storage/remote: improve symbol-table handling

On the incoming path, `writeHandler.write()` creates a new table for
each request.

`labelProtosToLabels` takes a `ScratchBuilder` now.

Call `NewScratchBuilder` as required in tests.

Signed-off-by: Bryan Boreham <bjboreham@gmail.com>

storage/remote/codec.go

@@ -176,12 +176,13 @@ func ToQueryResult(ss storage.SeriesSet, sampleLimit int) (*prompb.QueryResult,
 
 // FromQueryResult unpacks and sorts a QueryResult proto.
 func FromQueryResult(sortSeries bool, res *prompb.QueryResult) storage.SeriesSet {
+	b := labels.NewScratchBuilder(0)
 	series := make([]storage.Series, 0, len(res.Timeseries))
 	for _, ts := range res.Timeseries {
 		if err := validateLabelsAndMetricName(ts.Labels); err != nil {
 			return errSeriesSet{err: err}
 		}
-		lbls := labelProtosToLabels(ts.Labels)
+		lbls := labelProtosToLabels(&b, ts.Labels)
 		series = append(series, &concreteSeries{labels: lbls, floats: ts.Samples, histograms: ts.Histograms})
 	}
 
@@ -616,11 +617,11 @@ func FromLabelMatchers(matchers []*prompb.LabelMatcher) ([]*labels.Matcher, erro
 	return result, nil
 }
 
-func exemplarProtoToExemplar(ep prompb.Exemplar) exemplar.Exemplar {
+func exemplarProtoToExemplar(b *labels.ScratchBuilder, ep prompb.Exemplar) exemplar.Exemplar {
 	timestamp := ep.Timestamp
 
 	return exemplar.Exemplar{
-		Labels: labelProtosToLabels(ep.Labels),
+		Labels: labelProtosToLabels(b, ep.Labels),
 		Value:  ep.Value,
 		Ts:     timestamp,
 		HasTs:  timestamp != 0,
@@ -760,8 +761,8 @@ func LabelProtosToMetric(labelPairs []*prompb.Label) model.Metric {
 	return metric
 }
 
-func labelProtosToLabels(labelPairs []prompb.Label) labels.Labels {
-	b := labels.ScratchBuilder{}
+func labelProtosToLabels(b *labels.ScratchBuilder, labelPairs []prompb.Label) labels.Labels {
+	b.Reset()
 	for _, l := range labelPairs {
 		b.Add(l.Name, l.Value)
 	}

storage/remote/codec_test.go

@@ -788,10 +788,11 @@ func (m *mockWriter) Write(p []byte) (n int, err error) {
 type mockChunkSeriesSet struct {
 	chunkedSeries []*prompb.ChunkedSeries
 	index         int
+	builder       labels.ScratchBuilder
 }
 
 func newMockChunkSeriesSet(ss []*prompb.ChunkedSeries) storage.ChunkSeriesSet {
-	return &mockChunkSeriesSet{chunkedSeries: ss, index: -1}
+	return &mockChunkSeriesSet{chunkedSeries: ss, index: -1, builder: labels.NewScratchBuilder(0)}
 }
 
 func (c *mockChunkSeriesSet) Next() bool {
@@ -801,7 +802,7 @@ func (c *mockChunkSeriesSet) Next() bool {
 
 func (c *mockChunkSeriesSet) At() storage.ChunkSeries {
 	return &storage.ChunkSeriesEntry{
-		Lset: labelProtosToLabels(c.chunkedSeries[c.index].Labels),
+		Lset: labelProtosToLabels(&c.builder, c.chunkedSeries[c.index].Labels),
 		ChunkIteratorFn: func(chunks.Iterator) chunks.Iterator {
 			return &mockChunkIterator{
 				chunks: c.chunkedSeries[c.index].Chunks,

storage/remote/queue_manager_test.go

@@ -523,7 +523,7 @@ func TestShouldReshard(t *testing.T) {
 func createTimeseries(numSamples, numSeries int, extraLabels ...labels.Label) ([]record.RefSample, []record.RefSeries) {
 	samples := make([]record.RefSample, 0, numSamples)
 	series := make([]record.RefSeries, 0, numSeries)
-	lb := labels.ScratchBuilder{}
+	lb := labels.NewScratchBuilder(1 + len(extraLabels))
 	for i := 0; i < numSeries; i++ {
 		name := fmt.Sprintf("test_metric_%d", i)
 		for j := 0; j < numSamples; j++ {
@@ -760,9 +760,10 @@ func (c *TestWriteClient) Store(_ context.Context, req []byte, _ int) error {
 	if err := proto.Unmarshal(reqBuf, &reqProto); err != nil {
 		return err
 	}
+	builder := labels.NewScratchBuilder(0)
 	count := 0
 	for _, ts := range reqProto.Timeseries {
-		labels := labelProtosToLabels(ts.Labels)
+		labels := labelProtosToLabels(&builder, ts.Labels)
 		seriesName := labels.Get("__name__")
 		for _, sample := range ts.Samples {
 			count++
@@ -1370,7 +1371,7 @@ func createTimeseriesWithOldSamples(numSamples, numSeries int, extraLabels ...la
 	newSamples := make([]record.RefSample, 0, numSamples)
 	samples := make([]record.RefSample, 0, numSamples)
 	series := make([]record.RefSeries, 0, numSeries)
-	lb := labels.ScratchBuilder{}
+	lb := labels.NewScratchBuilder(1 + len(extraLabels))
 	for i := 0; i < numSeries; i++ {
 		name := fmt.Sprintf("test_metric_%d", i)
 		// We create half of the samples in the past.

