Move exemplar types to non-internal package (#5747)

Part of https://github.com/open-telemetry/opentelemetry-go/issues/5249

This makes all existing types designed to implement the public Exemplar
API public by moving most of `internal/exemplar` to `exemplar`. The only
types that are not being made public are `exemplar.Drop`, and
`exemplar.FilteredReservoir`. Those types are moved to
`internal/aggregate`, and are renamed to `DropReservoir` and
`FilteredExemplarReservoir`.

The following types are made public:

* `exemplar.Exemplar`
* `exemplar.Filter`
* `exemplar.SampledFilter`
* `exemplar.AlwaysOnFilter`
* `exemplar.HistogramReservoir`
* `exemplar.FixedSizeReservoir`
* `exemplar.Reservoir`
* `exemplar.Value`
* `exemplar.ValueType`

CHANGELOG.md

@@ -8,6 +8,10 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 ## [Unreleased]
 
+### Added
+
+- Add `go.opentelemetry.io/otel/sdk/metric/exemplar` package which includes `Exemplar`, `Filter`, `SampledFilter`, `AlwaysOnFilter`, `HistogramReservoir`, `FixedSizeReservoir`, `Reservoir`, `Value` and `ValueType` types. These will be used for configuring the exemplar reservoir for the metrics sdk. (#5747)
+
 ### Changed
 
 - Enable exemplars by default in `go.opentelemetry.io/otel/sdk/metric`. Exemplars can be disabled by setting `OTEL_METRICS_EXEMPLAR_FILTER=always_off` (#5778)

sdk/metric/exemplar.go

@@ -8,7 +8,8 @@ import (
 	"runtime"
 	"slices"
 
-	"go.opentelemetry.io/otel/sdk/metric/internal/exemplar"
+	"go.opentelemetry.io/otel/sdk/metric/exemplar"
+	"go.opentelemetry.io/otel/sdk/metric/internal/aggregate"
 )
 
 // reservoirFunc returns the appropriately configured exemplar reservoir
@@ -18,7 +19,7 @@ import (
 // Note: This will only return non-nil values when the experimental exemplar
 // feature is enabled and the OTEL_METRICS_EXEMPLAR_FILTER environment variable
 // is not set to always_off.
-func reservoirFunc[N int64 | float64](agg Aggregation) func() exemplar.FilteredReservoir[N] {
+func reservoirFunc[N int64 | float64](agg Aggregation) func() aggregate.FilteredExemplarReservoir[N] {
 	// https://github.com/open-telemetry/opentelemetry-specification/blob/d4b241f451674e8f611bb589477680341006ad2b/specification/configuration/sdk-environment-variables.md#exemplar
 	const filterEnvKey = "OTEL_METRICS_EXEMPLAR_FILTER"
 
@@ -28,7 +29,7 @@ func reservoirFunc[N int64 | float64](agg Aggregation) func() exemplar.FilteredR
 	case "always_on":
 		filter = exemplar.AlwaysOnFilter
 	case "always_off":
-		return exemplar.Drop
+		return aggregate.DropReservoir
 	case "trace_based":
 		fallthrough
 	default:
@@ -41,9 +42,9 @@ func reservoirFunc[N int64 | float64](agg Aggregation) func() exemplar.FilteredR
 	a, ok := agg.(AggregationExplicitBucketHistogram)
 	if ok && len(a.Boundaries) > 0 {
 		cp := slices.Clone(a.Boundaries)
-		return func() exemplar.FilteredReservoir[N] {
+		return func() aggregate.FilteredExemplarReservoir[N] {
 			bounds := cp
-			return exemplar.NewFilteredReservoir[N](filter, exemplar.Histogram(bounds))
+			return aggregate.NewFilteredExemplarReservoir[N](filter, exemplar.NewHistogramReservoir(bounds))
 		}
 	}
 
@@ -71,7 +72,7 @@ func reservoirFunc[N int64 | float64](agg Aggregation) func() exemplar.FilteredR
 		}
 	}
 
-	return func() exemplar.FilteredReservoir[N] {
+	return func() aggregate.FilteredExemplarReservoir[N] {
-		return exemplar.NewFilteredReservoir[N](filter, exemplar.FixedSize(n))
+		return aggregate.NewFilteredExemplarReservoir[N](filter, exemplar.NewFixedSizeReservoir(n))
 	}
 }

sdk/metric/exemplar/README.md

@@ -0,0 +1,3 @@
+# Metric SDK Exemplars
+
+[![PkgGoDev](https://pkg.go.dev/badge/go.opentelemetry.io/otel/sdk/metric/exemplar)](https://pkg.go.dev/go.opentelemetry.io/otel/sdk/metric/exemplar)

sdk/metric/exemplar/doc.go

@@ -3,4 +3,4 @@
 
 // Package exemplar provides an implementation of the OpenTelemetry exemplar
 // reservoir to be used in metric collection pipelines.
-package exemplar // import "go.opentelemetry.io/otel/sdk/metric/internal/exemplar"
+package exemplar // import "go.opentelemetry.io/otel/sdk/metric/exemplar"

sdk/metric/exemplar/exemplar.go

@@ -1,7 +1,7 @@
 // Copyright The OpenTelemetry Authors
 // SPDX-License-Identifier: Apache-2.0
 
