Merge 358410fbf6 into 25aee26a57

model/labels/labels_common.go

@@ -215,7 +215,7 @@ func (b *Builder) Range(f func(l Label)) {
 	// Take a copy of add and del, so they are unaffected by calls to Set() or Del().
 	origAdd, origDel := append(addStack[:0], b.add...), append(delStack[:0], b.del...)
 	b.base.Range(func(l Label) {
-		if !slices.Contains(origDel, l.Name) && !contains(origAdd, l.Name) {
+		if !slices.Contains(origDel, l.Name) && !Contains(origAdd, l.Name) {
 			f(l)
 		}
 	})
@@ -224,7 +224,8 @@ func (b *Builder) Range(f func(l Label)) {
 	}
 }
 
-func contains(s []Label, n string) bool {
+// Contains returns true if the label name n is present in s, otherwise false.
+func Contains(s []Label, n string) bool {
 	for _, a := range s {
 		if a.Name == n {
 			return true

model/labels/labels_dedupelabels.go

@@ -464,6 +464,18 @@ func New(ls ...Label) Labels {
 	return Labels{syms: syms.nameTable, data: yoloString(buf)}
 }
 
+// NewFromSorted returns sorted Labels from the given
+// sorted labels. In case of slices it returns the
+// input.
+func NewFromSorted(ls []Label) Labels {
+	syms := NewSymbolTable()
+	var stackSpace [16]int
+	size, nums := mapLabelsToNumbers(syms, ls, stackSpace[:])
+	buf := make([]byte, size)
+	marshalNumbersToSizedBuffer(nums, buf)
+	return Labels{syms: syms.nameTable, data: yoloString(buf)}
+}
+
 // FromStrings creates new labels from pairs of strings.
 func FromStrings(ss ...string) Labels {
 	if len(ss)%2 != 0 {

model/labels/labels_slicelabels.go

@@ -279,6 +279,13 @@ func New(ls ...Label) Labels {
 	return set
 }
 
+// NewFromSorted returns sorted Labels from the given
+// sorted labels. In case of slices it returns the
+// input. This function does NOT copy!
+func NewFromSorted(ls []Label) Labels {
+	return ls
+}
+
 // FromStrings creates new labels from pairs of strings.
 func FromStrings(ss ...string) Labels {
 	if len(ss)%2 != 0 {
@@ -423,7 +430,7 @@ func (b *Builder) Labels() Labels {
 	}
 	res := make(Labels, 0, expectedSize)
 	for _, l := range b.base {
-		if slices.Contains(b.del, l.Name) || contains(b.add, l.Name) {
+		if slices.Contains(b.del, l.Name) || Contains(b.add, l.Name) {
 			continue
 		}
 		res = append(res, l)

model/labels/labels_stringlabels.go

@@ -314,6 +314,16 @@ func New(ls ...Label) Labels {
 	return Labels{data: yoloString(buf)}
 }
 
+// NewFromSorted returns sorted Labels from the given
+// sorted labels. In case of slices it returns the
+// input.
+func NewFromSorted(ls []Label) Labels {
+	size := labelsSize(ls)
+	buf := make([]byte, size)
+	marshalLabelsToSizedBuffer(ls, buf)
+	return Labels{data: yoloString(buf)}
+}
+
 // FromStrings creates new labels from pairs of strings.
 func FromStrings(ss ...string) Labels {
 	if len(ss)%2 != 0 {

storage/remote/otlptranslator/prometheusremotewrite/combined_appender.go

@@ -0,0 +1,214 @@
+// Copyright 2025 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package prometheusremotewrite
+
+import (
+	"errors"
+	"fmt"
+	"log/slog"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+
+	"github.com/prometheus/prometheus/model/exemplar"
+	"github.com/prometheus/prometheus/model/histogram"
+	modelLabels "github.com/prometheus/prometheus/model/labels"
+	"github.com/prometheus/prometheus/model/metadata"
+	"github.com/prometheus/prometheus/storage"
+	"github.com/prometheus/prometheus/storage/remote/otlptranslator/prometheusremotewrite/labels"
+)
+
+// CombinedAppender is similar to storage.Appender, but combines updates to
+// metadata, created timestamps, exemplars and samples into a single call.
+type CombinedAppender interface {
+	// AppendSample appends a sample and related exemplars, metadata, and
+	// created timestamp to the storage.
+	AppendSample(metricFamilyName string, ls labels.Labels, meta metadata.Metadata, t, ct int64, v float64, es []exemplar.Exemplar) error
+	// AppendSample appends a histogram and related exemplars, metadata, and
+	// created timestamp to the storage.
+	AppendHistogram(metricFamilyName string, ls labels.Labels, meta metadata.Metadata, t, ct int64, h *histogram.Histogram, es []exemplar.Exemplar) error
+	// Commit finalizes the ongoing transaction in storage.
+	Commit() error
+}
+
+// NewCombinedAppender creates a combined appender that sets start times and
+// updates metadata for each series only once, and appends samples and
+// exemplars for each call.
+func NewCombinedAppender(app storage.Appender, logger *slog.Logger, reg prometheus.Registerer, ingestCTZeroSample bool) CombinedAppender {
+	return &combinedAppender{
+		app:                app,
+		logger:             logger,
+		ingestCTZeroSample: ingestCTZeroSample,
+		refs:               make(map[uint64]labelsRef),
+		samplesAppendedWithoutMetadata: promauto.With(reg).NewCounter(prometheus.CounterOpts{
+			Namespace: "prometheus",
+			Subsystem: "api",
+			Name:      "otlp_without_metadata_appended_samples_total",
+			Help:      "The total number of received OTLP data points which were ingested without corresponding metadata.",
+		}),
+		outOfOrderExemplars: promauto.With(reg).NewCounter(prometheus.CounterOpts{
+			Namespace: "prometheus",
+			Subsystem: "api",
+			Name:      "otlp_out_of_order_exemplars_total",
+			Help:      "The total number of received OTLP exemplars which were rejected because they were out of order.",
+		}),
+	}
+}
+
+type labelsRef struct {
+	ref storage.SeriesRef
+	ls  modelLabels.Labels
+}
+
+type combinedAppender struct {
+	app                            storage.Appender
+	logger                         *slog.Logger
+	samplesAppendedWithoutMetadata prometheus.Counter
+	outOfOrderExemplars            prometheus.Counter
+	ingestCTZeroSample             bool
+	// Used to ensure we only update metadata and created timestamps once, and to share storage.SeriesRefs.
+	// To detect hash collision it also stores the labels.
+	// There is no overflow/conflict list, the TSDB will handle that part.
+	refs map[uint64]labelsRef
+}
+
+func (b *combinedAppender) AppendSample(_ string, rawls labels.Labels, meta metadata.Metadata, t, ct int64, v float64, es []exemplar.Exemplar) (err error) {
+	ls := modelLabels.NewFromSorted(rawls)
+	hash := ls.Hash()
+	lref, exists := b.refs[hash]
+	ref := lref.ref
+	if exists && !modelLabels.Equal(lref.ls, ls) {
+		// Hash collision, this is a new series.
+		exists = false
+	}
+	if !exists {
+		if ct != 0 && b.ingestCTZeroSample {
+			ref, err = b.app.AppendCTZeroSample(ref, ls, t, ct)
+			if err != nil && !errors.Is(err, storage.ErrOutOfOrderCT) {
+				// Even for the first sample OOO is a common scenario because
+				// we can't tell if a CT was already ingested in a previous request.
+				// We ignore the error.
+				b.logger.Debug("Error when appending float CT from OTLP", "err", err, "series", ls.String(), "created_timestamp", ct, "timestamp", t)
+			}
+		}
+	}
+	ref, err = b.app.Append(ref, ls, t, v)
+	if err != nil {
+		// Although AppendHistogram does not currently return ErrDuplicateSampleForTimestamp there is
+		// a note indicating its inclusion in the future.
+		if errors.Is(err, storage.ErrOutOfOrderSample) ||
+			errors.Is(err, storage.ErrOutOfBounds) ||
+			errors.Is(err, storage.ErrDuplicateSampleForTimestamp) {
+			b.logger.Error("Error when appending float sample from OTLP", "err", err.Error(), "series", ls.String(), "timestamp", t)
+		}
+	}
+
+	if ref == 0 {
+		// We cannot update metadata or add exemplars on non existent series.
+		return
+	}
+
+	if !exists {
+		b.refs[hash] = labelsRef{
+			ref: ref,
+			ls:  ls,
+		}
+		// If this is the first time we see this series, set the metadata.
+		ref, err = b.app.UpdateMetadata(0, ls, meta)
+		if err != nil {
+			b.samplesAppendedWithoutMetadata.Add(1)
+			b.logger.Debug("Error while updating metadata from OTLP", "err", err)
+		}
+	}
+
+	b.appendExemplars(ref, ls, es)
+
+	return
+}
+
+func (b *combinedAppender) AppendHistogram(_ string, rawls labels.Labels, meta metadata.Metadata, t, ct int64, h *histogram.Histogram, es []exemplar.Exemplar) (err error) {
+	ls := modelLabels.NewFromSorted(rawls)
+	hash := ls.Hash()
+	lref, exists := b.refs[hash]
+	ref := lref.ref
+	if exists && !modelLabels.Equal(lref.ls, ls) {
+		// Hash collision, this is a new series.
+		exists = false
+	}
+	if !exists {
+		if ct != 0 && b.ingestCTZeroSample {
+			ref, err = b.app.AppendHistogramCTZeroSample(ref, ls, t, ct, h, nil)
+			if err != nil && !errors.Is(err, storage.ErrOutOfOrderCT) {
+				// Even for the first sample OOO is a common scenario because
+				// we can't tell if a CT was already ingested in a previous request.
+				// We ignore the error.
+				b.logger.Debug("Error when appending Histogram CT from OTLP", "err", err, "series", ls.String(), "created_timestamp", ct, "timestamp", t)
+			}
+		}
+	}
+
+	ref, err = b.app.AppendHistogram(ref, ls, t, h, nil)
+	if err != nil {
+		// Although AppendHistogram does not currently return ErrDuplicateSampleForTimestamp there is
+		// a note indicating its inclusion in the future.
+		if errors.Is(err, storage.ErrOutOfOrderSample) ||
+			errors.Is(err, storage.ErrOutOfBounds) ||
+			errors.Is(err, storage.ErrDuplicateSampleForTimestamp) {
+			b.logger.Error("Error when appending histogram sample from OTLP", "err", err.Error(), "series", ls.String(), "timestamp", t)
+		}
+	}
+
+	if ref == 0 {
+		// We cannot update metadata or add exemplars on non existent series.
+		return
+	}
+
+	if !exists {
+		b.refs[hash] = labelsRef{
+			ref: ref,
+			ls:  ls,
+		}
+		// If this is the first time we see this series, set the metadata.
+		ref, err = b.app.UpdateMetadata(0, ls, meta)
+		if err != nil {
+			b.samplesAppendedWithoutMetadata.Add(1)
+			b.logger.Debug("Error while updating metadata from OTLP", "err", err)
+		}
+	}
+
+	b.appendExemplars(ref, ls, es)
+
+	return
+}
+
+func (b *combinedAppender) Commit() error {
+	return b.app.Commit()
+}
+
+func (b *combinedAppender) appendExemplars(ref storage.SeriesRef, ls modelLabels.Labels, es []exemplar.Exemplar) storage.SeriesRef {
+	var err error
+	for _, e := range es {
+		if ref, err = b.app.AppendExemplar(ref, ls, e); err != nil {
+			switch {
+			case errors.Is(err, storage.ErrOutOfOrderExemplar):
+				b.outOfOrderExemplars.Add(1)
+				b.logger.Debug("Out of order exemplar from OTLP", "series", ls.String(), "exemplar", fmt.Sprintf("%+v", e))
+			default:
+				// Since exemplar storage is still experimental, we don't fail the request on ingestion errors
+				b.logger.Debug("Error while adding exemplar from OTLP", "series", ls.String(), "exemplar", fmt.Sprintf("%+v", e), "err", err)
+			}
+		}
+	}
+	return ref
+}

storage/remote/otlptranslator/prometheusremotewrite/combined_appender_test.go

@@ -0,0 +1,471 @@
+// Copyright 2025 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package prometheusremotewrite
+
+import (
+	"context"
+	"math"
+	"testing"
+	"time"
+
+	"github.com/google/go-cmp/cmp"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/common/model"
+	"github.com/prometheus/common/promslog"
+	"github.com/stretchr/testify/require"
+
+	"github.com/prometheus/prometheus/model/exemplar"
+	"github.com/prometheus/prometheus/model/histogram"
+	modelLabels "github.com/prometheus/prometheus/model/labels"
+	"github.com/prometheus/prometheus/model/metadata"
+	"github.com/prometheus/prometheus/storage"
+	"github.com/prometheus/prometheus/storage/remote/otlptranslator/prometheusremotewrite/labels"
+	"github.com/prometheus/prometheus/tsdb"
+	"github.com/prometheus/prometheus/tsdb/chunkenc"
+	"github.com/prometheus/prometheus/tsdb/tsdbutil"
+	"github.com/prometheus/prometheus/util/testutil"
+)
+
+type mockCombinedAppender struct {
+	pendingSamples    []combinedSample
+	pendingHistograms []combinedHistogram
+
+	samples    []combinedSample
+	histograms []combinedHistogram
+}
+
+type combinedSample struct {
+	metricFamilyName string
+	ls               labels.Labels
+	meta             metadata.Metadata
+	t                int64
+	ct               int64
+	v                float64
+	es               []exemplar.Exemplar
+}
+
+type combinedHistogram struct {
+	metricFamilyName string
+	ls               labels.Labels
+	meta             metadata.Metadata
+	t                int64
+	ct               int64
+	h                *histogram.Histogram
+	es               []exemplar.Exemplar
+}
+
+func (m *mockCombinedAppender) AppendSample(metricFamilyName string, ls labels.Labels, meta metadata.Metadata, t, ct int64, v float64, es []exemplar.Exemplar) error {
+	m.pendingSamples = append(m.pendingSamples, combinedSample{
+		metricFamilyName: metricFamilyName,
+		ls:               ls,
+		meta:             meta,
+		t:                t,
+		ct:               ct,
+		v:                v,
+		es:               es,
+	})
+	return nil
+}
+
+func (m *mockCombinedAppender) AppendHistogram(metricFamilyName string, ls labels.Labels, meta metadata.Metadata, t, ct int64, h *histogram.Histogram, es []exemplar.Exemplar) error {
+	m.pendingHistograms = append(m.pendingHistograms, combinedHistogram{
+		metricFamilyName: metricFamilyName,
+		ls:               ls,
+		meta:             meta,
+		t:                t,
+		ct:               ct,
+		h:                h,
+		es:               es,
+	})
+	return nil
+}
+
+func (m *mockCombinedAppender) Commit() error {
+	m.samples = append(m.samples, m.pendingSamples...)
+	m.pendingSamples = m.pendingSamples[:0]
+	m.histograms = append(m.histograms, m.pendingHistograms...)
+	m.pendingHistograms = m.pendingHistograms[:0]
+	return nil
+}
+
+func requireEqual(t testing.TB, expected, actual interface{}, msgAndArgs ...interface{}) {
+	testutil.RequireEqualWithOptions(t, expected, actual, []cmp.Option{cmp.AllowUnexported(combinedSample{}, combinedHistogram{})}, msgAndArgs...)
+}
+
+// TestCombinedAppenderOnTSDB runs some basic tests on a real TSDB to check
+// that the combinedAppender works on a real TSDB.
+func TestCombinedAppenderOnTSDB(t *testing.T) {
+	t.Run("ingestCTZeroSample=false", func(t *testing.T) { testCombinedAppenderOnTSDB(t, false) })
+
+	t.Run("ingestCTZeroSample=true", func(t *testing.T) { testCombinedAppenderOnTSDB(t, true) })
+}
+
+func testCombinedAppenderOnTSDB(t *testing.T, ingestCTZeroSample bool) {
+	t.Helper()
+
+	now := time.Now()
+
+	testExemplars := []exemplar.Exemplar{
+		{
+			Labels: modelLabels.FromStrings("tracid", "122"),
+			Value:  1337,
+		},
+		{
+			Labels: modelLabels.FromStrings("tracid", "132"),
+			Value:  7777,
+		},
+	}
+	expectedExemplars := []exemplar.QueryResult{
+		{
+			SeriesLabels: modelLabels.FromStrings(
+				model.MetricNameLabel, "test_bytes_total",
+				"foo", "bar",
+			),
+			Exemplars: testExemplars,
+		},
+	}
+
+	testCases := map[string]struct {
+		appendFunc        func(CombinedAppender) error
+		expectedSamples   []sample
+		expectedExemplars []exemplar.QueryResult
+	}{
+		"single float sample, zero CT": {
+			appendFunc: func(app CombinedAppender) error {
+				return app.AppendSample("test_bytes_total", labels.FromStrings(
+					model.MetricNameLabel, "test_bytes_total",
+					"foo", "bar",
+				), metadata.Metadata{
+					Type: model.MetricTypeCounter,
+					Unit: "bytes",
+					Help: "some help",
+				}, now.UnixMilli(), 0, 42.0, testExemplars)
+			},
+			expectedSamples: []sample{
+				{
+					t: now.UnixMilli(),
+					f: 42.0,
+				},
+			},
+			expectedExemplars: expectedExemplars,
+		},
+		"single float sample, very old CT": {
+			appendFunc: func(app CombinedAppender) error {
+				return app.AppendSample("test_bytes_total", labels.FromStrings(
+					model.MetricNameLabel, "test_bytes_total",
+					"foo", "bar",
+				), metadata.Metadata{
+					Type: model.MetricTypeCounter,
+					Unit: "bytes",
+					Help: "some help",
+				}, now.UnixMilli(), 1, 42.0, nil)
+			},
+			expectedSamples: []sample{
+				{
+					t: now.UnixMilli(),
+					f: 42.0,
+				},
+			},
+		},
+		"single float sample, normal CT": {
+			appendFunc: func(app CombinedAppender) error {
+				return app.AppendSample("test_bytes_total", labels.FromStrings(
+					model.MetricNameLabel, "test_bytes_total",
+					"foo", "bar",
+				), metadata.Metadata{
+					Type: model.MetricTypeCounter,
+					Unit: "bytes",
+					Help: "some help",
+				}, now.UnixMilli(), now.Add(-2*time.Minute).UnixMilli(), 42.0, nil)
+			},
+			expectedSamples: []sample{
+				{
+					ctZero: true,
+					t:      now.Add(-2 * time.Minute).UnixMilli(),
+				},
+				{
+					t: now.UnixMilli(),
+					f: 42.0,
+				},
+			},
+		},
+		"single float sample, CT name time as sample": {
+			appendFunc: func(app CombinedAppender) error {
+				return app.AppendSample("test_bytes_total", labels.FromStrings(
+					model.MetricNameLabel, "test_bytes_total",
+					"foo", "bar",
+				), metadata.Metadata{
+					Type: model.MetricTypeCounter,
+					Unit: "bytes",
+					Help: "some help",
+				}, now.UnixMilli(), now.UnixMilli(), 42.0, nil)
+			},
+			expectedSamples: []sample{
+				{
+					t: now.UnixMilli(),
+					f: 42.0,
+				},
+			},
+		},
+		"single float sample, CT in the future of the sample": {
+			appendFunc: func(app CombinedAppender) error {
+				return app.AppendSample("test_bytes_total", labels.FromStrings(
+					model.MetricNameLabel, "test_bytes_total",
+					"foo", "bar",
+				), metadata.Metadata{
+					Type: model.MetricTypeCounter,
+					Unit: "bytes",
+					Help: "some help",
+				}, now.UnixMilli(), now.Add(time.Minute).UnixMilli(), 42.0, nil)
+			},
+			expectedSamples: []sample{
+				{
+					t: now.UnixMilli(),
+					f: 42.0,
+				},
+			},
+		},
+		"single histogram sample, zero CT": {
+			appendFunc: func(app CombinedAppender) error {
+				return app.AppendHistogram("test_bytes_total", labels.FromStrings(
+					model.MetricNameLabel, "test_bytes_total",
+					"foo", "bar",
+				), metadata.Metadata{
+					Type: model.MetricTypeCounter,
+					Unit: "bytes",
+					Help: "some help",
+				}, now.UnixMilli(), 0, tsdbutil.GenerateTestHistogram(42), testExemplars)
+			},
+			expectedSamples: []sample{
+				{
+					t: now.UnixMilli(),
+					h: tsdbutil.GenerateTestHistogram(42),
+				},
+			},
+			expectedExemplars: expectedExemplars,
+		},
+		"single histogram sample, very old CT": {
+			appendFunc: func(app CombinedAppender) error {
+				return app.AppendHistogram("test_bytes_total", labels.FromStrings(
+					model.MetricNameLabel, "test_bytes_total",
+					"foo", "bar",
+				), metadata.Metadata{
+					Type: model.MetricTypeCounter,
+					Unit: "bytes",
+					Help: "some help",
+				}, now.UnixMilli(), 1, tsdbutil.GenerateTestHistogram(42), nil)
+			},
+			expectedSamples: []sample{
+				{
+					t: now.UnixMilli(),
+					h: tsdbutil.GenerateTestHistogram(42),
+				},
+			},
+		},
+		"single histogram sample, normal CT": {
+			appendFunc: func(app CombinedAppender) error {
+				return app.AppendHistogram("test_bytes_total", labels.FromStrings(
+					model.MetricNameLabel, "test_bytes_total",
+					"foo", "bar",
+				), metadata.Metadata{
+					Type: model.MetricTypeCounter,
+					Unit: "bytes",
+					Help: "some help",
+				}, now.UnixMilli(), now.Add(-2*time.Minute).UnixMilli(), tsdbutil.GenerateTestHistogram(42), nil)
+			},
+			expectedSamples: []sample{
+				{
+					ctZero: true,
+					t:      now.Add(-2 * time.Minute).UnixMilli(),
+					h:      &histogram.Histogram{},
+				},
+				{
+					t: now.UnixMilli(),
+					h: tsdbutil.GenerateTestHistogram(42),
+				},
+			},
+		},
+		"single histogram sample, CT name time as sample": {
+			appendFunc: func(app CombinedAppender) error {
+				return app.AppendHistogram("test_bytes_total", labels.FromStrings(
+					model.MetricNameLabel, "test_bytes_total",
+					"foo", "bar",
+				), metadata.Metadata{
+					Type: model.MetricTypeCounter,
+					Unit: "bytes",
+					Help: "some help",
+				}, now.UnixMilli(), now.UnixMilli(), tsdbutil.GenerateTestHistogram(42), nil)
+			},
+			expectedSamples: []sample{
+				{
+					t: now.UnixMilli(),
+					h: tsdbutil.GenerateTestHistogram(42),
+				},
+			},
+		},
+		"single histogram sample, CT in the future of the sample": {
+			appendFunc: func(app CombinedAppender) error {
+				return app.AppendHistogram("test_bytes_total", labels.FromStrings(
+					model.MetricNameLabel, "test_bytes_total",
+					"foo", "bar",
+				), metadata.Metadata{
+					Type: model.MetricTypeCounter,
+					Unit: "bytes",
+					Help: "some help",
+				}, now.UnixMilli(), now.Add(time.Minute).UnixMilli(), tsdbutil.GenerateTestHistogram(42), nil)
+			},
+			expectedSamples: []sample{
+				{
+					t: now.UnixMilli(),
+					h: tsdbutil.GenerateTestHistogram(42),
+				},
+			},
+		},
+		"multiple float samples": {
+			appendFunc: func(app CombinedAppender) error {
+				err := app.AppendSample("test_bytes_total", labels.FromStrings(
+					model.MetricNameLabel, "test_bytes_total",
+					"foo", "bar",
+				), metadata.Metadata{
+					Type: model.MetricTypeCounter,
+					Unit: "bytes",
+					Help: "some help",
+				}, now.UnixMilli(), 0, 42.0, nil)
+				if err != nil {
+					return err
+				}
+				return app.AppendSample("test_bytes_total", labels.FromStrings(
+					model.MetricNameLabel, "test_bytes_total",
+					"foo", "bar",
+				), metadata.Metadata{
+					Type: model.MetricTypeCounter,
+					Unit: "bytes",
+					Help: "some help",
+				}, now.Add(15*time.Second).UnixMilli(), 0, 62.0, nil)
+			},
+			expectedSamples: []sample{
+				{
+					t: now.UnixMilli(),
+					f: 42.0,
+				},
+				{
+					t: now.Add(15 * time.Second).UnixMilli(),
+					f: 62.0,
+				},
+			},
+		},
+		"multiple histogram samples": {
+			appendFunc: func(app CombinedAppender) error {
+				err := app.AppendHistogram("test_bytes_total", labels.FromStrings(
+					model.MetricNameLabel, "test_bytes_total",
+					"foo", "bar",
+				), metadata.Metadata{
+					Type: model.MetricTypeCounter,
+					Unit: "bytes",
+					Help: "some help",
+				}, now.UnixMilli(), 0, tsdbutil.GenerateTestHistogram(42), nil)
+				if err != nil {
+					return err
+				}
+				return app.AppendHistogram("test_bytes_total", labels.FromStrings(
+					model.MetricNameLabel, "test_bytes_total",
+					"foo", "bar",
+				), metadata.Metadata{
+					Type: model.MetricTypeCounter,
+					Unit: "bytes",
+					Help: "some help",
+				}, now.Add(15*time.Second).UnixMilli(), 0, tsdbutil.GenerateTestHistogram(62), nil)
+			},
+			expectedSamples: []sample{
+				{
+					t: now.UnixMilli(),
+					h: tsdbutil.GenerateTestHistogram(42),
+				},
+				{
+					t: now.Add(15 * time.Second).UnixMilli(),
+					h: tsdbutil.GenerateTestHistogram(62),
+				},
+			},
+		},
+	}
+
+	for name, tc := range testCases {
+		t.Run(name, func(t *testing.T) {
+			dir := t.TempDir()
+			opts := tsdb.DefaultOptions()
+			opts.EnableExemplarStorage = true
+			opts.MaxExemplars = 100
+			opts.EnableNativeHistograms = true
+			db, err := tsdb.Open(dir, promslog.NewNopLogger(), prometheus.NewRegistry(), opts, nil)
+			require.NoError(t, err)
+
+			t.Cleanup(func() { db.Close() })
+
+			ctx := context.Background()
+			capp := NewCombinedAppender(db.Appender(ctx), promslog.NewNopLogger(), prometheus.NewRegistry(), ingestCTZeroSample)
+
+			require.NoError(t, tc.appendFunc(capp))
+
+			require.NoError(t, capp.Commit())
+
+			q, err := db.Querier(int64(math.MinInt64), int64(math.MaxInt64))
+			require.NoError(t, err)
+
+			ss := q.Select(ctx, false, &storage.SelectHints{
+				Start: int64(math.MinInt64),
+				End:   int64(math.MaxInt64),
+			}, modelLabels.MustNewMatcher(modelLabels.MatchEqual, model.MetricNameLabel, "test_bytes_total"))
+
+			require.NoError(t, ss.Err())
+
+			require.True(t, ss.Next())
+			series := ss.At()
+			it := series.Iterator(nil)
+			for _, sample := range tc.expectedSamples {
+				if !ingestCTZeroSample && sample.ctZero {
+					continue
+				}
+				if sample.h == nil {
+					require.Equal(t, chunkenc.ValFloat, it.Next())
+					ts, v := it.At()
+					require.Equal(t, sample.t, ts)
+					require.Equal(t, sample.f, v)
+				} else {
+					require.Equal(t, chunkenc.ValHistogram, it.Next())
+					ts, h := it.AtHistogram(nil)
+					require.Equal(t, sample.t, ts)
+					require.Equal(t, sample.h.Count, h.Count)
+				}
+			}
+			require.False(t, ss.Next())
+
+			eq, err := db.ExemplarQuerier(ctx)
+			require.NoError(t, err)
+			exResult, err := eq.Select(int64(math.MinInt64), int64(math.MaxInt64), []*modelLabels.Matcher{modelLabels.MustNewMatcher(modelLabels.MatchEqual, model.MetricNameLabel, "test_bytes_total")})
+			require.NoError(t, err)
+			if tc.expectedExemplars == nil {
+				tc.expectedExemplars = []exemplar.QueryResult{}
+			}
+			require.Equal(t, tc.expectedExemplars, exResult)
+		})
+	}
+}
+
+type sample struct {
+	ctZero bool
+
+	t int64
+	f float64
+	h *histogram.Histogram
+}

storage/remote/otlptranslator/prometheusremotewrite/helper.go

@@ -23,22 +23,24 @@ import (
 	"log"
 	"math"
 	"slices"
-	"sort"
 	"strconv"
 	"strings"
 	"time"
 	"unicode/utf8"
 
-	"github.com/cespare/xxhash/v2"
 	"github.com/prometheus/common/model"
 	"github.com/prometheus/otlptranslator"
 	"go.opentelemetry.io/collector/pdata/pcommon"
 	"go.opentelemetry.io/collector/pdata/pmetric"
 	conventions "go.opentelemetry.io/collector/semconv/v1.6.1"
 
+	"github.com/prometheus/prometheus/model/exemplar"
+	modelLabels "github.com/prometheus/prometheus/model/labels"
+	"github.com/prometheus/prometheus/model/metadata"
 	"github.com/prometheus/prometheus/model/timestamp"
 	"github.com/prometheus/prometheus/model/value"
 	"github.com/prometheus/prometheus/prompb"
+	"github.com/prometheus/prometheus/storage/remote/otlptranslator/prometheusremotewrite/labels"
 )
 
 const (
@@ -62,177 +64,115 @@ const (
 	defaultLookbackDelta = 5 * time.Minute
 )
 
-type bucketBoundsData struct {
-	ts    *prompb.TimeSeries
-	bound float64
-}
-
-// byBucketBoundsData enables the usage of sort.Sort() with a slice of bucket bounds.
-type byBucketBoundsData []bucketBoundsData
-
-func (m byBucketBoundsData) Len() int           { return len(m) }
-func (m byBucketBoundsData) Less(i, j int) bool { return m[i].bound < m[j].bound }
-func (m byBucketBoundsData) Swap(i, j int)      { m[i], m[j] = m[j], m[i] }
-
-// ByLabelName enables the usage of sort.Sort() with a slice of labels.
-type ByLabelName []prompb.Label
-
-func (a ByLabelName) Len() int           { return len(a) }
-func (a ByLabelName) Less(i, j int) bool { return a[i].Name < a[j].Name }
-func (a ByLabelName) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }
-
-// timeSeriesSignature returns a hashed label set signature.
-// The label slice should not contain duplicate label names; this method sorts the slice by label name before creating
-// the signature.
-// The algorithm is the same as in Prometheus' labels.StableHash function.
-func timeSeriesSignature(labels []prompb.Label) uint64 {
-	sort.Sort(ByLabelName(labels))
-
-	// Use xxhash.Sum64(b) for fast path as it's faster.
-	b := make([]byte, 0, 1024)
-	for i, v := range labels {
-		if len(b)+len(v.Name)+len(v.Value)+2 >= cap(b) {
-			// If labels entry is 1KB+ do not allocate whole entry.
-			h := xxhash.New()
-			_, _ = h.Write(b)
-			for _, v := range labels[i:] {
-				_, _ = h.WriteString(v.Name)
-				_, _ = h.Write(seps)
-				_, _ = h.WriteString(v.Value)
-				_, _ = h.Write(seps)
-			}
-			return h.Sum64()
-		}
-
-		b = append(b, v.Name...)
-		b = append(b, seps[0])
-		b = append(b, v.Value...)
-		b = append(b, seps[0])
-	}
-	return xxhash.Sum64(b)
-}
-
-var seps = []byte{'\xff'}
-
 // createAttributes creates a slice of Prometheus Labels with OTLP attributes and pairs of string values.
 // Unpaired string values are ignored. String pairs overwrite OTLP labels if collisions happen and
 // if logOnOverwrite is true, the overwrite is logged. Resulting label names are sanitized.
 // If settings.PromoteResourceAttributes is not empty, it's a set of resource attributes that should be promoted to labels.
-func createAttributes(resource pcommon.Resource, attributes pcommon.Map, scope scope, settings Settings,
-	ignoreAttrs []string, logOnOverwrite bool, metadata prompb.MetricMetadata, extras ...string,
-) ([]prompb.Label, error) {
+func (c *PrometheusConverter) createAttributes(resource pcommon.Resource, attributes pcommon.Map, scope scope, settings Settings,
+	ignoreAttrs []string, logOnOverwrite bool, meta metadata.Metadata, extras ...string,
+) (labels.Labels, error) {
 	resourceAttrs := resource.Attributes()
 	serviceName, haveServiceName := resourceAttrs.Get(conventions.AttributeServiceName)
 	instance, haveInstanceID := resourceAttrs.Get(conventions.AttributeServiceInstanceID)
 
