Histogram aggregator functional options (#1434)

* Add a Config/Option for histogram

* Just one option here

* Test fixes

* Support and test int64 histograms

* Changelog

* Lint

* Un-export three things.

CHANGELOG.md

@@ -36,6 +36,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - Unify endpoint API that related to OTel exporter. (#1401)
 - Optimize metric histogram aggregator to re-use its slice of buckets. (#1435)
 - Metric aggregator Count() and histogram Bucket.Counts are consistently `uint64`. (1430)
+- Histogram aggregator accepts functional options, uses default boundaries if none given. (#1434)
 - `SamplingResult` now passed a `Tracestate` from the parent `SpanContext` (#1432)
 - Moved gRPC driver for OTLP exporter to `exporters/otlp/otlpgrpc`. (#1420)
 - The `TraceContext` propagator now correctly propagates `TraceState` through the `SpanContext`. (#1447)

example/prom-collector/main.go

@@ -29,6 +29,7 @@ import (
 	"go.opentelemetry.io/otel/exporters/otlp/otlpgrpc"
 	"go.opentelemetry.io/otel/label"
 	"go.opentelemetry.io/otel/metric"
+	"go.opentelemetry.io/otel/sdk/metric/aggregator/histogram"
 	controller "go.opentelemetry.io/otel/sdk/metric/controller/basic"
 	processor "go.opentelemetry.io/otel/sdk/metric/processor/basic"
 	"go.opentelemetry.io/otel/sdk/metric/selector/simple"
@@ -59,9 +60,11 @@ func initMeter() {
 
 	cont := controller.New(
 		processor.New(
-			simple.NewWithHistogramDistribution([]float64{
-				0.001, 0.01, 0.1, 1, 10, 100, 1000,
-			}),
+			simple.NewWithHistogramDistribution(
+				histogram.WithExplicitBoundaries([]float64{
+					0.001, 0.01, 0.1, 1, 10, 100, 1000,
+				}),
+			),
 			otlpExporter, // otlpExporter is an ExportKindSelector
 			processor.WithMemory(true),
 		),

exporters/metric/prometheus/prometheus.go

@@ -32,9 +32,10 @@ import (
 	"go.opentelemetry.io/otel/metric/number"
 	export "go.opentelemetry.io/otel/sdk/export/metric"
 	"go.opentelemetry.io/otel/sdk/export/metric/aggregation"
+	"go.opentelemetry.io/otel/sdk/metric/aggregator/histogram"
 	controller "go.opentelemetry.io/otel/sdk/metric/controller/basic"
 	processor "go.opentelemetry.io/otel/sdk/metric/processor/basic"
-	"go.opentelemetry.io/otel/sdk/metric/selector/simple"
+	selector "go.opentelemetry.io/otel/sdk/metric/selector/simple"
 )
 
 // Exporter supports Prometheus pulls.  It does not implement the
@@ -150,7 +151,9 @@ func InstallNewPipeline(config Config, options ...controller.Option) (*Exporter,
 func defaultController(config Config, options ...controller.Option) *controller.Controller {
 	return controller.New(
 		processor.New(
-			simple.NewWithHistogramDistribution(config.DefaultHistogramBoundaries),
+			selector.NewWithHistogramDistribution(
+				histogram.WithExplicitBoundaries(config.DefaultHistogramBoundaries),
+			),
 			export.CumulativeExportKindSelector(),
 			processor.WithMemory(true),
 		),

exporters/otlp/otlp_metric_test.go

@@ -756,7 +756,7 @@ func runMetricExportTests(t *testing.T, opts []otlp.ExporterOption, rs []record,
 		if r.iKind.Adding() {
 			agg, ckpt = metrictest.Unslice2(sum.New(2))
 		} else {
-			agg, ckpt = metrictest.Unslice2(histogram.New(2, &desc, testHistogramBoundaries))
+			agg, ckpt = metrictest.Unslice2(histogram.New(2, &desc, histogram.WithExplicitBoundaries(testHistogramBoundaries)))
 		}
 
 		ctx := context.Background()

