feat(telemetry): instrument inference duration and frame age

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

@@ -0,0 +1,270 @@
+// 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 histogram // import "go.opentelemetry.io/otel/sdk/metric/aggregator/histogram"
+
+import (
+	"context"
+	"sort"
+	"sync"
+
+	"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"
+)
+
+// Note: This code uses a Mutex to govern access to the exclusive
+// aggregator state.  This is in contrast to a lock-free approach
+// (as in the Go prometheus client) that was reverted here:
+// https://github.com/open-telemetry/opentelemetry-go/pull/669
+
+type (
+	// Aggregator observe events and counts them in pre-determined buckets.
+	// It also calculates the sum and count of all events.
+	Aggregator struct {
+		lock       sync.Mutex
+		boundaries []float64
+		kind       number.Kind
+		state      *state
+	}
+
+	// config describes how the histogram is aggregated.
+	config struct {
+		// explicitBoundaries support arbitrary bucketing schemes.  This
+		// is the general case.
+		explicitBoundaries []float64
+	}
+
+	// Option configures a histogram config.
+	Option interface {
+		// apply sets one or more config fields.
+		apply(*config)
+	}
+
+	// state represents the state of a histogram, consisting of
+	// the sum and counts for all observed values and
+	// the less than equal bucket count for the pre-determined boundaries.
+	state struct {
+		bucketCounts []uint64
+		sum          number.Number
+		count        uint64
+	}
+)
+
+// WithExplicitBoundaries sets the ExplicitBoundaries configuration option of a config.
+func WithExplicitBoundaries(explicitBoundaries []float64) Option {
+	return explicitBoundariesOption{explicitBoundaries}
+}
+
+type explicitBoundariesOption struct {
+	boundaries []float64
+}
+
+func (o explicitBoundariesOption) apply(config *config) {
+	config.explicitBoundaries = o.boundaries
+}
+
+// defaultExplicitBoundaries have been copied from prometheus.DefBuckets.
+//
+// Note we anticipate the use of a high-precision histogram sketch as
+// the standard histogram aggregator for OTLP export.
+// (https://github.com/open-telemetry/opentelemetry-specification/issues/982).
+var defaultFloat64ExplicitBoundaries = []float64{.005, .01, .025, .05, .1, .25, .5, 1, 2.5, 5, 10}
+
+// defaultInt64ExplicitBoundaryMultiplier determines the default
+// integer histogram boundaries.
+const defaultInt64ExplicitBoundaryMultiplier = 1e6
+
+// defaultInt64ExplicitBoundaries applies a multiplier to the default
+// float64 boundaries: [ 5K, 10K, 25K, ..., 2.5M, 5M, 10M ]
+var defaultInt64ExplicitBoundaries = func(bounds []float64) (asint []float64) {
+	for _, f := range bounds {
+		asint = append(asint, defaultInt64ExplicitBoundaryMultiplier*f)
+	}
+	return
+}(defaultFloat64ExplicitBoundaries)
+
+var _ export.Aggregator = &Aggregator{}
+var _ aggregation.Sum = &Aggregator{}
+var _ aggregation.Count = &Aggregator{}
+var _ aggregation.Histogram = &Aggregator{}
+
+// New returns a new aggregator for computing Histograms.
+//
+// A Histogram observe events and counts them in pre-defined buckets.
+// And also provides the total sum and count of all observations.
+//
+// Note that this aggregator maintains each value using independent
+// atomic operations, which introduces the possibility that
+// checkpoints are inconsistent.
+func New(cnt int, desc *sdkapi.Descriptor, opts ...Option) []Aggregator {
+	var cfg config
+
+	if desc.NumberKind() == number.Int64Kind {
+		cfg.explicitBoundaries = defaultInt64ExplicitBoundaries
+	} else {
+		cfg.explicitBoundaries = defaultFloat64ExplicitBoundaries
+	}
+
+	for _, opt := range opts {
+		opt.apply(&cfg)
+	}
+
+	aggs := make([]Aggregator, cnt)
+
+	// Boundaries MUST be ordered otherwise the histogram could not
+	// be properly computed.
+	sortedBoundaries := make([]float64, len(cfg.explicitBoundaries))
+
+	copy(sortedBoundaries, cfg.explicitBoundaries)
+	sort.Float64s(sortedBoundaries)
+
+	for i := range aggs {
+		aggs[i] = Aggregator{
+			kind:       desc.NumberKind(),
+			boundaries: sortedBoundaries,
+		}
+		aggs[i].state = aggs[i].newState()
+	}
+	return aggs
+}
+
+// Aggregation returns an interface for reading the state of this aggregator.