-	promotedAttrs := settings.PromoteResourceAttributes.promotedAttributes(resourceAttrs)
-
 	promoteScope := settings.PromoteScopeMetadata && scope.name != ""
-	scopeLabelCount := 0
-	if promoteScope {
-		// Include name, version and schema URL.
-		scopeLabelCount = scope.attributes.Len() + 3
-	}
-
-	// Calculate the maximum possible number of labels we could return so we can preallocate l.
-	maxLabelCount := attributes.Len() + len(settings.ExternalLabels) + len(promotedAttrs) + scopeLabelCount + len(extras)/2
-
-	if haveServiceName {
-		maxLabelCount++
-	}
-	if haveInstanceID {
-		maxLabelCount++
-	}
-	if settings.EnableTypeAndUnitLabels {
-		maxLabelCount += 2
-	}
 
 	// Ensure attributes are sorted by key for consistent merging of keys which
 	// collide when sanitized.
-	labels := make([]prompb.Label, 0, maxLabelCount)
+	c.scratchBuilder.Reset()
+
 	// XXX: Should we always drop service namespace/service name/service instance ID from the labels
 	// (as they get mapped to other Prometheus labels)?
 	attributes.Range(func(key string, value pcommon.Value) bool {
 		if !slices.Contains(ignoreAttrs, key) {
-			labels = append(labels, prompb.Label{Name: key, Value: value.AsString()})
+			c.scratchBuilder.Add(key, value.AsString())
 		}
 		return true
 	})
-	sort.Stable(ByLabelName(labels))
+	c.scratchBuilder.Sort()
+	sortedLabels := c.scratchBuilder.Labels()
 
-	// map ensures no duplicate label names.
-	l := make(map[string]string, maxLabelCount)
 	labelNamer := otlptranslator.LabelNamer{UTF8Allowed: settings.AllowUTF8}
-	for _, label := range labels {
-		finalKey, err := labelNamer.Build(label.Name)
-		if err != nil {
-			return nil, err
-		}
-		if existingValue, alreadyExists := l[finalKey]; alreadyExists {
-			l[finalKey] = existingValue + ";" + label.Value
-		} else {
-			l[finalKey] = label.Value
-		}
-	}
 
-	for _, lbl := range promotedAttrs {
-		normalized, err := labelNamer.Build(lbl.Name)
-		if err != nil {
-			return nil, err
-		}
-		if _, exists := l[normalized]; !exists {
-			l[normalized] = lbl.Value
-		}
-	}
-	if promoteScope {
-		var rangeErr error
-		scope.attributes.Range(func(k string, v pcommon.Value) bool {
-			name, err := labelNamer.Build("otel_scope_" + k)
-			if err != nil {
-				rangeErr = err
-				return false
+	if settings.AllowUTF8 {
+		// UTF8 is allowed, so conflicts aren't possible.
+		c.builder.Reset(sortedLabels)
+	} else {
+		// Now that we have sorted and filtered the labels, build the actual list
+		// of labels, and handle conflicts by appending values.
+		c.builder.Reset(labels.EmptyLabels())
+		var sortErr error
+		sortedLabels.Range(func(l modelLabels.Label) {
+			finalKey, err := labelNamer.Build(l.Name)
+			if err != nil && sortErr == nil {
+				sortErr = err
+				return
+			}
+			if existingValue := c.builder.Get(finalKey); existingValue != "" {
+				c.builder.Set(finalKey, existingValue+";"+l.Value)
+			} else {
+				c.builder.Set(finalKey, l.Value)
 			}
-			l[name] = v.AsString()
-			return true
 		})
-		if rangeErr != nil {
-			return nil, rangeErr
+		if sortErr != nil {
+			return nil, sortErr
 		}
-		// Scope Name, Version and Schema URL are added after attributes to ensure they are not overwritten by attributes.
-		l["otel_scope_name"] = scope.name
-		l["otel_scope_version"] = scope.version
-		l["otel_scope_schema_url"] = scope.schemaURL
 	}
 
 	if settings.EnableTypeAndUnitLabels {
 		unitNamer := otlptranslator.UnitNamer{UTF8Allowed: settings.AllowUTF8}
-		if metadata.Type != prompb.MetricMetadata_UNKNOWN {
-			l["__type__"] = strings.ToLower(metadata.Type.String())
+		if meta.Type != model.MetricTypeUnknown {
+			c.builder.Set("__type__", strings.ToLower(string(meta.Type)))
 		}
-		if metadata.Unit != "" {
-			l["__unit__"] = unitNamer.Build(metadata.Unit)
+		if meta.Unit != "" {
+			c.builder.Set("__unit__", unitNamer.Build(meta.Unit))
 		}
 	}
 
+	err := settings.PromoteResourceAttributes.addPromotedAttributes(c.builder, resourceAttrs, settings.AllowUTF8)
+	if err != nil {
+		return nil, err
+	}
+	if promoteScope {
+		// Scope Name, Version and Schema URL are added after attributes to ensure they are not overwritten by attributes.
+		c.builder.Set("otel_scope_name", scope.name)
+		c.builder.Set("otel_scope_version", scope.version)
+		c.builder.Set("otel_scope_schema_url", scope.schemaURL)
+		var scopeErr error
+		scope.attributes.Range(func(k string, v pcommon.Value) bool {
+			name := "otel_scope_" + k
+			var err error
+			name, err = labelNamer.Build(name)
+			if err != nil && scopeErr == nil {
+				scopeErr = err
+				return false
+			}
+			c.builder.Set(name, v.AsString())
+			return true
+		})
+		if scopeErr != nil {
+			return nil, scopeErr
+		}
+	}
 	// Map service.name + service.namespace to job.
 	if haveServiceName {
 		val := serviceName.AsString()
 		if serviceNamespace, ok := resourceAttrs.Get(conventions.AttributeServiceNamespace); ok {
 			val = fmt.Sprintf("%s/%s", serviceNamespace.AsString(), val)
 		}
-		l[model.JobLabel] = val
+		c.builder.Set(model.JobLabel, val)
 	}
 	// Map service.instance.id to instance.
 	if haveInstanceID {
-		l[model.InstanceLabel] = instance.AsString()
+		c.builder.Set(model.InstanceLabel, instance.AsString())
 	}
 	for key, value := range settings.ExternalLabels {
 		// External labels have already been sanitized.
-		if _, alreadyExists := l[key]; alreadyExists {
+		if existingValue := c.builder.Get(key); existingValue != "" {
 			// Skip external labels if they are overridden by metric attributes.
 			continue
 		}
-		l[key] = value
+		c.builder.Set(key, value)
 	}
 
 	for i := 0; i < len(extras); i += 2 {
@@ -241,8 +181,7 @@ func createAttributes(resource pcommon.Resource, attributes pcommon.Map, scope s
 		}
 
 		name := extras[i]
-		_, found := l[name]
-		if found && logOnOverwrite {
+		if existingValue := c.builder.Get(name); existingValue != "" && logOnOverwrite {
 			log.Println("label " + name + " is overwritten. Check if Prometheus reserved labels are used.")
 		}
 		// internal labels should be maintained.
@@ -253,15 +192,10 @@ func createAttributes(resource pcommon.Resource, attributes pcommon.Map, scope s
 				return nil, err
 			}
 		}
-		l[name] = extras[i+1]
+		c.builder.Set(name, extras[i+1])
 	}
 
-	labels = labels[:0]
-	for k, v := range l {
-		labels = append(labels, prompb.Label{Name: k, Value: v})
-	}
-
-	return labels, nil
+	return c.builder.Labels(), nil
 }
 
 func aggregationTemporality(metric pmetric.Metric) (pmetric.AggregationTemporality, bool, error) {
@@ -287,7 +221,7 @@ func aggregationTemporality(metric pmetric.Metric) (pmetric.AggregationTemporali
 // However, work is under way to resolve this shortcoming through a feature called native histograms custom buckets:
 // https://github.com/prometheus/prometheus/issues/13485.
 func (c *PrometheusConverter) addHistogramDataPoints(ctx context.Context, dataPoints pmetric.HistogramDataPointSlice,
-	resource pcommon.Resource, settings Settings, metadata prompb.MetricMetadata, scope scope,
+	resource pcommon.Resource, settings Settings, baseName string, scope scope, meta metadata.Metadata,
 ) error {
 	for x := 0; x < dataPoints.Len(); x++ {
 		if err := c.everyN.checkContext(ctx); err != nil {
@@ -296,7 +230,8 @@ func (c *PrometheusConverter) addHistogramDataPoints(ctx context.Context, dataPo
 
 		pt := dataPoints.At(x)
 		timestamp := convertTimeStamp(pt.Timestamp())
-		baseLabels, err := createAttributes(resource, pt.Attributes(), scope, settings, nil, false, metadata)
+		startTimestamp := convertTimeStamp(pt.StartTimestamp())
+		baseLabels, err := c.createAttributes(resource, pt.Attributes(), scope, settings, nil, false, meta)
 		if err != nil {
 			return err
 		}
@@ -305,35 +240,36 @@ func (c *PrometheusConverter) addHistogramDataPoints(ctx context.Context, dataPo
 		// omitted
 		if pt.HasSum() {
 			// treat sum as a sample in an individual TimeSeries
-			sum := &prompb.Sample{
-				Value:     pt.Sum(),
-				Timestamp: timestamp,
-			}
+			val := pt.Sum()
 			if pt.Flags().NoRecordedValue() {
-				sum.Value = math.Float64frombits(value.StaleNaN)
+				val = math.Float64frombits(value.StaleNaN)
 			}
 
-			sumlabels := createLabels(metadata.MetricFamilyName+sumStr, baseLabels)
-			c.addSample(sum, sumlabels)
+			sumlabels := c.addLabels(baseName+sumStr, baseLabels)
+			if err := c.appender.AppendSample(baseName, sumlabels, meta, timestamp, startTimestamp, val, nil); err != nil {
+				return err
+			}
 		}
 
 		// treat count as a sample in an individual TimeSeries
-		count := &prompb.Sample{
-			Value:     float64(pt.Count()),
-			Timestamp: timestamp,
-		}
+		val := float64(pt.Count())
 		if pt.Flags().NoRecordedValue() {
-			count.Value = math.Float64frombits(value.StaleNaN)
+			val = math.Float64frombits(value.StaleNaN)
 		}
 
-		countlabels := createLabels(metadata.MetricFamilyName+countStr, baseLabels)
-		c.addSample(count, countlabels)
+		countlabels := c.addLabels(baseName+countStr, baseLabels)
+		if err := c.appender.AppendSample(baseName, countlabels, meta, timestamp, startTimestamp, val, nil); err != nil {
+			return err
+		}
+		exemplars, err := c.getPromExemplars(ctx, pt.Exemplars())
+		if err != nil {
+			return err
+		}
+		nextExemplarIdx := 0
 
 		// cumulative count for conversion to cumulative histogram
 		var cumulativeCount uint64
 
-		var bucketBounds []bucketBoundsData
-
 		// process each bound, based on histograms proto definition, # of buckets = # of explicit bounds + 1
 		for i := 0; i < pt.ExplicitBounds().Len() && i < pt.BucketCounts().Len(); i++ {
 			if err := c.everyN.checkContext(ctx); err != nil {
@@ -342,116 +278,110 @@ func (c *PrometheusConverter) addHistogramDataPoints(ctx context.Context, dataPo
 
 			bound := pt.ExplicitBounds().At(i)
 			cumulativeCount += pt.BucketCounts().At(i)
-			bucket := &prompb.Sample{
-				Value:     float64(cumulativeCount),
-				Timestamp: timestamp,
+
+			// Find exemplars that belong to this bucket. Both exemplars and
+			// buckets are sorted in ascending order.
+			var currentBucketExemplars []exemplar.Exemplar
+			for ; nextExemplarIdx < len(exemplars); nextExemplarIdx++ {
+				ex := exemplars[nextExemplarIdx]
+				if ex.Value > bound {
+					// This exemplar belongs in a higher bucket.
+					break
+				}
+				currentBucketExemplars = append(currentBucketExemplars, ex)
 			}
+			val := float64(cumulativeCount)
 			if pt.Flags().NoRecordedValue() {
-				bucket.Value = math.Float64frombits(value.StaleNaN)
+				val = math.Float64frombits(value.StaleNaN)
 			}
 			boundStr := strconv.FormatFloat(bound, 'f', -1, 64)
-			labels := createLabels(metadata.MetricFamilyName+bucketStr, baseLabels, leStr, boundStr)
-			ts := c.addSample(bucket, labels)
-
-			bucketBounds = append(bucketBounds, bucketBoundsData{ts: ts, bound: bound})
+			labels := c.addLabels(baseName+bucketStr, baseLabels, leStr, boundStr)
+			if err := c.appender.AppendSample(baseName, labels, meta, timestamp, startTimestamp, val, currentBucketExemplars); err != nil {
+				return err
+			}
 		}
 		// add le=+Inf bucket
-		infBucket := &prompb.Sample{
-			Timestamp: timestamp,
-		}
+		val = float64(pt.Count())
 		if pt.Flags().NoRecordedValue() {
-			infBucket.Value = math.Float64frombits(value.StaleNaN)
-		} else {
-			infBucket.Value = float64(pt.Count())
+			val = math.Float64frombits(value.StaleNaN)
 		}
-		infLabels := createLabels(metadata.MetricFamilyName+bucketStr, baseLabels, leStr, pInfStr)
-		ts := c.addSample(infBucket, infLabels)
-
-		bucketBounds = append(bucketBounds, bucketBoundsData{ts: ts, bound: math.Inf(1)})
-		if err := c.addExemplars(ctx, pt, bucketBounds); err != nil {
+		infLabels := c.addLabels(baseName+bucketStr, baseLabels, leStr, pInfStr)
+		if err := c.appender.AppendSample(baseName, infLabels, meta, timestamp, startTimestamp, val, exemplars[nextExemplarIdx:]); err != nil {
 			return err
 		}
 
-		startTimestamp := pt.StartTimestamp()
-		if settings.ExportCreatedMetric && startTimestamp != 0 {
-			labels := createLabels(metadata.MetricFamilyName+createdSuffix, baseLabels)
-			c.addTimeSeriesIfNeeded(labels, startTimestamp, pt.Timestamp())
+		if settings.ExportCreatedMetric && pt.StartTimestamp() != 0 {
+			labels := c.addLabels(baseName+createdSuffix, baseLabels)
+			if c.timeSeriesIsNew(labels) {
+				if err := c.appender.AppendSample(baseName, labels, meta, timestamp, 0, float64(startTimestamp), nil); err != nil {
+					return err
+				}
+			}
 		}
 	}
 
 	return nil
 }
 
-type exemplarType interface {
-	pmetric.ExponentialHistogramDataPoint | pmetric.HistogramDataPoint | pmetric.NumberDataPoint
-	Exemplars() pmetric.ExemplarSlice
-}
-
-func getPromExemplars[T exemplarType](ctx context.Context, everyN *everyNTimes, pt T) ([]prompb.Exemplar, error) {
-	promExemplars := make([]prompb.Exemplar, 0, pt.Exemplars().Len())
-	for i := 0; i < pt.Exemplars().Len(); i++ {
-		if err := everyN.checkContext(ctx); err != nil {
+func (c *PrometheusConverter) getPromExemplars(ctx context.Context, exemplars pmetric.ExemplarSlice) ([]exemplar.Exemplar, error) {
+	if exemplars.Len() == 0 {
+		return nil, nil
+	}
+	outputExemplars := make([]exemplar.Exemplar, 0, exemplars.Len())
+	for i := 0; i < exemplars.Len(); i++ {
+		if err := c.everyN.checkContext(ctx); err != nil {
 			return nil, err
 		}
 
-		exemplar := pt.Exemplars().At(i)
+		ex := exemplars.At(i)
 		exemplarRunes := 0
 
-		promExemplar := prompb.Exemplar{
-			Timestamp: timestamp.FromTime(exemplar.Timestamp().AsTime()),
+		ts := timestamp.FromTime(ex.Timestamp().AsTime())
+		newExemplar := exemplar.Exemplar{
+			Ts:    ts,
+			HasTs: ts != 0,
 		}
-		switch exemplar.ValueType() {
+		c.scratchBuilder.Reset()
+		switch ex.ValueType() {
 		case pmetric.ExemplarValueTypeInt:
-			promExemplar.Value = float64(exemplar.IntValue())
+			newExemplar.Value = float64(ex.IntValue())
 		case pmetric.ExemplarValueTypeDouble:
-			promExemplar.Value = exemplar.DoubleValue()
+			newExemplar.Value = ex.DoubleValue()
 		default:
-			return nil, fmt.Errorf("unsupported exemplar value type: %v", exemplar.ValueType())
+			return nil, fmt.Errorf("unsupported exemplar value type: %v", ex.ValueType())
 		}
 
-		if traceID := exemplar.TraceID(); !traceID.IsEmpty() {
+		if traceID := ex.TraceID(); !traceID.IsEmpty() {
 			val := hex.EncodeToString(traceID[:])
 			exemplarRunes += utf8.RuneCountInString(traceIDKey) + utf8.RuneCountInString(val)
-			promLabel := prompb.Label{
-				Name:  traceIDKey,
-				Value: val,
-			}
-			promExemplar.Labels = append(promExemplar.Labels, promLabel)
+			c.scratchBuilder.Add(traceIDKey, val)
 		}
-		if spanID := exemplar.SpanID(); !spanID.IsEmpty() {
+		if spanID := ex.SpanID(); !spanID.IsEmpty() {
 			val := hex.EncodeToString(spanID[:])
 			exemplarRunes += utf8.RuneCountInString(spanIDKey) + utf8.RuneCountInString(val)
-			promLabel := prompb.Label{
-				Name:  spanIDKey,
-				Value: val,
-			}
-			promExemplar.Labels = append(promExemplar.Labels, promLabel)
+			c.scratchBuilder.Add(spanIDKey, val)
 		}
 
-		attrs := exemplar.FilteredAttributes()
-		labelsFromAttributes := make([]prompb.Label, 0, attrs.Len())
+		attrs := ex.FilteredAttributes()
 		attrs.Range(func(key string, value pcommon.Value) bool {
-			val := value.AsString()
-			exemplarRunes += utf8.RuneCountInString(key) + utf8.RuneCountInString(val)
-			promLabel := prompb.Label{
-				Name:  key,
-				Value: val,
-			}
-
-			labelsFromAttributes = append(labelsFromAttributes, promLabel)
-
+			exemplarRunes += utf8.RuneCountInString(key) + utf8.RuneCountInString(value.AsString())
 			return true
 		})
-		if exemplarRunes <= maxExemplarRunes {
-			// only append filtered attributes if it does not cause exemplar
-			// labels to exceed the max number of runes
-			promExemplar.Labels = append(promExemplar.Labels, labelsFromAttributes...)
-		}
 
-		promExemplars = append(promExemplars, promExemplar)
+		// Only append filtered attributes if it does not cause exemplar
+		// labels to exceed the max number of runes.
+		if exemplarRunes <= maxExemplarRunes {
+			attrs.Range(func(key string, value pcommon.Value) bool {
+				c.scratchBuilder.Add(key, value.AsString())
+				return true
+			})
+		}
+		c.scratchBuilder.Sort()
+		newExemplar.Labels = modelLabels.NewFromSorted(c.scratchBuilder.Labels())
+		outputExemplars = append(outputExemplars, newExemplar)
 	}
 
-	return promExemplars, nil
+	return outputExemplars, nil
 }
 
 // findMinAndMaxTimestamps returns the minimum of minTimestamp and the earliest timestamp in metric and
@@ -500,7 +430,7 @@ func findMinAndMaxTimestamps(metric pmetric.Metric, minTimestamp, maxTimestamp p
 }
 
 func (c *PrometheusConverter) addSummaryDataPoints(ctx context.Context, dataPoints pmetric.SummaryDataPointSlice, resource pcommon.Resource,
-	settings Settings, metadata prompb.MetricMetadata, scope scope,
+	settings Settings, baseName string, scope scope, meta metadata.Metadata,
 ) error {
 	for x := 0; x < dataPoints.Len(); x++ {
 		if err := c.everyN.checkContext(ctx); err != nil {
@@ -509,75 +439,73 @@ func (c *PrometheusConverter) addSummaryDataPoints(ctx context.Context, dataPoin
 
 		pt := dataPoints.At(x)
 		timestamp := convertTimeStamp(pt.Timestamp())
-		baseLabels, err := createAttributes(resource, pt.Attributes(), scope, settings, nil, false, metadata)
+		startTimestamp := convertTimeStamp(pt.StartTimestamp())
+		baseLabels, err := c.createAttributes(resource, pt.Attributes(), scope, settings, nil, false, meta)
 		if err != nil {
 			return err
 		}
 
 		// treat sum as a sample in an individual TimeSeries
-		sum := &prompb.Sample{
-			Value:     pt.Sum(),
-			Timestamp: timestamp,
-		}
+		val := pt.Sum()
 		if pt.Flags().NoRecordedValue() {
-			sum.Value = math.Float64frombits(value.StaleNaN)
+			val = math.Float64frombits(value.StaleNaN)
 		}
 		// sum and count of the summary should append suffix to baseName
-		sumlabels := createLabels(metadata.MetricFamilyName+sumStr, baseLabels)
-		c.addSample(sum, sumlabels)
+		sumlabels := c.addLabels(baseName+sumStr, baseLabels)
+		if err := c.appender.AppendSample(baseName, sumlabels, meta, timestamp, startTimestamp, val, nil); err != nil {
+			return err
+		}
 
 		// treat count as a sample in an individual TimeSeries
-		count := &prompb.Sample{
-			Value:     float64(pt.Count()),
-			Timestamp: timestamp,
-		}
+		val = float64(pt.Count())
 		if pt.Flags().NoRecordedValue() {
-			count.Value = math.Float64frombits(value.StaleNaN)
+			val = math.Float64frombits(value.StaleNaN)
+		}
+		countlabels := c.addLabels(baseName+countStr, baseLabels)
+		if err := c.appender.AppendSample(baseName, countlabels, meta, timestamp, startTimestamp, val, nil); err != nil {
+			return err
 		}
-		countlabels := createLabels(metadata.MetricFamilyName+countStr, baseLabels)
-		c.addSample(count, countlabels)
 
 		// process each percentile/quantile
 		for i := 0; i < pt.QuantileValues().Len(); i++ {
 			qt := pt.QuantileValues().At(i)
-			quantile := &prompb.Sample{
-				Value:     qt.Value(),
-				Timestamp: timestamp,
-			}
+			val = qt.Value()
 			if pt.Flags().NoRecordedValue() {
-				quantile.Value = math.Float64frombits(value.StaleNaN)
+				val = math.Float64frombits(value.StaleNaN)
 			}
 			percentileStr := strconv.FormatFloat(qt.Quantile(), 'f', -1, 64)
-			qtlabels := createLabels(metadata.MetricFamilyName, baseLabels, quantileStr, percentileStr)
-			c.addSample(quantile, qtlabels)
+			qtlabels := c.addLabels(baseName, baseLabels, quantileStr, percentileStr)
+			if err := c.appender.AppendSample(baseName, qtlabels, meta, timestamp, startTimestamp, val, nil); err != nil {
+				return err
+			}
 		}
 
-		startTimestamp := pt.StartTimestamp()
-		if settings.ExportCreatedMetric && startTimestamp != 0 {
-			createdLabels := createLabels(metadata.MetricFamilyName+createdSuffix, baseLabels)
-			c.addTimeSeriesIfNeeded(createdLabels, startTimestamp, pt.Timestamp())
+		if settings.ExportCreatedMetric && pt.StartTimestamp() != 0 {
+			createdLabels := c.addLabels(baseName+createdSuffix, baseLabels)
+			if c.timeSeriesIsNew(createdLabels) {
+				if err := c.appender.AppendSample(baseName, createdLabels, meta, timestamp, 0, float64(startTimestamp), nil); err != nil {
+					return err
+				}
+			}
 		}
 	}
 
 	return nil
 }
 
-// createLabels returns a copy of baseLabels, adding to it the pair model.MetricNameLabel=name.
+// addLabels returns a copy of baseLabels, adding to it the pair model.MetricNameLabel=name.
 // If extras are provided, corresponding label pairs are also added to the returned slice.
 // If extras is uneven length, the last (unpaired) extra will be ignored.
-func createLabels(name string, baseLabels []prompb.Label, extras ...string) []prompb.Label {
-	extraLabelCount := len(extras) / 2
-	labels := make([]prompb.Label, len(baseLabels), len(baseLabels)+extraLabelCount+1) // +1 for name
-	copy(labels, baseLabels)
+func (c *PrometheusConverter) addLabels(name string, baseLabels labels.Labels, extras ...string) labels.Labels {
+	c.builder.Reset(baseLabels)
 
 	n := len(extras)
 	n -= n % 2
 	for extrasIdx := 0; extrasIdx < n; extrasIdx += 2 {
-		labels = append(labels, prompb.Label{Name: extras[extrasIdx], Value: extras[extrasIdx+1]})
+		c.builder.Set(extras[extrasIdx], extras[extrasIdx+1])
 	}
-
-	labels = append(labels, prompb.Label{Name: model.MetricNameLabel, Value: name})
-	return labels
+	c.builder.Set(model.MetricNameLabel, name)
+	return c.builder.Labels()
 }
 
 // addTypeAndUnitLabels appends type and unit labels to the given labels slice.
@@ -596,57 +524,35 @@ func addTypeAndUnitLabels(labels []prompb.Label, metadata prompb.MetricMetadata,
 
 // getOrCreateTimeSeries returns the time series corresponding to the label set if existent, and false.
 // Otherwise it creates a new one and returns that, and true.
-func (c *PrometheusConverter) getOrCreateTimeSeries(lbls []prompb.Label) (*prompb.TimeSeries, bool) {
-	h := timeSeriesSignature(lbls)
-	ts := c.unique[h]
-	if ts != nil {
-		if isSameMetric(ts, lbls) {
+func (c *PrometheusConverter) timeSeriesIsNew(lbls labels.Labels) bool {
+	h := lbls.Hash()
+	uLabels, ok := c.unique[h]
+	if ok {
+		if labels.Equal(uLabels, lbls) {
 			// We already have this metric
-			return ts, false
+			return false
 		}
 
 		// Look for a matching conflict
-		for _, cTS := range c.conflicts[h] {
-			if isSameMetric(cTS, lbls) {
+		for _, cLabels := range c.conflicts[h] {
+			if labels.Equal(cLabels, lbls) {
 				// We already have this metric
-				return cTS, false
+				return false
 			}
 		}
 
 		// New conflict
-		ts = &prompb.TimeSeries{
-			Labels: lbls,
-		}
-		c.conflicts[h] = append(c.conflicts[h], ts)
-		return ts, true
+		c.conflicts[h] = append(c.conflicts[h], uLabels)
+		return true
 	}
 
 	// This metric is new
-	ts = &prompb.TimeSeries{
-		Labels: lbls,
-	}
-	c.unique[h] = ts
-	return ts, true
-}
-
-// addTimeSeriesIfNeeded adds a corresponding time series if it doesn't already exist.
-// If the time series doesn't already exist, it gets added with startTimestamp for its value and timestamp for its timestamp,
-// both converted to milliseconds.
-func (c *PrometheusConverter) addTimeSeriesIfNeeded(lbls []prompb.Label, startTimestamp, timestamp pcommon.Timestamp) {
-	ts, created := c.getOrCreateTimeSeries(lbls)
-	if created {
-		ts.Samples = []prompb.Sample{
-			{
-				// convert ns to ms
-				Value:     float64(convertTimeStamp(startTimestamp)),
-				Timestamp: convertTimeStamp(timestamp),
-			},
-		}
-	}
+	c.unique[h] = uLabels
+	return true
 }
 
 // addResourceTargetInfo converts the resource to the target info metric.
-func addResourceTargetInfo(resource pcommon.Resource, settings Settings, earliestTimestamp, latestTimestamp time.Time, converter *PrometheusConverter) error {
+func (c *PrometheusConverter) addResourceTargetInfo(resource pcommon.Resource, settings Settings, earliestTimestamp, latestTimestamp time.Time) error {
 	if settings.DisableTargetInfo {
 		return nil
 	}
@@ -679,17 +585,21 @@ func addResourceTargetInfo(resource pcommon.Resource, settings Settings, earlies
 		// Do not pass identifying attributes as ignoreAttrs below.
 		identifyingAttrs = nil
 	}
-	labels, err := createAttributes(resource, attributes, scope{}, settings, identifyingAttrs, false, prompb.MetricMetadata{}, model.MetricNameLabel, name)
+	meta := metadata.Metadata{
+		Type: model.MetricTypeGauge,
+		Help: "Target metadata",
+	}
+	// TODO: should target info have the __type__ metadata label?
+	lbls, err := c.createAttributes(resource, attributes, scope{}, settings, identifyingAttrs, false, metadata.Metadata{}, model.MetricNameLabel, name)
 	if err != nil {
 		return err
 	}
 	haveIdentifier := false
-	for _, l := range labels {
+	lbls.Range(func(l modelLabels.Label) {
 		if l.Name == model.JobLabel || l.Name == model.InstanceLabel {
 			haveIdentifier = true
-			break
 		}
-	}
+	})
 
 	if !haveIdentifier {
 		// We need at least one identifying label to generate target_info.
@@ -704,18 +614,13 @@ func addResourceTargetInfo(resource pcommon.Resource, settings Settings, earlies
 		settings.LookbackDelta = defaultLookbackDelta
 	}
 	interval := settings.LookbackDelta / 2
-	ts, _ := converter.getOrCreateTimeSeries(labels)
-	for timestamp := earliestTimestamp; timestamp.Before(latestTimestamp); timestamp = timestamp.Add(interval) {
-		ts.Samples = append(ts.Samples, prompb.Sample{
-			Value:     float64(1),
-			Timestamp: timestamp.UnixMilli(),
-		})
+	timestamp := earliestTimestamp
+	for ; timestamp.Before(latestTimestamp); timestamp = timestamp.Add(interval) {
+		if err := c.appender.AppendSample(name, lbls, meta, timestamp.UnixMilli(), 0, float64(1), nil); err != nil {
+			return err
+		}
 	}
-	ts.Samples = append(ts.Samples, prompb.Sample{
-		Value:     float64(1),
-		Timestamp: latestTimestamp.UnixMilli(),
-	})
-	return nil
+	return c.appender.AppendSample(name, lbls, meta, latestTimestamp.UnixMilli(), 0, float64(1), nil)
 }
 
 // convertTimeStamp converts OTLP timestamp in ns to timestamp in ms.

storage/remote/otlptranslator/prometheusremotewrite/histograms.go

@@ -26,8 +26,8 @@ import (
 	"go.opentelemetry.io/collector/pdata/pmetric"
 
 	"github.com/prometheus/prometheus/model/histogram"
+	"github.com/prometheus/prometheus/model/metadata"
 	"github.com/prometheus/prometheus/model/value"
-	"github.com/prometheus/prometheus/prompb"
 	"github.com/prometheus/prometheus/util/annotations"
 )
 
@@ -36,7 +36,8 @@ const defaultZeroThreshold = 1e-128
 // addExponentialHistogramDataPoints adds OTel exponential histogram data points to the corresponding time series
 // as native histogram samples.
 func (c *PrometheusConverter) addExponentialHistogramDataPoints(ctx context.Context, dataPoints pmetric.ExponentialHistogramDataPointSlice,
-	resource pcommon.Resource, settings Settings, metadata prompb.MetricMetadata, temporality pmetric.AggregationTemporality, scope scope,
+	resource pcommon.Resource, settings Settings, promName string, temporality pmetric.AggregationTemporality,
+	scope scope, meta metadata.Metadata,
 ) (annotations.Annotations, error) {
 	var annots annotations.Annotations
 	for x := 0; x < dataPoints.Len(); x++ {
@@ -46,34 +47,36 @@ func (c *PrometheusConverter) addExponentialHistogramDataPoints(ctx context.Cont
 
 		pt := dataPoints.At(x)
 
-		histogram, ws, err := exponentialToNativeHistogram(pt, temporality)
+		hp, ws, err := exponentialToNativeHistogram(pt, temporality)
 		annots.Merge(ws)
 		if err != nil {
 			return annots, err
 		}
 
-		lbls, err := createAttributes(
+		lbls, err := c.createAttributes(
 			resource,
 			pt.Attributes(),
 			scope,
 			settings,
 			nil,
 			true,
-			metadata,
+			meta,
 			model.MetricNameLabel,
-			metadata.MetricFamilyName,
+			promName,
 		)
-		if err != nil {
-			return nil, err
-		}
-		ts, _ := c.getOrCreateTimeSeries(lbls)
-		ts.Histograms = append(ts.Histograms, histogram)
-
-		exemplars, err := getPromExemplars[pmetric.ExponentialHistogramDataPoint](ctx, &c.everyN, pt)
 		if err != nil {
 			return annots, err
 		}
-		ts.Exemplars = append(ts.Exemplars, exemplars...)
+		ts := convertTimeStamp(pt.Timestamp())
+		ct := convertTimeStamp(pt.StartTimestamp())
+		exemplars, err := c.getPromExemplars(ctx, pt.Exemplars())
+		if err != nil {
+			return annots, err
+		}
+		// OTel exponential histograms are always Int Histograms.
+		if err = c.appender.AppendHistogram(promName, lbls, meta, ts, ct, hp, exemplars); err != nil {
+			return annots, err
+		}
 	}
 
 	return annots, nil
@@ -81,11 +84,11 @@ func (c *PrometheusConverter) addExponentialHistogramDataPoints(ctx context.Cont
 