-package exemplar // import "go.opentelemetry.io/otel/sdk/metric/internal/exemplar"
+package exemplar // import "go.opentelemetry.io/otel/sdk/metric/exemplar"
 
 import (
 	"time"

sdk/metric/exemplar/filter.go

@@ -1,7 +1,7 @@
 // Copyright The OpenTelemetry Authors
 // SPDX-License-Identifier: Apache-2.0
 
-package exemplar // import "go.opentelemetry.io/otel/sdk/metric/internal/exemplar"
+package exemplar // import "go.opentelemetry.io/otel/sdk/metric/exemplar"
 
 import (
 	"context"

sdk/metric/exemplar/filter_test.go

@@ -1,7 +1,7 @@
 // Copyright The OpenTelemetry Authors
 // SPDX-License-Identifier: Apache-2.0
 
-package exemplar // import "go.opentelemetry.io/otel/sdk/metric/internal/exemplar"
+package exemplar // import "go.opentelemetry.io/otel/sdk/metric/exemplar"
 
 import (
 	"context"

sdk/metric/exemplar/fixed_size_reservoir.go

@@ -1,7 +1,7 @@
 // Copyright The OpenTelemetry Authors
 // SPDX-License-Identifier: Apache-2.0
 
-package exemplar // import "go.opentelemetry.io/otel/sdk/metric/internal/exemplar"
+package exemplar // import "go.opentelemetry.io/otel/sdk/metric/exemplar"
 
 import (
 	"context"
@@ -12,15 +12,21 @@ import (
 	"go.opentelemetry.io/otel/attribute"
 )
 
-// FixedSize returns a [Reservoir] that samples at most k exemplars. If there
+// NewFixedSizeReservoir returns a [FixedSizeReservoir] that samples at most
-// are k or less measurements made, the Reservoir will sample each one. If
+// k exemplars. If there are k or less measurements made, the Reservoir will
-// there are more than k, the Reservoir will then randomly sample all
+// sample each one. If there are more than k, the Reservoir will then randomly
-// additional measurement with a decreasing probability.
+// sample all additional measurement with a decreasing probability.
-func FixedSize(k int) Reservoir {
+func NewFixedSizeReservoir(k int) *FixedSizeReservoir {
-	return newRandRes(newStorage(k))
+	return newFixedSizeReservoir(newStorage(k))
 }
 
-type randRes struct {
+var _ Reservoir = &FixedSizeReservoir{}
+
+// FixedSizeReservoir is a [Reservoir] that samples at most k exemplars. If
+// there are k or less measurements made, the Reservoir will sample each one.
+// If there are more than k, the Reservoir will then randomly sample all
+// additional measurement with a decreasing probability.
+type FixedSizeReservoir struct {
 	*storage
 
 	// count is the number of measurement seen.
@@ -39,8 +45,8 @@ type randRes struct {
 	rng *rand.Rand
 }
 
-func newRandRes(s *storage) *randRes {
+func newFixedSizeReservoir(s *storage) *FixedSizeReservoir {
-	r := &randRes{
+	r := &FixedSizeReservoir{
 		storage: s,
 		rng:     rand.New(rand.NewSource(time.Now().UnixNano())),
 	}
@@ -50,7 +56,7 @@ func newRandRes(s *storage) *randRes {
 
 // randomFloat64 returns, as a float64, a uniform pseudo-random number in the
 // open interval (0.0,1.0).
-func (r *randRes) randomFloat64() float64 {
+func (r *FixedSizeReservoir) randomFloat64() float64 {
 	// TODO: This does not return a uniform number. rng.Float64 returns a
 	// uniformly random int in [0,2^53) that is divided by 2^53. Meaning it
 	// returns multiples of 2^-53, and not all floating point numbers between 0
@@ -75,7 +81,18 @@ func (r *randRes) randomFloat64() float64 {
 	return f
 }
 