+func (c *Aggregator) Aggregation() aggregation.Aggregation {
+	return c
+}
+
+// Kind returns aggregation.HistogramKind.
+func (c *Aggregator) Kind() aggregation.Kind {
+	return aggregation.HistogramKind
+}
+
+// Sum returns the sum of all values in the checkpoint.
+func (c *Aggregator) Sum() (number.Number, error) {
+	return c.state.sum, nil
+}
+
+// Count returns the number of values in the checkpoint.
+func (c *Aggregator) Count() (uint64, error) {
+	return c.state.count, nil
+}
+
+// Histogram returns the count of events in pre-determined buckets.
+func (c *Aggregator) Histogram() (aggregation.Buckets, error) {
+	return aggregation.Buckets{
+		Boundaries: c.boundaries,
+		Counts:     c.state.bucketCounts,
+	}, nil
+}
+
+// SynchronizedMove saves the current state into oa and resets the current state to
+// the empty set.  Since no locks are taken, there is a chance that
+// the independent Sum, Count and Bucket Count are not consistent with each
+// other.
+func (c *Aggregator) SynchronizedMove(oa export.Aggregator, desc *sdkapi.Descriptor) error {
+	o, _ := oa.(*Aggregator)
+
+	if oa != nil && o == nil {
+		return aggregator.NewInconsistentAggregatorError(c, oa)
+	}
+
+	if o != nil {
+		// Swap case: This is the ordinary case for a
+		// synchronous instrument, where the SDK allocates two
+		// Aggregators and lock contention is anticipated.
+		// Reset the target state before swapping it under the
+		// lock below.
+		o.clearState()
+	}
+
+	c.lock.Lock()
+	if o != nil {
+		c.state, o.state = o.state, c.state
+	} else {
+		// No swap case: This is the ordinary case for an
+		// asynchronous instrument, where the SDK allocates a
+		// single Aggregator and there is no anticipated lock
+		// contention.
+		c.clearState()
+	}
+	c.lock.Unlock()
+
+	return nil
+}
+
+func (c *Aggregator) newState() *state {
+	return &state{
+		bucketCounts: make([]uint64, len(c.boundaries)+1),
+	}
+}
+
+func (c *Aggregator) clearState() {
+	for i := range c.state.bucketCounts {
+		c.state.bucketCounts[i] = 0
+	}
+	c.state.sum = 0
+	c.state.count = 0
+}
+
+// Update adds the recorded measurement to the current data set.
+func (c *Aggregator) Update(_ context.Context, number number.Number, desc *sdkapi.Descriptor) error {
+	kind := desc.NumberKind()
+	asFloat := number.CoerceToFloat64(kind)
+
+	bucketID := len(c.boundaries)
+	for i, boundary := range c.boundaries {
+		if asFloat < boundary {
+			bucketID = i
+			break
+		}
+	}
+	// Note: Binary-search was compared using the benchmarks. The following
+	// code is equivalent to the linear search above:
+	//
+	//     bucketID := sort.Search(len(c.boundaries), func(i int) bool {
+	//         return asFloat < c.boundaries[i]
+	//     })
+	//
+	// The binary search wins for very large boundary sets, but
+	// the linear search performs better up through arrays between
+	// 256 and 512 elements, which is a relatively large histogram, so we
+	// continue to prefer linear search.
+
+	c.lock.Lock()
+	defer c.lock.Unlock()
+
+	c.state.count++
+	c.state.sum.AddNumber(kind, number)
+	c.state.bucketCounts[bucketID]++
+
+	return nil
+}
+
+// Merge combines two histograms that have the same buckets into a single one.
+func (c *Aggregator) Merge(oa export.Aggregator, desc *sdkapi.Descriptor) error {
+	o, _ := oa.(*Aggregator)
+	if o == nil {
+		return aggregator.NewInconsistentAggregatorError(c, oa)
+	}
+
+	c.state.sum.AddNumber(desc.NumberKind(), o.state.sum)
+	c.state.count += o.state.count
+
+	for i := 0; i < len(c.state.bucketCounts); i++ {
+		c.state.bucketCounts[i] += o.state.bucketCounts[i]
+	}
+	return nil
+}