feat(telemetry): instrument inference duration and frame age

vendor/go.opentelemetry.io/otel/sdk/metric/aggregator/exact/exact.go

@@ -0,0 +1,130 @@
+// 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.
+
+package exact // import "go.opentelemetry.io/otel/sdk/metric/aggregator/exact"
+
+import (
+	"context"
+	"sync"
+	"time"
+
+	"go.opentelemetry.io/otel/metric/number"
+	"go.opentelemetry.io/otel/metric/sdkapi"
+	export "go.opentelemetry.io/otel/sdk/export/metric"
+	"go.opentelemetry.io/otel/sdk/export/metric/aggregation"
+	"go.opentelemetry.io/otel/sdk/metric/aggregator"
+)
+
+type (
+	// Aggregator aggregates events that form a distribution, keeping
+	// an array with the exact set of values.
+	Aggregator struct {
+		lock    sync.Mutex
+		samples []aggregation.Point
+	}
+)
+
+var _ export.Aggregator = &Aggregator{}
+var _ aggregation.Points = &Aggregator{}
+var _ aggregation.Count = &Aggregator{}
+
+// New returns cnt many new exact aggregators, which aggregate recorded
+// measurements by storing them in an array.  This type uses a mutex
+// for Update() and SynchronizedMove() concurrency.
+func New(cnt int) []Aggregator {
+	return make([]Aggregator, cnt)
+}
+
+// Aggregation returns an interface for reading the state of this aggregator.
+func (c *Aggregator) Aggregation() aggregation.Aggregation {
+	return c
+}
+
+// Kind returns aggregation.ExactKind.
+func (c *Aggregator) Kind() aggregation.Kind {
+	return aggregation.ExactKind
+}
+
+// Count returns the number of values in the checkpoint.
+func (c *Aggregator) Count() (uint64, error) {
+	return uint64(len(c.samples)), nil
+}
+
+// Points returns access to the raw data set.
+func (c *Aggregator) Points() ([]aggregation.Point, error) {
+	return c.samples, nil
+}
+
+// SynchronizedMove saves the current state to oa and resets the current state to
+// the empty set, taking a lock to prevent concurrent Update() calls.
+func (c *Aggregator) SynchronizedMove(oa export.Aggregator, desc *sdkapi.Descriptor) error {
+	o, _ := oa.(*Aggregator)
+
+	if oa != nil && o == nil {
+		return aggregator.NewInconsistentAggregatorError(c, oa)
+	}
+
+	c.lock.Lock()
+	defer c.lock.Unlock()
+
+	if o != nil {
+		o.samples = c.samples
+	}
+	c.samples = nil
+
+	return nil
+}
+
+// Update adds the recorded measurement to the current data set.
+// Update takes a lock to prevent concurrent Update() and SynchronizedMove()
+// calls.
+func (c *Aggregator) Update(_ context.Context, number number.Number, desc *sdkapi.Descriptor) error {
+	now := time.Now()
+	c.lock.Lock()
+	defer c.lock.Unlock()
+	c.samples = append(c.samples, aggregation.Point{
+		Number: number,
+		Time:   now,
+	})
+
+	return nil
+}
+
+// Merge combines two data sets into one.
+func (c *Aggregator) Merge(oa export.Aggregator, desc *sdkapi.Descriptor) error {
+	o, _ := oa.(*Aggregator)
+	if o == nil {
+		return aggregator.NewInconsistentAggregatorError(c, oa)
+	}
+
+	c.samples = combine(c.samples, o.samples)
+	return nil
+}
+
+func combine(a, b []aggregation.Point) []aggregation.Point {
+	result := make([]aggregation.Point, 0, len(a)+len(b))
+
+	for len(a) != 0 && len(b) != 0 {
+		if a[0].Time.Before(b[0].Time) {
+			result = append(result, a[0])
+			a = a[1:]
+		} else {
+			result = append(result, b[0])
+			b = b[1:]
+		}
+	}
+	result = append(result, a...)
+	result = append(result, b...)
+	return result
+}