-func (r *randRes) Offer(ctx context.Context, t time.Time, n Value, a []attribute.KeyValue) {
+// Offer accepts the parameters associated with a measurement. The
+// parameters will be stored as an exemplar if the Reservoir decides to
+// sample the measurement.
+//
+// The passed ctx needs to contain any baggage or span that were active
+// when the measurement was made. This information may be used by the
+// Reservoir in making a sampling decision.
+//
+// The time t is the time when the measurement was made. The v and a
+// parameters are the value and dropped (filtered) attributes of the
+// measurement respectively.
+func (r *FixedSizeReservoir) Offer(ctx context.Context, t time.Time, n Value, a []attribute.KeyValue) {
 	// The following algorithm is "Algorithm L" from Li, Kim-Hung (4 December
 	// 1994). "Reservoir-Sampling Algorithms of Time Complexity
 	// O(n(1+log(N/n)))". ACM Transactions on Mathematical Software. 20 (4):
@@ -131,7 +148,7 @@ func (r *randRes) Offer(ctx context.Context, t time.Time, n Value, a []attribute
 }
 
 // reset resets r to the initial state.
-func (r *randRes) reset() {
+func (r *FixedSizeReservoir) reset() {
 	// This resets the number of exemplars known.
 	r.count = 0
 	// Random index inserts should only happen after the storage is full.
@@ -153,7 +170,7 @@ func (r *randRes) reset() {
 
 // advance updates the count at which the offered measurement will overwrite an
 // existing exemplar.
-func (r *randRes) advance() {
+func (r *FixedSizeReservoir) advance() {
 	// Calculate the next value in the random number series.
 	//
 	// The current value of r.w is based on the max of a distribution of random
@@ -180,7 +197,10 @@ func (r *randRes) advance() {
 	r.next += int64(math.Log(r.randomFloat64())/math.Log(1-r.w)) + 1
 }
 
-func (r *randRes) Collect(dest *[]Exemplar) {
+// Collect returns all the held exemplars.
+//
+// The Reservoir state is preserved after this call.
+func (r *FixedSizeReservoir) Collect(dest *[]Exemplar) {
 	r.storage.Collect(dest)
 	// Call reset here even though it will reset r.count and restart the random
 	// number series. This will persist any old exemplars as long as no new

sdk/metric/exemplar/fixed_size_reservoir_test.go

@@ -14,17 +14,17 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
-func TestFixedSize(t *testing.T) {
+func TestNewFixedSizeReservoir(t *testing.T) {
 	t.Run("Int64", ReservoirTest[int64](func(n int) (Reservoir, int) {
-		return FixedSize(n), n
+		return NewFixedSizeReservoir(n), n
 	}))
 
 	t.Run("Float64", ReservoirTest[float64](func(n int) (Reservoir, int) {
-		return FixedSize(n), n
+		return NewFixedSizeReservoir(n), n
 	}))
 }
 
-func TestFixedSizeSamplingCorrectness(t *testing.T) {
+func TestNewFixedSizeReservoirSamplingCorrectness(t *testing.T) {
 	intensity := 0.1
 	sampleSize := 1000
 
@@ -38,13 +38,13 @@ func TestFixedSizeSamplingCorrectness(t *testing.T) {
 	// Sort to test position bias.
 	slices.Sort(data)
 
-	r := FixedSize(sampleSize)
+	r := NewFixedSizeReservoir(sampleSize)
 	for _, value := range data {
 		r.Offer(context.Background(), staticTime, NewValue(value), nil)
 	}
 
 	var sum float64
-	for _, m := range r.(*randRes).store {
+	for _, m := range r.store {
 		sum += m.Value.Float64()
 	}
 	mean := sum / float64(sampleSize)

sdk/metric/exemplar/histogram_reservoir.go

@@ -0,0 +1,62 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package exemplar // import "go.opentelemetry.io/otel/sdk/metric/exemplar"
+
+import (
+	"context"
+	"slices"
+	"sort"
+	"time"
+
+	"go.opentelemetry.io/otel/attribute"
+)
+
+// NewHistogramReservoir returns a [HistogramReservoir] that samples the last
+// measurement that falls within a histogram bucket. The histogram bucket
+// upper-boundaries are define by bounds.
+//
+// The passed bounds will be sorted by this function.
+func NewHistogramReservoir(bounds []float64) *HistogramReservoir {
+	slices.Sort(bounds)
+	return &HistogramReservoir{
+		bounds:  bounds,
+		storage: newStorage(len(bounds) + 1),
+	}
+}
+
+var _ Reservoir = &HistogramReservoir{}
+
+// HistogramReservoir is a [Reservoir] that samples the last measurement that
+// falls within a histogram bucket. The histogram bucket upper-boundaries are
+// define by bounds.
+type HistogramReservoir struct {
+	*storage
+
+	// bounds are bucket bounds in ascending order.
+	bounds []float64
+}
+
+// Offer accepts the parameters associated with a measurement. The
+// parameters will be stored as an exemplar if the Reservoir decides to
+// sample the measurement.
+//
+// The passed ctx needs to contain any baggage or span that were active
+// when the measurement was made. This information may be used by the
+// Reservoir in making a sampling decision.
+//
+// The time t is the time when the measurement was made. The v and a
+// parameters are the value and dropped (filtered) attributes of the
+// measurement respectively.
+func (r *HistogramReservoir) Offer(ctx context.Context, t time.Time, v Value, a []attribute.KeyValue) {
+	var x float64
+	switch v.Type() {
+	case Int64ValueType:
+		x = float64(v.Int64())
+	case Float64ValueType:
+		x = v.Float64()
+	default:
+		panic("unknown value type")
+	}
+	r.store[sort.SearchFloat64s(r.bounds, x)] = newMeasurement(ctx, t, v, a)
+}