 // exponentialToNativeHistogram translates an OTel Exponential Histogram data point
 // to a Prometheus Native Histogram.
-func exponentialToNativeHistogram(p pmetric.ExponentialHistogramDataPoint, temporality pmetric.AggregationTemporality) (prompb.Histogram, annotations.Annotations, error) {
+func exponentialToNativeHistogram(p pmetric.ExponentialHistogramDataPoint, temporality pmetric.AggregationTemporality) (*histogram.Histogram, annotations.Annotations, error) {
 	var annots annotations.Annotations
 	scale := p.Scale()
 	if scale < -4 {
-		return prompb.Histogram{}, annots,
+		return nil, annots,
 			fmt.Errorf("cannot convert exponential to native histogram."+
 				" Scale must be >= -4, was %d", scale)
 	}
@@ -108,41 +111,36 @@ func exponentialToNativeHistogram(p pmetric.ExponentialHistogramDataPoint, tempo
 	// need to know here if it was used for the detection.
 	// Ref: https://github.com/open-telemetry/opentelemetry-collector-contrib/pull/28663#issuecomment-1810577303
 	// Counter reset detection in Prometheus: https://github.com/prometheus/prometheus/blob/f997c72f294c0f18ca13fa06d51889af04135195/tsdb/chunkenc/histogram.go#L232
-	resetHint := prompb.Histogram_UNKNOWN
+	resetHint := histogram.UnknownCounterReset
 
 	if temporality == pmetric.AggregationTemporalityDelta {
 		// If the histogram has delta temporality, set the reset hint to gauge to avoid unnecessary chunk cutting.
 		// We're in an early phase of implementing delta support (proposal: https://github.com/prometheus/proposals/pull/48/).
 		// This might be changed to a different hint name as gauge type might be misleading for samples that should be
 		// summed over time.
-		resetHint = prompb.Histogram_GAUGE
+		resetHint = histogram.GaugeType
 	}
-
-	h := prompb.Histogram{
-		ResetHint: resetHint,
-		Schema:    scale,
-
-		ZeroCount: &prompb.Histogram_ZeroCountInt{ZeroCountInt: p.ZeroCount()},
+	h := &histogram.Histogram{
+		CounterResetHint: resetHint,
+		Schema:           scale,
 		// TODO use zero_threshold, if set, see
 		// https://github.com/open-telemetry/opentelemetry-proto/pull/441
-		ZeroThreshold: defaultZeroThreshold,
-
-		PositiveSpans:  pSpans,
-		PositiveDeltas: pDeltas,
-		NegativeSpans:  nSpans,
-		NegativeDeltas: nDeltas,
-
-		Timestamp: convertTimeStamp(p.Timestamp()),
+		ZeroThreshold:   defaultZeroThreshold,
+		ZeroCount:       p.ZeroCount(),
+		PositiveSpans:   pSpans,
+		PositiveBuckets: pDeltas,
+		NegativeSpans:   nSpans,
+		NegativeBuckets: nDeltas,
 	}
 
 	if p.Flags().NoRecordedValue() {
 		h.Sum = math.Float64frombits(value.StaleNaN)
-		h.Count = &prompb.Histogram_CountInt{CountInt: value.StaleNaN}
+		h.Count = value.StaleNaN
 	} else {
 		if p.HasSum() {
 			h.Sum = p.Sum()
 		}
-		h.Count = &prompb.Histogram_CountInt{CountInt: p.Count()}
+		h.Count = p.Count()
 		if p.Count() == 0 && h.Sum != 0 {
 			annots.Add(fmt.Errorf("exponential histogram data point has zero count, but non-zero sum: %f", h.Sum))
 		}
@@ -167,13 +165,13 @@ func exponentialToNativeHistogram(p pmetric.ExponentialHistogramDataPoint, tempo
 //
 // When converting from OTel Explicit Histograms to Native Histograms with Custom Buckets,
 // the bucket indexes are not scaled, and the indices are not adjusted by 1.
-func convertBucketsLayout(bucketCounts []uint64, offset, scaleDown int32, adjustOffset bool) ([]prompb.BucketSpan, []int64) {
+func convertBucketsLayout(bucketCounts []uint64, offset, scaleDown int32, adjustOffset bool) ([]histogram.Span, []int64) {
 	if len(bucketCounts) == 0 {
 		return nil, nil
 	}
 
 	var (
-		spans     []prompb.BucketSpan
+		spans     []histogram.Span
 		deltas    []int64
 		count     int64
 		prevCount int64
@@ -196,7 +194,7 @@ func convertBucketsLayout(bucketCounts []uint64, offset, scaleDown int32, adjust
 		initialOffset = initialOffset>>scaleDown + 1
 	}
 
-	spans = append(spans, prompb.BucketSpan{
+	spans = append(spans, histogram.Span{
 		Offset: initialOffset,
 		Length: 0,
 	})
@@ -217,7 +215,7 @@ func convertBucketsLayout(bucketCounts []uint64, offset, scaleDown int32, adjust
 			// We have to create a new span, because we have found a gap
 			// of more than two buckets. The constant 2 is copied from the logic in
 			// https://github.com/prometheus/client_golang/blob/27f0506d6ebbb117b6b697d0552ee5be2502c5f2/prometheus/histogram.go#L1296
-			spans = append(spans, prompb.BucketSpan{
+			spans = append(spans, histogram.Span{
 				Offset: gap,
 				Length: 0,
 			})
@@ -239,7 +237,7 @@ func convertBucketsLayout(bucketCounts []uint64, offset, scaleDown int32, adjust
 		// We have to create a new span, because we have found a gap
 		// of more than two buckets. The constant 2 is copied from the logic in
 		// https://github.com/prometheus/client_golang/blob/27f0506d6ebbb117b6b697d0552ee5be2502c5f2/prometheus/histogram.go#L1296
-		spans = append(spans, prompb.BucketSpan{
+		spans = append(spans, histogram.Span{
 			Offset: gap,
 			Length: 0,
 		})
@@ -256,7 +254,8 @@ func convertBucketsLayout(bucketCounts []uint64, offset, scaleDown int32, adjust
 }
 
 func (c *PrometheusConverter) addCustomBucketsHistogramDataPoints(ctx context.Context, dataPoints pmetric.HistogramDataPointSlice,
-	resource pcommon.Resource, settings Settings, metadata prompb.MetricMetadata, temporality pmetric.AggregationTemporality, scope scope,
+	resource pcommon.Resource, settings Settings, promName string, temporality pmetric.AggregationTemporality,
+	scope scope, meta metadata.Metadata,
 ) (annotations.Annotations, error) {
 	var annots annotations.Annotations
 
@@ -267,41 +266,41 @@ func (c *PrometheusConverter) addCustomBucketsHistogramDataPoints(ctx context.Co
 
 		pt := dataPoints.At(x)
 
-		histogram, ws, err := explicitHistogramToCustomBucketsHistogram(pt, temporality)
+		hp, ws, err := explicitHistogramToCustomBucketsHistogram(pt, temporality)
 		annots.Merge(ws)
 		if err != nil {
 			return annots, err
 		}
 
-		lbls, err := createAttributes(
+		lbls, err := c.createAttributes(
 			resource,
 			pt.Attributes(),
 			scope,
 			settings,
 			nil,
 			true,
-			metadata,
+			meta,
 			model.MetricNameLabel,
-			metadata.MetricFamilyName,
+			promName,
 		)
-		if err != nil {
-			return nil, err
-		}
-
-		ts, _ := c.getOrCreateTimeSeries(lbls)
-		ts.Histograms = append(ts.Histograms, histogram)
-
-		exemplars, err := getPromExemplars[pmetric.HistogramDataPoint](ctx, &c.everyN, pt)
 		if err != nil {
 			return annots, err
 		}
-		ts.Exemplars = append(ts.Exemplars, exemplars...)
+		ts := convertTimeStamp(pt.Timestamp())
+		ct := convertTimeStamp(pt.StartTimestamp())
+		exemplars, err := c.getPromExemplars(ctx, pt.Exemplars())
+		if err != nil {
+			return annots, err
+		}
+		if err = c.appender.AppendHistogram(promName, lbls, meta, ts, ct, hp, exemplars); err != nil {
+			return annots, err
+		}
 	}
 
 	return annots, nil
 }
 
-func explicitHistogramToCustomBucketsHistogram(p pmetric.HistogramDataPoint, temporality pmetric.AggregationTemporality) (prompb.Histogram, annotations.Annotations, error) {
+func explicitHistogramToCustomBucketsHistogram(p pmetric.HistogramDataPoint, temporality pmetric.AggregationTemporality) (*histogram.Histogram, annotations.Annotations, error) {
 	var annots annotations.Annotations
 
 	buckets := p.BucketCounts().AsRaw()
@@ -318,23 +317,22 @@ func explicitHistogramToCustomBucketsHistogram(p pmetric.HistogramDataPoint, tem
 	// need to know here if it was used for the detection.
 	// Ref: https://github.com/open-telemetry/opentelemetry-collector-contrib/pull/28663#issuecomment-1810577303
 	// Counter reset detection in Prometheus: https://github.com/prometheus/prometheus/blob/f997c72f294c0f18ca13fa06d51889af04135195/tsdb/chunkenc/histogram.go#L232
-	resetHint := prompb.Histogram_UNKNOWN
+	resetHint := histogram.UnknownCounterReset
 
 	if temporality == pmetric.AggregationTemporalityDelta {
 		// If the histogram has delta temporality, set the reset hint to gauge to avoid unnecessary chunk cutting.
 		// We're in an early phase of implementing delta support (proposal: https://github.com/prometheus/proposals/pull/48/).
 		// This might be changed to a different hint name as gauge type might be misleading for samples that should be
 		// summed over time.
-		resetHint = prompb.Histogram_GAUGE
+		resetHint = histogram.GaugeType
 	}
 
 	// TODO(carrieedwards): Add setting to limit maximum bucket count
-	h := prompb.Histogram{
-		ResetHint: resetHint,
-		Schema:    histogram.CustomBucketsSchema,
-
-		PositiveSpans:  positiveSpans,
-		PositiveDeltas: positiveDeltas,
+	h := &histogram.Histogram{
+		CounterResetHint: resetHint,
+		Schema:           histogram.CustomBucketsSchema,
+		PositiveSpans:    positiveSpans,
+		PositiveBuckets:  positiveDeltas,
 		// Note: OTel explicit histograms have an implicit +Inf bucket, which has a lower bound
 		// of the last element in the explicit_bounds array.
 		// This is similar to the custom_values array in native histograms with custom buckets.
@@ -342,18 +340,16 @@ func explicitHistogramToCustomBucketsHistogram(p pmetric.HistogramDataPoint, tem
 		// can be mapped directly to the custom_values array.
 		// See: https://github.com/open-telemetry/opentelemetry-proto/blob/d7770822d70c7bd47a6891fc9faacc66fc4af3d3/opentelemetry/proto/metrics/v1/metrics.proto#L469
 		CustomValues: p.ExplicitBounds().AsRaw(),
-
-		Timestamp: convertTimeStamp(p.Timestamp()),
 	}
 
 	if p.Flags().NoRecordedValue() {
 		h.Sum = math.Float64frombits(value.StaleNaN)
-		h.Count = &prompb.Histogram_CountInt{CountInt: value.StaleNaN}
+		h.Count = value.StaleNaN
 	} else {
 		if p.HasSum() {
 			h.Sum = p.Sum()
 		}
-		h.Count = &prompb.Histogram_CountInt{CountInt: p.Count()}
+		h.Count = p.Count()
 		if p.Count() == 0 && h.Sum != 0 {
 			annots.Add(fmt.Errorf("histogram data point has zero count, but non-zero sum: %f", h.Sum))
 		}

storage/remote/otlptranslator/prometheusremotewrite/histograms_test.go

@@ -28,11 +28,14 @@ import (
 	"go.opentelemetry.io/collector/pdata/pcommon"
 	"go.opentelemetry.io/collector/pdata/pmetric"
 
-	"github.com/prometheus/prometheus/prompb"
+	"github.com/prometheus/prometheus/model/exemplar"
+	"github.com/prometheus/prometheus/model/histogram"
+	"github.com/prometheus/prometheus/model/metadata"
+	"github.com/prometheus/prometheus/storage/remote/otlptranslator/prometheusremotewrite/labels"
 )
 
 type expectedBucketLayout struct {
-	wantSpans  []prompb.BucketSpan
+	wantSpans  []histogram.Span
 	wantDeltas []int64
 }
 
@@ -52,7 +55,7 @@ func TestConvertBucketsLayout(t *testing.T) {
 			},
 			wantLayout: map[int32]expectedBucketLayout{
 				0: {
-					wantSpans: []prompb.BucketSpan{
+					wantSpans: []histogram.Span{
 						{
 							Offset: 1,
 							Length: 4,
@@ -61,7 +64,7 @@ func TestConvertBucketsLayout(t *testing.T) {
 					wantDeltas: []int64{4, -1, -1, -1},
 				},
 				1: {
-					wantSpans: []prompb.BucketSpan{
+					wantSpans: []histogram.Span{
 						{
 							Offset: 1,
 							Length: 2,
@@ -71,7 +74,7 @@ func TestConvertBucketsLayout(t *testing.T) {
 					wantDeltas: []int64{7, -4},
 				},
 				2: {
-					wantSpans: []prompb.BucketSpan{
+					wantSpans: []histogram.Span{
 						{
 							Offset: 1,
 							Length: 1,
@@ -92,7 +95,7 @@ func TestConvertBucketsLayout(t *testing.T) {
 			},
 			wantLayout: map[int32]expectedBucketLayout{
 				0: {
-					wantSpans: []prompb.BucketSpan{
+					wantSpans: []histogram.Span{
 						{
 							Offset: 2,
 							Length: 4,
@@ -101,7 +104,7 @@ func TestConvertBucketsLayout(t *testing.T) {
 					wantDeltas: []int64{4, -1, -1, -1},
 				},
 				1: {
-					wantSpans: []prompb.BucketSpan{
+					wantSpans: []histogram.Span{
 						{
 							Offset: 1,
 							Length: 3,
@@ -110,7 +113,7 @@ func TestConvertBucketsLayout(t *testing.T) {
 					wantDeltas: []int64{4, 1, -4}, // 0+4, 3+2, 1+0 = 4, 5, 1
 				},
 				2: {
-					wantSpans: []prompb.BucketSpan{
+					wantSpans: []histogram.Span{
 						{
 							Offset: 1,
 							Length: 2,
@@ -130,7 +133,7 @@ func TestConvertBucketsLayout(t *testing.T) {
 			},
 			wantLayout: map[int32]expectedBucketLayout{
 				0: {
-					wantSpans: []prompb.BucketSpan{
+					wantSpans: []histogram.Span{
 						{
 							Offset: 5,
 							Length: 4,
@@ -143,7 +146,7 @@ func TestConvertBucketsLayout(t *testing.T) {
 					wantDeltas: []int64{4, -2, -2, 2, -1},
 				},
 				1: {
-					wantSpans: []prompb.BucketSpan{
+					wantSpans: []histogram.Span{
 						{
 							Offset: 3,
 							Length: 2,
@@ -158,7 +161,7 @@ func TestConvertBucketsLayout(t *testing.T) {
 					wantDeltas: []int64{6, -4, -1},
 				},
 				2: {
-					wantSpans: []prompb.BucketSpan{
+					wantSpans: []histogram.Span{
 						{
 							Offset: 2,
 							Length: 1,
@@ -185,7 +188,7 @@ func TestConvertBucketsLayout(t *testing.T) {
 			},
 			wantLayout: map[int32]expectedBucketLayout{
 				0: {
-					wantSpans: []prompb.BucketSpan{
+					wantSpans: []histogram.Span{
 						{
 							Offset: 5,
 							Length: 4,
@@ -198,7 +201,7 @@ func TestConvertBucketsLayout(t *testing.T) {
 					wantDeltas: []int64{4, -2, -2, 2, -1},
 				},
 				1: {
-					wantSpans: []prompb.BucketSpan{
+					wantSpans: []histogram.Span{
 						{
 							Offset: 3,
 							Length: 2,
@@ -213,7 +216,7 @@ func TestConvertBucketsLayout(t *testing.T) {
 					wantDeltas: []int64{6, -4, -1},
 				},
 				2: {
-					wantSpans: []prompb.BucketSpan{
+					wantSpans: []histogram.Span{
 						{
 							Offset: 2,
 							Length: 4,
@@ -236,7 +239,7 @@ func TestConvertBucketsLayout(t *testing.T) {
 			},
 			wantLayout: map[int32]expectedBucketLayout{
 				0: {
-					wantSpans: []prompb.BucketSpan{
+					wantSpans: []histogram.Span{
 						{
 							Offset: -1,
 							Length: 2,
@@ -249,7 +252,7 @@ func TestConvertBucketsLayout(t *testing.T) {
 					wantDeltas: []int64{3, -2, 0},
 				},
 				1: {
-					wantSpans: []prompb.BucketSpan{
+					wantSpans: []histogram.Span{
 						{
 							Offset: 0,
 							Length: 3,
@@ -260,7 +263,7 @@ func TestConvertBucketsLayout(t *testing.T) {
 					wantDeltas: []int64{4, -4, 1},
 				},
 				2: {
-					wantSpans: []prompb.BucketSpan{
+					wantSpans: []histogram.Span{
 						{
 							Offset: 0,
 							Length: 2,
@@ -282,7 +285,7 @@ func TestConvertBucketsLayout(t *testing.T) {
 			},
 			wantLayout: map[int32]expectedBucketLayout{
 				0: {
-					wantSpans: []prompb.BucketSpan{
+					wantSpans: []histogram.Span{
 						{
 							Offset: -1,
 							Length: 6,
@@ -291,7 +294,7 @@ func TestConvertBucketsLayout(t *testing.T) {
 					wantDeltas: []int64{3, -2, -1, 1, -1, 1},
 				},
 				1: {
-					wantSpans: []prompb.BucketSpan{
+					wantSpans: []histogram.Span{
 						{
 							Offset: 0,
 							Length: 3,
@@ -302,7 +305,7 @@ func TestConvertBucketsLayout(t *testing.T) {
 					wantDeltas: []int64{4, -3, 0},
 				},
 				2: {
-					wantSpans: []prompb.BucketSpan{
+					wantSpans: []histogram.Span{
 						{
 							Offset: 0,
 							Length: 2,
@@ -324,7 +327,7 @@ func TestConvertBucketsLayout(t *testing.T) {
 			},
 			wantLayout: map[int32]expectedBucketLayout{
 				0: {
-					wantSpans: []prompb.BucketSpan{
+					wantSpans: []histogram.Span{
 						{
 							Offset: -1,
 							Length: 7,
@@ -333,7 +336,7 @@ func TestConvertBucketsLayout(t *testing.T) {
 					wantDeltas: []int64{3, -3, 0, 1, -1, 0, 1},
 				},
 				1: {
-					wantSpans: []prompb.BucketSpan{
+					wantSpans: []histogram.Span{
 						{
 							Offset: 0,
 							Length: 4,
@@ -344,7 +347,7 @@ func TestConvertBucketsLayout(t *testing.T) {
 					wantDeltas: []int64{3, -2, -1, 1},
 				},
 				2: {
-					wantSpans: []prompb.BucketSpan{
+					wantSpans: []histogram.Span{
 						{
 							Offset: 0,
 							Length: 3,
@@ -379,8 +382,8 @@ func TestConvertBucketsLayout(t *testing.T) {
 		for scaleDown, wantLayout := range tt.wantLayout {
 			t.Run(fmt.Sprintf("%s-scaleby-%d", tt.name, scaleDown), func(t *testing.T) {
 				gotSpans, gotDeltas := convertBucketsLayout(tt.buckets().BucketCounts().AsRaw(), tt.buckets().Offset(), scaleDown, true)
-				require.Equal(t, wantLayout.wantSpans, gotSpans)
-				require.Equal(t, wantLayout.wantDeltas, gotDeltas)
+				requireEqual(t, wantLayout.wantSpans, gotSpans)
+				requireEqual(t, wantLayout.wantDeltas, gotDeltas)
 			})
 		}
 	}
@@ -418,7 +421,7 @@ func TestExponentialToNativeHistogram(t *testing.T) {
 	tests := []struct {
 		name            string
 		exponentialHist func() pmetric.ExponentialHistogramDataPoint
-		wantNativeHist  func() prompb.Histogram
+		wantNativeHist  func() *histogram.Histogram
 		wantErrMessage  string
 	}{
 		{
@@ -440,18 +443,17 @@ func TestExponentialToNativeHistogram(t *testing.T) {
 
 				return pt
 			},
-			wantNativeHist: func() prompb.Histogram {
-				return prompb.Histogram{
-					Count:          &prompb.Histogram_CountInt{CountInt: 4},
-					Sum:            10.1,
-					Schema:         1,
-					ZeroThreshold:  defaultZeroThreshold,
-					ZeroCount:      &prompb.Histogram_ZeroCountInt{ZeroCountInt: 1},
-					NegativeSpans:  []prompb.BucketSpan{{Offset: 2, Length: 2}},
-					NegativeDeltas: []int64{1, 0},
-					PositiveSpans:  []prompb.BucketSpan{{Offset: 2, Length: 2}},
-					PositiveDeltas: []int64{1, 0},
-					Timestamp:      500,
+			wantNativeHist: func() *histogram.Histogram {
+				return &histogram.Histogram{
+					Count:           4,
+					Sum:             10.1,
+					Schema:          1,
+					ZeroThreshold:   defaultZeroThreshold,
+					ZeroCount:       1,
+					NegativeSpans:   []histogram.Span{{Offset: 2, Length: 2}},
+					NegativeBuckets: []int64{1, 0},
+					PositiveSpans:   []histogram.Span{{Offset: 2, Length: 2}},
+					PositiveBuckets: []int64{1, 0},
 				}
 			},
 		},
@@ -474,17 +476,16 @@ func TestExponentialToNativeHistogram(t *testing.T) {
 
 				return pt
 			},
-			wantNativeHist: func() prompb.Histogram {
-				return prompb.Histogram{
-					Count:          &prompb.Histogram_CountInt{CountInt: 4},
-					Schema:         1,
-					ZeroThreshold:  defaultZeroThreshold,
-					ZeroCount:      &prompb.Histogram_ZeroCountInt{ZeroCountInt: 1},
-					NegativeSpans:  []prompb.BucketSpan{{Offset: 2, Length: 2}},
-					NegativeDeltas: []int64{1, 0},
-					PositiveSpans:  []prompb.BucketSpan{{Offset: 2, Length: 2}},
-					PositiveDeltas: []int64{1, 0},
-					Timestamp:      500,
+			wantNativeHist: func() *histogram.Histogram {
+				return &histogram.Histogram{
+					Count:           4,
+					Schema:          1,
+					ZeroThreshold:   defaultZeroThreshold,
+					ZeroCount:       1,
+					NegativeSpans:   []histogram.Span{{Offset: 2, Length: 2}},
+					NegativeBuckets: []int64{1, 0},
+					PositiveSpans:   []histogram.Span{{Offset: 2, Length: 2}},
+					PositiveBuckets: []int64{1, 0},
 				}
 			},
 		},
@@ -515,18 +516,17 @@ func TestExponentialToNativeHistogram(t *testing.T) {
 				pt.Negative().SetOffset(2)
 				return pt
 			},
-			wantNativeHist: func() prompb.Histogram {
-				return prompb.Histogram{
-					Count:          &prompb.Histogram_CountInt{CountInt: 6},
-					Sum:            10.1,
-					Schema:         8,
-					ZeroThreshold:  defaultZeroThreshold,
-					ZeroCount:      &prompb.Histogram_ZeroCountInt{ZeroCountInt: 1},
-					PositiveSpans:  []prompb.BucketSpan{{Offset: 2, Length: 3}},
-					PositiveDeltas: []int64{1, 0, 0}, // 1, 1, 1
-					NegativeSpans:  []prompb.BucketSpan{{Offset: 3, Length: 3}},
-					NegativeDeltas: []int64{1, 0, 0}, // 1, 1, 1
-					Timestamp:      500,
+			wantNativeHist: func() *histogram.Histogram {
+				return &histogram.Histogram{
+					Count:           6,
+					Sum:             10.1,
+					Schema:          8,
+					ZeroThreshold:   defaultZeroThreshold,
+					ZeroCount:       1,
+					PositiveSpans:   []histogram.Span{{Offset: 2, Length: 3}},
+					PositiveBuckets: []int64{1, 0, 0}, // 1, 1, 1
+					NegativeSpans:   []histogram.Span{{Offset: 3, Length: 3}},
+					NegativeBuckets: []int64{1, 0, 0}, // 1, 1, 1
 				}
 			},
 		},
@@ -547,18 +547,17 @@ func TestExponentialToNativeHistogram(t *testing.T) {
 				pt.Negative().SetOffset(2)
 				return pt
 			},
-			wantNativeHist: func() prompb.Histogram {
-				return prompb.Histogram{
-					Count:          &prompb.Histogram_CountInt{CountInt: 6},
-					Sum:            10.1,
-					Schema:         8,
-					ZeroThreshold:  defaultZeroThreshold,
-					ZeroCount:      &prompb.Histogram_ZeroCountInt{ZeroCountInt: 1},
-					PositiveSpans:  []prompb.BucketSpan{{Offset: 1, Length: 2}},
-					PositiveDeltas: []int64{1, 1}, // 0+1, 1+1 = 1, 2
-					NegativeSpans:  []prompb.BucketSpan{{Offset: 2, Length: 2}},
-					NegativeDeltas: []int64{2, -1}, // 1+1, 1+0 = 2, 1
-					Timestamp:      500,
+			wantNativeHist: func() *histogram.Histogram {
+				return &histogram.Histogram{
+					Count:           6,
+					Sum:             10.1,
+					Schema:          8,
+					ZeroThreshold:   defaultZeroThreshold,
+					ZeroCount:       1,
+					PositiveSpans:   []histogram.Span{{Offset: 1, Length: 2}},
+					PositiveBuckets: []int64{1, 1}, // 0+1, 1+1 = 1, 2
+					NegativeSpans:   []histogram.Span{{Offset: 2, Length: 2}},
+					NegativeBuckets: []int64{2, -1}, // 1+1, 1+0 = 2, 1
 				}
 			},
 		},
@@ -599,20 +598,18 @@ func validateExponentialHistogramCount(t *testing.T, h pmetric.ExponentialHistog
 	require.Equal(t, h.Count(), actualCount, "exponential histogram count mismatch")
 }
 
-func validateNativeHistogramCount(t *testing.T, h prompb.Histogram) {
-	require.NotNil(t, h.Count)
-	require.IsType(t, &prompb.Histogram_CountInt{}, h.Count)
-	want := h.Count.(*prompb.Histogram_CountInt).CountInt
+func validateNativeHistogramCount(t *testing.T, h *histogram.Histogram) {
+	want := h.Count
 	var (
 		actualCount uint64
 		prevBucket  int64
 	)
-	for _, delta := range h.PositiveDeltas {
+	for _, delta := range h.PositiveBuckets {
 		prevBucket += delta
 		actualCount += uint64(prevBucket)
 	}
 	prevBucket = 0
-	for _, delta := range h.NegativeDeltas {
+	for _, delta := range h.NegativeBuckets {
 		prevBucket += delta
 		actualCount += uint64(prevBucket)
 	}
@@ -636,7 +633,7 @@ func TestPrometheusConverter_addExponentialHistogramDataPoints(t *testing.T) {
 		metric       func() pmetric.Metric
 		scope        scope
 		promoteScope bool
-		wantSeries   func() map[uint64]*prompb.TimeSeries
+		wantSeries   func() []combinedHistogram
 	}{
 		{
 			name: "histogram data points with same labels and without scope promotion",
@@ -665,36 +662,43 @@ func TestPrometheusConverter_addExponentialHistogramDataPoints(t *testing.T) {
 			},
 			scope:        defaultScope,
 			promoteScope: false,
-			wantSeries: func() map[uint64]*prompb.TimeSeries {
-				labels := []prompb.Label{
-					{Name: model.MetricNameLabel, Value: "test_hist"},
-					{Name: "attr", Value: "test_attr"},
-				}
-				return map[uint64]*prompb.TimeSeries{
-					timeSeriesSignature(labels): {
-						Labels: labels,
-						Histograms: []prompb.Histogram{
-							{
-								Count:          &prompb.Histogram_CountInt{CountInt: 7},
-								Schema:         1,
-								ZeroThreshold:  defaultZeroThreshold,
-								ZeroCount:      &prompb.Histogram_ZeroCountInt{ZeroCountInt: 0},
-								PositiveSpans:  []prompb.BucketSpan{{Offset: 0, Length: 2}},
-								PositiveDeltas: []int64{4, -2},
-							},
-							{
-								Count:          &prompb.Histogram_CountInt{CountInt: 4},
-								Schema:         1,
-								ZeroThreshold:  defaultZeroThreshold,
-								ZeroCount:      &prompb.Histogram_ZeroCountInt{ZeroCountInt: 0},
-								PositiveSpans:  []prompb.BucketSpan{{Offset: 0, Length: 3}},
-								PositiveDeltas: []int64{4, -2, -1},
-							},
+			wantSeries: func() []combinedHistogram {
+				lbls := labels.FromStrings(
+					model.MetricNameLabel, "test_hist",
+					"attr", "test_attr",
+				)
+				return []combinedHistogram{
+					{
+						metricFamilyName: "test_hist",
+						ls:               lbls,
+						meta:             metadata.Metadata{},
+						t:                0,
+						ct:               0,
+						h: &histogram.Histogram{
+							Count:           7,
+							Schema:          1,
+							ZeroThreshold:   defaultZeroThreshold,
+							ZeroCount:       0,
+							PositiveSpans:   []histogram.Span{{Offset: 0, Length: 2}},
+							PositiveBuckets: []int64{4, -2},
 						},
-						Exemplars: []prompb.Exemplar{
-							{Value: 1},
-							{Value: 2},
+						es: []exemplar.Exemplar{{Value: 1}},
+					},
+					{
+						metricFamilyName: "test_hist",
+						ls:               lbls,
+						meta:             metadata.Metadata{},
+						t:                0,
+						ct:               0,
+						h: &histogram.Histogram{
+							Count:           4,
+							Schema:          1,
+							ZeroThreshold:   defaultZeroThreshold,
+							ZeroCount:       0,
+							PositiveSpans:   []histogram.Span{{Offset: 0, Length: 3}},
+							PositiveBuckets: []int64{4, -2, -1},
 						},
+						es: []exemplar.Exemplar{{Value: 2}},
 					},
 				}
 			},
@@ -726,41 +730,48 @@ func TestPrometheusConverter_addExponentialHistogramDataPoints(t *testing.T) {
 			},
 			scope:        defaultScope,
 			promoteScope: true,
-			wantSeries: func() map[uint64]*prompb.TimeSeries {
-				labels := []prompb.Label{
-					{Name: model.MetricNameLabel, Value: "test_hist"},
-					{Name: "attr", Value: "test_attr"},
-					{Name: "otel_scope_name", Value: defaultScope.name},
-					{Name: "otel_scope_schema_url", Value: defaultScope.schemaURL},
-					{Name: "otel_scope_version", Value: defaultScope.version},
-					{Name: "otel_scope_attr1", Value: "value1"},
-					{Name: "otel_scope_attr2", Value: "value2"},
-				}
-				return map[uint64]*prompb.TimeSeries{
-					timeSeriesSignature(labels): {
-						Labels: labels,
-						Histograms: []prompb.Histogram{
-							{
-								Count:          &prompb.Histogram_CountInt{CountInt: 7},
-								Schema:         1,
-								ZeroThreshold:  defaultZeroThreshold,
-								ZeroCount:      &prompb.Histogram_ZeroCountInt{ZeroCountInt: 0},
-								PositiveSpans:  []prompb.BucketSpan{{Offset: 0, Length: 2}},
-								PositiveDeltas: []int64{4, -2},
-							},
-							{
-								Count:          &prompb.Histogram_CountInt{CountInt: 4},
-								Schema:         1,
-								ZeroThreshold:  defaultZeroThreshold,
-								ZeroCount:      &prompb.Histogram_ZeroCountInt{ZeroCountInt: 0},
-								PositiveSpans:  []prompb.BucketSpan{{Offset: 0, Length: 3}},
-								PositiveDeltas: []int64{4, -2, -1},
-							},
+			wantSeries: func() []combinedHistogram {
+				lbls := labels.FromStrings(
+					model.MetricNameLabel, "test_hist",
+					"attr", "test_attr",
+					"otel_scope_name", defaultScope.name,
+					"otel_scope_schema_url", defaultScope.schemaURL,
+					"otel_scope_version", defaultScope.version,
+					"otel_scope_attr1", "value1",
+					"otel_scope_attr2", "value2",
+				)
+				return []combinedHistogram{
+					{
+						metricFamilyName: "test_hist",
+						ls:               lbls,
+						meta:             metadata.Metadata{},
+						t:                0,
+						ct:               0,
+						h: &histogram.Histogram{
+							Count:           7,
+							Schema:          1,
+							ZeroThreshold:   defaultZeroThreshold,
+							ZeroCount:       0,
+							PositiveSpans:   []histogram.Span{{Offset: 0, Length: 2}},
+							PositiveBuckets: []int64{4, -2},
 						},
-						Exemplars: []prompb.Exemplar{
-							{Value: 1},
-							{Value: 2},
+						es: []exemplar.Exemplar{{Value: 1}},
+					},
+					{
+						metricFamilyName: "test_hist",
+						ls:               lbls,
+						meta:             metadata.Metadata{},
+						t:                0,
+						ct:               0,
+						h: &histogram.Histogram{
+							Count:           4,
+							Schema:          1,
+							ZeroThreshold:   defaultZeroThreshold,
+							ZeroCount:       0,
+							PositiveSpans:   []histogram.Span{{Offset: 0, Length: 3}},
+							PositiveBuckets: []int64{4, -2, -1},
 						},
+						es: []exemplar.Exemplar{{Value: 2}},
 					},
 				}
 			},
@@ -792,48 +803,48 @@ func TestPrometheusConverter_addExponentialHistogramDataPoints(t *testing.T) {
 			},
 			scope:        defaultScope,
 			promoteScope: false,
-			wantSeries: func() map[uint64]*prompb.TimeSeries {
-				labels := []prompb.Label{
-					{Name: model.MetricNameLabel, Value: "test_hist"},
-					{Name: "attr", Value: "test_attr"},
-				}
-				labelsAnother := []prompb.Label{
-					{Name: model.MetricNameLabel, Value: "test_hist"},
-					{Name: "attr", Value: "test_attr_two"},
-				}
+			wantSeries: func() []combinedHistogram {
+				lbls := labels.FromStrings(
+					model.MetricNameLabel, "test_hist",
+					"attr", "test_attr",
+				)
+				labelsAnother := labels.FromStrings(
+					model.MetricNameLabel, "test_hist",
+					"attr", "test_attr_two",
+				)
 