sdk/metric/aggregator/histogram/benchmark_test.go

@@ -39,7 +39,7 @@ func benchmarkHistogramSearchFloat64(b *testing.B, size int) {
 		values[i] = rand.Float64() * inputRange
 	}
 	desc := aggregatortest.NewAggregatorTest(metric.ValueRecorderInstrumentKind, number.Float64Kind)
-	agg := &histogram.New(1, desc, boundaries)[0]
+	agg := &histogram.New(1, desc, histogram.WithExplicitBoundaries(boundaries))[0]
 	ctx := context.Background()
 
 	b.ReportAllocs()
@@ -90,7 +90,7 @@ func benchmarkHistogramSearchInt64(b *testing.B, size int) {
 		values[i] = int64(rand.Float64() * inputRange)
 	}
 	desc := aggregatortest.NewAggregatorTest(metric.ValueRecorderInstrumentKind, number.Int64Kind)
-	agg := &histogram.New(1, desc, boundaries)[0]
+	agg := &histogram.New(1, desc, histogram.WithExplicitBoundaries(boundaries))[0]
 	ctx := context.Background()
 
 	b.ReportAllocs()

sdk/metric/aggregator/histogram/histogram.go

@@ -41,6 +41,19 @@ type (
 		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.
@@ -51,6 +64,39 @@ type (
 	}
 )
 
+// 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{}
@@ -64,14 +110,26 @@ var _ aggregation.Histogram = &Aggregator{}
 // Note that this aggregator maintains each value using independent
 // atomic operations, which introduces the possibility that
 // checkpoints are inconsistent.
-func New(cnt int, desc *metric.Descriptor, boundaries []float64) []Aggregator {
+func New(cnt int, desc *metric.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(boundaries))
+	sortedBoundaries := make([]float64, len(cfg.explicitBoundaries))
 
-	copy(sortedBoundaries, boundaries)
+	copy(sortedBoundaries, cfg.explicitBoundaries)
 	sort.Float64s(sortedBoundaries)
 
 	for i := range aggs {

sdk/metric/aggregator/histogram/histogram_test.go

@@ -15,6 +15,7 @@
 package histogram_test
 
 import (
+	"context"
 	"math"
 	"math/rand"
 	"sort"
@@ -59,16 +60,16 @@ var (
 		},
 	}
 
-	boundaries = []float64{500, 250, 750}
+	testBoundaries = []float64{500, 250, 750}
 )
 
-func new2(desc *metric.Descriptor) (_, _ *histogram.Aggregator) {
-	alloc := histogram.New(2, desc, boundaries)
+func new2(desc *metric.Descriptor, options ...histogram.Option) (_, _ *histogram.Aggregator) {
+	alloc := histogram.New(2, desc, options...)
 	return &alloc[0], &alloc[1]
 }
 
-func new4(desc *metric.Descriptor) (_, _, _, _ *histogram.Aggregator) {
-	alloc := histogram.New(4, desc, boundaries)
+func new4(desc *metric.Descriptor, options ...histogram.Option) (_, _, _, _ *histogram.Aggregator) {
+	alloc := histogram.New(4, desc, options...)
 	return &alloc[0], &alloc[1], &alloc[2], &alloc[3]
 }
 
@@ -84,11 +85,10 @@ func checkZero(t *testing.T, agg *histogram.Aggregator, desc *metric.Descriptor)
 	buckets, err := agg.Histogram()
 	require.NoError(t, err)
 
-	require.Equal(t, len(buckets.Counts), len(boundaries)+1, "There should be b + 1 counts, where b is the number of boundaries")
+	require.Equal(t, len(buckets.Counts), len(testBoundaries)+1, "There should be b + 1 counts, where b is the number of boundaries")
 	for i, bCount := range buckets.Counts {
 		require.Equal(t, uint64(0), uint64(bCount), "Bucket #%d must have 0 observed values", i)
 	}
-
 }
 
 func TestHistogramAbsolute(t *testing.T) {
@@ -113,7 +113,7 @@ func TestHistogramPositiveAndNegative(t *testing.T) {
 func testHistogram(t *testing.T, profile aggregatortest.Profile, policy policy) {
 	descriptor := aggregatortest.NewAggregatorTest(metric.ValueRecorderInstrumentKind, profile.NumberKind)
 
-	agg, ckpt := new2(descriptor)
+	agg, ckpt := new2(descriptor, histogram.WithExplicitBoundaries(testBoundaries))
 