sdk/metric/exemplar/histogram_reservoir_test.go

@@ -8,10 +8,10 @@ import "testing"
 func TestHist(t *testing.T) {
 	bounds := []float64{0, 100}
 	t.Run("Int64", ReservoirTest[int64](func(int) (Reservoir, int) {
-		return Histogram(bounds), len(bounds)
+		return NewHistogramReservoir(bounds), len(bounds)
 	}))
 
 	t.Run("Float64", ReservoirTest[float64](func(int) (Reservoir, int) {
-		return Histogram(bounds), len(bounds)
+		return NewHistogramReservoir(bounds), len(bounds)
 	}))
 }

sdk/metric/exemplar/reservoir.go

@@ -1,7 +1,7 @@
 // Copyright The OpenTelemetry Authors
 // SPDX-License-Identifier: Apache-2.0
 
-package exemplar // import "go.opentelemetry.io/otel/sdk/metric/internal/exemplar"
+package exemplar // import "go.opentelemetry.io/otel/sdk/metric/exemplar"
 
 import (
 	"context"

sdk/metric/exemplar/storage.go

@@ -1,7 +1,7 @@
 // Copyright The OpenTelemetry Authors
 // SPDX-License-Identifier: Apache-2.0
 
-package exemplar // import "go.opentelemetry.io/otel/sdk/metric/internal/exemplar"
+package exemplar // import "go.opentelemetry.io/otel/sdk/metric/exemplar"
 
 import (
 	"context"
@@ -35,7 +35,7 @@ func (r *storage) Collect(dest *[]Exemplar) {
 			continue
 		}
 
-		m.Exemplar(&(*dest)[n])
+		m.exemplar(&(*dest)[n])
 		n++
 	}
 	*dest = (*dest)[:n]
@@ -66,8 +66,8 @@ func newMeasurement(ctx context.Context, ts time.Time, v Value, droppedAttr []at
 	}
 }
 
-// Exemplar returns m as an [Exemplar].
+// exemplar returns m as an [Exemplar].
-func (m measurement) Exemplar(dest *Exemplar) {
+func (m measurement) exemplar(dest *Exemplar) {
 	dest.FilteredAttributes = m.FilteredAttributes
 	dest.Time = m.Time
 	dest.Value = m.Value

sdk/metric/exemplar/value.go

@@ -1,7 +1,7 @@
 // Copyright The OpenTelemetry Authors
 // SPDX-License-Identifier: Apache-2.0
 
-package exemplar // import "go.opentelemetry.io/otel/sdk/metric/internal/exemplar"
+package exemplar // import "go.opentelemetry.io/otel/sdk/metric/exemplar"
 
 import "math"
 

sdk/metric/internal/aggregate/aggregate.go

@@ -8,7 +8,6 @@ import (
 	"time"
 
 	"go.opentelemetry.io/otel/attribute"
-	"go.opentelemetry.io/otel/sdk/metric/internal/exemplar"
 	"go.opentelemetry.io/otel/sdk/metric/metricdata"
 )
 
@@ -38,8 +37,8 @@ type Builder[N int64 | float64] struct {
 	// create new exemplar reservoirs for a new seen attribute set.
 	//
 	// If this is not provided a default factory function that returns an
-	// exemplar.Drop reservoir will be used.
+	// DropReservoir reservoir will be used.
-	ReservoirFunc func() exemplar.FilteredReservoir[N]
+	ReservoirFunc func() FilteredExemplarReservoir[N]
 	// AggregationLimit is the cardinality limit of measurement attributes. Any
 	// measurement for new attributes once the limit has been reached will be
 	// aggregated into a single aggregate for the "otel.metric.overflow"
@@ -50,12 +49,12 @@ type Builder[N int64 | float64] struct {
 	AggregationLimit int
 }
 
-func (b Builder[N]) resFunc() func() exemplar.FilteredReservoir[N] {
+func (b Builder[N]) resFunc() func() FilteredExemplarReservoir[N] {
 	if b.ReservoirFunc != nil {
 		return b.ReservoirFunc
 	}
 