-				return map[uint64]*prompb.TimeSeries{
-					timeSeriesSignature(labels): {
-						Labels: labels,
-						Histograms: []prompb.Histogram{
-							{
-								Count:          &prompb.Histogram_CountInt{CountInt: 7},
-								Schema:         1,
-								ZeroThreshold:  defaultZeroThreshold,
-								ZeroCount:      &prompb.Histogram_ZeroCountInt{ZeroCountInt: 0},
-								PositiveSpans:  []prompb.BucketSpan{{Offset: 0, Length: 2}},
-								PositiveDeltas: []int64{4, -2},
-							},
-						},
-						Exemplars: []prompb.Exemplar{
-							{Value: 1},
+				return []combinedHistogram{
+					{
+						metricFamilyName: "test_hist",
+						ls:               lbls,
+						meta:             metadata.Metadata{},
+						t:                0,
+						ct:               0,
+						h: &histogram.Histogram{
+							Count:           7,
+							Schema:          1,
+							ZeroThreshold:   defaultZeroThreshold,
+							ZeroCount:       0,
+							PositiveSpans:   []histogram.Span{{Offset: 0, Length: 2}},
+							PositiveBuckets: []int64{4, -2},
 						},
+						es: []exemplar.Exemplar{{Value: 1}},
 					},
-					timeSeriesSignature(labelsAnother): {
-						Labels: labelsAnother,
-						Histograms: []prompb.Histogram{
-							{
-								Count:          &prompb.Histogram_CountInt{CountInt: 4},
-								Schema:         1,
-								ZeroThreshold:  defaultZeroThreshold,
-								ZeroCount:      &prompb.Histogram_ZeroCountInt{ZeroCountInt: 0},
-								NegativeSpans:  []prompb.BucketSpan{{Offset: 0, Length: 3}},
-								NegativeDeltas: []int64{4, -2, -1},
-							},
-						},
-						Exemplars: []prompb.Exemplar{
-							{Value: 2},
+					{
+						metricFamilyName: "test_hist",
+						ls:               labelsAnother,
+						meta:             metadata.Metadata{},
+						t:                0,
+						ct:               0,
+						h: &histogram.Histogram{
+							Count:           4,
+							Schema:          1,
+							ZeroThreshold:   defaultZeroThreshold,
+							ZeroCount:       0,
+							NegativeSpans:   []histogram.Span{{Offset: 0, Length: 3}},
+							NegativeBuckets: []int64{4, -2, -1},
 						},
+						es: []exemplar.Exemplar{{Value: 2}},
 					},
 				}
 			},
@@ -843,7 +854,8 @@ func TestPrometheusConverter_addExponentialHistogramDataPoints(t *testing.T) {
 		t.Run(tt.name, func(t *testing.T) {
 			metric := tt.metric()
 
-			converter := NewPrometheusConverter()
+			mockAppender := &mockCombinedAppender{}
+			converter := NewPrometheusConverter(mockAppender)
 			namer := otlptranslator.MetricNamer{
 				WithMetricSuffixes: true,
 			}
@@ -857,14 +869,17 @@ func TestPrometheusConverter_addExponentialHistogramDataPoints(t *testing.T) {
 					ExportCreatedMetric:  true,
 					PromoteScopeMetadata: tt.promoteScope,
 				},
-				prompb.MetricMetadata{MetricFamilyName: name},
+				name,
 				pmetric.AggregationTemporalityCumulative,
 				tt.scope,
+				metadata.Metadata{},
 			)
 			require.NoError(t, err)
 			require.Empty(t, annots)
 
-			require.Equal(t, tt.wantSeries(), converter.unique)
+			require.NoError(t, mockAppender.Commit())
+
+			requireEqual(t, tt.wantSeries(), mockAppender.histograms)
 			require.Empty(t, converter.conflicts)
 		})
 	}
@@ -880,7 +895,7 @@ func TestConvertExplicitHistogramBucketsToNHCBLayout(t *testing.T) {
 			name:    "zero offset",
 			buckets: []uint64{4, 3, 2, 1},
 			wantLayout: expectedBucketLayout{
-				wantSpans: []prompb.BucketSpan{
+				wantSpans: []histogram.Span{
 					{
 						Offset: 0,
 						Length: 4,
@@ -893,7 +908,7 @@ func TestConvertExplicitHistogramBucketsToNHCBLayout(t *testing.T) {
 			name:    "leading empty buckets",
 			buckets: []uint64{0, 0, 1, 1, 2, 3},
 			wantLayout: expectedBucketLayout{
-				wantSpans: []prompb.BucketSpan{
+				wantSpans: []histogram.Span{
 					{
 						Offset: 2,
 						Length: 4,
@@ -906,7 +921,7 @@ func TestConvertExplicitHistogramBucketsToNHCBLayout(t *testing.T) {
 			name:    "trailing empty buckets",
 			buckets: []uint64{0, 0, 1, 1, 2, 3, 0, 0}, // TODO: add tests for 3 trailing buckets
 			wantLayout: expectedBucketLayout{
-				wantSpans: []prompb.BucketSpan{
+				wantSpans: []histogram.Span{
 					{
 						Offset: 2,
 						Length: 6,
@@ -919,7 +934,7 @@ func TestConvertExplicitHistogramBucketsToNHCBLayout(t *testing.T) {
 			name:    "bucket gap of 2",
 			buckets: []uint64{1, 2, 0, 0, 2},
 			wantLayout: expectedBucketLayout{
-				wantSpans: []prompb.BucketSpan{
+				wantSpans: []histogram.Span{
 					{
 						Offset: 0,
 						Length: 5,
@@ -932,7 +947,7 @@ func TestConvertExplicitHistogramBucketsToNHCBLayout(t *testing.T) {
 			name:    "bucket gap > 2",
 			buckets: []uint64{1, 2, 0, 0, 0, 2, 4, 4},
 			wantLayout: expectedBucketLayout{
-				wantSpans: []prompb.BucketSpan{
+				wantSpans: []histogram.Span{
 					{
 						Offset: 0,
 						Length: 2,
@@ -949,7 +964,7 @@ func TestConvertExplicitHistogramBucketsToNHCBLayout(t *testing.T) {
 			name:    "multiple bucket gaps",
 			buckets: []uint64{0, 0, 1, 2, 0, 0, 0, 2, 4, 4, 0, 0},
 			wantLayout: expectedBucketLayout{
-				wantSpans: []prompb.BucketSpan{
+				wantSpans: []histogram.Span{
 					{
 						Offset: 2,
 						Length: 2,
@@ -1008,7 +1023,7 @@ func TestHistogramToCustomBucketsHistogram(t *testing.T) {
 	tests := []struct {
 		name           string
 		hist           func() pmetric.HistogramDataPoint
-		wantNativeHist func() prompb.Histogram
+		wantNativeHist func() *histogram.Histogram
 		wantErrMessage string
 	}{
 		{
@@ -1024,15 +1039,14 @@ func TestHistogramToCustomBucketsHistogram(t *testing.T) {
 				pt.ExplicitBounds().FromRaw([]float64{0, 1})
 				return pt
 			},
-			wantNativeHist: func() prompb.Histogram {
-				return prompb.Histogram{
-					Count:          &prompb.Histogram_CountInt{CountInt: 2},
-					Sum:            10.1,
-					Schema:         -53,
-					PositiveSpans:  []prompb.BucketSpan{{Offset: 0, Length: 2}},
-					PositiveDeltas: []int64{1, 0},
-					CustomValues:   []float64{0, 1},
-					Timestamp:      500,
+			wantNativeHist: func() *histogram.Histogram {
+				return &histogram.Histogram{
+					Count:           2,
+					Sum:             10.1,
+					Schema:          -53,
+					PositiveSpans:   []histogram.Span{{Offset: 0, Length: 2}},
+					PositiveBuckets: []int64{1, 0},
+					CustomValues:    []float64{0, 1},
 				}
 			},
 		},
@@ -1048,14 +1062,13 @@ func TestHistogramToCustomBucketsHistogram(t *testing.T) {
 				pt.ExplicitBounds().FromRaw([]float64{0, 1})
 				return pt
 			},
-			wantNativeHist: func() prompb.Histogram {
-				return prompb.Histogram{
-					Count:          &prompb.Histogram_CountInt{CountInt: 4},
-					Schema:         -53,
-					PositiveSpans:  []prompb.BucketSpan{{Offset: 0, Length: 2}},
-					PositiveDeltas: []int64{2, 0},
-					CustomValues:   []float64{0, 1},
-					Timestamp:      500,
+			wantNativeHist: func() *histogram.Histogram {
+				return &histogram.Histogram{
+					Count:           4,
+					Schema:          -53,
+					PositiveSpans:   []histogram.Span{{Offset: 0, Length: 2}},
+					PositiveBuckets: []int64{2, 0},
+					CustomValues:    []float64{0, 1},
 				}
 			},
 		},
@@ -1094,7 +1107,7 @@ func TestPrometheusConverter_addCustomBucketsHistogramDataPoints(t *testing.T) {
 		metric       func() pmetric.Metric
 		scope        scope
 		promoteScope bool
-		wantSeries   func() map[uint64]*prompb.TimeSeries
+		wantSeries   func() []combinedHistogram
 	}{
 		{
 			name: "histogram data points with same labels and without scope promotion",
@@ -1123,36 +1136,43 @@ func TestPrometheusConverter_addCustomBucketsHistogramDataPoints(t *testing.T) {
 			},
 			scope:        defaultScope,
 			promoteScope: false,
-			wantSeries: func() map[uint64]*prompb.TimeSeries {
-				labels := []prompb.Label{
-					{Name: model.MetricNameLabel, Value: "test_hist_to_nhcb"},
-					{Name: "attr", Value: "test_attr"},
-				}
-				return map[uint64]*prompb.TimeSeries{
-					timeSeriesSignature(labels): {
-						Labels: labels,
-						Histograms: []prompb.Histogram{
-							{
-								Count:          &prompb.Histogram_CountInt{CountInt: 3},
-								Sum:            3,
-								Schema:         -53,
-								PositiveSpans:  []prompb.BucketSpan{{Offset: 0, Length: 3}},
-								PositiveDeltas: []int64{2, -2, 1},
-								CustomValues:   []float64{5, 10},
-							},
-							{
-								Count:          &prompb.Histogram_CountInt{CountInt: 11},
-								Sum:            5,
-								Schema:         -53,
-								PositiveSpans:  []prompb.BucketSpan{{Offset: 0, Length: 3}},
-								PositiveDeltas: []int64{3, 5, -8},
-								CustomValues:   []float64{0, 1},
-							},
+			wantSeries: func() []combinedHistogram {
+				lbls := labels.FromStrings(
+					model.MetricNameLabel, "test_hist_to_nhcb",
+					"attr", "test_attr",
+				)
+				return []combinedHistogram{
+					{
+						metricFamilyName: "test_hist_to_nhcb",
+						ls:               lbls,
+						meta:             metadata.Metadata{},
+						t:                0,
+						ct:               0,
+						h: &histogram.Histogram{
+							Count:           3,
+							Sum:             3,
+							Schema:          -53,
+							PositiveSpans:   []histogram.Span{{Offset: 0, Length: 3}},
+							PositiveBuckets: []int64{2, -2, 1},
+							CustomValues:    []float64{5, 10},
 						},
-						Exemplars: []prompb.Exemplar{
-							{Value: 1},
-							{Value: 2},
+						es: []exemplar.Exemplar{{Value: 1}},
+					},
+					{
+						metricFamilyName: "test_hist_to_nhcb",
+						ls:               lbls,
+						meta:             metadata.Metadata{},
+						t:                0,
+						ct:               0,
+						h: &histogram.Histogram{
+							Count:           11,
+							Sum:             5,
+							Schema:          -53,
+							PositiveSpans:   []histogram.Span{{Offset: 0, Length: 3}},
+							PositiveBuckets: []int64{3, 5, -8},
+							CustomValues:    []float64{0, 1},
 						},
+						es: []exemplar.Exemplar{{Value: 2}},
 					},
 				}
 			},
@@ -1184,41 +1204,48 @@ func TestPrometheusConverter_addCustomBucketsHistogramDataPoints(t *testing.T) {
 			},
 			scope:        defaultScope,
 			promoteScope: true,
-			wantSeries: func() map[uint64]*prompb.TimeSeries {
-				labels := []prompb.Label{
-					{Name: model.MetricNameLabel, Value: "test_hist_to_nhcb"},
-					{Name: "attr", Value: "test_attr"},
-					{Name: "otel_scope_name", Value: defaultScope.name},
-					{Name: "otel_scope_schema_url", Value: defaultScope.schemaURL},
-					{Name: "otel_scope_version", Value: defaultScope.version},
-					{Name: "otel_scope_attr1", Value: "value1"},
-					{Name: "otel_scope_attr2", Value: "value2"},
-				}
-				return map[uint64]*prompb.TimeSeries{
-					timeSeriesSignature(labels): {
-						Labels: labels,
-						Histograms: []prompb.Histogram{
-							{
-								Count:          &prompb.Histogram_CountInt{CountInt: 3},
-								Sum:            3,
-								Schema:         -53,
-								PositiveSpans:  []prompb.BucketSpan{{Offset: 0, Length: 3}},
-								PositiveDeltas: []int64{2, -2, 1},
-								CustomValues:   []float64{5, 10},
-							},
-							{
-								Count:          &prompb.Histogram_CountInt{CountInt: 11},
-								Sum:            5,
-								Schema:         -53,
-								PositiveSpans:  []prompb.BucketSpan{{Offset: 0, Length: 3}},
-								PositiveDeltas: []int64{3, 5, -8},
-								CustomValues:   []float64{0, 1},
-							},
+			wantSeries: func() []combinedHistogram {
+				lbls := labels.FromStrings(
+					model.MetricNameLabel, "test_hist_to_nhcb",
+					"attr", "test_attr",
+					"otel_scope_name", defaultScope.name,
+					"otel_scope_schema_url", defaultScope.schemaURL,
+					"otel_scope_version", defaultScope.version,
+					"otel_scope_attr1", "value1",
+					"otel_scope_attr2", "value2",
+				)
+				return []combinedHistogram{
+					{
+						metricFamilyName: "test_hist_to_nhcb",
+						ls:               lbls,
+						meta:             metadata.Metadata{},
+						t:                0,
+						ct:               0,
+						h: &histogram.Histogram{
+							Count:           3,
+							Sum:             3,
+							Schema:          -53,
+							PositiveSpans:   []histogram.Span{{Offset: 0, Length: 3}},
+							PositiveBuckets: []int64{2, -2, 1},
+							CustomValues:    []float64{5, 10},
 						},
-						Exemplars: []prompb.Exemplar{
-							{Value: 1},
-							{Value: 2},
+						es: []exemplar.Exemplar{{Value: 1}},
+					},
+					{
+						metricFamilyName: "test_hist_to_nhcb",
+						ls:               lbls,
+						meta:             metadata.Metadata{},
+						t:                0,
+						ct:               0,
+						h: &histogram.Histogram{
+							Count:           11,
+							Sum:             5,
+							Schema:          -53,
+							PositiveSpans:   []histogram.Span{{Offset: 0, Length: 3}},
+							PositiveBuckets: []int64{3, 5, -8},
+							CustomValues:    []float64{0, 1},
 						},
+						es: []exemplar.Exemplar{{Value: 2}},
 					},
 				}
 			},
@@ -1250,48 +1277,48 @@ func TestPrometheusConverter_addCustomBucketsHistogramDataPoints(t *testing.T) {
 			},
 			scope:        defaultScope,
 			promoteScope: false,
-			wantSeries: func() map[uint64]*prompb.TimeSeries {
-				labels := []prompb.Label{
-					{Name: model.MetricNameLabel, Value: "test_hist_to_nhcb"},
-					{Name: "attr", Value: "test_attr"},
-				}
-				labelsAnother := []prompb.Label{
-					{Name: model.MetricNameLabel, Value: "test_hist_to_nhcb"},
-					{Name: "attr", Value: "test_attr_two"},
-				}
+			wantSeries: func() []combinedHistogram {
+				lbls := labels.FromStrings(
+					model.MetricNameLabel, "test_hist_to_nhcb",
+					"attr", "test_attr",
+				)
+				labelsAnother := labels.FromStrings(
+					model.MetricNameLabel, "test_hist_to_nhcb",
+					"attr", "test_attr_two",
+				)
 
-				return map[uint64]*prompb.TimeSeries{
-					timeSeriesSignature(labels): {
-						Labels: labels,
-						Histograms: []prompb.Histogram{
-							{
-								Count:          &prompb.Histogram_CountInt{CountInt: 6},
-								Sum:            3,
-								Schema:         -53,
-								PositiveSpans:  []prompb.BucketSpan{{Offset: 0, Length: 2}},
-								PositiveDeltas: []int64{4, -2},
-								CustomValues:   []float64{0, 1},
-							},
-						},
-						Exemplars: []prompb.Exemplar{
-							{Value: 1},
+				return []combinedHistogram{
+					{
+						metricFamilyName: "test_hist_to_nhcb",
+						ls:               lbls,
+						meta:             metadata.Metadata{},
+						t:                0,
+						ct:               0,
+						h: &histogram.Histogram{
+							Count:           6,
+							Sum:             3,
+							Schema:          -53,
+							PositiveSpans:   []histogram.Span{{Offset: 0, Length: 2}},
+							PositiveBuckets: []int64{4, -2},
+							CustomValues:    []float64{0, 1},
 						},
+						es: []exemplar.Exemplar{{Value: 1}},
 					},
-					timeSeriesSignature(labelsAnother): {
-						Labels: labelsAnother,
-						Histograms: []prompb.Histogram{
-							{
-								Count:          &prompb.Histogram_CountInt{CountInt: 11},
-								Sum:            5,
-								Schema:         -53,
-								PositiveSpans:  []prompb.BucketSpan{{Offset: 0, Length: 2}},
-								PositiveDeltas: []int64{3, 5},
-								CustomValues:   []float64{0, 1},
-							},
-						},
-						Exemplars: []prompb.Exemplar{
-							{Value: 2},
+					{
+						metricFamilyName: "test_hist_to_nhcb",
+						ls:               labelsAnother,
+						meta:             metadata.Metadata{},
+						t:                0,
+						ct:               0,
+						h: &histogram.Histogram{
+							Count:           11,
+							Sum:             5,
+							Schema:          -53,
+							PositiveSpans:   []histogram.Span{{Offset: 0, Length: 2}},
+							PositiveBuckets: []int64{3, 5},
+							CustomValues:    []float64{0, 1},
 						},
+						es: []exemplar.Exemplar{{Value: 2}},
 					},
 				}
 			},
@@ -1301,7 +1328,8 @@ func TestPrometheusConverter_addCustomBucketsHistogramDataPoints(t *testing.T) {
 		t.Run(tt.name, func(t *testing.T) {
 			metric := tt.metric()
 
-			converter := NewPrometheusConverter()
+			mockAppender := &mockCombinedAppender{}
+			converter := NewPrometheusConverter(mockAppender)
 			namer := otlptranslator.MetricNamer{
 				WithMetricSuffixes: true,
 			}
@@ -1316,15 +1344,18 @@ func TestPrometheusConverter_addCustomBucketsHistogramDataPoints(t *testing.T) {
 					ConvertHistogramsToNHCB: true,
 					PromoteScopeMetadata:    tt.promoteScope,
 				},
-				prompb.MetricMetadata{MetricFamilyName: name},
+				name,
 				pmetric.AggregationTemporalityCumulative,
 				tt.scope,
+				metadata.Metadata{},
 			)
 
 			require.NoError(t, err)
 			require.Empty(t, annots)
 
-			require.Equal(t, tt.wantSeries(), converter.unique)
+			require.NoError(t, mockAppender.Commit())
+
+			requireEqual(t, tt.wantSeries(), mockAppender.histograms)
 			require.Empty(t, converter.conflicts)
 		})
 	}

storage/remote/otlptranslator/prometheusremotewrite/labels/labels.go

@@ -0,0 +1,318 @@
+// Copyright 2025 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// This file is copied from model/labels/labels_slicelabels.go and
+// labels_common.go. Unused functions are removed.
+
+package labels
+
+import (
+	"slices"
+	"strings"
+	"unsafe"
+
+	"github.com/cespare/xxhash/v2"
+
+	common "github.com/prometheus/prometheus/model/labels"
+)
+
+const sep = '\xff'     // Used between labels in `Bytes` and `Hash`.
+var seps = []byte{sep} // Used with Hash, which has no WriteByte method.
+
+// Labels is a sorted set of labels. Order has to be guaranteed upon
+// instantiation.
+type Labels []common.Label
+
+func (ls Labels) Len() int           { return len(ls) }
+func (ls Labels) Swap(i, j int)      { ls[i], ls[j] = ls[j], ls[i] }
+func (ls Labels) Less(i, j int) bool { return ls[i].Name < ls[j].Name }
+
+// Hash returns a hash value for the label set.
+// Note: the result is not guaranteed to be consistent across different runs of Prometheus.
+func (ls Labels) Hash() uint64 {
+	// Use xxhash.Sum64(b) for fast path as it's faster.
+	b := make([]byte, 0, 1024)
+	for i, v := range ls {
+		if len(b)+len(v.Name)+len(v.Value)+2 >= cap(b) {
+			// If labels entry is 1KB+ do not allocate whole entry.
+			h := xxhash.New()
+			_, _ = h.Write(b)
+			for _, v := range ls[i:] {
+				_, _ = h.WriteString(v.Name)
+				_, _ = h.Write(seps)
+				_, _ = h.WriteString(v.Value)
+				_, _ = h.Write(seps)
+			}
+			return h.Sum64()
+		}
+
+		b = append(b, v.Name...)
+		b = append(b, sep)
+		b = append(b, v.Value...)
+		b = append(b, sep)
+	}
+	return xxhash.Sum64(b)
+}
+
+// Get returns the value for the label with the given name.
+// Returns an empty string if the label doesn't exist.
+func (ls Labels) Get(name string) string {
+	for _, l := range ls {
+		if l.Name == name {
+			return l.Value
+		}
+	}
+	return ""
+}
+
+// Has returns true if the label with the given name is present.
+func (ls Labels) Has(name string) bool {
+	for _, l := range ls {
+		if l.Name == name {
+			return true
+		}
+	}
+	return false
+}
+
+// Equal returns whether the two label sets are equal.
+func Equal(ls, o Labels) bool {
+	return slices.Equal(ls, o)
+}
+
+// EmptyLabels returns n empty Labels value, for convenience.
+func EmptyLabels() Labels {
+	return Labels{}
+}
+
+// FromStrings creates new labels from pairs of strings.
+func FromStrings(ss ...string) Labels {
+	if len(ss)%2 != 0 {
+		panic("invalid number of strings")
+	}
+	res := make(Labels, 0, len(ss)/2)
+	for i := 0; i < len(ss); i += 2 {
+		res = append(res, common.Label{Name: ss[i], Value: ss[i+1]})
+	}
+
+	slices.SortFunc(res, func(a, b common.Label) int { return strings.Compare(a.Name, b.Name) })
+	return res
+}
+
+// Range calls f on each label.
+func (ls Labels) Range(f func(l common.Label)) {
+	for _, l := range ls {
+		f(l)
+	}
+}
+
+// Builder allows modifying Labels.
+type Builder struct {
+	base Labels
+	del  []string
+	add  []common.Label
+}
+
+// NewBuilder returns a new LabelsBuilder.
+func NewBuilder(base Labels) *Builder {
+	b := &Builder{
+		del: make([]string, 0, 5),
+		add: make([]common.Label, 0, 5),
+	}
+	b.Reset(base)
+	return b
+}
+
+// Reset clears all current state for the builder.
+func (b *Builder) Reset(base Labels) {
+	b.base = base
+	b.del = b.del[:0]
+	b.add = b.add[:0]
+	b.base.Range(func(l common.Label) {
+		if l.Value == "" {
+			b.del = append(b.del, l.Name)
+		}
+	})
+}
+
+// Del deletes the label of the given name.
+func (b *Builder) Del(ns ...string) *Builder {
+	for _, n := range ns {
+		for i, a := range b.add {
+			if a.Name == n {
+				b.add = append(b.add[:i], b.add[i+1:]...)
+			}
+		}
+		b.del = append(b.del, n)
+	}
+	return b
+}
+
+// Keep removes all labels from the base except those with the given names.
+func (b *Builder) Keep(ns ...string) *Builder {
+	b.base.Range(func(l common.Label) {
+		if slices.Contains(ns, l.Name) {
+			return
+		}
+		b.del = append(b.del, l.Name)
+	})
+	return b
+}
+
+// Set the name/value pair as a label. A value of "" means delete that label.
+func (b *Builder) Set(n, v string) *Builder {
+	if v == "" {
+		// Empty labels are the same as missing labels.
+		return b.Del(n)
+	}
+	for i, a := range b.add {
+		if a.Name == n {
+			b.add[i].Value = v
+			return b
+		}
+	}
+	b.add = append(b.add, common.Label{Name: n, Value: v})
+
+	return b
+}
+
+func (b *Builder) Get(n string) string {
+	// Del() removes entries from .add but Set() does not remove from .del, so check .add first.
+	for _, a := range b.add {
+		if a.Name == n {
+			return a.Value
+		}
+	}
+	if slices.Contains(b.del, n) {
+		return ""
+	}
+	return b.base.Get(n)
+}
+
+// Range calls f on each label in the Builder.
+func (b *Builder) Range(f func(l common.Label)) {
+	// Stack-based arrays to avoid heap allocation in most cases.
+	var addStack [128]common.Label
+	var delStack [128]string
+	// Take a copy of add and del, so they are unaffected by calls to Set() or Del().
+	origAdd, origDel := append(addStack[:0], b.add...), append(delStack[:0], b.del...)
+	b.base.Range(func(l common.Label) {
+		if !slices.Contains(origDel, l.Name) && !common.Contains(origAdd, l.Name) {
+			f(l)
+		}
+	})
+	for _, a := range origAdd {
+		f(a)
+	}
+}
+
+// Labels returns the labels from the builder.
+// If no modifications were made, the original labels are returned.
+func (b *Builder) Labels() Labels {
+	if len(b.del) == 0 && len(b.add) == 0 {
+		return b.base
+	}
+
+	expectedSize := len(b.base) + len(b.add) - len(b.del)
+	if expectedSize < 1 {
+		expectedSize = 1
+	}
+	res := make(Labels, 0, expectedSize)
+	for _, l := range b.base {
+		if slices.Contains(b.del, l.Name) || common.Contains(b.add, l.Name) {
+			continue
+		}
+		res = append(res, l)
+	}
+	if len(b.add) > 0 { // Base is already in order, so we only need to sort if we add to it.
+		res = append(res, b.add...)
+		slices.SortFunc(res, func(a, b common.Label) int { return strings.Compare(a.Name, b.Name) })
+	}
+	return res
+}
+
+// ScratchBuilder allows efficient construction of a Labels from scratch.
+type ScratchBuilder struct {
+	add Labels
+}
+
+// SymbolTable is no-op, just for api parity with dedupelabels.
+type SymbolTable struct{}
+
+func NewSymbolTable() *SymbolTable { return nil }
+
+func (t *SymbolTable) Len() int { return 0 }
+
+// NewScratchBuilder creates a ScratchBuilder initialized for Labels with n entries.
+func NewScratchBuilder(n int) ScratchBuilder {
+	return ScratchBuilder{add: make([]common.Label, 0, n)}
+}
+
+// NewBuilderWithSymbolTable creates a Builder, for api parity with dedupelabels.
+func NewBuilderWithSymbolTable(_ *SymbolTable) *Builder {
+	return NewBuilder(EmptyLabels())
+}
+
+// NewScratchBuilderWithSymbolTable creates a ScratchBuilder, for api parity with dedupelabels.
+func NewScratchBuilderWithSymbolTable(_ *SymbolTable, n int) ScratchBuilder {
+	return NewScratchBuilder(n)
+}
+
+func (b *ScratchBuilder) SetSymbolTable(_ *SymbolTable) {
+	// no-op
+}
+
+func (b *ScratchBuilder) Reset() {
+	b.add = b.add[:0]
+}
+
+// Add a name/value pair.
+// Note if you Add the same name twice you will get a duplicate label, which is invalid.
+func (b *ScratchBuilder) Add(name, value string) {
+	b.add = append(b.add, common.Label{Name: name, Value: value})
+}
+
+// UnsafeAddBytes adds a name/value pair, using []byte instead of string.
+// The '-tags stringlabels' version of this function is unsafe, hence the name.
+// This version is safe - it copies the strings immediately - but we keep the same name so everything compiles.
+func (b *ScratchBuilder) UnsafeAddBytes(name, value []byte) {
+	b.add = append(b.add, common.Label{Name: string(name), Value: string(value)})
+}
+
+// Sort the labels added so far by name.
+func (b *ScratchBuilder) Sort() {
+	slices.SortFunc(b.add, func(a, b common.Label) int { return strings.Compare(a.Name, b.Name) })
+}
+
+// Assign is for when you already have a Labels which you want this ScratchBuilder to return.
+func (b *ScratchBuilder) Assign(ls Labels) {
+	b.add = append(b.add[:0], ls...) // Copy on top of our slice, so we don't retain the input slice.
+}
+
+// Labels returns the name/value pairs added so far as a Labels object.
+// Note: if you want them sorted, call Sort() first.
+func (b *ScratchBuilder) Labels() Labels {
+	// Copy the slice, so the next use of ScratchBuilder doesn't overwrite.
+	return append([]common.Label{}, b.add...)
+}
+
+// Overwrite the newly-built Labels out to ls.
+// Callers must ensure that there are no other references to ls, or any strings fetched from it.
+func (b *ScratchBuilder) Overwrite(ls *Labels) {
+	*ls = append((*ls)[:0], b.add...)
+}
+
+// SizeOfLabels returns the approximate space required for n copies of a label.
+func SizeOfLabels(name, value string, n uint64) uint64 {
+	return (uint64(len(name)) + uint64(unsafe.Sizeof(name)) + uint64(len(value)) + uint64(unsafe.Sizeof(value))) * n
+}

