go.opentelemetry.io/otel/sdk/metric v1.37.0: WithAggregationSelector

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify go.opentelemetry.io/otel/sdk/metric.WithAggregationSelector in pkg:golang/go.opentelemetry.io/otel/sdk/metric@v1.37.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/go.opentelemetry.io/otel/sdk/metric@v1.37.0
Demonstrate these symbols/APIs:
  - go.opentelemetry.io/otel/sdk/metric.WithAggregationSelector

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:df377db05ea5f37bf1412893f10fcfee60168182440b04819fdaf3d46cfea3e4","contract":["metric.WithAggregationSelector configures reader with custom aggregation selector.","custom AggregationSelector returning AggregationDrop drops metrics of the selected instrument kind.","custom AggregationSelector applies custom explicit histogram bucket boundaries.","AggregationSelector returning nil falls back to DefaultAggregationSelector for that instrument kind.","DefaultAggregationSelector returns valid Aggregation for Counter and Histogram kinds."],"goal":"verify go.opentelemetry.io/otel/sdk/metric.WithAggregationSelector in pkg:golang/go.opentelemetry.io/otel/sdk/metric@v1.37.0","kind":"HOW","packages":["pkg:golang/go.opentelemetry.io/otel/sdk/metric@v1.37.0"],"schemaVersion":1,"symbols":["go.opentelemetry.io/otel/sdk/metric.WithAggregationSelector"]},"contractCommand":["go","run","./test"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"golang","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"go","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/go.opentelemetry.io/otel/sdk/metric@v1.37.0"],"schemaVersion":1,"subject":"pkg:golang/go.opentelemetry.io/otel/sdk/metric@v1.37.0","symbols":["go.opentelemetry.io/otel/sdk/metric.WithAggregationSelector"],"verifierAdapter":"golang@1"}

module sample

go 1.26.6

require go.opentelemetry.io/otel/sdk/metric v1.37.0

require (
	github.com/go-logr/logr v1.4.3 // indirect
	github.com/go-logr/stdr v1.2.2 // indirect
	github.com/google/uuid v1.6.0 // indirect
	go.opentelemetry.io/auto/sdk v1.1.0 // indirect
	go.opentelemetry.io/otel v1.37.0 // indirect
	go.opentelemetry.io/otel/metric v1.37.0 // indirect
	go.opentelemetry.io/otel/sdk v1.37.0 // indirect
	go.opentelemetry.io/otel/trace v1.37.0 // indirect
	golang.org/x/sys v0.33.0 // indirect
)

github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
github.com/go-logr/logr v1.2.2/go.mod h1:jdQByPbusPIv2/zmleS9BjJVeZ6kBagPoEUsqbVz/1A=
github.com/go-logr/logr v1.4.3 h1:CjnDlHq8ikf6E492q6eKboGOC0T8CDaOvkHCIg8idEI=
github.com/go-logr/logr v1.4.3/go.mod h1:9T104GzyrTigFIr8wt5mBrctHMim0Nb2HLGrmQ40KvY=
github.com/go-logr/stdr v1.2.2 h1:hSWxHoqTgW2S2qGc0LTAI563KZ5YKYRhT3MFKZMbjag=
github.com/go-logr/stdr v1.2.2/go.mod h1:mMo/vtBO5dYbehREoey6XUKy/eSumjCCveDpRre4VKE=
github.com/google/go-cmp v0.7.0 h1:wk8382ETsv4JYUZwIsn6YpYiWiBsYLSJiTsyBybVuN8=
github.com/google/go-cmp v0.7.0/go.mod h1:pXiqmnSA92OHEEa9HXL2W4E7lf9JzCmGVUdgjX3N/iU=
github.com/google/uuid v1.6.0 h1:NIvaJDMOsjHA8n1jAhLSgzrAzy1Hgr+hNrb57e+94F0=
github.com/google/uuid v1.6.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
github.com/stretchr/testify v1.10.0 h1:Xv5erBjTwe/5IxqUQTdXv5kgmIvbHo3QQyRwhJsOfJA=
github.com/stretchr/testify v1.10.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
go.opentelemetry.io/auto/sdk v1.1.0 h1:cH53jehLUN6UFLY71z+NDOiNJqDdPRaXzTel0sJySYA=
go.opentelemetry.io/auto/sdk v1.1.0/go.mod h1:3wSPjt5PWp2RhlCcmmOial7AvC4DQqZb7a7wCow3W8A=
go.opentelemetry.io/otel v1.37.0 h1:9zhNfelUvx0KBfu/gb+ZgeAfAgtWrfHJZcAqFC228wQ=
go.opentelemetry.io/otel v1.37.0/go.mod h1:ehE/umFRLnuLa/vSccNq9oS1ErUlkkK71gMcN34UG8I=
go.opentelemetry.io/otel/metric v1.37.0 h1:mvwbQS5m0tbmqML4NqK+e3aDiO02vsf/WgbsdpcPoZE=
go.opentelemetry.io/otel/metric v1.37.0/go.mod h1:04wGrZurHYKOc+RKeye86GwKiTb9FKm1WHtO+4EVr2E=
go.opentelemetry.io/otel/sdk v1.37.0 h1:ItB0QUqnjesGRvNcmAcU0LyvkVyGJ2xftD29bWdDvKI=
go.opentelemetry.io/otel/sdk v1.37.0/go.mod h1:VredYzxUvuo2q3WRcDnKDjbdvmO0sCzOvVAiY+yUkAg=
go.opentelemetry.io/otel/sdk/metric v1.37.0 h1:90lI228XrB9jCMuSdA0673aubgRobVZFhbjxHHspCPc=
go.opentelemetry.io/otel/sdk/metric v1.37.0/go.mod h1:cNen4ZWfiD37l5NhS+Keb5RXVWZWpRE+9WyVCpbo5ps=
go.opentelemetry.io/otel/trace v1.37.0 h1:HLdcFNbRQBE2imdSEgm/kwqmQj1Or1l/7bW6mxVK7z4=
go.opentelemetry.io/otel/trace v1.37.0/go.mod h1:TlgrlQ+PtQO5XFerSPUYG0JSgGyryXewPGyayAWSBS0=
golang.org/x/sys v0.33.0 h1:q3i8TbbEz+JRD9ywIRlyRAQbM0qF7hu24q3teo2hbuw=
golang.org/x/sys v0.33.0/go.mod h1:BJP2sWEmIv4KK5OTEluFJCKSidICx8ciO85XgH3Ak8k=
gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