-	return exemplar.Drop
+	return DropReservoir
 }
 
 type fltrMeasure[N int64 | float64] func(ctx context.Context, value N, fltrAttr attribute.Set, droppedAttr []attribute.KeyValue)

sdk/metric/internal/aggregate/aggregate_test.go

@@ -13,7 +13,6 @@ import (
 	"github.com/stretchr/testify/assert"
 
 	"go.opentelemetry.io/otel/attribute"
-	"go.opentelemetry.io/otel/sdk/metric/internal/exemplar"
 	"go.opentelemetry.io/otel/sdk/metric/metricdata"
 	"go.opentelemetry.io/otel/sdk/metric/metricdata/metricdatatest"
 )
@@ -73,8 +72,8 @@ func (c *clock) Register() (unregister func()) {
 	return func() { now = orig }
 }
 
-func dropExemplars[N int64 | float64]() exemplar.FilteredReservoir[N] {
+func dropExemplars[N int64 | float64]() FilteredExemplarReservoir[N] {
-	return exemplar.Drop[N]()
+	return DropReservoir[N]()
 }
 
 func TestBuilderFilter(t *testing.T) {

sdk/metric/internal/aggregate/drop.go

@@ -1,16 +1,17 @@
 // Copyright The OpenTelemetry Authors
 // SPDX-License-Identifier: Apache-2.0
 
-package exemplar // import "go.opentelemetry.io/otel/sdk/metric/internal/exemplar"
+package aggregate // import "go.opentelemetry.io/otel/sdk/metric/internal/aggregate"
 
 import (
 	"context"
 
 	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/sdk/metric/exemplar"
 )
 
-// Drop returns a [FilteredReservoir] that drops all measurements it is offered.
+// DropReservoir returns a [FilteredReservoir] that drops all measurements it is offered.
-func Drop[N int64 | float64]() FilteredReservoir[N] { return &dropRes[N]{} }
+func DropReservoir[N int64 | float64]() FilteredExemplarReservoir[N] { return &dropRes[N]{} }
 
 type dropRes[N int64 | float64] struct{}
 
@@ -18,6 +19,6 @@ type dropRes[N int64 | float64] struct{}
 func (r *dropRes[N]) Offer(context.Context, N, []attribute.KeyValue) {}
 
 // Collect resets dest. No exemplars will ever be returned.
-func (r *dropRes[N]) Collect(dest *[]Exemplar) {
+func (r *dropRes[N]) Collect(dest *[]exemplar.Exemplar) {
 	*dest = (*dest)[:0]
 }

sdk/metric/internal/aggregate/drop_test.go

@@ -1,12 +1,14 @@
 // Copyright The OpenTelemetry Authors
 // SPDX-License-Identifier: Apache-2.0
 
-package exemplar
+package aggregate
 
 import (
 	"testing"
 
 	"github.com/stretchr/testify/assert"
+
+	"go.opentelemetry.io/otel/sdk/metric/exemplar"
 )
 
 func TestDrop(t *testing.T) {
@@ -15,9 +17,9 @@ func TestDrop(t *testing.T) {
 }
 
 func testDropFiltered[N int64 | float64](t *testing.T) {
-	r := Drop[N]()
+	r := DropReservoir[N]()
 
-	var dest []Exemplar
+	var dest []exemplar.Exemplar
 	r.Collect(&dest)
 
 	assert.Empty(t, dest, "non-sampled context should not be offered")

sdk/metric/internal/aggregate/exemplar.go

@@ -6,7 +6,7 @@ package aggregate // import "go.opentelemetry.io/otel/sdk/metric/internal/aggreg
 import (
 	"sync"
 
-	"go.opentelemetry.io/otel/sdk/metric/internal/exemplar"
+	"go.opentelemetry.io/otel/sdk/metric/exemplar"
 	"go.opentelemetry.io/otel/sdk/metric/metricdata"
 )
 

sdk/metric/internal/aggregate/exemplar_test.go

@@ -10,7 +10,7 @@ import (
 	"github.com/stretchr/testify/assert"
 
 	"go.opentelemetry.io/otel/attribute"
-	"go.opentelemetry.io/otel/sdk/metric/internal/exemplar"
+	"go.opentelemetry.io/otel/sdk/metric/exemplar"
 	"go.opentelemetry.io/otel/sdk/metric/metricdata"
 )
 

sdk/metric/internal/aggregate/exponential_histogram.go

@@ -12,7 +12,6 @@ import (
 
 	"go.opentelemetry.io/otel"
 	"go.opentelemetry.io/otel/attribute"
-	"go.opentelemetry.io/otel/sdk/metric/internal/exemplar"
 	"go.opentelemetry.io/otel/sdk/metric/metricdata"
 )
 