storage/remote/otlptranslator/prometheusremotewrite/labels/labels_test.go

@@ -0,0 +1,424 @@
+// Copyright 2025 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package labels
+
+import (
+	"fmt"
+	"net/http"
+	"strconv"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	common "github.com/prometheus/prometheus/model/labels"
+)
+
+func TestLabels_Equal(t *testing.T) {
+	labels := FromStrings(
+		"aaa", "111",
+		"bbb", "222")
+
+	tests := []struct {
+		compared Labels
+		expected bool
+	}{
+		{
+			compared: FromStrings(
+				"aaa", "111",
+				"bbb", "222",
+				"ccc", "333"),
+			expected: false,
+		},
+		{
+			compared: FromStrings(
+				"aaa", "111",
+				"bar", "222"),
+			expected: false,
+		},
+		{
+			compared: FromStrings(
+				"aaa", "111",
+				"bbb", "233"),
+			expected: false,
+		},
+		{
+			compared: FromStrings(
+				"aaa", "111",
+				"bbb", "222"),
+			expected: true,
+		},
+	}
+
+	for i, test := range tests {
+		got := Equal(labels, test.compared)
+		require.Equal(t, test.expected, got, "unexpected comparison result for test case %d", i)
+	}
+}
+
+func TestLabels_FromStrings(t *testing.T) {
+	labels := FromStrings("aaa", "111", "bbb", "222")
+	x := 0
+	labels.Range(func(l common.Label) {
+		switch x {
+		case 0:
+			require.Equal(t, common.Label{Name: "aaa", Value: "111"}, l, "unexpected value")
+		case 1:
+			require.Equal(t, common.Label{Name: "bbb", Value: "222"}, l, "unexpected value")
+		default:
+			t.Fatalf("unexpected labelset value %d: %v", x, l)
+		}
+		x++
+	})
+
+	require.Panics(t, func() { FromStrings("aaa", "111", "bbb") }) //nolint:staticcheck // Ignore SA5012, error is intentional test.
+}
+
+func TestLabels_Has(t *testing.T) {
+	tests := []struct {
+		input    string
+		expected bool
+	}{
+		{
+			input:    "foo",
+			expected: false,
+		},
+		{
+			input:    "aaa",
+			expected: true,
+		},
+	}
+
+	labelsSet := FromStrings(
+		"aaa", "111",
+		"bbb", "222")
+
+	for i, test := range tests {
+		got := labelsSet.Has(test.input)
+		require.Equal(t, test.expected, got, "unexpected comparison result for test case %d", i)
+	}
+}
+
+func TestLabels_Get(t *testing.T) {
+	require.Empty(t, FromStrings("aaa", "111", "bbb", "222").Get("foo"))
+	require.Equal(t, "111", FromStrings("aaaa", "111", "bbb", "222").Get("aaaa"))
+	require.Equal(t, "222", FromStrings("aaaa", "111", "bbb", "222").Get("bbb"))
+}
+
+func ScratchBuilderForBenchmark() ScratchBuilder {
+	// (Only relevant to -tags dedupelabels: stuff the symbol table before adding the real labels, to avoid having everything fitting into 1 byte.)
+	b := NewScratchBuilder(256)
+	for i := 0; i < 256; i++ {
+		b.Add(fmt.Sprintf("name%d", i), fmt.Sprintf("value%d", i))
+	}
+	b.Labels()
+	b.Reset()
+	return b
+}
+
+func NewForBenchmark(ls ...common.Label) Labels {
+	b := ScratchBuilderForBenchmark()
+	for _, l := range ls {
+		b.Add(l.Name, l.Value)
+	}
+	b.Sort()
+	return b.Labels()
+}
+
+func FromStringsForBenchmark(ss ...string) Labels {
+	if len(ss)%2 != 0 {
+		panic("invalid number of strings")
+	}
+	b := ScratchBuilderForBenchmark()
+	for i := 0; i < len(ss); i += 2 {
+		b.Add(ss[i], ss[i+1])
+	}
+	b.Sort()
+	return b.Labels()
+}
+
+// BenchmarkLabels_Get was written to check whether a binary search can improve the performance vs the linear search implementation
+// The results have shown that binary search would only be better when searching last labels in scenarios with more than 10 labels.
+// In the following list, `old` is the linear search while `new` is the binary search implementation (without calling sort.Search, which performs even worse here)
+//
+//	name                                        old time/op    new time/op    delta
+//	Labels_Get/with_5_labels/get_first_label      5.12ns ± 0%   14.24ns ± 0%   ~     (p=1.000 n=1+1)
+//	Labels_Get/with_5_labels/get_middle_label     13.5ns ± 0%    18.5ns ± 0%   ~     (p=1.000 n=1+1)
+//	Labels_Get/with_5_labels/get_last_label       21.9ns ± 0%    18.9ns ± 0%   ~     (p=1.000 n=1+1)
+//	Labels_Get/with_10_labels/get_first_label     5.11ns ± 0%   19.47ns ± 0%   ~     (p=1.000 n=1+1)
+//	Labels_Get/with_10_labels/get_middle_label    26.2ns ± 0%    19.3ns ± 0%   ~     (p=1.000 n=1+1)
+//	Labels_Get/with_10_labels/get_last_label      42.8ns ± 0%    23.4ns ± 0%   ~     (p=1.000 n=1+1)
+//	Labels_Get/with_30_labels/get_first_label     5.10ns ± 0%   24.63ns ± 0%   ~     (p=1.000 n=1+1)
+//	Labels_Get/with_30_labels/get_middle_label    75.8ns ± 0%    29.7ns ± 0%   ~     (p=1.000 n=1+1)
+//	Labels_Get/with_30_labels/get_last_label       169ns ± 0%      29ns ± 0%   ~     (p=1.000 n=1+1)
+func BenchmarkLabels_Get(b *testing.B) {
+	maxLabels := 30
+	allLabels := make([]common.Label, maxLabels)
+	for i := 0; i < maxLabels; i++ {
+		allLabels[i] = common.Label{Name: strings.Repeat(string('a'+byte(i)), 5+(i%5))}
+	}
+	for _, size := range []int{5, 10, maxLabels} {
+		b.Run(fmt.Sprintf("with %d labels", size), func(b *testing.B) {
+			labels := NewForBenchmark(allLabels[:size]...)
+			for _, scenario := range []struct {
+				desc, label string
+			}{
+				{"first label", allLabels[0].Name},
+				{"middle label", allLabels[size/2].Name},
+				{"last label", allLabels[size-1].Name},
+				{"not-found label", "benchmark"},
+			} {
+				b.Run(scenario.desc, func(b *testing.B) {
+					b.Run("get", func(b *testing.B) {
+						for i := 0; i < b.N; i++ {
+							_ = labels.Get(scenario.label)
+						}
+					})
+					b.Run("has", func(b *testing.B) {
+						for i := 0; i < b.N; i++ {
+							_ = labels.Has(scenario.label)
+						}
+					})
+				})
+			}
+		})
+	}
+}
+
+var comparisonBenchmarkScenarios = []struct {
+	desc        string
+	base, other Labels
+}{
+	{
+		"equal",
+		FromStringsForBenchmark("a_label_name", "a_label_value", "another_label_name", "another_label_value"),
+		FromStringsForBenchmark("a_label_name", "a_label_value", "another_label_name", "another_label_value"),
+	},
+	{
+		"not equal",
+		FromStringsForBenchmark("a_label_name", "a_label_value", "another_label_name", "another_label_value"),
+		FromStringsForBenchmark("a_label_name", "a_label_value", "another_label_name", "a_different_label_value"),
+	},
+	{
+		"different sizes",
+		FromStringsForBenchmark("a_label_name", "a_label_value", "another_label_name", "another_label_value"),
+		FromStringsForBenchmark("a_label_name", "a_label_value"),
+	},
+	{
+		"lots",
+		FromStringsForBenchmark("aaa", "bbb", "ccc", "ddd", "eee", "fff", "ggg", "hhh", "iii", "jjj", "kkk", "lll", "mmm", "nnn", "ooo", "ppp", "qqq", "rrz"),
+		FromStringsForBenchmark("aaa", "bbb", "ccc", "ddd", "eee", "fff", "ggg", "hhh", "iii", "jjj", "kkk", "lll", "mmm", "nnn", "ooo", "ppp", "qqq", "rrr"),
+	},
+	{
+		"real long equal",
+		FromStringsForBenchmark("__name__", "kube_pod_container_status_last_terminated_exitcode", "cluster", "prod-af-north-0", " container", "prometheus", "instance", "kube-state-metrics-0:kube-state-metrics:ksm", "job", "kube-state-metrics/kube-state-metrics", " namespace", "observability-prometheus", "pod", "observability-prometheus-0", "uid", "d3ec90b2-4975-4607-b45d-b9ad64bb417e"),
+		FromStringsForBenchmark("__name__", "kube_pod_container_status_last_terminated_exitcode", "cluster", "prod-af-north-0", " container", "prometheus", "instance", "kube-state-metrics-0:kube-state-metrics:ksm", "job", "kube-state-metrics/kube-state-metrics", " namespace", "observability-prometheus", "pod", "observability-prometheus-0", "uid", "d3ec90b2-4975-4607-b45d-b9ad64bb417e"),
+	},
+	{
+		"real long different end",
+		FromStringsForBenchmark("__name__", "kube_pod_container_status_last_terminated_exitcode", "cluster", "prod-af-north-0", " container", "prometheus", "instance", "kube-state-metrics-0:kube-state-metrics:ksm", "job", "kube-state-metrics/kube-state-metrics", " namespace", "observability-prometheus", "pod", "observability-prometheus-0", "uid", "d3ec90b2-4975-4607-b45d-b9ad64bb417e"),
+		FromStringsForBenchmark("__name__", "kube_pod_container_status_last_terminated_exitcode", "cluster", "prod-af-north-0", " container", "prometheus", "instance", "kube-state-metrics-0:kube-state-metrics:ksm", "job", "kube-state-metrics/kube-state-metrics", " namespace", "observability-prometheus", "pod", "observability-prometheus-0", "uid", "deadbeef-0000-1111-2222-b9ad64bb417e"),
+	},
+}
+
+func BenchmarkLabels_Equals(b *testing.B) {
+	for _, scenario := range comparisonBenchmarkScenarios {
+		b.Run(scenario.desc, func(b *testing.B) {
+			b.ResetTimer()
+			for i := 0; i < b.N; i++ {
+				_ = Equal(scenario.base, scenario.other)
+			}
+		})
+	}
+}
+
+func TestBuilder(t *testing.T) {
+	reuseBuilder := NewBuilderWithSymbolTable(NewSymbolTable())
+	for i, tcase := range []struct {
+		base Labels
+		del  []string
+		keep []string
+		set  []common.Label
+		want Labels
+	}{
+		{
+			base: FromStrings("aaa", "111"),
+			want: FromStrings("aaa", "111"),
+		},
+		{
+			base: EmptyLabels(),
+			set:  []common.Label{{Name: "aaa", Value: "444"}, {Name: "bbb", Value: "555"}, {Name: "ccc", Value: "666"}},
+			want: FromStrings("aaa", "444", "bbb", "555", "ccc", "666"),
+		},
+		{
+			base: FromStrings("aaa", "111", "bbb", "222", "ccc", "333"),
+			set:  []common.Label{{Name: "aaa", Value: "444"}, {Name: "bbb", Value: "555"}, {Name: "ccc", Value: "666"}},
+			want: FromStrings("aaa", "444", "bbb", "555", "ccc", "666"),
+		},
+		{
+			base: FromStrings("aaa", "111", "bbb", "222", "ccc", "333"),
+			del:  []string{"bbb"},
+			want: FromStrings("aaa", "111", "ccc", "333"),
+		},
+		{
+			set:  []common.Label{{Name: "aaa", Value: "111"}, {Name: "bbb", Value: "222"}, {Name: "ccc", Value: "333"}},
+			del:  []string{"bbb"},
+			want: FromStrings("aaa", "111", "ccc", "333"),
+		},
+		{
+			base: FromStrings("aaa", "111"),
+			set:  []common.Label{{Name: "bbb", Value: "222"}},
+			want: FromStrings("aaa", "111", "bbb", "222"),
+		},
+		{
+			base: FromStrings("aaa", "111"),
+			set:  []common.Label{{Name: "bbb", Value: "222"}, {Name: "bbb", Value: "333"}},
+			want: FromStrings("aaa", "111", "bbb", "333"),
+		},
+		{
+			base: FromStrings("aaa", "111", "bbb", "222", "ccc", "333"),
+			del:  []string{"bbb"},
+			set:  []common.Label{{Name: "ddd", Value: "444"}},
+			want: FromStrings("aaa", "111", "ccc", "333", "ddd", "444"),
+		},
+		{ // Blank value is interpreted as delete.
+			base: FromStrings("aaa", "111", "bbb", "", "ccc", "333"),
+			want: FromStrings("aaa", "111", "ccc", "333"),
+		},
+		{
+			base: FromStrings("aaa", "111", "bbb", "222", "ccc", "333"),
+			set:  []common.Label{{Name: "bbb", Value: ""}},
+			want: FromStrings("aaa", "111", "ccc", "333"),
+		},
+		{
+			base: FromStrings("aaa", "111", "bbb", "222", "ccc", "333"),
+			keep: []string{"bbb"},
+			want: FromStrings("bbb", "222"),
+		},
+		{
+			base: FromStrings("aaa", "111", "bbb", "222", "ccc", "333"),
+			keep: []string{"aaa", "ccc"},
+			want: FromStrings("aaa", "111", "ccc", "333"),
+		},
+		{
+			base: FromStrings("aaa", "111", "bbb", "222", "ccc", "333"),
+			del:  []string{"bbb"},
+			set:  []common.Label{{Name: "ddd", Value: "444"}},
+			keep: []string{"aaa", "ddd"},
+			want: FromStrings("aaa", "111", "ddd", "444"),
+		},
+	} {
+		test := func(t *testing.T, b *Builder) {
+			for _, lbl := range tcase.set {
+				b.Set(lbl.Name, lbl.Value)
+			}
+			if len(tcase.keep) > 0 {
+				b.Keep(tcase.keep...)
+			}
+			b.Del(tcase.del...)
+			require.True(t, Equal(tcase.want, b.Labels()))
+
+			// Check what happens when we call Range and mutate the builder.
+			b.Range(func(l common.Label) {
+				if l.Name == "aaa" || l.Name == "bbb" {
+					b.Del(l.Name)
+				}
+			})
+			// require.Equal(t, tcase.want.BytesWithoutLabels(nil, "aaa", "bbb"), b.Labels().Bytes(nil))
+		}
+		t.Run(fmt.Sprintf("NewBuilder %d", i), func(t *testing.T) {
+			test(t, NewBuilder(tcase.base))
+		})
+		t.Run(fmt.Sprintf("NewSymbolTable %d", i), func(t *testing.T) {
+			b := NewBuilderWithSymbolTable(NewSymbolTable())
+			b.Reset(tcase.base)
+			test(t, b)
+		})
+		t.Run(fmt.Sprintf("reuseBuilder %d", i), func(t *testing.T) {
+			reuseBuilder.Reset(tcase.base)
+			test(t, reuseBuilder)
+		})
+	}
+	t.Run("set_after_del", func(t *testing.T) {
+		b := NewBuilder(FromStrings("aaa", "111"))
+		b.Del("bbb")
+		b.Set("bbb", "222")
+		require.Equal(t, FromStrings("aaa", "111", "bbb", "222"), b.Labels())
+		require.Equal(t, "222", b.Get("bbb"))
+	})
+}
+
+func TestScratchBuilder(t *testing.T) {
+	for i, tcase := range []struct {
+		add  []common.Label
+		want Labels
+	}{
+		{
+			add:  []common.Label{},
+			want: EmptyLabels(),
+		},
+		{
+			add:  []common.Label{{Name: "aaa", Value: "111"}},
+			want: FromStrings("aaa", "111"),
+		},
+		{
+			add:  []common.Label{{Name: "aaa", Value: "111"}, {Name: "bbb", Value: "222"}, {Name: "ccc", Value: "333"}},
+			want: FromStrings("aaa", "111", "bbb", "222", "ccc", "333"),
+		},
+		{
+			add:  []common.Label{{Name: "bbb", Value: "222"}, {Name: "aaa", Value: "111"}, {Name: "ccc", Value: "333"}},
+			want: FromStrings("aaa", "111", "bbb", "222", "ccc", "333"),
+		},
+		{
+			add:  []common.Label{{Name: "ddd", Value: "444"}},
+			want: FromStrings("ddd", "444"),
+		},
+	} {
+		t.Run(strconv.Itoa(i), func(t *testing.T) {
+			b := NewScratchBuilder(len(tcase.add))
+			for _, lbl := range tcase.add {
+				b.Add(lbl.Name, lbl.Value)
+			}
+			b.Sort()
+			require.True(t, Equal(tcase.want, b.Labels()))
+			b.Assign(tcase.want)
+			require.True(t, Equal(tcase.want, b.Labels()))
+		})
+	}
+}
+
+var benchmarkLabels = []common.Label{
+	{Name: "job", Value: "node"},
+	{Name: "instance", Value: "123.123.1.211:9090"},
+	{Name: "path", Value: "/api/v1/namespaces/<namespace>/deployments/<name>"},
+	{Name: "method", Value: http.MethodGet},
+	{Name: "namespace", Value: "system"},
+	{Name: "status", Value: "500"},
+	{Name: "prometheus", Value: "prometheus-core-1"},
+	{Name: "datacenter", Value: "eu-west-1"},
+	{Name: "pod_name", Value: "abcdef-99999-defee"},
+}
+
+func BenchmarkBuilder(b *testing.B) {
+	var l Labels
+	builder := NewBuilder(EmptyLabels())
+	for i := 0; i < b.N; i++ {
+		builder.Reset(EmptyLabels())
+		for _, l := range benchmarkLabels {
+			builder.Set(l.Name, l.Value)
+		}
+		l = builder.Labels()
+	}
+	require.Equal(b, 9, l.Len())
+}

storage/remote/otlptranslator/prometheusremotewrite/metrics_to_prw.go

@@ -21,7 +21,6 @@ import (
 	"errors"
 	"fmt"
 	"math"
-	"sort"
 	"time"
 
 	"github.com/prometheus/otlptranslator"
@@ -30,7 +29,8 @@ import (
 	"go.uber.org/multierr"
 
 	"github.com/prometheus/prometheus/config"
-	"github.com/prometheus/prometheus/prompb"
+	"github.com/prometheus/prometheus/model/metadata"
+	"github.com/prometheus/prometheus/storage/remote/otlptranslator/prometheusremotewrite/labels"
 	"github.com/prometheus/prometheus/util/annotations"
 )
 
@@ -59,16 +59,21 @@ type Settings struct {
 
 // PrometheusConverter converts from OTel write format to Prometheus remote write format.
 type PrometheusConverter struct {
-	unique    map[uint64]*prompb.TimeSeries
-	conflicts map[uint64][]*prompb.TimeSeries
-	everyN    everyNTimes
-	metadata  []prompb.MetricMetadata
+	unique         map[uint64]labels.Labels
+	conflicts      map[uint64][]labels.Labels
+	everyN         everyNTimes
+	scratchBuilder labels.ScratchBuilder
+	builder        *labels.Builder
+	appender       CombinedAppender
 }
 
-func NewPrometheusConverter() *PrometheusConverter {
+func NewPrometheusConverter(appender CombinedAppender) *PrometheusConverter {
 	return &PrometheusConverter{
-		unique:    map[uint64]*prompb.TimeSeries{},
-		conflicts: map[uint64][]*prompb.TimeSeries{},
+		unique:         map[uint64]labels.Labels{},
+		conflicts:      map[uint64][]labels.Labels{},
+		scratchBuilder: labels.NewScratchBuilder(0),
+		builder:        labels.NewBuilder(labels.EmptyLabels()),
+		appender:       appender,
 	}
 }
 
@@ -121,6 +126,7 @@ func (c *PrometheusConverter) FromMetrics(ctx context.Context, md pmetric.Metric
 		WithMetricSuffixes: settings.AddMetricSuffixes,
 		UTF8Allowed:        settings.AllowUTF8,
 	}
+	unitNamer := otlptranslator.UnitNamer{}
 	c.everyN = everyNTimes{n: 128}
 	resourceMetricsSlice := md.ResourceMetrics()
 
@@ -131,7 +137,6 @@ func (c *PrometheusConverter) FromMetrics(ctx context.Context, md pmetric.Metric
 			numMetrics += scopeMetricsSlice.At(j).Metrics().Len()
 		}
 	}
-	c.metadata = make([]prompb.MetricMetadata, 0, numMetrics)
 
 	for i := 0; i < resourceMetricsSlice.Len(); i++ {
 		resourceMetrics := resourceMetricsSlice.At(i)
@@ -176,13 +181,11 @@ func (c *PrometheusConverter) FromMetrics(ctx context.Context, md pmetric.Metric
 					errs = multierr.Append(errs, err)
 					continue
 				}
-				metadata := prompb.MetricMetadata{
-					Type:             otelMetricTypeToPromMetricType(metric),
-					MetricFamilyName: promName,
-					Help:             metric.Description(),
-					Unit:             metric.Unit(),
+				meta := metadata.Metadata{
+					Type: otelMetricTypeToPromMetricType(metric),
+					Unit: unitNamer.Build(metric.Unit()),
+					Help: metric.Description(),
 				}
-				c.metadata = append(c.metadata, metadata)
 
 				// handle individual metrics based on type
 				//exhaustive:enforce
@@ -193,7 +196,7 @@ func (c *PrometheusConverter) FromMetrics(ctx context.Context, md pmetric.Metric
 						errs = multierr.Append(errs, fmt.Errorf("empty data points. %s is dropped", metric.Name()))
 						break
 					}
-					if err := c.addGaugeNumberDataPoints(ctx, dataPoints, resource, settings, metadata, scope); err != nil {
+					if err := c.addGaugeNumberDataPoints(ctx, dataPoints, resource, settings, promName, scope, meta); err != nil {
 						errs = multierr.Append(errs, err)
 						if errors.Is(err, context.Canceled) || errors.Is(err, context.DeadlineExceeded) {
 							return
@@ -205,7 +208,7 @@ func (c *PrometheusConverter) FromMetrics(ctx context.Context, md pmetric.Metric
 						errs = multierr.Append(errs, fmt.Errorf("empty data points. %s is dropped", metric.Name()))
 						break
 					}
-					if err := c.addSumNumberDataPoints(ctx, dataPoints, resource, metric, settings, metadata, scope); err != nil {
+					if err := c.addSumNumberDataPoints(ctx, dataPoints, resource, metric, settings, promName, scope, meta); err != nil {
 						errs = multierr.Append(errs, err)
 						if errors.Is(err, context.Canceled) || errors.Is(err, context.DeadlineExceeded) {
 							return
@@ -219,7 +222,7 @@ func (c *PrometheusConverter) FromMetrics(ctx context.Context, md pmetric.Metric
 					}
 					if settings.ConvertHistogramsToNHCB {
 						ws, err := c.addCustomBucketsHistogramDataPoints(
-							ctx, dataPoints, resource, settings, metadata, temporality, scope,
+							ctx, dataPoints, resource, settings, promName, temporality, scope, meta,
 						)
 						annots.Merge(ws)
 						if err != nil {
@@ -229,7 +232,7 @@ func (c *PrometheusConverter) FromMetrics(ctx context.Context, md pmetric.Metric
 							}
 						}
 					} else {
-						if err := c.addHistogramDataPoints(ctx, dataPoints, resource, settings, metadata, scope); err != nil {
+						if err := c.addHistogramDataPoints(ctx, dataPoints, resource, settings, promName, scope, meta); err != nil {
 							errs = multierr.Append(errs, err)
 							if errors.Is(err, context.Canceled) || errors.Is(err, context.DeadlineExceeded) {
 								return
@@ -247,9 +250,10 @@ func (c *PrometheusConverter) FromMetrics(ctx context.Context, md pmetric.Metric
 						dataPoints,
 						resource,
 						settings,
-						metadata,
+						promName,
 						temporality,
 						scope,
+						meta,
 					)
 					annots.Merge(ws)
 					if err != nil {
@@ -264,7 +268,7 @@ func (c *PrometheusConverter) FromMetrics(ctx context.Context, md pmetric.Metric
 						errs = multierr.Append(errs, fmt.Errorf("empty data points. %s is dropped", metric.Name()))
 						break
 					}
-					if err := c.addSummaryDataPoints(ctx, dataPoints, resource, settings, metadata, scope); err != nil {
+					if err := c.addSummaryDataPoints(ctx, dataPoints, resource, settings, promName, scope, meta); err != nil {
 						errs = multierr.Append(errs, err)
 						if errors.Is(err, context.Canceled) || errors.Is(err, context.DeadlineExceeded) {
 							return
@@ -278,72 +282,16 @@ func (c *PrometheusConverter) FromMetrics(ctx context.Context, md pmetric.Metric
 		if earliestTimestamp < pcommon.Timestamp(math.MaxUint64) {
 			// We have at least one metric sample for this resource.
 			// Generate a corresponding target_info series.
-			err := addResourceTargetInfo(resource, settings, earliestTimestamp.AsTime(), latestTimestamp.AsTime(), c)
-			if err != nil {
+			if err := c.addResourceTargetInfo(resource, settings, earliestTimestamp.AsTime(), latestTimestamp.AsTime()); err != nil {
 				errs = multierr.Append(errs, err)
 			}
 		}
 	}
 
-	return annots, errs
-}
+	err := c.appender.Commit()
+	errs = multierr.Append(errs, err)
 
-func isSameMetric(ts *prompb.TimeSeries, lbls []prompb.Label) bool {
-	if len(ts.Labels) != len(lbls) {
-		return false
-	}
-	for i, l := range ts.Labels {
-		if l.Name != ts.Labels[i].Name || l.Value != ts.Labels[i].Value {
-			return false
-		}
-	}
-	return true
-}
-
-// addExemplars adds exemplars for the dataPoint. For each exemplar, if it can find a bucket bound corresponding to its value,
-// the exemplar is added to the bucket bound's time series, provided that the time series' has samples.
-func (c *PrometheusConverter) addExemplars(ctx context.Context, dataPoint pmetric.HistogramDataPoint, bucketBounds []bucketBoundsData) error {
-	if len(bucketBounds) == 0 {
-		return nil
-	}
-
-	exemplars, err := getPromExemplars(ctx, &c.everyN, dataPoint)
-	if err != nil {
-		return err
-	}
-	if len(exemplars) == 0 {
-		return nil
-	}
-
-	sort.Sort(byBucketBoundsData(bucketBounds))
-	for _, exemplar := range exemplars {
-		for _, bound := range bucketBounds {
-			if err := c.everyN.checkContext(ctx); err != nil {
-				return err
-			}
-			if len(bound.ts.Samples) > 0 && exemplar.Value <= bound.bound {
-				bound.ts.Exemplars = append(bound.ts.Exemplars, exemplar)
-				break
-			}
-		}
-	}
-
-	return nil
-}
-
-// addSample finds a TimeSeries that corresponds to lbls, and adds sample to it.
-// If there is no corresponding TimeSeries already, it's created.
-// The corresponding TimeSeries is returned.
-// If either lbls is nil/empty or sample is nil, nothing is done.
-func (c *PrometheusConverter) addSample(sample *prompb.Sample, lbls []prompb.Label) *prompb.TimeSeries {
-	if sample == nil || len(lbls) == 0 {
-		// This shouldn't happen
-		return nil
-	}
-
-	ts, _ := c.getOrCreateTimeSeries(lbls)
-	ts.Samples = append(ts.Samples, *sample)
-	return ts
+	return
 }
 
 func NewPromoteResourceAttributes(otlpCfg config.OTLPConfig) *PromoteResourceAttributes {
@@ -361,30 +309,43 @@ func NewPromoteResourceAttributes(otlpCfg config.OTLPConfig) *PromoteResourceAtt
 	}
 }
 
-// promotedAttributes returns labels for promoted resourceAttributes.
-func (s *PromoteResourceAttributes) promotedAttributes(resourceAttributes pcommon.Map) []prompb.Label {
+// addPromotedAttributes adds labels for promoted resourceAttributes to the builder.
+func (s *PromoteResourceAttributes) addPromotedAttributes(builder *labels.Builder, resourceAttributes pcommon.Map, allowUTF8 bool) error {
 	if s == nil {
 		return nil
 	}
 
-	var promotedAttrs []prompb.Label
+	labelNamer := otlptranslator.LabelNamer{UTF8Allowed: allowUTF8}
 	if s.promoteAll {
-		promotedAttrs = make([]prompb.Label, 0, resourceAttributes.Len())
+		var err error
 		resourceAttributes.Range(func(name string, value pcommon.Value) bool {
 			if _, exists := s.attrs[name]; !exists {
-				promotedAttrs = append(promotedAttrs, prompb.Label{Name: name, Value: value.AsString()})
-			}
-			return true
-		})
-	} else {
-		promotedAttrs = make([]prompb.Label, 0, len(s.attrs))
-		resourceAttributes.Range(func(name string, value pcommon.Value) bool {
-			if _, exists := s.attrs[name]; exists {
-				promotedAttrs = append(promotedAttrs, prompb.Label{Name: name, Value: value.AsString()})
+				var normalized string
+				normalized, err = labelNamer.Build(name)
+				if err != nil {
+					return false
+				}
+				if builder.Get(normalized) == "" {
+					builder.Set(normalized, value.AsString())
+				}
 			}
 			return true
 		})
+		return err
 	}
-	sort.Stable(ByLabelName(promotedAttrs))
-	return promotedAttrs
+	var err error
+	resourceAttributes.Range(func(name string, value pcommon.Value) bool {
+		if _, exists := s.attrs[name]; exists {
+			var normalized string
+			normalized, err = labelNamer.Build(name)
+			if err != nil {
+				return false
+			}
+			if builder.Get(normalized) == "" {
+				builder.Set(normalized, value.AsString())
+			}
+		}
+		return true
+	})
+	return err
 }

storage/remote/otlptranslator/prometheusremotewrite/metrics_to_prw_test.go

@@ -19,19 +19,20 @@ package prometheusremotewrite
 import (
 	"context"
 	"fmt"
-	"sort"
 	"testing"
 	"time"
 
+	"github.com/prometheus/common/model"
 	"github.com/prometheus/otlptranslator"
 	"github.com/stretchr/testify/require"
 	"go.opentelemetry.io/collector/pdata/pcommon"
 	"go.opentelemetry.io/collector/pdata/pmetric"
 	"go.opentelemetry.io/collector/pdata/pmetric/pmetricotlp"
 
-	"github.com/prometheus/prometheus/model/labels"
-	"github.com/prometheus/prometheus/prompb"
-	"github.com/prometheus/prometheus/util/testutil"
+	"github.com/prometheus/prometheus/model/histogram"
+	modelLabels "github.com/prometheus/prometheus/model/labels"
+	"github.com/prometheus/prometheus/model/metadata"
+	"github.com/prometheus/prometheus/storage/remote/otlptranslator/prometheusremotewrite/labels"
 )
 
 func TestFromMetrics(t *testing.T) {
@@ -77,9 +78,9 @@ func TestFromMetrics(t *testing.T) {
 			},
 		} {
 			t.Run(tc.name, func(t *testing.T) {
-				converter := NewPrometheusConverter()
+				mockAppender := &mockCombinedAppender{}
+				converter := NewPrometheusConverter(mockAppender)
 				payload, wantPromMetrics := createExportRequest(5, 128, 128, 2, 0, tc.settings, tc.temporality)
-				var expMetadata []prompb.MetricMetadata
 				seenFamilyNames := map[string]struct{}{}
 				for _, wantMetric := range wantPromMetrics {
 					if _, exists := seenFamilyNames[wantMetric.familyName]; exists {
@@ -90,12 +91,6 @@ func TestFromMetrics(t *testing.T) {
 					}
 
 					seenFamilyNames[wantMetric.familyName] = struct{}{}
-					expMetadata = append(expMetadata, prompb.MetricMetadata{
-						Type:             wantMetric.metricType,
-						MetricFamilyName: wantMetric.familyName,
-						Help:             wantMetric.description,
-						Unit:             wantMetric.unit,
-					})
 				}
 
 				annots, err := converter.FromMetrics(
@@ -106,16 +101,13 @@ func TestFromMetrics(t *testing.T) {
 				require.NoError(t, err)
 				require.Empty(t, annots)
 
-				testutil.RequireEqual(t, expMetadata, converter.Metadata())
-
-				ts := converter.TimeSeries()
+				ts := mockAppender.samples
 				require.Len(t, ts, 1536+1) // +1 for the target_info.
 
 				tgtInfoCount := 0
 				for _, s := range ts {
-					b := labels.NewScratchBuilder(2)
-					lbls := s.ToLabels(&b, nil)
-					if lbls.Get(labels.MetricName) == "target_info" {
+					lbls := s.ls
+					if lbls.Get(modelLabels.MetricName) == "target_info" {
 						tgtInfoCount++
 						require.Equal(t, "test-namespace/test-service", lbls.Get("job"))
 						require.Equal(t, "id1234", lbls.Get("instance"))
@@ -156,7 +148,8 @@ func TestFromMetrics(t *testing.T) {
 
 			generateAttributes(h.Attributes(), "series", 1)
 
