Add the Exponential Histogram and other aggregators for review LS-29757

lightstep/sdk/metric/aggregator/aggregation/aggregation.go

@@ -0,0 +1,128 @@
+// Copyright The OpenTelemetry 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.
+
+//go:generate stringer -type=Category,Kind
+
+package aggregation // import "github.com/lightstep/otel-launcher-go/lightstep/sdk/metric/aggregator/aggregation"
+
+import (
+	"github.com/lightstep/otel-launcher-go/lightstep/sdk/metric/number"
+	"github.com/lightstep/otel-launcher-go/lightstep/sdk/metric/sdkinstrument"
+)
+
+// These interfaces describe the various ways to access state from an
+// Aggregation.
+
+type (
+	// Aggregation is an interface returned by the Aggregator
+	// containing an interval of metric data.
+	Aggregation interface {
+		Kind() Kind
+	}
+
+	// HasASum includes Sum and Histogram aggregators.
+	HasASum interface {
+		Sum() number.Number
+	}
+
+	// Sum returns an aggregated sum.
+	Sum interface {
+		// Review NOTE: Should this be Total() or Value()?
+		HasASum
+		IsMonotonic() bool
+	}
+
+	// Gauge returns the latest value that was aggregated.
+	Gauge interface {
+		Aggregation
+
+		// Review NOTE: Should this be LastValue() or Value()?
+		Gauge() number.Number
+	}
+
+	// Histogram returns the count of events in exponential-scale
+	// buckets defined as a function of a scale parameter.  See a
+	// detailed explanation in the OpenTelemetry metrics data
+	// model:
+	// https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/datamodel.md#exponentialhistogram
+	Histogram interface {
+		Aggregation
+		Count() uint64
+		HasASum
+		Scale() int32
+		ZeroCount() uint64
+		Positive() Buckets
+		Negative() Buckets
+	}
+
+	// Buckets describes a range of consecutive buckets, starting
+	// at Offset().  This type is used to encode either the
+	// positive or negative ranges of an Histogram.
+	Buckets interface {
+		Offset() int32
+		Len() uint32
+		At(uint32) uint64
+	}
+)
+
+// Category constants describe semantic kind.  For the histogram
+// category there are multiple implementations, for those distinctions
+// as well as Drop, use Kind.
+type Category int
+
+const (
+	UndefinedCategory Category = iota
+	MonotonicSumCategory
+	NonMonotonicSumCategory
+	GaugeCategory
+	HistogramCategory
+)
+
+type Kind int
+
+const (
+	UndefinedKind Kind = iota
+	DropKind
+	AnySumKind
+	MonotonicSumKind
+	NonMonotonicSumKind
+	GaugeKind
+	HistogramKind
+)
+
+func (k Kind) Category(ik sdkinstrument.Kind) Category {
+	switch k {
+	case AnySumKind:
+		switch ik {
+		case sdkinstrument.HistogramKind, sdkinstrument.CounterKind, sdkinstrument.CounterObserverKind:
+			return MonotonicSumCategory
+		case sdkinstrument.UpDownCounterKind, sdkinstrument.UpDownCounterObserverKind:
+			return NonMonotonicSumCategory
+		}
+		return UndefinedCategory
+	case MonotonicSumKind:
+		return MonotonicSumCategory
+	case NonMonotonicSumKind:
+		return NonMonotonicSumCategory
+	case GaugeKind:
+		return GaugeCategory
+	case HistogramKind:
+		return HistogramCategory
+	default:
+		return UndefinedCategory
+	}
+}
+
+// KindSelector is a per-instrument-kind Kind choice.
+type KindSelector func(sdkinstrument.Kind) Kind

lightstep/sdk/metric/aggregator/aggregation/temporality.go

@@ -0,0 +1,51 @@
+// Copyright The OpenTelemetry 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.
+
+//go:generate stringer -type=Temporality
+
+package aggregation // import "github.com/lightstep/otel-launcher-go/lightstep/sdk/metric/aggregator/aggregation"
+
+import "github.com/lightstep/otel-launcher-go/lightstep/sdk/metric/sdkinstrument"
+
+type Temporality uint8
+
+const (
+	// UndefinedTemporality indicates that temporality is not defined.
+	UndefinedTemporality Temporality = 0
+
+	// CumulativeTemporality indicates that an Exporter expects a
+	// Cumulative Aggregation.
+	CumulativeTemporality Temporality = 1
+
+	// DeltaTemporality indicates that an Exporter expects a
+	// Delta Aggregation.
+	DeltaTemporality Temporality = 2
+)
+
+type TemporalitySelector func(sdkinstrument.Kind) Temporality
+
+type TemporalityTrait interface {
+	Temporality() Temporality
+}
+
+type DeltaTemporalityTrait struct{}
+type CumulativeTemporalityTrait struct{}
+
+func (DeltaTemporalityTrait) Temporality() Temporality {
+	return DeltaTemporality
+}
+
+func (CumulativeTemporalityTrait) Temporality() Temporality {
+	return CumulativeTemporality
+}