@@ -31,7 +30,7 @@ const (
 // expoHistogramDataPoint is a single data point in an exponential histogram.
 type expoHistogramDataPoint[N int64 | float64] struct {
 	attrs attribute.Set
-	res   exemplar.FilteredReservoir[N]
+	res   FilteredExemplarReservoir[N]
 
 	count uint64
 	min   N
@@ -284,7 +283,7 @@ func (b *expoBuckets) downscale(delta int32) {
 // newExponentialHistogram returns an Aggregator that summarizes a set of
 // measurements as an exponential histogram. Each histogram is scoped by attributes
 // and the aggregation cycle the measurements were made in.
-func newExponentialHistogram[N int64 | float64](maxSize, maxScale int32, noMinMax, noSum bool, limit int, r func() exemplar.FilteredReservoir[N]) *expoHistogram[N] {
+func newExponentialHistogram[N int64 | float64](maxSize, maxScale int32, noMinMax, noSum bool, limit int, r func() FilteredExemplarReservoir[N]) *expoHistogram[N] {
 	return &expoHistogram[N]{
 		noSum:    noSum,
 		noMinMax: noMinMax,
@@ -307,7 +306,7 @@ type expoHistogram[N int64 | float64] struct {
 	maxSize  int
 	maxScale int32
 
-	newRes   func() exemplar.FilteredReservoir[N]
+	newRes   func() FilteredExemplarReservoir[N]
 	limit    limiter[*expoHistogramDataPoint[N]]
 	values   map[attribute.Distinct]*expoHistogramDataPoint[N]
 	valuesMu sync.Mutex

sdk/metric/internal/aggregate/filtered_reservoir.go

@@ -0,0 +1,50 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package aggregate // import "go.opentelemetry.io/otel/sdk/metric/internal/aggregate"
+
+import (
+	"context"
+	"time"
+
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/sdk/metric/exemplar"
+)
+
+// FilteredExemplarReservoir wraps a [exemplar.Reservoir] with a filter.
+type FilteredExemplarReservoir[N int64 | float64] interface {
+	// Offer accepts the parameters associated with a measurement. The
+	// parameters will be stored as an exemplar if the filter decides to
+	// sample the measurement.
+	//
+	// The passed ctx needs to contain any baggage or span that were active
+	// when the measurement was made. This information may be used by the
+	// Reservoir in making a sampling decision.
+	Offer(ctx context.Context, val N, attr []attribute.KeyValue)
+	// Collect returns all the held exemplars in the reservoir.
+	Collect(dest *[]exemplar.Exemplar)
+}
+
+// filteredExemplarReservoir handles the pre-sampled exemplar of measurements made.
+type filteredExemplarReservoir[N int64 | float64] struct {
+	filter    exemplar.Filter
+	reservoir exemplar.Reservoir
+}
+
+// NewFilteredExemplarReservoir creates a [FilteredExemplarReservoir] which only offers values
+// that are allowed by the filter.
+func NewFilteredExemplarReservoir[N int64 | float64](f exemplar.Filter, r exemplar.Reservoir) FilteredExemplarReservoir[N] {
+	return &filteredExemplarReservoir[N]{
+		filter:    f,
+		reservoir: r,
+	}
+}
+
+func (f *filteredExemplarReservoir[N]) Offer(ctx context.Context, val N, attr []attribute.KeyValue) {
+	if f.filter(ctx) {
+		// only record the current time if we are sampling this measurement.
+		f.reservoir.Offer(ctx, time.Now(), exemplar.NewValue(val), attr)
+	}
+}
+
+func (f *filteredExemplarReservoir[N]) Collect(dest *[]exemplar.Exemplar) { f.reservoir.Collect(dest) }

sdk/metric/internal/aggregate/histogram.go

@@ -11,13 +11,12 @@ import (
 	"time"
 
 	"go.opentelemetry.io/otel/attribute"
-	"go.opentelemetry.io/otel/sdk/metric/internal/exemplar"
 	"go.opentelemetry.io/otel/sdk/metric/metricdata"
 )
 
 type buckets[N int64 | float64] struct {
 	attrs attribute.Set
-	res   exemplar.FilteredReservoir[N]
+	res   FilteredExemplarReservoir[N]
 
 	counts   []uint64
 	count    uint64
@@ -48,13 +47,13 @@ type histValues[N int64 | float64] struct {
 	noSum  bool
 	bounds []float64
 
-	newRes   func() exemplar.FilteredReservoir[N]
+	newRes   func() FilteredExemplarReservoir[N]
 	limit    limiter[*buckets[N]]
 	values   map[attribute.Distinct]*buckets[N]
 	valuesMu sync.Mutex
 }
 