-			converter := NewPrometheusConverter()
+			mockAppender := &mockCombinedAppender{}
+			converter := NewPrometheusConverter(mockAppender)
 			annots, err := converter.FromMetrics(
 				context.Background(),
 				request.Metrics(),
@@ -165,24 +158,19 @@ func TestFromMetrics(t *testing.T) {
 			require.NoError(t, err)
 			require.Empty(t, annots)
 
-			series := converter.TimeSeries()
-
 			if convertHistogramsToNHCB {
-				require.Len(t, series[0].Histograms, 1)
-				require.Empty(t, series[0].Samples)
+				require.Len(t, mockAppender.histograms, 1)
+				require.Empty(t, mockAppender.samples)
 			} else {
-				require.Len(t, series, 3)
-				for i := range series {
-					require.Len(t, series[i].Samples, 1)
-					require.Nil(t, series[i].Histograms)
-				}
+				require.Empty(t, mockAppender.histograms)
+				require.Len(t, mockAppender.samples, 3)
 			}
 		})
 	}
 
 	t.Run("context cancellation", func(t *testing.T) {
 		settings := Settings{}
-		converter := NewPrometheusConverter()
+		converter := NewPrometheusConverter(&mockCombinedAppender{})
 		ctx, cancel := context.WithCancel(context.Background())
 		// Verify that converter.FromMetrics respects cancellation.
 		cancel()
@@ -195,7 +183,7 @@ func TestFromMetrics(t *testing.T) {
 
 	t.Run("context timeout", func(t *testing.T) {
 		settings := Settings{}
-		converter := NewPrometheusConverter()
+		converter := NewPrometheusConverter(&mockCombinedAppender{})
 		// Verify that converter.FromMetrics respects timeout.
 		ctx, cancel := context.WithTimeout(context.Background(), 0)
 		t.Cleanup(cancel)
@@ -228,7 +216,7 @@ func TestFromMetrics(t *testing.T) {
 			generateAttributes(h.Attributes(), "series", 10)
 		}
 
-		converter := NewPrometheusConverter()
+		converter := NewPrometheusConverter(&mockCombinedAppender{})
 		annots, err := converter.FromMetrics(context.Background(), request.Metrics(), Settings{})
 		require.NoError(t, err)
 		require.NotEmpty(t, annots)
@@ -261,7 +249,7 @@ func TestFromMetrics(t *testing.T) {
 			generateAttributes(h.Attributes(), "series", 10)
 		}
 
-		converter := NewPrometheusConverter()
+		converter := NewPrometheusConverter(&mockCombinedAppender{})
 		annots, err := converter.FromMetrics(
 			context.Background(),
 			request.Metrics(),
@@ -292,7 +280,6 @@ func TestFromMetrics(t *testing.T) {
 		metrics := rm.ScopeMetrics().AppendEmpty().Metrics()
 		ts := pcommon.NewTimestampFromTime(time.Now())
 
-		var expMetadata []prompb.MetricMetadata
 		for i := range 3 {
 			m := metrics.AppendEmpty()
 			m.SetEmptyGauge()
@@ -308,68 +295,65 @@ func TestFromMetrics(t *testing.T) {
 				generateAttributes(point.Attributes(), "series", 2)
 				curTs = curTs.Add(defaultLookbackDelta / 4)
 			}
-
-			namer := otlptranslator.MetricNamer{}
-			name, err := namer.Build(TranslatorMetricFromOtelMetric(m))
-			require.NoError(t, err)
-			expMetadata = append(expMetadata, prompb.MetricMetadata{
-				Type:             otelMetricTypeToPromMetricType(m),
-				MetricFamilyName: name,
-				Help:             m.Description(),
-				Unit:             m.Unit(),
-			})
 		}
 
-		converter := NewPrometheusConverter()
-		annots, err := converter.FromMetrics(
-			context.Background(),
-			request.Metrics(),
-			Settings{
-				LookbackDelta: defaultLookbackDelta,
-			},
-		)
+		mockAppender := &mockCombinedAppender{}
+		converter := NewPrometheusConverter(mockAppender)
+		settings := Settings{
+			LookbackDelta: defaultLookbackDelta,
+		}
+
+		annots, err := converter.FromMetrics(context.Background(), request.Metrics(), settings)
 		require.NoError(t, err)
 		require.Empty(t, annots)
 
-		testutil.RequireEqual(t, expMetadata, converter.Metadata())
-
-		timeSeries := converter.TimeSeries()
-		tgtInfoCount := 0
-		for _, s := range timeSeries {
-			b := labels.NewScratchBuilder(2)
-			lbls := s.ToLabels(&b, nil)
-			if lbls.Get(labels.MetricName) != "target_info" {
-				continue
-			}
-
-			tgtInfoCount++
-			require.Equal(t, "test-namespace/test-service", lbls.Get("job"))
-			require.Equal(t, "id1234", lbls.Get("instance"))
-			require.False(t, lbls.Has("service_name"))
-			require.False(t, lbls.Has("service_namespace"))
-			require.False(t, lbls.Has("service_instance_id"))
-			// There should be a target_info sample at the earliest metric timestamp, then two spaced lookback delta/2 apart,
-			// then one at the latest metric timestamp.
-			testutil.RequireEqual(t, []prompb.Sample{
-				{
-					Value:     1,
-					Timestamp: ts.AsTime().UnixMilli(),
-				},
-				{
-					Value:     1,
-					Timestamp: ts.AsTime().Add(defaultLookbackDelta / 2).UnixMilli(),
-				},
-				{
-					Value:     1,
-					Timestamp: ts.AsTime().Add(defaultLookbackDelta).UnixMilli(),
-				},
-				{
-					Value:     1,
-					Timestamp: ts.AsTime().Add(defaultLookbackDelta + defaultLookbackDelta/4).UnixMilli(),
-				},
-			}, s.Samples)
+		require.Len(t, mockAppender.samples, 22)
+		// There should be a target_info sample at the earliest metric timestamp, then two spaced lookback delta/2 apart,
+		// then one at the latest metric timestamp.
+		targetInfoLabels := labels.FromStrings(
+			"__name__", "target_info",
+			"instance", "id1234",
+			"job", "test-namespace/test-service",
+			"resource_name_1", "value-1",
+			"resource_name_2", "value-2",
+			"resource_name_3", "value-3",
+			"resource_name_4", "value-4",
+			"resource_name_5", "value-5",
+		)
+		targetInfoMeta := metadata.Metadata{
+			Type: model.MetricTypeGauge,
+			Help: "Target metadata",
 		}
-		require.Equal(t, 1, tgtInfoCount)
+		requireEqual(t, []combinedSample{
+			{
+				metricFamilyName: "target_info",
+				v:                1,
+				t:                ts.AsTime().UnixMilli(),
+				ls:               targetInfoLabels,
+				meta:             targetInfoMeta,
+			},
+			{
+				metricFamilyName: "target_info",
+				v:                1,
+				t:                ts.AsTime().Add(defaultLookbackDelta / 2).UnixMilli(),
+				ls:               targetInfoLabels,
+				meta:             targetInfoMeta,
+			},
+			{
+				metricFamilyName: "target_info",
+				v:                1,
+				t:                ts.AsTime().Add(defaultLookbackDelta).UnixMilli(),
+				ls:               targetInfoLabels,
+				meta:             targetInfoMeta,
+			},
+			{
+				metricFamilyName: "target_info",
+				v:                1,
+				t:                ts.AsTime().Add(defaultLookbackDelta + defaultLookbackDelta/4).UnixMilli(),
+				ls:               targetInfoLabels,
+				meta:             targetInfoMeta,
+			},
+		}, mockAppender.samples[len(mockAppender.samples)-4:])
 	})
 }
 
@@ -377,12 +361,13 @@ func TestTemporality(t *testing.T) {
 	ts := time.Unix(100, 0)
 
 	tests := []struct {
-		name           string
-		allowDelta     bool
-		convertToNHCB  bool
-		inputSeries    []pmetric.Metric
-		expectedSeries []prompb.TimeSeries
-		expectedError  string
+		name               string
+		allowDelta         bool
+		convertToNHCB      bool
+		inputSeries        []pmetric.Metric
+		expectedSamples    []combinedSample
+		expectedHistograms []combinedHistogram
+		expectedError      string
 	}{
 		{
 			name:       "all cumulative when delta not allowed",
@@ -391,9 +376,9 @@ func TestTemporality(t *testing.T) {
 				createOtelSum("test_metric_1", pmetric.AggregationTemporalityCumulative, ts),
 				createOtelSum("test_metric_2", pmetric.AggregationTemporalityCumulative, ts),
 			},
-			expectedSeries: []prompb.TimeSeries{
-				createPromFloatSeries("test_metric_1", ts),
-				createPromFloatSeries("test_metric_2", ts),
+			expectedSamples: []combinedSample{
+				createPromFloatSeries("test_metric_1", ts, model.MetricTypeCounter),
+				createPromFloatSeries("test_metric_2", ts, model.MetricTypeCounter),
 			},
 		},
 		{
@@ -403,9 +388,9 @@ func TestTemporality(t *testing.T) {
 				createOtelSum("test_metric_1", pmetric.AggregationTemporalityDelta, ts),
 				createOtelSum("test_metric_2", pmetric.AggregationTemporalityDelta, ts),
 			},
-			expectedSeries: []prompb.TimeSeries{
-				createPromFloatSeries("test_metric_1", ts),
-				createPromFloatSeries("test_metric_2", ts),
+			expectedSamples: []combinedSample{
+				createPromFloatSeries("test_metric_1", ts, model.MetricTypeUnknown),
+				createPromFloatSeries("test_metric_2", ts, model.MetricTypeUnknown),
 			},
 		},
 		{
@@ -415,9 +400,9 @@ func TestTemporality(t *testing.T) {
 				createOtelSum("test_metric_1", pmetric.AggregationTemporalityDelta, ts),
 				createOtelSum("test_metric_2", pmetric.AggregationTemporalityCumulative, ts),
 			},
-			expectedSeries: []prompb.TimeSeries{
-				createPromFloatSeries("test_metric_1", ts),
-				createPromFloatSeries("test_metric_2", ts),
+			expectedSamples: []combinedSample{
+				createPromFloatSeries("test_metric_1", ts, model.MetricTypeUnknown),
+				createPromFloatSeries("test_metric_2", ts, model.MetricTypeCounter),
 			},
 		},
 		{
@@ -427,8 +412,8 @@ func TestTemporality(t *testing.T) {
 				createOtelSum("test_metric_1", pmetric.AggregationTemporalityCumulative, ts),
 				createOtelSum("test_metric_2", pmetric.AggregationTemporalityDelta, ts),
 			},
-			expectedSeries: []prompb.TimeSeries{
-				createPromFloatSeries("test_metric_1", ts),
+			expectedSamples: []combinedSample{
+				createPromFloatSeries("test_metric_1", ts, model.MetricTypeCounter),
 			},
 			expectedError: `invalid temporality and type combination for metric "test_metric_2"`,
 		},
@@ -439,8 +424,8 @@ func TestTemporality(t *testing.T) {
 				createOtelSum("test_metric_1", pmetric.AggregationTemporalityCumulative, ts),
 				createOtelSum("test_metric_2", pmetric.AggregationTemporalityUnspecified, ts),
 			},
-			expectedSeries: []prompb.TimeSeries{
-				createPromFloatSeries("test_metric_1", ts),
+			expectedSamples: []combinedSample{
+				createPromFloatSeries("test_metric_1", ts, model.MetricTypeCounter),
 			},
 			expectedError: `invalid temporality and type combination for metric "test_metric_2"`,
 		},
@@ -450,8 +435,8 @@ func TestTemporality(t *testing.T) {
 			inputSeries: []pmetric.Metric{
 				createOtelExponentialHistogram("test_histogram", pmetric.AggregationTemporalityCumulative, ts),
 			},
-			expectedSeries: []prompb.TimeSeries{
-				createPromNativeHistogramSeries("test_histogram", prompb.Histogram_UNKNOWN, ts),
+			expectedHistograms: []combinedHistogram{
+				createPromNativeHistogramSeries("test_histogram", histogram.UnknownCounterReset, ts, model.MetricTypeHistogram),
 			},
 		},
 		{
@@ -461,9 +446,9 @@ func TestTemporality(t *testing.T) {
 				createOtelExponentialHistogram("test_histogram_1", pmetric.AggregationTemporalityDelta, ts),
 				createOtelExponentialHistogram("test_histogram_2", pmetric.AggregationTemporalityCumulative, ts),
 			},
-			expectedSeries: []prompb.TimeSeries{
-				createPromNativeHistogramSeries("test_histogram_1", prompb.Histogram_GAUGE, ts),
-				createPromNativeHistogramSeries("test_histogram_2", prompb.Histogram_UNKNOWN, ts),
+			expectedHistograms: []combinedHistogram{
+				createPromNativeHistogramSeries("test_histogram_1", histogram.GaugeType, ts, model.MetricTypeUnknown),
+				createPromNativeHistogramSeries("test_histogram_2", histogram.UnknownCounterReset, ts, model.MetricTypeHistogram),
 			},
 		},
 		{
@@ -473,8 +458,8 @@ func TestTemporality(t *testing.T) {
 				createOtelExponentialHistogram("test_histogram_1", pmetric.AggregationTemporalityDelta, ts),
 				createOtelExponentialHistogram("test_histogram_2", pmetric.AggregationTemporalityCumulative, ts),
 			},
-			expectedSeries: []prompb.TimeSeries{
-				createPromNativeHistogramSeries("test_histogram_2", prompb.Histogram_UNKNOWN, ts),
+			expectedHistograms: []combinedHistogram{
+				createPromNativeHistogramSeries("test_histogram_2", histogram.UnknownCounterReset, ts, model.MetricTypeHistogram),
 			},
 			expectedError: `invalid temporality and type combination for metric "test_histogram_1"`,
 		},
@@ -485,8 +470,8 @@ func TestTemporality(t *testing.T) {
 			inputSeries: []pmetric.Metric{
 				createOtelExplicitHistogram("test_histogram", pmetric.AggregationTemporalityCumulative, ts),
 			},
-			expectedSeries: []prompb.TimeSeries{
-				createPromNHCBSeries("test_histogram", prompb.Histogram_UNKNOWN, ts),
+			expectedHistograms: []combinedHistogram{
+				createPromNHCBSeries("test_histogram", histogram.UnknownCounterReset, ts, model.MetricTypeHistogram),
 			},
 		},
 		{
@@ -497,9 +482,9 @@ func TestTemporality(t *testing.T) {
 				createOtelExplicitHistogram("test_histogram_1", pmetric.AggregationTemporalityDelta, ts),
 				createOtelExplicitHistogram("test_histogram_2", pmetric.AggregationTemporalityCumulative, ts),
 			},
-			expectedSeries: []prompb.TimeSeries{
-				createPromNHCBSeries("test_histogram_1", prompb.Histogram_GAUGE, ts),
-				createPromNHCBSeries("test_histogram_2", prompb.Histogram_UNKNOWN, ts),
+			expectedHistograms: []combinedHistogram{
+				createPromNHCBSeries("test_histogram_1", histogram.GaugeType, ts, model.MetricTypeUnknown),
+				createPromNHCBSeries("test_histogram_2", histogram.UnknownCounterReset, ts, model.MetricTypeHistogram),
 			},
 		},
 		{
@@ -510,8 +495,8 @@ func TestTemporality(t *testing.T) {
 				createOtelExplicitHistogram("test_histogram_1", pmetric.AggregationTemporalityDelta, ts),
 				createOtelExplicitHistogram("test_histogram_2", pmetric.AggregationTemporalityCumulative, ts),
 			},
-			expectedSeries: []prompb.TimeSeries{
-				createPromNHCBSeries("test_histogram_2", prompb.Histogram_UNKNOWN, ts),
+			expectedHistograms: []combinedHistogram{
+				createPromNHCBSeries("test_histogram_2", histogram.UnknownCounterReset, ts, model.MetricTypeHistogram),
 			},
 			expectedError: `invalid temporality and type combination for metric "test_histogram_1"`,
 		},
@@ -523,8 +508,8 @@ func TestTemporality(t *testing.T) {
 				createOtelExplicitHistogram("test_histogram_1", pmetric.AggregationTemporalityDelta, ts),
 				createOtelExplicitHistogram("test_histogram_2", pmetric.AggregationTemporalityCumulative, ts),
 			},
-			expectedSeries: createPromClassicHistogramSeries("test_histogram_2", ts),
-			expectedError:  `invalid temporality and type combination for metric "test_histogram_1"`,
+			expectedSamples: createPromClassicHistogramSeries("test_histogram_2", ts, model.MetricTypeHistogram),
+			expectedError:   `invalid temporality and type combination for metric "test_histogram_1"`,
 		},
 		{
 			name:          "delta histogram with buckets and convertToNHCB=false when allowed",
@@ -534,9 +519,9 @@ func TestTemporality(t *testing.T) {
 				createOtelExplicitHistogram("test_histogram_1", pmetric.AggregationTemporalityDelta, ts),
 				createOtelExplicitHistogram("test_histogram_2", pmetric.AggregationTemporalityCumulative, ts),
 			},
-			expectedSeries: append(
-				createPromClassicHistogramSeries("test_histogram_1", ts),
-				createPromClassicHistogramSeries("test_histogram_2", ts)...,
+			expectedSamples: append(
+				createPromClassicHistogramSeries("test_histogram_1", ts, model.MetricTypeUnknown),
+				createPromClassicHistogramSeries("test_histogram_2", ts, model.MetricTypeHistogram)...,
 			),
 		},
 		{
@@ -544,15 +529,15 @@ func TestTemporality(t *testing.T) {
 			inputSeries: []pmetric.Metric{
 				createOtelSummary("test_summary_1", ts),
 			},
-			expectedSeries: createPromSummarySeries("test_summary_1", ts),
+			expectedSamples: createPromSummarySeries("test_summary_1", ts),
 		},
 		{
 			name: "gauge does not have temporality",
 			inputSeries: []pmetric.Metric{
 				createOtelGauge("test_gauge_1", ts),
 			},
-			expectedSeries: []prompb.TimeSeries{
-				createPromFloatSeries("test_gauge_1", ts),
+			expectedSamples: []combinedSample{
+				createPromFloatSeries("test_gauge_1", ts, model.MetricTypeGauge),
 			},
 		},
 		{
@@ -560,8 +545,7 @@ func TestTemporality(t *testing.T) {
 			inputSeries: []pmetric.Metric{
 				createOtelEmptyType("test_empty"),
 			},
-			expectedSeries: []prompb.TimeSeries{},
-			expectedError:  `could not get aggregation temporality for test_empty as it has unsupported metric type Empty`,
+			expectedError: `could not get aggregation temporality for test_empty as it has unsupported metric type Empty`,
 		},
 	}
 
@@ -575,7 +559,8 @@ func TestTemporality(t *testing.T) {
 				s.CopyTo(sm.Metrics().AppendEmpty())
 			}
 
-			c := NewPrometheusConverter()
+			mockAppender := &mockCombinedAppender{}
+			c := NewPrometheusConverter(mockAppender)
 			settings := Settings{
 				AllowDeltaTemporality:   tc.allowDelta,
 				ConvertHistogramsToNHCB: tc.convertToNHCB,
@@ -589,10 +574,9 @@ func TestTemporality(t *testing.T) {
 				require.NoError(t, err)
 			}
 
-			series := c.TimeSeries()
-
 			// Sort series to make the test deterministic.
-			testutil.RequireEqual(t, sortTimeSeries(tc.expectedSeries), sortTimeSeries(series))
+			requireEqual(t, tc.expectedSamples, mockAppender.samples)
+			requireEqual(t, tc.expectedHistograms, mockAppender.histograms)
 		})
 	}
 }
@@ -603,6 +587,7 @@ func createOtelSum(name string, temporality pmetric.AggregationTemporality, ts t
 	m.SetName(name)
 	sum := m.SetEmptySum()
 	sum.SetAggregationTemporality(temporality)
+	sum.SetIsMonotonic(true)
 	dp := sum.DataPoints().AppendEmpty()
 	dp.SetDoubleValue(5)
 	dp.SetTimestamp(pcommon.NewTimestampFromTime(ts))
@@ -610,16 +595,15 @@ func createOtelSum(name string, temporality pmetric.AggregationTemporality, ts t
 	return m
 }
 
-func createPromFloatSeries(name string, ts time.Time) prompb.TimeSeries {
-	return prompb.TimeSeries{
-		Labels: []prompb.Label{
-			{Name: "__name__", Value: name},
-			{Name: "test_label", Value: "test_value"},
+func createPromFloatSeries(name string, ts time.Time, typ model.MetricType) combinedSample {
+	return combinedSample{
+		metricFamilyName: name,
+		ls:               labels.FromStrings("__name__", name, "test_label", "test_value"),
+		t:                ts.UnixMilli(),
+		v:                5,
+		meta: metadata.Metadata{
+			Type: typ,
 		},
-		Samples: []prompb.Sample{{
-			Value:     5,
-			Timestamp: ts.UnixMilli(),
-		}},
 	}
 }
 
@@ -649,22 +633,21 @@ func createOtelExponentialHistogram(name string, temporality pmetric.Aggregation
 	return m
 }
 
-func createPromNativeHistogramSeries(name string, hint prompb.Histogram_ResetHint, ts time.Time) prompb.TimeSeries {
-	return prompb.TimeSeries{
-		Labels: []prompb.Label{
-			{Name: "__name__", Value: name},
-			{Name: "test_label", Value: "test_value"},
+func createPromNativeHistogramSeries(name string, hint histogram.CounterResetHint, ts time.Time, typ model.MetricType) combinedHistogram {
+	return combinedHistogram{
+		metricFamilyName: name,
+		ls:               labels.FromStrings("__name__", name, "test_label", "test_value"),
+		t:                ts.UnixMilli(),
+		meta: metadata.Metadata{
+			Type: typ,
 		},
-		Histograms: []prompb.Histogram{
-			{
-				Count:         &prompb.Histogram_CountInt{CountInt: 1},
-				Sum:           5,
-				Schema:        0,
-				ZeroThreshold: 1e-128,
-				ZeroCount:     &prompb.Histogram_ZeroCountInt{ZeroCountInt: 0},
-				Timestamp:     ts.UnixMilli(),
-				ResetHint:     hint,
-			},
+		h: &histogram.Histogram{
+			Count:            1,
+			Sum:              5,
+			Schema:           0,
+			ZeroThreshold:    1e-128,
+			ZeroCount:        0,
+			CounterResetHint: hint,
 		},
 	}
 }
@@ -685,72 +668,77 @@ func createOtelExplicitHistogram(name string, temporality pmetric.AggregationTem
 	return m
 }
 
-func createPromNHCBSeries(name string, hint prompb.Histogram_ResetHint, ts time.Time) prompb.TimeSeries {
-	return prompb.TimeSeries{
-		Labels: []prompb.Label{
-			{Name: "__name__", Value: name},
-			{Name: "test_label", Value: "test_value"},
+func createPromNHCBSeries(name string, hint histogram.CounterResetHint, ts time.Time, typ model.MetricType) combinedHistogram {
+	return combinedHistogram{
+		metricFamilyName: name,
+		ls:               labels.FromStrings("__name__", name, "test_label", "test_value"),
+		meta: metadata.Metadata{
+			Type: typ,
 		},
-		Histograms: []prompb.Histogram{
-			{
-				Count:         &prompb.Histogram_CountInt{CountInt: 20},
-				Sum:           30,
-				Schema:        -53,
-				ZeroThreshold: 0,
-				ZeroCount:     nil,
-				PositiveSpans: []prompb.BucketSpan{
-					{
-						Length: 3,
-					},
+		t: ts.UnixMilli(),
+		h: &histogram.Histogram{
+			Count:         20,
+			Sum:           30,
+			Schema:        -53,
+			ZeroThreshold: 0,
+			PositiveSpans: []histogram.Span{
+				{
+					Length: 3,
 				},
-				PositiveDeltas: []int64{10, 0, -10},
-				CustomValues:   []float64{1, 2},
-				Timestamp:      ts.UnixMilli(),
-				ResetHint:      hint,
 			},
+			PositiveBuckets:  []int64{10, 0, -10},
+			CustomValues:     []float64{1, 2},
+			CounterResetHint: hint,
 		},
 	}
 }
 
-func createPromClassicHistogramSeries(name string, ts time.Time) []prompb.TimeSeries {
-	return []prompb.TimeSeries{
+func createPromClassicHistogramSeries(name string, ts time.Time, typ model.MetricType) []combinedSample {
+	return []combinedSample{
 		{
-			Labels: []prompb.Label{
-				{Name: "__name__", Value: name + "_bucket"},
-				{Name: "le", Value: "1"},
-				{Name: "test_label", Value: "test_value"},
+			metricFamilyName: name,
+			ls:               labels.FromStrings("__name__", name+"_sum", "test_label", "test_value"),
+			t:                ts.UnixMilli(),
+			v:                30,
+			meta: metadata.Metadata{
+				Type: typ,
 			},
-			Samples: []prompb.Sample{{Value: 10, Timestamp: ts.UnixMilli()}},
 		},
 		{
-			Labels: []prompb.Label{
-				{Name: "__name__", Value: name + "_bucket"},
-				{Name: "le", Value: "2"},
-				{Name: "test_label", Value: "test_value"},
+			metricFamilyName: name,
+			ls:               labels.FromStrings("__name__", name+"_count", "test_label", "test_value"),
+			t:                ts.UnixMilli(),
+			v:                20,
+			meta: metadata.Metadata{
+				Type: typ,
 			},
-			Samples: []prompb.Sample{{Value: 20, Timestamp: ts.UnixMilli()}},
 		},
 		{
-			Labels: []prompb.Label{
-				{Name: "__name__", Value: name + "_bucket"},
-				{Name: "le", Value: "+Inf"},
-				{Name: "test_label", Value: "test_value"},
+			metricFamilyName: name,
+			ls:               labels.FromStrings("__name__", name+"_bucket", "le", "1", "test_label", "test_value"),
+			t:                ts.UnixMilli(),
+			v:                10,
+			meta: metadata.Metadata{
+				Type: typ,
 			},
-			Samples: []prompb.Sample{{Value: 20, Timestamp: ts.UnixMilli()}},
 		},
 		{
-			Labels: []prompb.Label{
-				{Name: "__name__", Value: name + "_count"},
-				{Name: "test_label", Value: "test_value"},
+			metricFamilyName: name,
+			ls:               labels.FromStrings("__name__", name+"_bucket", "le", "2", "test_label", "test_value"),
+			t:                ts.UnixMilli(),
+			v:                20,
+			meta: metadata.Metadata{
+				Type: typ,
 			},
-			Samples: []prompb.Sample{{Value: 20, Timestamp: ts.UnixMilli()}},
 		},
 		{
-			Labels: []prompb.Label{
-				{Name: "__name__", Value: name + "_sum"},
-				{Name: "test_label", Value: "test_value"},
+			metricFamilyName: name,
+			ls:               labels.FromStrings("__name__", name+"_bucket", "le", "+Inf", "test_label", "test_value"),
+			t:                ts.UnixMilli(),
+			v:                20,
+			meta: metadata.Metadata{
+				Type: typ,
 			},
-			Samples: []prompb.Sample{{Value: 30, Timestamp: ts.UnixMilli()}},
 		},
 	}
 }
@@ -771,38 +759,34 @@ func createOtelSummary(name string, ts time.Time) pmetric.Metric {
 	return m
 }
 
-func createPromSummarySeries(name string, ts time.Time) []prompb.TimeSeries {
-	return []prompb.TimeSeries{
+func createPromSummarySeries(name string, ts time.Time) []combinedSample {
+	return []combinedSample{
 		{
-			Labels: []prompb.Label{
-				{Name: "__name__", Value: name + "_sum"},
-				{Name: "test_label", Value: "test_value"},
+			metricFamilyName: name,
+			ls:               labels.FromStrings("__name__", name+"_sum", "test_label", "test_value"),
+			t:                ts.UnixMilli(),
+			v:                18,
+			meta: metadata.Metadata{
+				Type: model.MetricTypeSummary,
 			},
-			Samples: []prompb.Sample{{
-				Value:     18,
-				Timestamp: ts.UnixMilli(),
-			}},
 		},
 		{
-			Labels: []prompb.Label{
-				{Name: "__name__", Value: name + "_count"},
-				{Name: "test_label", Value: "test_value"},
+			metricFamilyName: name,
+			ls:               labels.FromStrings("__name__", name+"_count", "test_label", "test_value"),
+			t:                ts.UnixMilli(),
+			v:                9,
+			meta: metadata.Metadata{
+				Type: model.MetricTypeSummary,
 			},
-			Samples: []prompb.Sample{{
-				Value:     9,
-				Timestamp: ts.UnixMilli(),
-			}},
 		},
 		{
-			Labels: []prompb.Label{
-				{Name: "__name__", Value: name},
-				{Name: "quantile", Value: "0.5"},
-				{Name: "test_label", Value: "test_value"},
+			metricFamilyName: name,
+			ls:               labels.FromStrings("__name__", name, "quantile", "0.5", "test_label", "test_value"),
+			t:                ts.UnixMilli(),
+			v:                2,
+			meta: metadata.Metadata{
+				Type: model.MetricTypeSummary,
 			},
-			Samples: []prompb.Sample{{
-				Value:     2,
-				Timestamp: ts.UnixMilli(),
-			}},
 		},
 	}
 }
@@ -814,20 +798,6 @@ func createOtelEmptyType(name string) pmetric.Metric {
 	return m
 }
 
-func sortTimeSeries(series []prompb.TimeSeries) []prompb.TimeSeries {
-	for i := range series {
-		sort.Slice(series[i].Labels, func(j, k int) bool {
-			return series[i].Labels[j].Name < series[i].Labels[k].Name
-		})
-	}
-
-	sort.Slice(series, func(i, j int) bool {
-		return fmt.Sprint(series[i].Labels) < fmt.Sprint(series[j].Labels)
-	})
-
-	return series
-}
-
 func TestTranslatorMetricFromOtelMetric(t *testing.T) {
 	tests := []struct {
 		name           string
@@ -968,7 +938,7 @@ func BenchmarkPrometheusConverter_FromMetrics(b *testing.B) {
 				b.Run(fmt.Sprintf("histogram count: %v", histogramCount), func(b *testing.B) {
 					nonHistogramCounts := []int{0, 1000}
 
-					if resourceAttributeCount == 0 && histogramCount == 0 {
+					if histogramCount == 0 {
 						// Don't bother running a scenario where we'll generate no series.
 						nonHistogramCounts = []int{1000}
 					}
@@ -992,12 +962,12 @@ func BenchmarkPrometheusConverter_FromMetrics(b *testing.B) {
 											b.ResetTimer()
 
 											for range b.N {
-												converter := NewPrometheusConverter()
+												mockAppender := &mockCombinedAppender{}
+												converter := NewPrometheusConverter(mockAppender)
 												annots, err := converter.FromMetrics(context.Background(), payload.Metrics(), settings)
 												require.NoError(b, err)
 												require.Empty(b, annots)
-												require.NotNil(b, converter.TimeSeries())
-												require.NotNil(b, converter.Metadata())
+												require.Positive(b, len(mockAppender.samples)+len(mockAppender.histograms))
 											}
 										})
 									}
@@ -1014,7 +984,7 @@ func BenchmarkPrometheusConverter_FromMetrics(b *testing.B) {
 type wantPrometheusMetric struct {
 	name        string
 	familyName  string
-	metricType  prompb.MetricMetadata_MetricType
+	metricType  model.MetricType
 	description string
 	unit        string
 }
@@ -1061,11 +1031,11 @@ func createExportRequest(resourceAttributeCount, histogramCount, nonHistogramCou
 		generateAttributes(h.Attributes(), "series", labelsPerMetric)
 		generateExemplars(h.Exemplars(), exemplarsPerSeries, ts)
 
-		metricType := prompb.MetricMetadata_HISTOGRAM
+		metricType := model.MetricTypeHistogram
 		if temporality != pmetric.AggregationTemporalityCumulative {
 			// We're in an early phase of implementing delta support (proposal: https://github.com/prometheus/proposals/pull/48/)
 			// We don't have a proper way to flag delta metrics yet, therefore marking the metric type as unknown for now.
-			metricType = prompb.MetricMetadata_UNKNOWN
+			metricType = model.MetricTypeUnknown
 		}
 		wantPromMetrics = append(wantPromMetrics, wantPrometheusMetric{
 			name:        fmt.Sprintf("histogram_%d%s_bucket", i, suffix),
@@ -1103,11 +1073,11 @@ func createExportRequest(resourceAttributeCount, histogramCount, nonHistogramCou
 		generateAttributes(point.Attributes(), "series", labelsPerMetric)
 		generateExemplars(point.Exemplars(), exemplarsPerSeries, ts)
 