 	// This needs to repeat at least 3 times to uncover a failure to reset
 	// for the overall sum and count fields, since the third time through
@@ -139,20 +139,20 @@ func TestHistogramInitial(t *testing.T) {
 	aggregatortest.RunProfiles(t, func(t *testing.T, profile aggregatortest.Profile) {
 		descriptor := aggregatortest.NewAggregatorTest(metric.ValueRecorderInstrumentKind, profile.NumberKind)
 
-		agg := &histogram.New(1, descriptor, boundaries)[0]
+		agg := &histogram.New(1, descriptor, histogram.WithExplicitBoundaries(testBoundaries))[0]
 		buckets, err := agg.Histogram()
 
 		require.NoError(t, err)
-		require.Equal(t, len(buckets.Counts), len(boundaries)+1)
-		require.Equal(t, len(buckets.Boundaries), len(boundaries))
+		require.Equal(t, len(buckets.Counts), len(testBoundaries)+1)
+		require.Equal(t, len(buckets.Boundaries), len(testBoundaries))
 	})
 }
 
 func TestHistogramMerge(t *testing.T) {
 	aggregatortest.RunProfiles(t, func(t *testing.T, profile aggregatortest.Profile) {
 		descriptor := aggregatortest.NewAggregatorTest(metric.ValueRecorderInstrumentKind, profile.NumberKind)
 
-		agg1, agg2, ckpt1, ckpt2 := new4(descriptor)
+		agg1, agg2, ckpt1, ckpt2 := new4(descriptor, histogram.WithExplicitBoundaries(testBoundaries))
 
 		all := aggregatortest.NewNumbers(profile.NumberKind)
 
@@ -180,7 +180,7 @@ func TestHistogramNotSet(t *testing.T) {
 	aggregatortest.RunProfiles(t, func(t *testing.T, profile aggregatortest.Profile) {
 		descriptor := aggregatortest.NewAggregatorTest(metric.ValueRecorderInstrumentKind, profile.NumberKind)
 
-		agg, ckpt := new2(descriptor)
+		agg, ckpt := new2(descriptor, histogram.WithExplicitBoundaries(testBoundaries))
 
 		err := agg.SynchronizedMove(ckpt, descriptor)
 		require.NoError(t, err)
@@ -212,11 +212,12 @@ func checkHistogram(t *testing.T, all aggregatortest.Numbers, profile aggregator
 	buckets, err := agg.Histogram()
 	require.NoError(t, err)
 
-	require.Equal(t, len(buckets.Counts), len(boundaries)+1,
+	require.Equal(t, len(buckets.Counts), len(testBoundaries)+1,
 		"There should be b + 1 counts, where b is the number of boundaries")
 
-	sortedBoundaries := make([]float64, len(boundaries))
-	copy(sortedBoundaries, boundaries)
+	sortedBoundaries := make([]float64, len(testBoundaries))
+	copy(sortedBoundaries, testBoundaries)
+
 	sort.Float64s(sortedBoundaries)
 
 	require.EqualValues(t, sortedBoundaries, buckets.Boundaries)
@@ -240,7 +241,56 @@ func TestSynchronizedMoveReset(t *testing.T) {
 		t,
 		metric.ValueRecorderInstrumentKind,
 		func(desc *metric.Descriptor) export.Aggregator {
-			return &histogram.New(1, desc, boundaries)[0]
+			return &histogram.New(1, desc, histogram.WithExplicitBoundaries(testBoundaries))[0]
 		},
 	)
 }
+
+func TestHistogramDefaultBoundaries(t *testing.T) {
+	aggregatortest.RunProfiles(t, func(t *testing.T, profile aggregatortest.Profile) {
+		ctx := context.Background()
+		descriptor := aggregatortest.NewAggregatorTest(metric.ValueRecorderInstrumentKind, profile.NumberKind)
+
+		agg, ckpt := new2(descriptor)
+
+		bounds := []float64{.005, .01, .025, .05, .1, .25, .5, 1, 2.5, 5, 10} // len 11
+		values := append(bounds, 100)                                         // len 12
+		expect := []uint64{1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1}                // len 12
+
+		for _, value := range values {
+			var num number.Number
+
+			value -= .001 // Avoid exact boundaries
+
+			if descriptor.NumberKind() == number.Int64Kind {
+				value *= 1e6
+				num = number.NewInt64Number(int64(value))
+			} else {
+				num = number.NewFloat64Number(value)
+			}
+
+			require.NoError(t, agg.Update(ctx, num, descriptor))
+		}
+
+		bucks, err := agg.Histogram()
+		require.NoError(t, err)
+
+		// Check for proper lengths, 1 count in each bucket.
+		require.Equal(t, len(values), len(bucks.Counts))
+		require.Equal(t, len(bounds), len(bucks.Boundaries))
+		require.EqualValues(t, expect, bucks.Counts)
+
+		require.Equal(t, expect, bucks.Counts)
+
+		// Move and repeat the test on `ckpt`.
+		err = agg.SynchronizedMove(ckpt, descriptor)
+		require.NoError(t, err)
+
+		bucks, err = ckpt.Histogram()
+		require.NoError(t, err)
+
+		require.Equal(t, len(values), len(bucks.Counts))
+		require.Equal(t, len(bounds), len(bucks.Boundaries))
+		require.EqualValues(t, expect, bucks.Counts)
+	})
+}