storage/remote/read_test.go

@@ -195,6 +195,7 @@ func TestSeriesSetFilter(t *testing.T) {
 type mockedRemoteClient struct {
 	got   *prompb.Query
 	store []*prompb.TimeSeries
+	b     labels.ScratchBuilder
 }
 
 func (c *mockedRemoteClient) Read(_ context.Context, query *prompb.Query) (*prompb.QueryResult, error) {
@@ -210,7 +211,7 @@ func (c *mockedRemoteClient) Read(_ context.Context, query *prompb.Query) (*prom
 
 	q := &prompb.QueryResult{}
 	for _, s := range c.store {
-		l := labelProtosToLabels(s.Labels)
+		l := labelProtosToLabels(&c.b, s.Labels)
 		var notMatch bool
 
 		for _, m := range matchers {
@@ -242,6 +243,7 @@ func TestSampleAndChunkQueryableClient(t *testing.T) {
 			{Labels: []prompb.Label{{Name: "a", Value: "b3"}, {Name: "region", Value: "us"}}},
 			{Labels: []prompb.Label{{Name: "a", Value: "b2"}, {Name: "region", Value: "europe"}}},
 		},
+		b: labels.NewScratchBuilder(0),
 	}
 
 	for _, tc := range []struct {

storage/remote/write_handler.go

@@ -25,6 +25,7 @@ import (
 	"github.com/prometheus/client_golang/prometheus"
 
 	"github.com/prometheus/prometheus/model/exemplar"
+	"github.com/prometheus/prometheus/model/labels"
 	"github.com/prometheus/prometheus/prompb"
 	"github.com/prometheus/prometheus/storage"
 	otlptranslator "github.com/prometheus/prometheus/storage/remote/otlptranslator/prometheusremotewrite"
@@ -112,9 +113,10 @@ func (h *writeHandler) write(ctx context.Context, req *prompb.WriteRequest) (err
 		err = app.Commit()
 	}()
 
+	b := labels.NewScratchBuilder(0)
 	var exemplarErr error
 	for _, ts := range req.Timeseries {
-		labels := labelProtosToLabels(ts.Labels)
+		labels := labelProtosToLabels(&b, ts.Labels)
 		if !labels.IsValid() {
 			level.Warn(h.logger).Log("msg", "Invalid metric names or labels", "got", labels.String())
 			samplesWithInvalidLabels++
@@ -137,7 +139,7 @@ func (h *writeHandler) write(ctx context.Context, req *prompb.WriteRequest) (err
 		}
 
 		for _, ep := range ts.Exemplars {
-			e := exemplarProtoToExemplar(ep)
+			e := exemplarProtoToExemplar(&b, ep)
 
 			_, exemplarErr = app.AppendExemplar(0, labels, e)
 			exemplarErr = h.checkAppendExemplarError(exemplarErr, e, &outOfOrderExemplarErrs)

storage/remote/write_handler_test.go

@@ -55,18 +55,19 @@ func TestRemoteWriteHandler(t *testing.T) {
 	resp := recorder.Result()
 	require.Equal(t, http.StatusNoContent, resp.StatusCode)
 
+	b := labels.NewScratchBuilder(0)
 	i := 0
 	j := 0
 	k := 0
 	for _, ts := range writeRequestFixture.Timeseries {
-		labels := labelProtosToLabels(ts.Labels)
+		labels := labelProtosToLabels(&b, ts.Labels)
 		for _, s := range ts.Samples {
 			requireEqual(t, mockSample{labels, s.Timestamp, s.Value}, appendable.samples[i])
 			i++
 		}
 
 		for _, e := range ts.Exemplars {
-			exemplarLabels := labelProtosToLabels(e.Labels)
+			exemplarLabels := labelProtosToLabels(&b, e.Labels)
 			requireEqual(t, mockExemplar{labels, exemplarLabels, e.Timestamp, e.Value}, appendable.exemplars[j])
 			j++
 		}