-		metricType := prompb.MetricMetadata_GAUGE
+		metricType := model.MetricTypeGauge
 		if temporality != pmetric.AggregationTemporalityCumulative {
 			// We're in an early phase of implementing delta support (proposal: https://github.com/prometheus/proposals/pull/48/)
 			// We don't have a proper way to flag delta metrics yet, therefore marking the metric type as unknown for now.
-			metricType = prompb.MetricMetadata_UNKNOWN
+			metricType = model.MetricTypeUnknown
 		}
 		wantPromMetrics = append(wantPromMetrics, wantPrometheusMetric{
 			name:        fmt.Sprintf("non_monotonic_sum_%d%s", i, suffix),
@@ -1137,11 +1107,11 @@ func createExportRequest(resourceAttributeCount, histogramCount, nonHistogramCou
 			counterSuffix = suffix + "_total"
 		}
 
-		metricType := prompb.MetricMetadata_COUNTER
+		metricType := model.MetricTypeCounter
 		if temporality != pmetric.AggregationTemporalityCumulative {
 			// We're in an early phase of implementing delta support (proposal: https://github.com/prometheus/proposals/pull/48/)
 			// We don't have a proper way to flag delta metrics yet, therefore marking the metric type as unknown for now.
-			metricType = prompb.MetricMetadata_UNKNOWN
+			metricType = model.MetricTypeUnknown
 		}
 		wantPromMetrics = append(wantPromMetrics, wantPrometheusMetric{
 			name:        fmt.Sprintf("monotonic_sum_%d%s", i, counterSuffix),
@@ -1167,7 +1137,7 @@ func createExportRequest(resourceAttributeCount, histogramCount, nonHistogramCou
 		wantPromMetrics = append(wantPromMetrics, wantPrometheusMetric{
 			name:        fmt.Sprintf("gauge_%d%s", i, suffix),
 			familyName:  fmt.Sprintf("gauge_%d%s", i, suffix),
-			metricType:  prompb.MetricMetadata_GAUGE,
+			metricType:  model.MetricTypeGauge,
 			unit:        "unit",
 			description: "gauge",
 		})

storage/remote/otlptranslator/prometheusremotewrite/number_data_points.go

@@ -24,12 +24,12 @@ import (
 	"go.opentelemetry.io/collector/pdata/pcommon"
 	"go.opentelemetry.io/collector/pdata/pmetric"
 
+	"github.com/prometheus/prometheus/model/metadata"
 	"github.com/prometheus/prometheus/model/value"
-	"github.com/prometheus/prometheus/prompb"
 )
 
 func (c *PrometheusConverter) addGaugeNumberDataPoints(ctx context.Context, dataPoints pmetric.NumberDataPointSlice,
-	resource pcommon.Resource, settings Settings, metadata prompb.MetricMetadata, scope scope,
+	resource pcommon.Resource, settings Settings, name string, scope scope, meta metadata.Metadata,
 ) error {
 	for x := 0; x < dataPoints.Len(); x++ {
 		if err := c.everyN.checkContext(ctx); err != nil {
@@ -37,42 +37,42 @@ func (c *PrometheusConverter) addGaugeNumberDataPoints(ctx context.Context, data
 		}
 
 		pt := dataPoints.At(x)
-		labels, err := createAttributes(
+		labels, err := c.createAttributes(
 			resource,
 			pt.Attributes(),
 			scope,
 			settings,
 			nil,
 			true,
-			metadata,
+			meta,
 			model.MetricNameLabel,
-			metadata.MetricFamilyName,
+			name,
 		)
 		if err != nil {
 			return err
 		}
-		sample := &prompb.Sample{
-			// convert ns to ms
-			Timestamp: convertTimeStamp(pt.Timestamp()),
-		}
+		var val float64
 		switch pt.ValueType() {
 		case pmetric.NumberDataPointValueTypeInt:
-			sample.Value = float64(pt.IntValue())
+			val = float64(pt.IntValue())
 		case pmetric.NumberDataPointValueTypeDouble:
-			sample.Value = pt.DoubleValue()
+			val = pt.DoubleValue()
 		}
 		if pt.Flags().NoRecordedValue() {
-			sample.Value = math.Float64frombits(value.StaleNaN)
+			val = math.Float64frombits(value.StaleNaN)
+		}
+		ts := convertTimeStamp(pt.Timestamp())
+		ct := convertTimeStamp(pt.StartTimestamp())
+		if err := c.appender.AppendSample(name, labels, meta, ts, ct, val, nil); err != nil {
+			return err
 		}
-
-		c.addSample(sample, labels)
 	}
 
 	return nil
 }
 
 func (c *PrometheusConverter) addSumNumberDataPoints(ctx context.Context, dataPoints pmetric.NumberDataPointSlice,
-	resource pcommon.Resource, metric pmetric.Metric, settings Settings, metadata prompb.MetricMetadata, scope scope,
+	resource pcommon.Resource, metric pmetric.Metric, settings Settings, name string, scope scope, meta metadata.Metadata,
 ) error {
 	for x := 0; x < dataPoints.Len(); x++ {
 		if err := c.everyN.checkContext(ctx); err != nil {
@@ -80,59 +80,51 @@ func (c *PrometheusConverter) addSumNumberDataPoints(ctx context.Context, dataPo
 		}
 
 		pt := dataPoints.At(x)
-		lbls, err := createAttributes(
+		lbls, err := c.createAttributes(
 			resource,
 			pt.Attributes(),
 			scope,
 			settings,
 			nil,
 			true,
-			metadata,
+			meta,
 			model.MetricNameLabel,
-			metadata.MetricFamilyName,
+			name,
 		)
+		if err != nil {
+			return nil
+		}
+		var val float64
+		switch pt.ValueType() {
+		case pmetric.NumberDataPointValueTypeInt:
+			val = float64(pt.IntValue())
+		case pmetric.NumberDataPointValueTypeDouble:
+			val = pt.DoubleValue()
+		}
+		if pt.Flags().NoRecordedValue() {
+			val = math.Float64frombits(value.StaleNaN)
+		}
+		ts := convertTimeStamp(pt.Timestamp())
+		ct := convertTimeStamp(pt.StartTimestamp())
+		exemplars, err := c.getPromExemplars(ctx, pt.Exemplars())
 		if err != nil {
 			return err
 		}
-		sample := &prompb.Sample{
-			// convert ns to ms
-			Timestamp: convertTimeStamp(pt.Timestamp()),
-		}
-		switch pt.ValueType() {
-		case pmetric.NumberDataPointValueTypeInt:
-			sample.Value = float64(pt.IntValue())
-		case pmetric.NumberDataPointValueTypeDouble:
-			sample.Value = pt.DoubleValue()
-		}
-		if pt.Flags().NoRecordedValue() {
-			sample.Value = math.Float64frombits(value.StaleNaN)
-		}
-
-		ts := c.addSample(sample, lbls)
-		if ts != nil {
-			exemplars, err := getPromExemplars[pmetric.NumberDataPoint](ctx, &c.everyN, pt)
-			if err != nil {
-				return err
-			}
-			ts.Exemplars = append(ts.Exemplars, exemplars...)
+		if err := c.appender.AppendSample(name, lbls, meta, ts, ct, val, exemplars); err != nil {
+			return err
 		}
 
 		// add created time series if needed
-		if settings.ExportCreatedMetric && metric.Sum().IsMonotonic() {
-			startTimestamp := pt.StartTimestamp()
-			if startTimestamp == 0 {
-				return nil
-			}
-
-			createdLabels := make([]prompb.Label, len(lbls))
-			copy(createdLabels, lbls)
-			for i, l := range createdLabels {
-				if l.Name == model.MetricNameLabel {
-					createdLabels[i].Value = metadata.MetricFamilyName + createdSuffix
-					break
+		if settings.ExportCreatedMetric && metric.Sum().IsMonotonic() && pt.StartTimestamp() != 0 {
+			c.builder.Reset(lbls)
+			// Add created suffix to the metric name for CT series.
+			c.builder.Set(model.MetricNameLabel, name+createdSuffix)
+			ls := c.builder.Labels()
+			if c.timeSeriesIsNew(ls) {
+				if err := c.appender.AppendSample(name, ls, meta, ts, 0, float64(ct), nil); err != nil {
+					return err
 				}
 			}
-			c.addTimeSeriesIfNeeded(createdLabels, startTimestamp, pt.Timestamp())
 		}
 	}
 

storage/remote/otlptranslator/prometheusremotewrite/number_data_points_test.go

@@ -26,7 +26,9 @@ import (
 	"go.opentelemetry.io/collector/pdata/pcommon"
 	"go.opentelemetry.io/collector/pdata/pmetric"
 
-	"github.com/prometheus/prometheus/prompb"
+	"github.com/prometheus/prometheus/model/exemplar"
+	"github.com/prometheus/prometheus/model/metadata"
+	"github.com/prometheus/prometheus/storage/remote/otlptranslator/prometheusremotewrite/labels"
 )
 
 func TestPrometheusConverter_addGaugeNumberDataPoints(t *testing.T) {
@@ -47,7 +49,7 @@ func TestPrometheusConverter_addGaugeNumberDataPoints(t *testing.T) {
 		metric       func() pmetric.Metric
 		scope        scope
 		promoteScope bool
-		want         func() map[uint64]*prompb.TimeSeries
+		want         func() []combinedSample
 	}{
 		{
 			name: "gauge without scope promotion",
@@ -60,19 +62,17 @@ func TestPrometheusConverter_addGaugeNumberDataPoints(t *testing.T) {
 			},
 			scope:        defaultScope,
 			promoteScope: false,
-			want: func() map[uint64]*prompb.TimeSeries {
-				labels := []prompb.Label{
-					{Name: model.MetricNameLabel, Value: "test"},
-				}
-				return map[uint64]*prompb.TimeSeries{
-					timeSeriesSignature(labels): {
-						Labels: labels,
-						Samples: []prompb.Sample{
-							{
-								Value:     1,
-								Timestamp: convertTimeStamp(pcommon.Timestamp(ts)),
-							},
-						},
+			want: func() []combinedSample {
+				lbls := labels.FromStrings(
+					model.MetricNameLabel, "test",
+				)
+				return []combinedSample{
+					{
+						metricFamilyName: "test",
+						ls:               lbls,
+						meta:             metadata.Metadata{},
+						t:                convertTimeStamp(pcommon.Timestamp(ts)),
+						v:                1,
 					},
 				}
 			},
@@ -88,24 +88,22 @@ func TestPrometheusConverter_addGaugeNumberDataPoints(t *testing.T) {
 			},
 			scope:        defaultScope,
 			promoteScope: true,
-			want: func() map[uint64]*prompb.TimeSeries {
-				labels := []prompb.Label{
-					{Name: model.MetricNameLabel, Value: "test"},
-					{Name: "otel_scope_name", Value: defaultScope.name},
-					{Name: "otel_scope_schema_url", Value: defaultScope.schemaURL},
-					{Name: "otel_scope_version", Value: defaultScope.version},
-					{Name: "otel_scope_attr1", Value: "value1"},
-					{Name: "otel_scope_attr2", Value: "value2"},
-				}
-				return map[uint64]*prompb.TimeSeries{
-					timeSeriesSignature(labels): {
-						Labels: labels,
-						Samples: []prompb.Sample{
-							{
-								Value:     1,
-								Timestamp: convertTimeStamp(pcommon.Timestamp(ts)),
-							},
-						},
+			want: func() []combinedSample {
+				lbls := labels.FromStrings(
+					model.MetricNameLabel, "test",
+					"otel_scope_name", defaultScope.name,
+					"otel_scope_schema_url", defaultScope.schemaURL,
+					"otel_scope_version", defaultScope.version,
+					"otel_scope_attr1", "value1",
+					"otel_scope_attr2", "value2",
+				)
+				return []combinedSample{
+					{
+						metricFamilyName: "test",
+						ls:               lbls,
+						meta:             metadata.Metadata{},
+						t:                convertTimeStamp(pcommon.Timestamp(ts)),
+						v:                1,
 					},
 				}
 			},
@@ -114,7 +112,8 @@ func TestPrometheusConverter_addGaugeNumberDataPoints(t *testing.T) {
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			metric := tt.metric()
-			converter := NewPrometheusConverter()
+			mockAppender := &mockCombinedAppender{}
+			converter := NewPrometheusConverter(mockAppender)
 
 			converter.addGaugeNumberDataPoints(
 				context.Background(),
@@ -124,11 +123,13 @@ func TestPrometheusConverter_addGaugeNumberDataPoints(t *testing.T) {
 					ExportCreatedMetric:  true,
 					PromoteScopeMetadata: tt.promoteScope,
 				},
-				prompb.MetricMetadata{MetricFamilyName: metric.Name()},
+				metric.Name(),
 				tt.scope,
+				metadata.Metadata{},
 			)
+			require.NoError(t, mockAppender.Commit())
 
-			require.Equal(t, tt.want(), converter.unique)
+			requireEqual(t, tt.want(), mockAppender.samples)
 			require.Empty(t, converter.conflicts)
 		})
 	}
@@ -152,7 +153,7 @@ func TestPrometheusConverter_addSumNumberDataPoints(t *testing.T) {
 		metric       func() pmetric.Metric
 		scope        scope
 		promoteScope bool
-		want         func() map[uint64]*prompb.TimeSeries
+		want         func() []combinedSample
 	}{
 		{
 			name: "sum without scope promotion",
@@ -166,19 +167,17 @@ func TestPrometheusConverter_addSumNumberDataPoints(t *testing.T) {
 			},
 			scope:        defaultScope,
 			promoteScope: false,
-			want: func() map[uint64]*prompb.TimeSeries {
-				labels := []prompb.Label{
-					{Name: model.MetricNameLabel, Value: "test"},
-				}
-				return map[uint64]*prompb.TimeSeries{
-					timeSeriesSignature(labels): {
-						Labels: labels,
-						Samples: []prompb.Sample{
-							{
-								Value:     1,
-								Timestamp: convertTimeStamp(ts),
-							},
-						},
+			want: func() []combinedSample {
+				lbls := labels.FromStrings(
+					model.MetricNameLabel, "test",
+				)
+				return []combinedSample{
+					{
+						metricFamilyName: "test",
+						ls:               lbls,
+						meta:             metadata.Metadata{},
+						t:                convertTimeStamp(ts),
+						v:                1,
 					},
 				}
 			},
@@ -195,24 +194,22 @@ func TestPrometheusConverter_addSumNumberDataPoints(t *testing.T) {
 			},
 			scope:        defaultScope,
 			promoteScope: true,
-			want: func() map[uint64]*prompb.TimeSeries {
-				labels := []prompb.Label{
-					{Name: model.MetricNameLabel, Value: "test"},
-					{Name: "otel_scope_name", Value: defaultScope.name},
-					{Name: "otel_scope_schema_url", Value: defaultScope.schemaURL},
-					{Name: "otel_scope_version", Value: defaultScope.version},
-					{Name: "otel_scope_attr1", Value: "value1"},
-					{Name: "otel_scope_attr2", Value: "value2"},
-				}
-				return map[uint64]*prompb.TimeSeries{
-					timeSeriesSignature(labels): {
-						Labels: labels,
-						Samples: []prompb.Sample{
-							{
-								Value:     1,
-								Timestamp: convertTimeStamp(ts),
-							},
-						},
+			want: func() []combinedSample {
+				lbls := labels.FromStrings(
+					model.MetricNameLabel, "test",
+					"otel_scope_name", defaultScope.name,
+					"otel_scope_schema_url", defaultScope.schemaURL,
+					"otel_scope_version", defaultScope.version,
+					"otel_scope_attr1", "value1",
+					"otel_scope_attr2", "value2",
+				)
+				return []combinedSample{
+					{
+						metricFamilyName: "test",
+						ls:               lbls,
+						meta:             metadata.Metadata{},
+						t:                convertTimeStamp(ts),
+						v:                1,
 					},
 				}
 			},
@@ -231,18 +228,18 @@ func TestPrometheusConverter_addSumNumberDataPoints(t *testing.T) {
 			},
 			scope:        defaultScope,
 			promoteScope: false,
-			want: func() map[uint64]*prompb.TimeSeries {
-				labels := []prompb.Label{
-					{Name: model.MetricNameLabel, Value: "test"},
-				}
-				return map[uint64]*prompb.TimeSeries{
-					timeSeriesSignature(labels): {
-						Labels: labels,
-						Samples: []prompb.Sample{{
-							Value:     1,
-							Timestamp: convertTimeStamp(ts),
-						}},
-						Exemplars: []prompb.Exemplar{
+			want: func() []combinedSample {
+				lbls := labels.FromStrings(
+					model.MetricNameLabel, "test",
+				)
+				return []combinedSample{
+					{
+						metricFamilyName: "test",
+						ls:               lbls,
+						meta:             metadata.Metadata{},
+						t:                convertTimeStamp(ts),
+						v:                1,
+						es: []exemplar.Exemplar{
 							{Value: 2},
 						},
 					},
@@ -266,25 +263,28 @@ func TestPrometheusConverter_addSumNumberDataPoints(t *testing.T) {
 			},
 			scope:        defaultScope,
 			promoteScope: false,
-			want: func() map[uint64]*prompb.TimeSeries {
-				labels := []prompb.Label{
-					{Name: model.MetricNameLabel, Value: "test_sum"},
-				}
-				createdLabels := []prompb.Label{
-					{Name: model.MetricNameLabel, Value: "test_sum" + createdSuffix},
-				}
-				return map[uint64]*prompb.TimeSeries{
-					timeSeriesSignature(labels): {
-						Labels: labels,
-						Samples: []prompb.Sample{
-							{Value: 1, Timestamp: convertTimeStamp(ts)},
-						},
+			want: func() []combinedSample {
+				lbls := labels.FromStrings(
+					model.MetricNameLabel, "test_sum",
+				)
+				createdLabels := labels.FromStrings(
+					model.MetricNameLabel, "test_sum"+createdSuffix,
+				)
+				return []combinedSample{
+					{
+						metricFamilyName: "test_sum",
+						ls:               lbls,
+						meta:             metadata.Metadata{},
+						t:                convertTimeStamp(ts),
+						ct:               convertTimeStamp(ts),
+						v:                1,
 					},
-					timeSeriesSignature(createdLabels): {
-						Labels: createdLabels,
-						Samples: []prompb.Sample{
-							{Value: float64(convertTimeStamp(ts)), Timestamp: convertTimeStamp(ts)},
-						},
+					{
+						metricFamilyName: "test_sum",
+						ls:               createdLabels,
+						meta:             metadata.Metadata{},
+						t:                convertTimeStamp(ts),
+						v:                float64(convertTimeStamp(ts)),
 					},
 				}
 			},
@@ -304,16 +304,17 @@ func TestPrometheusConverter_addSumNumberDataPoints(t *testing.T) {
 			},
 			scope:        defaultScope,
 			promoteScope: false,
-			want: func() map[uint64]*prompb.TimeSeries {
-				labels := []prompb.Label{
-					{Name: model.MetricNameLabel, Value: "test_sum"},
-				}
-				return map[uint64]*prompb.TimeSeries{
-					timeSeriesSignature(labels): {
-						Labels: labels,
-						Samples: []prompb.Sample{
-							{Value: 0, Timestamp: convertTimeStamp(ts)},
-						},
+			want: func() []combinedSample {
+				lbls := labels.FromStrings(
+					model.MetricNameLabel, "test_sum",
+				)
+				return []combinedSample{
+					{
+						metricFamilyName: "test_sum",
+						ls:               lbls,
+						meta:             metadata.Metadata{},
+						t:                convertTimeStamp(ts),
+						v:                0,
 					},
 				}
 			},
@@ -333,16 +334,17 @@ func TestPrometheusConverter_addSumNumberDataPoints(t *testing.T) {
 			},
 			scope:        defaultScope,
 			promoteScope: false,
-			want: func() map[uint64]*prompb.TimeSeries {
-				labels := []prompb.Label{
-					{Name: model.MetricNameLabel, Value: "test_sum"},
-				}
-				return map[uint64]*prompb.TimeSeries{
-					timeSeriesSignature(labels): {
-						Labels: labels,
-						Samples: []prompb.Sample{
-							{Value: 0, Timestamp: convertTimeStamp(ts)},
-						},
+			want: func() []combinedSample {
+				lbls := labels.FromStrings(
+					model.MetricNameLabel, "test_sum",
+				)
+				return []combinedSample{
+					{
+						metricFamilyName: "test_sum",
+						ls:               lbls,
+						meta:             metadata.Metadata{},
+						t:                convertTimeStamp(ts),
+						v:                0,
 					},
 				}
 			},
@@ -351,7 +353,8 @@ func TestPrometheusConverter_addSumNumberDataPoints(t *testing.T) {
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			metric := tt.metric()
-			converter := NewPrometheusConverter()
+			mockAppender := &mockCombinedAppender{}
+			converter := NewPrometheusConverter(mockAppender)
 
 			converter.addSumNumberDataPoints(
 				context.Background(),
@@ -362,11 +365,13 @@ func TestPrometheusConverter_addSumNumberDataPoints(t *testing.T) {
 					ExportCreatedMetric:  true,
 					PromoteScopeMetadata: tt.promoteScope,
 				},
-				prompb.MetricMetadata{MetricFamilyName: metric.Name()},
+				metric.Name(),
 				tt.scope,
+				metadata.Metadata{},
 			)
+			require.NoError(t, mockAppender.Commit())
 
-			require.Equal(t, tt.want(), converter.unique)
+			requireEqual(t, tt.want(), mockAppender.samples)
 			require.Empty(t, converter.conflicts)
 		})
 	}

storage/remote/otlptranslator/prometheusremotewrite/otlp_to_openmetrics_metadata.go

@@ -17,42 +17,41 @@
 package prometheusremotewrite
 
 import (
+	"github.com/prometheus/common/model"
 	"go.opentelemetry.io/collector/pdata/pmetric"
-
-	"github.com/prometheus/prometheus/prompb"
 )
 
-func otelMetricTypeToPromMetricType(otelMetric pmetric.Metric) prompb.MetricMetadata_MetricType {
+func otelMetricTypeToPromMetricType(otelMetric pmetric.Metric) model.MetricType {
 	switch otelMetric.Type() {
 	case pmetric.MetricTypeGauge:
-		return prompb.MetricMetadata_GAUGE
+		return model.MetricTypeGauge
 	case pmetric.MetricTypeSum:
-		metricType := prompb.MetricMetadata_GAUGE
+		metricType := model.MetricTypeGauge
 		if otelMetric.Sum().IsMonotonic() {
-			metricType = prompb.MetricMetadata_COUNTER
+			metricType = model.MetricTypeCounter
 		}
 		// We're in an early phase of implementing delta support (proposal: https://github.com/prometheus/proposals/pull/48/)
 		// We don't have a proper way to flag delta metrics yet, therefore marking the metric type as unknown for now.
 		if otelMetric.Sum().AggregationTemporality() == pmetric.AggregationTemporalityDelta {
-			metricType = prompb.MetricMetadata_UNKNOWN
+			metricType = model.MetricTypeUnknown
 		}
 		return metricType
 	case pmetric.MetricTypeHistogram:
 		// We're in an early phase of implementing delta support (proposal: https://github.com/prometheus/proposals/pull/48/)
 		// We don't have a proper way to flag delta metrics yet, therefore marking the metric type as unknown for now.
 		if otelMetric.Histogram().AggregationTemporality() == pmetric.AggregationTemporalityDelta {
-			return prompb.MetricMetadata_UNKNOWN
+			return model.MetricTypeUnknown
 		}
-		return prompb.MetricMetadata_HISTOGRAM
+		return model.MetricTypeHistogram
 	case pmetric.MetricTypeSummary:
-		return prompb.MetricMetadata_SUMMARY
+		return model.MetricTypeSummary
 	case pmetric.MetricTypeExponentialHistogram:
 		if otelMetric.ExponentialHistogram().AggregationTemporality() == pmetric.AggregationTemporalityDelta {
 			// We're in an early phase of implementing delta support (proposal: https://github.com/prometheus/proposals/pull/48/)
 			// We don't have a proper way to flag delta metrics yet, therefore marking the metric type as unknown for now.
-			return prompb.MetricMetadata_UNKNOWN
+			return model.MetricTypeUnknown
 		}
-		return prompb.MetricMetadata_HISTOGRAM
+		return model.MetricTypeHistogram
 	}
-	return prompb.MetricMetadata_UNKNOWN
+	return model.MetricTypeUnknown
 }

storage/remote/otlptranslator/prometheusremotewrite/timeseries.go

@@ -1,46 +0,0 @@
-// Copyright 2024 The Prometheus Authors
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-// http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-// Provenance-includes-location:
-// https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/95e8f8fdc2a9dc87230406c9a3cf02be4fd68bea/pkg/translator/prometheusremotewrite/metrics_to_prw.go
-// Provenance-includes-license: Apache-2.0
-// Provenance-includes-copyright: Copyright The OpenTelemetry Authors.
-
-package prometheusremotewrite
-
-import (
-	"github.com/prometheus/prometheus/prompb"
-)
-
-// TimeSeries returns a slice of the prompb.TimeSeries that were converted from OTel format.
-func (c *PrometheusConverter) TimeSeries() []prompb.TimeSeries {
-	conflicts := 0
-	for _, ts := range c.conflicts {
-		conflicts += len(ts)
-	}
-	allTS := make([]prompb.TimeSeries, 0, len(c.unique)+conflicts)
-	for _, ts := range c.unique {
-		allTS = append(allTS, *ts)
-	}
-	for _, cTS := range c.conflicts {
-		for _, ts := range cTS {
-			allTS = append(allTS, *ts)
-		}
-	}
-
-	return allTS
-}
-
-// Metadata returns a slice of the prompb.Metadata that were converted from OTel format.
-func (c *PrometheusConverter) Metadata() []prompb.MetricMetadata {
-	return c.metadata
-}

storage/remote/write_handler.go

@@ -535,25 +535,28 @@ type OTLPOptions struct {
 	LookbackDelta time.Duration
 	// Add type and unit labels to the metrics.
 	EnableTypeAndUnitLabels bool
+	// IngestCTZeroSample enables writing zero samples based on the start time
+	// of metrics.
+	IngestCTZeroSample bool
 }
 
 // NewOTLPWriteHandler creates a http.Handler that accepts OTLP write requests and
 // writes them to the provided appendable.
-func NewOTLPWriteHandler(logger *slog.Logger, _ prometheus.Registerer, appendable storage.Appendable, configFunc func() config.Config, opts OTLPOptions) http.Handler {
+func NewOTLPWriteHandler(logger *slog.Logger, reg prometheus.Registerer, appendable storage.Appendable, configFunc func() config.Config, opts OTLPOptions) http.Handler {
 	if opts.NativeDelta && opts.ConvertDelta {
 		// This should be validated when iterating through feature flags, so not expected to fail here.
 		panic("cannot enable native delta ingestion and delta2cumulative conversion at the same time")
 	}
 
 	ex := &rwExporter{
-		writeHandler: &writeHandler{
-			logger:     logger,
-			appendable: appendable,
-		},
+		logger:                  logger,
+		appendable:              appendable,
 		config:                  configFunc,
 		allowDeltaTemporality:   opts.NativeDelta,
 		lookbackDelta:           opts.LookbackDelta,
+		ingestCTZeroSample:      opts.IngestCTZeroSample,
 		enableTypeAndUnitLabels: opts.EnableTypeAndUnitLabels,
+		reg:                     reg,
 	}
 
 	wh := &otlpWriteHandler{logger: logger, defaultConsumer: ex}
@@ -587,18 +590,24 @@ func NewOTLPWriteHandler(logger *slog.Logger, _ prometheus.Registerer, appendabl
 }
 
 type rwExporter struct {
-	*writeHandler
+	logger                  *slog.Logger
+	appendable              storage.Appendable
 	config                  func() config.Config
 	allowDeltaTemporality   bool
 	lookbackDelta           time.Duration
+	ingestCTZeroSample      bool
 	enableTypeAndUnitLabels bool
+	reg                     prometheus.Registerer
 }
 
 func (rw *rwExporter) ConsumeMetrics(ctx context.Context, md pmetric.Metrics) error {
 	otlpCfg := rw.config().OTLPConfig
-
-	converter := otlptranslator.NewPrometheusConverter()
-
+	app := &timeLimitAppender{
+		Appender: rw.appendable.Appender(ctx),
+		maxTime:  timestamp.FromTime(time.Now().Add(maxAheadTime)),
+	}
+	combinedAppender := otlptranslator.NewCombinedAppender(app, rw.logger, rw.reg, rw.ingestCTZeroSample)
+	converter := otlptranslator.NewPrometheusConverter(combinedAppender)
 	annots, err := converter.FromMetrics(ctx, md, otlptranslator.Settings{
 		AddMetricSuffixes:                 otlpCfg.TranslationStrategy.ShouldAddSuffixes(),
 		AllowUTF8:                         !otlpCfg.TranslationStrategy.ShouldEscape(),
@@ -610,18 +619,18 @@ func (rw *rwExporter) ConsumeMetrics(ctx context.Context, md pmetric.Metrics) er
 		LookbackDelta:                     rw.lookbackDelta,
 		EnableTypeAndUnitLabels:           rw.enableTypeAndUnitLabels,
 	})
-	if err != nil {
-		rw.logger.Warn("Error translating OTLP metrics to Prometheus write request", "err", err)
-	}
+
+	defer func() {
+		if err != nil {
+			_ = app.Rollback()
+			return
+		}
+		err = app.Commit()
+	}()
 	ws, _ := annots.AsStrings("", 0, 0)
 	if len(ws) > 0 {
 		rw.logger.Warn("Warnings translating OTLP metrics to Prometheus write request", "warnings", ws)
 	}
-
-	err = rw.write(ctx, &prompb.WriteRequest{
-		Timeseries: converter.TimeSeries(),
-		Metadata:   converter.Metadata(),
-	})
 	return err
 }
 

storage/remote/write_test.go

@@ -44,6 +44,7 @@ import (
 	"github.com/prometheus/prometheus/config"
 	"github.com/prometheus/prometheus/model/histogram"
 	"github.com/prometheus/prometheus/model/labels"
+	"github.com/prometheus/prometheus/model/metadata"
 	"github.com/prometheus/prometheus/model/relabel"
 	"github.com/prometheus/prometheus/storage"
 )
@@ -381,14 +382,16 @@ func TestWriteStorageApplyConfig_PartialUpdate(t *testing.T) {
 	require.NoError(t, s.Close())
 }
 