-func newHistValues[N int64 | float64](bounds []float64, noSum bool, limit int, r func() exemplar.FilteredReservoir[N]) *histValues[N] {
+func newHistValues[N int64 | float64](bounds []float64, noSum bool, limit int, r func() FilteredExemplarReservoir[N]) *histValues[N] {
 	// The responsibility of keeping all buckets correctly associated with the
 	// passed boundaries is ultimately this type's responsibility. Make a copy
 	// here so we can always guarantee this. Or, in the case of failure, have
@@ -109,7 +108,7 @@ func (s *histValues[N]) measure(ctx context.Context, value N, fltrAttr attribute
 
 // newHistogram returns an Aggregator that summarizes a set of measurements as
 // an histogram.
-func newHistogram[N int64 | float64](boundaries []float64, noMinMax, noSum bool, limit int, r func() exemplar.FilteredReservoir[N]) *histogram[N] {
+func newHistogram[N int64 | float64](boundaries []float64, noMinMax, noSum bool, limit int, r func() FilteredExemplarReservoir[N]) *histogram[N] {
 	return &histogram[N]{
 		histValues: newHistValues[N](boundaries, noSum, limit, r),
 		noMinMax:   noMinMax,

sdk/metric/internal/aggregate/lastvalue.go

@@ -9,7 +9,6 @@ import (
 	"time"
 
 	"go.opentelemetry.io/otel/attribute"
-	"go.opentelemetry.io/otel/sdk/metric/internal/exemplar"
 	"go.opentelemetry.io/otel/sdk/metric/metricdata"
 )
 
@@ -17,10 +16,10 @@ import (
 type datapoint[N int64 | float64] struct {
 	attrs attribute.Set
 	value N
-	res   exemplar.FilteredReservoir[N]
+	res   FilteredExemplarReservoir[N]
 }
 
-func newLastValue[N int64 | float64](limit int, r func() exemplar.FilteredReservoir[N]) *lastValue[N] {
+func newLastValue[N int64 | float64](limit int, r func() FilteredExemplarReservoir[N]) *lastValue[N] {
 	return &lastValue[N]{
 		newRes: r,
 		limit:  newLimiter[datapoint[N]](limit),
@@ -33,7 +32,7 @@ func newLastValue[N int64 | float64](limit int, r func() exemplar.FilteredReserv
 type lastValue[N int64 | float64] struct {
 	sync.Mutex
 
-	newRes func() exemplar.FilteredReservoir[N]
+	newRes func() FilteredExemplarReservoir[N]
 	limit  limiter[datapoint[N]]
 	values map[attribute.Distinct]datapoint[N]
 	start  time.Time
@@ -115,7 +114,7 @@ func (s *lastValue[N]) copyDpts(dest *[]metricdata.DataPoint[N], t time.Time) in
 
 // newPrecomputedLastValue returns an aggregator that summarizes a set of
 // observations as the last one made.
-func newPrecomputedLastValue[N int64 | float64](limit int, r func() exemplar.FilteredReservoir[N]) *precomputedLastValue[N] {
+func newPrecomputedLastValue[N int64 | float64](limit int, r func() FilteredExemplarReservoir[N]) *precomputedLastValue[N] {
 	return &precomputedLastValue[N]{lastValue: newLastValue[N](limit, r)}
 }
 

sdk/metric/internal/aggregate/sum.go

@@ -9,25 +9,24 @@ import (
 	"time"
 
 	"go.opentelemetry.io/otel/attribute"
-	"go.opentelemetry.io/otel/sdk/metric/internal/exemplar"
 	"go.opentelemetry.io/otel/sdk/metric/metricdata"
 )
 
 type sumValue[N int64 | float64] struct {
 	n     N
-	res   exemplar.FilteredReservoir[N]
+	res   FilteredExemplarReservoir[N]
 	attrs attribute.Set
 }
 
 // valueMap is the storage for sums.
 type valueMap[N int64 | float64] struct {
 	sync.Mutex
-	newRes func() exemplar.FilteredReservoir[N]
+	newRes func() FilteredExemplarReservoir[N]
 	limit  limiter[sumValue[N]]
 	values map[attribute.Distinct]sumValue[N]
 }
 