package main

import (
	"context"
	"fmt"

	"go.opentelemetry.io/otel/sdk/metric"
	"go.opentelemetry.io/otel/sdk/metric/metricdata"
)

func main() {
	// Define custom AggregationSelector
	customSelector := func(kind metric.InstrumentKind) metric.Aggregation {
		switch kind {
		case metric.InstrumentKindCounter:
			return metric.AggregationDrop{}
		case metric.InstrumentKindHistogram:
			return metric.AggregationExplicitBucketHistogram{
				Boundaries: []float64{10, 50, 100},
			}
		default:
			return metric.DefaultAggregationSelector(kind)
		}
	}

	// Use WithAggregationSelector to configure ManualReader
	reader := metric.NewManualReader(metric.WithAggregationSelector(customSelector))
	provider := metric.NewMeterProvider(metric.WithReader(reader))
	defer func() {
		_ = provider.Shutdown(context.Background())
	}()

	meter := provider.Meter("example-meter")

	// Histogram will use custom boundaries [10, 50, 100]
	hist, err := meter.Float64Histogram("latency")
	if err != nil {
		panic(err)
	}
	hist.Record(context.Background(), 25.0)

	// Counter will be dropped
	counter, err := meter.Int64Counter("requests")
	if err != nil {
		panic(err)
	}
	counter.Add(context.Background(), 1)

	var rm metricdata.ResourceMetrics
	if err := reader.Collect(context.Background(), &rm); err != nil {
		panic(err)
	}

	for _, sm := range rm.ScopeMetrics {
		for _, m := range sm.Metrics {
			fmt.Printf("Collected metric: %s\n", m.Name)
		}
	}
}

{
  "schemaVersion": 1,
  "goal": "verify go.opentelemetry.io/otel/sdk/metric.WithAggregationSelector in pkg:golang/go.opentelemetry.io/otel/sdk/metric@v1.37.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/go.opentelemetry.io/otel/sdk/metric@v1.37.0"
  ],
  "symbols": [
    "go.opentelemetry.io/otel/sdk/metric.WithAggregationSelector"
  ]
}

package main

import (
	"context"
	"fmt"
	"os"

	"go.opentelemetry.io/otel/sdk/metric"
	"go.opentelemetry.io/otel/sdk/metric/metricdata"
)

func main() {
	ctx := context.Background()

	// Assertion 1: metric.WithAggregationSelector configures reader with custom aggregation selector.
	var selectorCalled bool
	customSelector := func(kind metric.InstrumentKind) metric.Aggregation {
		selectorCalled = true
		if kind == metric.InstrumentKindCounter {
			return metric.AggregationDrop{}
		}
		if kind == metric.InstrumentKindHistogram {
			return metric.AggregationExplicitBucketHistogram{
				Boundaries: []float64{10, 50, 100},
			}
		}
		return nil
	}

	opt := metric.WithAggregationSelector(customSelector)
	if opt == nil {
		fmt.Fprintf(os.Stderr, "FAIL: expected non-nil ManualReaderOption from WithAggregationSelector\n")
		os.Exit(1)
	}

	reader := metric.NewManualReader(opt)
	provider := metric.NewMeterProvider(metric.WithReader(reader))
	defer func() {
		_ = provider.Shutdown(ctx)
	}()

	meter := provider.Meter("contract-meter")