sdk/metric/histogram_stress_test.go

@@ -30,7 +30,7 @@ import (
 func TestStressInt64Histogram(t *testing.T) {
 	desc := metric.NewDescriptor("some_metric", metric.ValueRecorderInstrumentKind, number.Int64Kind)
 
-	alloc := histogram.New(2, &desc, []float64{25, 50, 75})
+	alloc := histogram.New(2, &desc, histogram.WithExplicitBoundaries([]float64{25, 50, 75}))
 	h, ckpt := &alloc[0], &alloc[1]
 
 	ctx, cancelFunc := context.WithCancel(context.Background())

sdk/metric/processor/processortest/test.go

@@ -184,7 +184,7 @@ func (testAggregatorSelector) AggregatorFor(desc *metric.Descriptor, aggPtrs ...
 			*aggPtrs[i] = &aggs[i]
 		}
 	case strings.HasSuffix(desc.Name(), ".histogram"):
-		aggs := histogram.New(len(aggPtrs), desc, nil)
+		aggs := histogram.New(len(aggPtrs), desc)
 		for i := range aggPtrs {
 			*aggPtrs[i] = &aggs[i]
 		}

sdk/metric/selector/simple/simple.go

@@ -28,7 +28,7 @@ type (
 	selectorInexpensive struct{}
 	selectorExact       struct{}
 	selectorHistogram   struct {
-		boundaries []float64
+		options []histogram.Option
 	}
 )
 
@@ -59,8 +59,8 @@ func NewWithExactDistribution() export.AggregatorSelector {
 // NewWithHistogramDistribution returns a simple aggregator selector
 // that uses histogram aggregators for `ValueRecorder` instruments.
 // This selector is a good default choice for most metric exporters.
-func NewWithHistogramDistribution(boundaries []float64) export.AggregatorSelector {
-	return selectorHistogram{boundaries: boundaries}
+func NewWithHistogramDistribution(options ...histogram.Option) export.AggregatorSelector {
+	return selectorHistogram{options: options}
 }
 
 func sumAggs(aggPtrs []*export.Aggregator) {
@@ -110,7 +110,7 @@ func (s selectorHistogram) AggregatorFor(descriptor *metric.Descriptor, aggPtrs
 	case metric.ValueObserverInstrumentKind:
 		lastValueAggs(aggPtrs)
 	case metric.ValueRecorderInstrumentKind:
-		aggs := histogram.New(len(aggPtrs), descriptor, s.boundaries)
+		aggs := histogram.New(len(aggPtrs), descriptor, s.options...)
 		for i := range aggPtrs {
 			*aggPtrs[i] = &aggs[i]
 		}

sdk/metric/selector/simple/simple_test.go

@@ -66,7 +66,7 @@ func TestExactDistribution(t *testing.T) {
 }
 
 func TestHistogramDistribution(t *testing.T) {
-	hist := simple.NewWithHistogramDistribution(nil)
+	hist := simple.NewWithHistogramDistribution()
 	require.IsType(t, (*histogram.Aggregator)(nil), oneAgg(hist, &testValueRecorderDesc))
 	testFixedSelectors(t, hist)
 }