-func TestOTLPWriteHandler(t *testing.T) {
+func TestOTLPWriteHandlerNaming(t *testing.T) {
 	timestamp := time.Now()
-	exportRequest := generateOTLPWriteRequest(timestamp)
+	var zeroTime time.Time
+	exportRequest := generateOTLPWriteRequest(timestamp, zeroTime)
 	for _, testCase := range []struct {
 		name              string
 		otlpCfg           config.OTLPConfig
 		typeAndUnitLabels bool
 		expectedSamples   []mockSample
+		expectedMetadata  []mockMetadata
 	}{
 		{
 			name: "NoTranslation/NoTypeAndUnitLabels",
@@ -397,24 +400,70 @@ func TestOTLPWriteHandler(t *testing.T) {
 			},
 			expectedSamples: []mockSample{
 				{
-					l: labels.New(labels.Label{Name: "__name__", Value: "test.counter"},
-						labels.Label{Name: "foo.bar", Value: "baz"},
-						labels.Label{Name: "instance", Value: "test-instance"},
-						labels.Label{Name: "job", Value: "test-service"}),
+					l: labels.FromStrings(model.MetricNameLabel, "test.counter", "foo.bar", "baz", "instance", "test-instance", "job", "test-service"),
 					t: timestamp.UnixMilli(),
 					v: 10.0,
 				},
 				{
-					l: labels.New(
-						labels.Label{Name: "__name__", Value: "target_info"},
-						labels.Label{Name: "host.name", Value: "test-host"},
-						labels.Label{Name: "instance", Value: "test-instance"},
-						labels.Label{Name: "job", Value: "test-service"},
-					),
+					l: labels.FromStrings(model.MetricNameLabel, "target_info", "host.name", "test-host", "instance", "test-instance", "job", "test-service"),
 					t: timestamp.UnixMilli(),
 					v: 1,
 				},
 			},
+			expectedMetadata: []mockMetadata{
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.counter", "foo.bar", "baz", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeCounter, Unit: "bytes", Help: "test-counter-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.gauge", "foo.bar", "baz", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeGauge, Unit: "bytes", Help: "test-gauge-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.histogram_sum", "foo.bar", "baz", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.histogram_count", "foo.bar", "baz", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.histogram_bucket", "foo.bar", "baz", "instance", "test-instance", "job", "test-service", "le", "0"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.histogram_bucket", "foo.bar", "baz", "instance", "test-instance", "job", "test-service", "le", "1"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.histogram_bucket", "foo.bar", "baz", "instance", "test-instance", "job", "test-service", "le", "2"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.histogram_bucket", "foo.bar", "baz", "instance", "test-instance", "job", "test-service", "le", "3"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.histogram_bucket", "foo.bar", "baz", "instance", "test-instance", "job", "test-service", "le", "4"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.histogram_bucket", "foo.bar", "baz", "instance", "test-instance", "job", "test-service", "le", "5"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.histogram_bucket", "foo.bar", "baz", "instance", "test-instance", "job", "test-service", "le", "+Inf"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.exponential.histogram", "foo.bar", "baz", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-exponential-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "target_info", "host.name", "test-host", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeGauge, Unit: "", Help: "Target metadata"},
+				},
+			},
 		},
 		{
 			name: "NoTranslation/WithTypeAndUnitLabels",
@@ -424,26 +473,71 @@ func TestOTLPWriteHandler(t *testing.T) {
 			typeAndUnitLabels: true,
 			expectedSamples: []mockSample{
 				{
-					l: labels.New(labels.Label{Name: "__name__", Value: "test.counter"},
-						labels.Label{Name: "__type__", Value: "counter"},
-						labels.Label{Name: "__unit__", Value: "bytes"},
-						labels.Label{Name: "foo.bar", Value: "baz"},
-						labels.Label{Name: "instance", Value: "test-instance"},
-						labels.Label{Name: "job", Value: "test-service"}),
+					l: labels.FromStrings(model.MetricNameLabel, "test.counter", "__type__", "counter", "__unit__", "bytes", "foo.bar", "baz", "instance", "test-instance", "job", "test-service"),
 					t: timestamp.UnixMilli(),
 					v: 10.0,
 				},
 				{
-					l: labels.New(
-						labels.Label{Name: "__name__", Value: "target_info"},
-						labels.Label{Name: "host.name", Value: "test-host"},
-						labels.Label{Name: "instance", Value: "test-instance"},
-						labels.Label{Name: "job", Value: "test-service"},
-					),
+					l: labels.FromStrings(model.MetricNameLabel, "target_info", "host.name", "test-host", "instance", "test-instance", "job", "test-service"),
 					t: timestamp.UnixMilli(),
 					v: 1,
 				},
 			},
+			expectedMetadata: []mockMetadata{
+				{
+					// Metadata labels follow series labels.
+					l: labels.FromStrings(model.MetricNameLabel, "test.counter", "__type__", "counter", "__unit__", "bytes", "foo.bar", "baz", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeCounter, Unit: "bytes", Help: "test-counter-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.gauge", "__type__", "gauge", "__unit__", "bytes", "foo.bar", "baz", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeGauge, Unit: "bytes", Help: "test-gauge-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.histogram_sum", "__type__", "histogram", "__unit__", "bytes", "foo.bar", "baz", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.histogram_count", "__type__", "histogram", "__unit__", "bytes", "foo.bar", "baz", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.histogram_bucket", "__type__", "histogram", "__unit__", "bytes", "foo.bar", "baz", "instance", "test-instance", "job", "test-service", "le", "0"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.histogram_bucket", "__type__", "histogram", "__unit__", "bytes", "foo.bar", "baz", "instance", "test-instance", "job", "test-service", "le", "1"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.histogram_bucket", "__type__", "histogram", "__unit__", "bytes", "foo.bar", "baz", "instance", "test-instance", "job", "test-service", "le", "2"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.histogram_bucket", "__type__", "histogram", "__unit__", "bytes", "foo.bar", "baz", "instance", "test-instance", "job", "test-service", "le", "3"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.histogram_bucket", "__type__", "histogram", "__unit__", "bytes", "foo.bar", "baz", "instance", "test-instance", "job", "test-service", "le", "4"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.histogram_bucket", "__type__", "histogram", "__unit__", "bytes", "foo.bar", "baz", "instance", "test-instance", "job", "test-service", "le", "5"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.histogram_bucket", "__type__", "histogram", "__unit__", "bytes", "foo.bar", "baz", "instance", "test-instance", "job", "test-service", "le", "+Inf"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.exponential.histogram", "__type__", "histogram", "__unit__", "bytes", "foo.bar", "baz", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-exponential-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "target_info", "host.name", "test-host", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeGauge, Unit: "", Help: "Target metadata"},
+				},
+			},
 		},
 		{
 			name: "UnderscoreEscapingWithSuffixes/NoTypeAndUnitLabels",
@@ -452,24 +546,71 @@ func TestOTLPWriteHandler(t *testing.T) {
 			},
 			expectedSamples: []mockSample{
 				{
-					l: labels.New(labels.Label{Name: "__name__", Value: "test_counter_bytes_total"},
-						labels.Label{Name: "foo_bar", Value: "baz"},
-						labels.Label{Name: "instance", Value: "test-instance"},
-						labels.Label{Name: "job", Value: "test-service"}),
+					l: labels.FromStrings(model.MetricNameLabel, "test_counter_bytes_total", "foo_bar", "baz", "instance", "test-instance", "job", "test-service"),
 					t: timestamp.UnixMilli(),
 					v: 10.0,
 				},
 				{
-					l: labels.New(
-						labels.Label{Name: "__name__", Value: "target_info"},
-						labels.Label{Name: "host_name", Value: "test-host"},
-						labels.Label{Name: "instance", Value: "test-instance"},
-						labels.Label{Name: "job", Value: "test-service"},
-					),
+					l: labels.FromStrings(model.MetricNameLabel, "target_info", "host_name", "test-host", "instance", "test-instance", "job", "test-service"),
 					t: timestamp.UnixMilli(),
 					v: 1,
 				},
 			},
+			expectedMetadata: []mockMetadata{
+				// All get _bytes unit suffix and counter also gets _total.
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test_counter_bytes_total", "foo_bar", "baz", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeCounter, Unit: "bytes", Help: "test-counter-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test_gauge_bytes", "foo_bar", "baz", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeGauge, Unit: "bytes", Help: "test-gauge-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test_histogram_bytes_sum", "foo_bar", "baz", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test_histogram_bytes_count", "foo_bar", "baz", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test_histogram_bytes_bucket", "foo_bar", "baz", "instance", "test-instance", "job", "test-service", "le", "0"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test_histogram_bytes_bucket", "foo_bar", "baz", "instance", "test-instance", "job", "test-service", "le", "1"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test_histogram_bytes_bucket", "foo_bar", "baz", "instance", "test-instance", "job", "test-service", "le", "2"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test_histogram_bytes_bucket", "foo_bar", "baz", "instance", "test-instance", "job", "test-service", "le", "3"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test_histogram_bytes_bucket", "foo_bar", "baz", "instance", "test-instance", "job", "test-service", "le", "4"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test_histogram_bytes_bucket", "foo_bar", "baz", "instance", "test-instance", "job", "test-service", "le", "5"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test_histogram_bytes_bucket", "foo_bar", "baz", "instance", "test-instance", "job", "test-service", "le", "+Inf"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test_exponential_histogram_bytes", "foo_bar", "baz", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-exponential-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "target_info", "host_name", "test-host", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeGauge, Unit: "", Help: "Target metadata"},
+				},
+			},
 		},
 		{
 			name: "UnderscoreEscapingWithoutSuffixes",
@@ -478,24 +619,70 @@ func TestOTLPWriteHandler(t *testing.T) {
 			},
 			expectedSamples: []mockSample{
 				{
-					l: labels.New(labels.Label{Name: "__name__", Value: "test_counter"},
-						labels.Label{Name: "foo_bar", Value: "baz"},
-						labels.Label{Name: "instance", Value: "test-instance"},
-						labels.Label{Name: "job", Value: "test-service"}),
+					l: labels.FromStrings(model.MetricNameLabel, "test_counter", "foo_bar", "baz", "instance", "test-instance", "job", "test-service"),
 					t: timestamp.UnixMilli(),
 					v: 10.0,
 				},
 				{
-					l: labels.New(
-						labels.Label{Name: "__name__", Value: "target_info"},
-						labels.Label{Name: "host_name", Value: "test-host"},
-						labels.Label{Name: "instance", Value: "test-instance"},
-						labels.Label{Name: "job", Value: "test-service"},
-					),
+					l: labels.FromStrings(model.MetricNameLabel, "target_info", "host_name", "test-host", "instance", "test-instance", "job", "test-service"),
 					t: timestamp.UnixMilli(),
 					v: 1,
 				},
 			},
+			expectedMetadata: []mockMetadata{
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test_counter", "foo_bar", "baz", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeCounter, Unit: "bytes", Help: "test-counter-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test_gauge", "foo_bar", "baz", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeGauge, Unit: "bytes", Help: "test-gauge-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test_histogram_sum", "foo_bar", "baz", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test_histogram_count", "foo_bar", "baz", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test_histogram_bucket", "foo_bar", "baz", "instance", "test-instance", "job", "test-service", "le", "0"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test_histogram_bucket", "foo_bar", "baz", "instance", "test-instance", "job", "test-service", "le", "1"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test_histogram_bucket", "foo_bar", "baz", "instance", "test-instance", "job", "test-service", "le", "2"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test_histogram_bucket", "foo_bar", "baz", "instance", "test-instance", "job", "test-service", "le", "3"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test_histogram_bucket", "foo_bar", "baz", "instance", "test-instance", "job", "test-service", "le", "4"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test_histogram_bucket", "foo_bar", "baz", "instance", "test-instance", "job", "test-service", "le", "5"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test_histogram_bucket", "foo_bar", "baz", "instance", "test-instance", "job", "test-service", "le", "+Inf"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test_exponential_histogram", "foo_bar", "baz", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-exponential-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "target_info", "host_name", "test-host", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeGauge, Unit: "", Help: "Target metadata"},
+				},
+			},
 		},
 		{
 			name: "UnderscoreEscapingWithSuffixes/WithTypeAndUnitLabels",
@@ -525,6 +712,60 @@ func TestOTLPWriteHandler(t *testing.T) {
 					v: 1,
 				},
 			},
+			expectedMetadata: []mockMetadata{
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test_counter_bytes_total", "__type__", "counter", "__unit__", "bytes", "foo_bar", "baz", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeCounter, Unit: "bytes", Help: "test-counter-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test_gauge_bytes", "__type__", "gauge", "__unit__", "bytes", "foo_bar", "baz", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeGauge, Unit: "bytes", Help: "test-gauge-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test_histogram_bytes_sum", "__type__", "histogram", "__unit__", "bytes", "foo_bar", "baz", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test_histogram_bytes_count", "__type__", "histogram", "__unit__", "bytes", "foo_bar", "baz", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test_histogram_bytes_bucket", "__type__", "histogram", "__unit__", "bytes", "foo_bar", "baz", "instance", "test-instance", "job", "test-service", "le", "0"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test_histogram_bytes_bucket", "__type__", "histogram", "__unit__", "bytes", "foo_bar", "baz", "instance", "test-instance", "job", "test-service", "le", "1"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test_histogram_bytes_bucket", "__type__", "histogram", "__unit__", "bytes", "foo_bar", "baz", "instance", "test-instance", "job", "test-service", "le", "2"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test_histogram_bytes_bucket", "__type__", "histogram", "__unit__", "bytes", "foo_bar", "baz", "instance", "test-instance", "job", "test-service", "le", "3"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test_histogram_bytes_bucket", "__type__", "histogram", "__unit__", "bytes", "foo_bar", "baz", "instance", "test-instance", "job", "test-service", "le", "4"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test_histogram_bytes_bucket", "__type__", "histogram", "__unit__", "bytes", "foo_bar", "baz", "instance", "test-instance", "job", "test-service", "le", "5"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test_histogram_bytes_bucket", "__type__", "histogram", "__unit__", "bytes", "foo_bar", "baz", "instance", "test-instance", "job", "test-service", "le", "+Inf"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test_exponential_histogram_bytes", "__type__", "histogram", "__unit__", "bytes", "foo_bar", "baz", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-exponential-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "target_info", "host_name", "test-host", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeGauge, Unit: "", Help: "Target metadata"},
+				},
+			},
 		},
 		{
 			name: "NoUTF8EscapingWithSuffixes/NoTypeAndUnitLabels",
@@ -533,24 +774,71 @@ func TestOTLPWriteHandler(t *testing.T) {
 			},
 			expectedSamples: []mockSample{
 				{
-					l: labels.New(labels.Label{Name: "__name__", Value: "test.counter_bytes_total"},
-						labels.Label{Name: "foo.bar", Value: "baz"},
-						labels.Label{Name: "instance", Value: "test-instance"},
-						labels.Label{Name: "job", Value: "test-service"}),
+					l: labels.FromStrings(model.MetricNameLabel, "test.counter_bytes_total", "foo.bar", "baz", "instance", "test-instance", "job", "test-service"),
 					t: timestamp.UnixMilli(),
 					v: 10.0,
 				},
 				{
-					l: labels.New(
-						labels.Label{Name: "__name__", Value: "target_info"},
-						labels.Label{Name: "host.name", Value: "test-host"},
-						labels.Label{Name: "instance", Value: "test-instance"},
-						labels.Label{Name: "job", Value: "test-service"},
-					),
+					l: labels.FromStrings(model.MetricNameLabel, "target_info", "host.name", "test-host", "instance", "test-instance", "job", "test-service"),
 					t: timestamp.UnixMilli(),
 					v: 1,
 				},
 			},
+			expectedMetadata: []mockMetadata{
+				// All get _bytes unit suffix and counter also gets _total.
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.counter_bytes_total", "foo.bar", "baz", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeCounter, Unit: "bytes", Help: "test-counter-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.gauge_bytes", "foo.bar", "baz", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeGauge, Unit: "bytes", Help: "test-gauge-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.histogram_bytes_sum", "foo.bar", "baz", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.histogram_bytes_count", "foo.bar", "baz", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.histogram_bytes_bucket", "foo.bar", "baz", "instance", "test-instance", "job", "test-service", "le", "0"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.histogram_bytes_bucket", "foo.bar", "baz", "instance", "test-instance", "job", "test-service", "le", "1"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.histogram_bytes_bucket", "foo.bar", "baz", "instance", "test-instance", "job", "test-service", "le", "2"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.histogram_bytes_bucket", "foo.bar", "baz", "instance", "test-instance", "job", "test-service", "le", "3"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.histogram_bytes_bucket", "foo.bar", "baz", "instance", "test-instance", "job", "test-service", "le", "4"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.histogram_bytes_bucket", "foo.bar", "baz", "instance", "test-instance", "job", "test-service", "le", "5"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.histogram_bytes_bucket", "foo.bar", "baz", "instance", "test-instance", "job", "test-service", "le", "+Inf"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.exponential.histogram_bytes", "foo.bar", "baz", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-exponential-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "target_info", "host.name", "test-host", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeGauge, Unit: "", Help: "Target metadata"},
+				},
+			},
 		},
 		{
 			name: "NoUTF8EscapingWithSuffixes/WithTypeAndUnitLabels",
@@ -560,40 +848,268 @@ func TestOTLPWriteHandler(t *testing.T) {
 			typeAndUnitLabels: true,
 			expectedSamples: []mockSample{
 				{
-					l: labels.New(labels.Label{Name: "__name__", Value: "test.counter_bytes_total"},
-						labels.Label{Name: "__type__", Value: "counter"},
-						labels.Label{Name: "__unit__", Value: "bytes"},
-						labels.Label{Name: "foo.bar", Value: "baz"},
-						labels.Label{Name: "instance", Value: "test-instance"},
-						labels.Label{Name: "job", Value: "test-service"}),
+					l: labels.FromStrings(model.MetricNameLabel, "test.counter_bytes_total", "__type__", "counter", "__unit__", "bytes", "foo.bar", "baz", "instance", "test-instance", "job", "test-service"),
 					t: timestamp.UnixMilli(),
 					v: 10.0,
 				},
 				{
-					l: labels.New(
-						labels.Label{Name: "__name__", Value: "target_info"},
-						labels.Label{Name: "host.name", Value: "test-host"},
-						labels.Label{Name: "instance", Value: "test-instance"},
-						labels.Label{Name: "job", Value: "test-service"},
-					),
+					l: labels.FromStrings(model.MetricNameLabel, "target_info", "host.name", "test-host", "instance", "test-instance", "job", "test-service"),
 					t: timestamp.UnixMilli(),
 					v: 1,
 				},
 			},
+			expectedMetadata: []mockMetadata{
+				// All get _bytes unit suffix and counter also gets _total.
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.counter_bytes_total", "__type__", "counter", "__unit__", "bytes", "foo.bar", "baz", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeCounter, Unit: "bytes", Help: "test-counter-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.gauge_bytes", "__type__", "gauge", "__unit__", "bytes", "foo.bar", "baz", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeGauge, Unit: "bytes", Help: "test-gauge-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.histogram_bytes_sum", "__type__", "histogram", "__unit__", "bytes", "foo.bar", "baz", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.histogram_bytes_count", "__type__", "histogram", "__unit__", "bytes", "foo.bar", "baz", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.histogram_bytes_bucket", "__type__", "histogram", "__unit__", "bytes", "foo.bar", "baz", "instance", "test-instance", "job", "test-service", "le", "0"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.histogram_bytes_bucket", "__type__", "histogram", "__unit__", "bytes", "foo.bar", "baz", "instance", "test-instance", "job", "test-service", "le", "1"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.histogram_bytes_bucket", "__type__", "histogram", "__unit__", "bytes", "foo.bar", "baz", "instance", "test-instance", "job", "test-service", "le", "2"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.histogram_bytes_bucket", "__type__", "histogram", "__unit__", "bytes", "foo.bar", "baz", "instance", "test-instance", "job", "test-service", "le", "3"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.histogram_bytes_bucket", "__type__", "histogram", "__unit__", "bytes", "foo.bar", "baz", "instance", "test-instance", "job", "test-service", "le", "4"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.histogram_bytes_bucket", "__type__", "histogram", "__unit__", "bytes", "foo.bar", "baz", "instance", "test-instance", "job", "test-service", "le", "5"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.histogram_bytes_bucket", "__type__", "histogram", "__unit__", "bytes", "foo.bar", "baz", "instance", "test-instance", "job", "test-service", "le", "+Inf"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "test.exponential.histogram_bytes", "__type__", "histogram", "__unit__", "bytes", "foo.bar", "baz", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeHistogram, Unit: "bytes", Help: "test-exponential-histogram-description"},
+				},
+				{
+					l: labels.FromStrings(model.MetricNameLabel, "target_info", "host.name", "test-host", "instance", "test-instance", "job", "test-service"),
+					m: metadata.Metadata{Type: model.MetricTypeGauge, Unit: "", Help: "Target metadata"},
+				},
+			},
 		},
 	} {
 		t.Run(testCase.name, func(t *testing.T) {
-			appendable := handleOTLP(t, exportRequest, testCase.otlpCfg, testCase.typeAndUnitLabels)
+			otlpOpts := OTLPOptions{
+				EnableTypeAndUnitLabels: testCase.typeAndUnitLabels,
+			}
+			appendable := handleOTLP(t, exportRequest, testCase.otlpCfg, otlpOpts)
 			for _, sample := range testCase.expectedSamples {
 				requireContainsSample(t, appendable.samples, sample)
 			}
+			for _, meta := range testCase.expectedMetadata {
+				requireContainsMetadata(t, appendable.metadata, meta)
+			}
 			require.Len(t, appendable.samples, 12)   // 1 (counter) + 1 (gauge) + 1 (target_info) + 7 (hist_bucket) + 2 (hist_sum, hist_count)
 			require.Len(t, appendable.histograms, 1) // 1 (exponential histogram)
+			require.Len(t, appendable.metadata, 13)  // for each float and histogram sample
 			require.Len(t, appendable.exemplars, 1)  // 1 (exemplar)
 		})
 	}
 }
 
+// Check that start time is ingested if ingestCTZeroSample is enabled
+// and the start time is actually set (non-zero).
+func TestOTLPWRiteHandlerStartTime(t *testing.T) {
+	timestamp := time.Now()
+	startTime := timestamp.Add(-1 * time.Millisecond)
+	var zeroTime time.Time
+
+	expectedSamples := []mockSample{
+		{
+			l: labels.FromStrings(model.MetricNameLabel, "test.counter", "foo.bar", "baz", "instance", "test-instance", "job", "test-service"),
+			t: timestamp.UnixMilli(),
+			v: 10.0,
+		},
+		{
+			l: labels.FromStrings(model.MetricNameLabel, "test.gauge", "foo.bar", "baz", "instance", "test-instance", "job", "test-service"),
+			t: timestamp.UnixMilli(),
+			v: 10.0,
+		},
+		{
+			l: labels.FromStrings(model.MetricNameLabel, "test.histogram_sum", "foo.bar", "baz", "instance", "test-instance", "job", "test-service"),
+			t: timestamp.UnixMilli(),
+			v: 30.0,
+		},
+		{
+			l: labels.FromStrings(model.MetricNameLabel, "test.histogram_count", "foo.bar", "baz", "instance", "test-instance", "job", "test-service"),
+			t: timestamp.UnixMilli(),
+			v: 12.0,
+		},
+		{
+			l: labels.FromStrings(model.MetricNameLabel, "test.histogram_bucket", "foo.bar", "baz", "instance", "test-instance", "job", "test-service", "le", "0"),
+			t: timestamp.UnixMilli(),
+			v: 2.0,
+		},
+		{
+			l: labels.FromStrings(model.MetricNameLabel, "test.histogram_bucket", "foo.bar", "baz", "instance", "test-instance", "job", "test-service", "le", "1"),
+			t: timestamp.UnixMilli(),
+			v: 4.0,
+		},
+		{
+			l: labels.FromStrings(model.MetricNameLabel, "test.histogram_bucket", "foo.bar", "baz", "instance", "test-instance", "job", "test-service", "le", "2"),
+			t: timestamp.UnixMilli(),
+			v: 6.0,
+		},
+		{
+			l: labels.FromStrings(model.MetricNameLabel, "test.histogram_bucket", "foo.bar", "baz", "instance", "test-instance", "job", "test-service", "le", "3"),
+			t: timestamp.UnixMilli(),
+			v: 8.0,
+		},
+		{
+			l: labels.FromStrings(model.MetricNameLabel, "test.histogram_bucket", "foo.bar", "baz", "instance", "test-instance", "job", "test-service", "le", "4"),
+			t: timestamp.UnixMilli(),
+			v: 10.0,
+		},
+		{
+			l: labels.FromStrings(model.MetricNameLabel, "test.histogram_bucket", "foo.bar", "baz", "instance", "test-instance", "job", "test-service", "le", "5"),
+			t: timestamp.UnixMilli(),
+			v: 12.0,
+		},
+		{
+			l: labels.FromStrings(model.MetricNameLabel, "test.histogram_bucket", "foo.bar", "baz", "instance", "test-instance", "job", "test-service", "le", "+Inf"),
+			t: timestamp.UnixMilli(),
+			v: 12.0,
+		},
+		{
+			l: labels.FromStrings(model.MetricNameLabel, "target_info", "host.name", "test-host", "instance", "test-instance", "job", "test-service"),
+			t: timestamp.UnixMilli(),
+			v: 1.0,
+		},
+	}
+	expectedHistograms := []mockHistogram{
+		{
+			l: labels.FromStrings(model.MetricNameLabel, "test.exponential.histogram", "foo.bar", "baz", "instance", "test-instance", "job", "test-service"),
+			t: timestamp.UnixMilli(),
+			h: &histogram.Histogram{
+				Schema:          2,
+				ZeroThreshold:   1e-128,
+				ZeroCount:       2,
+				Count:           10,
+				Sum:             30,
+				PositiveSpans:   []histogram.Span{{Offset: 1, Length: 5}},
+				PositiveBuckets: []int64{2, 0, 0, 0, 0},
+			},
+		},
+	}
+
+	expectedSamplesWithCTZero := make([]mockSample, 0, len(expectedSamples)*2-1) // All samples will get CT zero, except target_info.
+	for _, s := range expectedSamples {
+		if s.l.Get(model.MetricNameLabel) != "target_info" {
+			expectedSamplesWithCTZero = append(expectedSamplesWithCTZero, mockSample{
+				l: s.l.Copy(),
+				t: startTime.UnixMilli(),
+				v: 0,
+			})
+		}
+		expectedSamplesWithCTZero = append(expectedSamplesWithCTZero, s)
+	}
+	expectedHistogramsWithCTZero := make([]mockHistogram, 0, len(expectedHistograms)*2)
+	for _, s := range expectedHistograms {
+		if s.l.Get(model.MetricNameLabel) != "target_info" {
+			expectedHistogramsWithCTZero = append(expectedHistogramsWithCTZero, mockHistogram{
+				l: s.l.Copy(),
+				t: startTime.UnixMilli(),
+				h: &histogram.Histogram{},
+			})
+		}
+		expectedHistogramsWithCTZero = append(expectedHistogramsWithCTZero, s)
+	}
+
+	for _, testCase := range []struct {
+		name               string
+		otlpOpts           OTLPOptions
+		startTime          time.Time
+		expectCTZero       bool
+		expectedSamples    []mockSample
+		expectedHistograms []mockHistogram
+	}{
+		{
+			name: "IngestCTZero=false/startTime=0",
+			otlpOpts: OTLPOptions{
+				IngestCTZeroSample: false,
+			},
+			startTime:          zeroTime,
+			expectedSamples:    expectedSamples,
+			expectedHistograms: expectedHistograms,
+		},
+		{
+			name: "IngestCTZero=true/startTime=0",
+			otlpOpts: OTLPOptions{
+				IngestCTZeroSample: true,
+			},
+			startTime:          zeroTime,
+			expectedSamples:    expectedSamples,
+			expectedHistograms: expectedHistograms,
+		},
+		{
+			name: "IngestCTZero=false/startTime=ts-1ms",
+			otlpOpts: OTLPOptions{
+				IngestCTZeroSample: false,
+			},
+			startTime:          startTime,
+			expectedSamples:    expectedSamples,
+			expectedHistograms: expectedHistograms,
+		},
+		{
+			name: "IngestCTZero=true/startTime=ts-1ms",
+			otlpOpts: OTLPOptions{
+				IngestCTZeroSample: true,
+			},
+			startTime:          startTime,
+			expectedSamples:    expectedSamplesWithCTZero,
+			expectedHistograms: expectedHistogramsWithCTZero,
+		},
+	} {
+		t.Run(testCase.name, func(t *testing.T) {
+			exportRequest := generateOTLPWriteRequest(timestamp, testCase.startTime)
+			appendable := handleOTLP(t, exportRequest, config.OTLPConfig{
+				TranslationStrategy: otlptranslator.NoTranslation,
+			}, testCase.otlpOpts)
+			for i, expect := range testCase.expectedSamples {
+				actual := appendable.samples[i]
+				require.True(t, labels.Equal(expect.l, actual.l), "sample labels,pos=%v", i)
+				require.Equal(t, expect.t, actual.t, "sample timestamp,pos=%v", i)
+				require.Equal(t, expect.v, actual.v, "sample value,pos=%v", i)
+			}
+			for i, expect := range testCase.expectedHistograms {
+				actual := appendable.histograms[i]
+				require.True(t, labels.Equal(expect.l, actual.l), "histogram labels,pos=%v", i)
+				require.Equal(t, expect.t, actual.t, "histogram timestamp,pos=%v", i)
+				require.True(t, expect.h.Equals(actual.h), "histogram value,pos=%v", i)
+			}
+			require.Len(t, appendable.samples, len(testCase.expectedSamples))
+			require.Len(t, appendable.histograms, len(testCase.expectedHistograms))
+		})
+	}
+}
+
 func requireContainsSample(t *testing.T, actual []mockSample, expected mockSample) {
 	t.Helper()
 
@@ -607,7 +1123,20 @@ func requireContainsSample(t *testing.T, actual []mockSample, expected mockSampl
 		"actual  : %v", expected, actual))
 }
 
-func handleOTLP(t *testing.T, exportRequest pmetricotlp.ExportRequest, otlpCfg config.OTLPConfig, typeAndUnitLabels bool) *mockAppendable {
+func requireContainsMetadata(t *testing.T, actual []mockMetadata, expected mockMetadata) {
+	t.Helper()
+
+	for _, got := range actual {
+		if labels.Equal(expected.l, got.l) && expected.m.Type == got.m.Type && expected.m.Unit == got.m.Unit && expected.m.Help == got.m.Help {
+			return
+		}
+	}
+	require.Fail(t, fmt.Sprintf("Metadata not found: \n"+
+		"expected: %v\n"+
+		"actual  : %v", expected, actual))
+}
+
+func handleOTLP(t *testing.T, exportRequest pmetricotlp.ExportRequest, otlpCfg config.OTLPConfig, otlpOpts OTLPOptions) *mockAppendable {
 	buf, err := exportRequest.MarshalProto()
 	require.NoError(t, err)
 
@@ -615,12 +1144,13 @@ func handleOTLP(t *testing.T, exportRequest pmetricotlp.ExportRequest, otlpCfg c
 	require.NoError(t, err)
 	req.Header.Set("Content-Type", "application/x-protobuf")
 
+	log := slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{Level: slog.LevelWarn}))
 	appendable := &mockAppendable{}
-	handler := NewOTLPWriteHandler(nil, nil, appendable, func() config.Config {
+	handler := NewOTLPWriteHandler(log, nil, appendable, func() config.Config {
 		return config.Config{
 			OTLPConfig: otlpCfg,
 		}
-	}, OTLPOptions{EnableTypeAndUnitLabels: typeAndUnitLabels})
+	}, otlpOpts)
 	recorder := httptest.NewRecorder()
 	handler.ServeHTTP(recorder, req)
 
@@ -630,7 +1160,7 @@ func handleOTLP(t *testing.T, exportRequest pmetricotlp.ExportRequest, otlpCfg c
 	return appendable
 }
 
-func generateOTLPWriteRequest(timestamp time.Time) pmetricotlp.ExportRequest {
+func generateOTLPWriteRequest(timestamp, startTime time.Time) pmetricotlp.ExportRequest {
 	d := pmetric.NewMetrics()
 
 	// Generate One Counter, One Gauge, One Histogram, One Exponential-Histogram
@@ -655,6 +1185,7 @@ func generateOTLPWriteRequest(timestamp time.Time) pmetricotlp.ExportRequest {
 
 	counterDataPoint := counterMetric.Sum().DataPoints().AppendEmpty()
 	counterDataPoint.SetTimestamp(pcommon.NewTimestampFromTime(timestamp))
+	counterDataPoint.SetStartTimestamp(pcommon.NewTimestampFromTime(startTime))
 	counterDataPoint.SetDoubleValue(10.0)
 	counterDataPoint.Attributes().PutStr("foo.bar", "baz")
 
@@ -674,6 +1205,7 @@ func generateOTLPWriteRequest(timestamp time.Time) pmetricotlp.ExportRequest {
 
 	gaugeDataPoint := gaugeMetric.Gauge().DataPoints().AppendEmpty()
 	gaugeDataPoint.SetTimestamp(pcommon.NewTimestampFromTime(timestamp))
+	gaugeDataPoint.SetStartTimestamp(pcommon.NewTimestampFromTime(startTime))
 	gaugeDataPoint.SetDoubleValue(10.0)
 	gaugeDataPoint.Attributes().PutStr("foo.bar", "baz")
 
@@ -687,9 +1219,10 @@ func generateOTLPWriteRequest(timestamp time.Time) pmetricotlp.ExportRequest {
 
 	histogramDataPoint := histogramMetric.Histogram().DataPoints().AppendEmpty()
 	histogramDataPoint.SetTimestamp(pcommon.NewTimestampFromTime(timestamp))
+	histogramDataPoint.SetStartTimestamp(pcommon.NewTimestampFromTime(startTime))
 	histogramDataPoint.ExplicitBounds().FromRaw([]float64{0.0, 1.0, 2.0, 3.0, 4.0, 5.0})
 	histogramDataPoint.BucketCounts().FromRaw([]uint64{2, 2, 2, 2, 2, 2})
-	histogramDataPoint.SetCount(10)
+	histogramDataPoint.SetCount(12)
 	histogramDataPoint.SetSum(30.0)
 	histogramDataPoint.Attributes().PutStr("foo.bar", "baz")
 
@@ -703,6 +1236,7 @@ func generateOTLPWriteRequest(timestamp time.Time) pmetricotlp.ExportRequest {
 
 	exponentialHistogramDataPoint := exponentialHistogramMetric.ExponentialHistogram().DataPoints().AppendEmpty()
 	exponentialHistogramDataPoint.SetTimestamp(pcommon.NewTimestampFromTime(timestamp))
+	exponentialHistogramDataPoint.SetStartTimestamp(pcommon.NewTimestampFromTime(startTime))
 	exponentialHistogramDataPoint.SetScale(2.0)
 	exponentialHistogramDataPoint.Positive().BucketCounts().FromRaw([]uint64{2, 2, 2, 2, 2})
 	exponentialHistogramDataPoint.SetZeroCount(2)

web/api/v1/api.go

@@ -317,6 +317,7 @@ func NewAPI(
 			ConvertDelta:            otlpDeltaToCumulative,
 			NativeDelta:             otlpNativeDeltaIngestion,
 			LookbackDelta:           lookbackDelta,
+			IngestCTZeroSample:      ctZeroIngestionEnabled,
 			EnableTypeAndUnitLabels: enableTypeAndUnitLabels,
 		})
 	}