TestQueryWithDeletedHistograms(t *testing.T) {
+	testcases := map[string]func(int) (*histogram.Histogram, *histogram.FloatHistogram){
+		"intCounter": func(i int) (*histogram.Histogram, *histogram.FloatHistogram) {
+			return tsdbutil.GenerateTestHistogram(i), nil
+		},
+		"intgauge": func(i int) (*histogram.Histogram, *histogram.FloatHistogram) {
+			return tsdbutil.GenerateTestGaugeHistogram(rand.Int() % 1000), nil
+		},
+		"floatCounter": func(i int) (*histogram.Histogram, *histogram.FloatHistogram) {
+			return nil, tsdbutil.GenerateTestFloatHistogram(i)
+		},
+		"floatGauge": func(i int) (*histogram.Histogram, *histogram.FloatHistogram) {
+			return nil, tsdbutil.GenerateTestGaugeFloatHistogram(rand.Int() % 1000)
+		},
+	}
+
+	for name, tc := range testcases {
+		t.Run(name, func(t *testing.T) {
+			db := openTestDB(t, nil, nil)
+			defer func() {
+				require.NoError(t, db.Close())
+			}()
+
+			db.EnableNativeHistograms()
+			appender := db.Appender(context.Background())
+
+			var (
+				err       error
+				seriesRef storage.SeriesRef
+			)
+			lbs := labels.FromStrings("__name__", "test", "type", name)
+
+			for i := 0; i < 100; i++ {
+				h, fh := tc(i)
+				seriesRef, err = appender.AppendHistogram(seriesRef, lbs, int64(i), h, fh)
+				require.NoError(t, err)
+			}
+
+			err = appender.Commit()
+			require.NoError(t, err)
+
+			matcher, err := labels.NewMatcher(labels.MatchEqual, "__name__", "test")
+			require.NoError(t, err)
+
+			// Delete the last 20.
+			err = db.Delete(80, 100, matcher)
+			require.NoError(t, err)
+
+			chunkQuerier, err := db.ChunkQuerier(context.Background(), 0, 100)
+			require.NoError(t, err)
+
+			css := chunkQuerier.Select(false, nil, matcher)
+
+			seriesCount := 0
+			for css.Next() {
+				seriesCount++
+				series := css.At()
+
+				sampleCount := 0
+				it := series.Iterator(nil)
+				for it.Next() {
+					chk := it.At()
+					for cit := chk.Chunk.Iterator(nil); cit.Next() != chunkenc.ValNone; {
+						sampleCount++
+					}
+				}
+				require.NoError(t, it.Err())
+				require.Equal(t, 80, sampleCount)
+			}
+			require.NoError(t, css.Err())
+			require.Equal(t, 1, seriesCount)
+		})
+	}
+}

tsdb/tsdbutil/chunks.go

@@ -71,9 +71,19 @@ func ChunkFromSamplesGeneric(s Samples) chunks.Meta {
 		case chunkenc.ValFloat:
 			ca.Append(s.Get(i).T(), s.Get(i).F())
 		case chunkenc.ValHistogram:
-			ca.AppendHistogram(s.Get(i).T(), s.Get(i).H())
+			h := s.Get(i).H()
+			ca.AppendHistogram(s.Get(i).T(), h)
+			if i == 0 && h.CounterResetHint == histogram.GaugeType {
+				hc := c.(*chunkenc.HistogramChunk)
+				hc.SetCounterResetHeader(chunkenc.GaugeType)
+			}
 		case chunkenc.ValFloatHistogram:
-			ca.AppendFloatHistogram(s.Get(i).T(), s.Get(i).FH())
+			fh := s.Get(i).FH()
+			ca.AppendFloatHistogram(s.Get(i).T(), fh)
+			if i == 0 && fh.CounterResetHint == histogram.GaugeType {
+				hc := c.(*chunkenc.FloatHistogramChunk)
+				hc.SetCounterResetHeader(chunkenc.GaugeType)
+			}
 		default:
 			panic(fmt.Sprintf("unknown sample type %s", sampleType.String()))
 		}

tsdb/tsdbutil/histogram.go

@@ -108,3 +108,13 @@ func GenerateTestGaugeFloatHistogram(i int) *histogram.FloatHistogram {
 	h.CounterResetHint = histogram.GaugeType
 	return h
 }
+
+func SetHistogramNotCounterReset(h *histogram.Histogram) *histogram.Histogram {
+	h.CounterResetHint = histogram.NotCounterReset
+	return h
+}
+
+func SetFloatHistogramNotCounterReset(h *histogram.FloatHistogram) *histogram.FloatHistogram {
+	h.CounterResetHint = histogram.NotCounterReset
+	return h
+}