-func newValueMap[N int64 | float64](limit int, r func() exemplar.FilteredReservoir[N]) *valueMap[N] {
+func newValueMap[N int64 | float64](limit int, r func() FilteredExemplarReservoir[N]) *valueMap[N] {
 	return &valueMap[N]{
 		newRes: r,
 		limit:  newLimiter[sumValue[N]](limit),
@@ -55,7 +54,7 @@ func (s *valueMap[N]) measure(ctx context.Context, value N, fltrAttr attribute.S
 // newSum returns an aggregator that summarizes a set of measurements as their
 // arithmetic sum. Each sum is scoped by attributes and the aggregation cycle
 // the measurements were made in.
-func newSum[N int64 | float64](monotonic bool, limit int, r func() exemplar.FilteredReservoir[N]) *sum[N] {
+func newSum[N int64 | float64](monotonic bool, limit int, r func() FilteredExemplarReservoir[N]) *sum[N] {
 	return &sum[N]{
 		valueMap:  newValueMap[N](limit, r),
 		monotonic: monotonic,
@@ -144,7 +143,7 @@ func (s *sum[N]) cumulative(dest *metricdata.Aggregation) int {
 // newPrecomputedSum returns an aggregator that summarizes a set of
 // observations as their arithmetic sum. Each sum is scoped by attributes and
 // the aggregation cycle the measurements were made in.
-func newPrecomputedSum[N int64 | float64](monotonic bool, limit int, r func() exemplar.FilteredReservoir[N]) *precomputedSum[N] {
+func newPrecomputedSum[N int64 | float64](monotonic bool, limit int, r func() FilteredExemplarReservoir[N]) *precomputedSum[N] {
 	return &precomputedSum[N]{
 		valueMap:  newValueMap[N](limit, r),
 		monotonic: monotonic,

sdk/metric/internal/exemplar/filtered_reservoir.go

@@ -1,49 +0,0 @@
-// Copyright The OpenTelemetry Authors
-// SPDX-License-Identifier: Apache-2.0
-
-package exemplar // import "go.opentelemetry.io/otel/sdk/metric/internal/exemplar"
-
-import (
-	"context"
-	"time"
-
-	"go.opentelemetry.io/otel/attribute"
-)
-
-// FilteredReservoir wraps a [Reservoir] with a filter.
-type FilteredReservoir[N int64 | float64] interface {
-	// Offer accepts the parameters associated with a measurement. The
-	// parameters will be stored as an exemplar if the filter decides to
-	// sample the measurement.
-	//
-	// The passed ctx needs to contain any baggage or span that were active
-	// when the measurement was made. This information may be used by the
-	// Reservoir in making a sampling decision.
-	Offer(ctx context.Context, val N, attr []attribute.KeyValue)
-	// Collect returns all the held exemplars in the reservoir.
-	Collect(dest *[]Exemplar)
-}
-
-// filteredReservoir handles the pre-sampled exemplar of measurements made.
-type filteredReservoir[N int64 | float64] struct {
-	filter    Filter
-	reservoir Reservoir
-}
-
-// NewFilteredReservoir creates a [FilteredReservoir] which only offers values
-// that are allowed by the filter.
-func NewFilteredReservoir[N int64 | float64](f Filter, r Reservoir) FilteredReservoir[N] {
-	return &filteredReservoir[N]{
-		filter:    f,
-		reservoir: r,
-	}
-}
-
-func (f *filteredReservoir[N]) Offer(ctx context.Context, val N, attr []attribute.KeyValue) {
-	if f.filter(ctx) {
-		// only record the current time if we are sampling this measurement.
-		f.reservoir.Offer(ctx, time.Now(), NewValue(val), attr)
-	}
-}
-
-func (f *filteredReservoir[N]) Collect(dest *[]Exemplar) { f.reservoir.Collect(dest) }

sdk/metric/internal/exemplar/hist.go

@@ -1,46 +0,0 @@
-// Copyright The OpenTelemetry Authors
-// SPDX-License-Identifier: Apache-2.0
-
-package exemplar // import "go.opentelemetry.io/otel/sdk/metric/internal/exemplar"
-
-import (
-	"context"
-	"slices"
-	"sort"
-	"time"
-
-	"go.opentelemetry.io/otel/attribute"
-)
-
-// Histogram returns a [Reservoir] that samples the last measurement that falls
-// within a histogram bucket. The histogram bucket upper-boundaries are define
-// by bounds.
-//
-// The passed bounds will be sorted by this function.
-func Histogram(bounds []float64) Reservoir {
-	slices.Sort(bounds)
-	return &histRes{
-		bounds:  bounds,
-		storage: newStorage(len(bounds) + 1),
-	}
-}
-
-type histRes struct {
-	*storage
-
-	// bounds are bucket bounds in ascending order.
-	bounds []float64
-}
-
-func (r *histRes) Offer(ctx context.Context, t time.Time, v Value, a []attribute.KeyValue) {
-	var x float64
-	switch v.Type() {
-	case Int64ValueType:
-		x = float64(v.Int64())
-	case Float64ValueType:
-		x = v.Float64()
-	default:
-		panic("unknown value type")
-	}
-	r.store[sort.SearchFloat64s(r.bounds, x)] = newMeasurement(ctx, t, v, a)
-}