	// Assertion 2: custom AggregationSelector returning AggregationDrop drops metrics of the selected instrument kind.
	droppedCounter, err := meter.Int64Counter("dropped_counter")
	if err != nil {
		fmt.Fprintf(os.Stderr, "FAIL: could not create counter: %v\n", err)
		os.Exit(1)
	}
	droppedCounter.Add(ctx, 42)

	// Assertion 3: custom AggregationSelector applies custom explicit histogram bucket boundaries.
	customHist, err := meter.Float64Histogram("custom_hist")
	if err != nil {
		fmt.Fprintf(os.Stderr, "FAIL: could not create histogram: %v\n", err)
		os.Exit(1)
	}
	customHist.Record(ctx, 25.0)

	var rm metricdata.ResourceMetrics
	if err := reader.Collect(ctx, &rm); err != nil {
		fmt.Fprintf(os.Stderr, "FAIL: reader.Collect failed: %v\n", err)
		os.Exit(1)
	}

	if !selectorCalled {
		fmt.Fprintf(os.Stderr, "FAIL: expected custom AggregationSelector to be invoked\n")
		os.Exit(1)
	}

	var foundCounter bool
	var foundHist bool
	var histBounds []float64

	for _, sm := range rm.ScopeMetrics {
		for _, m := range sm.Metrics {
			if m.Name == "dropped_counter" {
				foundCounter = true
			}
			if m.Name == "custom_hist" {
				foundHist = true
				if histData, ok := m.Data.(metricdata.Histogram[float64]); ok {
					if len(histData.DataPoints) > 0 {
						histBounds = histData.DataPoints[0].Bounds
					}
				}
			}
		}
	}

	if foundCounter {
		fmt.Fprintf(os.Stderr, "FAIL: expected dropped_counter to be dropped by AggregationDrop\n")
		os.Exit(1)
	}

	if !foundHist {
		fmt.Fprintf(os.Stderr, "FAIL: expected custom_hist to be collected\n")
		os.Exit(1)
	}

	expectedBounds := []float64{10, 50, 100}
	if len(histBounds) != len(expectedBounds) {
		fmt.Fprintf(os.Stderr, "FAIL: expected histogram bounds %v, got %v\n", expectedBounds, histBounds)
		os.Exit(1)
	}
	for i := range expectedBounds {
		if histBounds[i] != expectedBounds[i] {
			fmt.Fprintf(os.Stderr, "FAIL: expected bound %f, got %f at index %d\n", expectedBounds[i], histBounds[i], i)
			os.Exit(1)
		}
	}

	// Assertion 4: AggregationSelector returning nil falls back to DefaultAggregationSelector for that instrument kind.
	nilSelector := func(kind metric.InstrumentKind) metric.Aggregation {
		return nil // All kinds fall back to default
	}
	reader2 := metric.NewManualReader(metric.WithAggregationSelector(nilSelector))
	provider2 := metric.NewMeterProvider(metric.WithReader(reader2))
	defer func() {
		_ = provider2.Shutdown(ctx)
	}()

	meter2 := provider2.Meter("fallback-meter")
	fallbackCounter, err := meter2.Int64Counter("fallback_counter")
	if err != nil {
		fmt.Fprintf(os.Stderr, "FAIL: could not create fallback counter: %v\n", err)
		os.Exit(1)
	}
	fallbackCounter.Add(ctx, 10)

	var rm2 metricdata.ResourceMetrics
	if err := reader2.Collect(ctx, &rm2); err != nil {
		fmt.Fprintf(os.Stderr, "FAIL: reader2.Collect failed: %v\n", err)
		os.Exit(1)
	}

	var foundFallbackCounter bool
	for _, sm := range rm2.ScopeMetrics {
		for _, m := range sm.Metrics {
			if m.Name == "fallback_counter" {
				if sumData, ok := m.Data.(metricdata.Sum[int64]); ok {
					if len(sumData.DataPoints) > 0 && sumData.DataPoints[0].Value == 10 {
						foundFallbackCounter = true
					}
				}
			}
		}
	}

	if !foundFallbackCounter {
		fmt.Fprintf(os.Stderr, "FAIL: expected fallback_counter to be aggregated as Sum by DefaultAggregationSelector\n")
		os.Exit(1)
	}

	// Assertion 5: DefaultAggregationSelector returns valid Aggregation for Counter and Histogram kinds.
	defaultCounterAgg := metric.DefaultAggregationSelector(metric.InstrumentKindCounter)
	if defaultCounterAgg == nil {
		fmt.Fprintf(os.Stderr, "FAIL: DefaultAggregationSelector returned nil for Counter\n")
		os.Exit(1)
	}
	defaultHistAgg := metric.DefaultAggregationSelector(metric.InstrumentKindHistogram)
	if defaultHistAgg == nil {
		fmt.Fprintf(os.Stderr, "FAIL: DefaultAggregationSelector returned nil for Histogram\n")
		os.Exit(1)
	}

	fmt.Println("PASS: all WithAggregationSelector contract assertions passed.")
}