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

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.ManualReader 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.ManualReader

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:sha256:8c7d086d8f6fdcc7f22ae106bcb0c78cc056e8959149dfeb355bc61f8ace4031","contract":["NewManualReader creates a ManualReader implementing metric.Reader that collects recorded metrics on demand from MeterProvider.","Collect returns ErrReaderNotRegistered before ManualReader is registered with a MeterProvider.","ManualReader accepts WithTemporalitySelector to configure aggregation temporality such as DeltaTemporality.","Collect and Shutdown return ErrReaderShutdown after ManualReader has been shut down once.","ManualReader accepts WithAggregationSelector to configure aggregation such as AggregationDrop."],"goal":"verify go.opentelemetry.io/otel/sdk/metric.ManualReader 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.ManualReader"]},"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.ManualReader"],"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"
	"log"

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

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

	// Create a new ManualReader instance
	reader := metric.NewManualReader()

	// Register the ManualReader with a MeterProvider
	mp := metric.NewMeterProvider(metric.WithReader(reader))
	defer func() {
		if err := mp.Shutdown(ctx); err != nil {
			log.Fatalf("failed to shutdown meter provider: %v", err)
		}
	}()

	meter := mp.Meter("example.com/demo")
	counter, err := meter.Int64Counter("demo_counter")
	if err != nil {
		log.Fatalf("failed to create counter: %v", err)
	}

	counter.Add(ctx, 42)

	// Collect metrics manually on demand
	var rm metricdata.ResourceMetrics
	if err := reader.Collect(ctx, &rm); err != nil {
		log.Fatalf("failed to collect metrics: %v", err)
	}

	fmt.Printf("Collected %d scope metrics\n", len(rm.ScopeMetrics))
}

{
  "schemaVersion": 1,
  "goal": "verify go.opentelemetry.io/otel/sdk/metric.ManualReader 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.ManualReader"
  ]
}

package main

import (
	"context"
	"errors"
	"fmt"
	"os"

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

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

	// 1. NewManualReader creates a ManualReader implementing metric.Reader that collects recorded metrics on demand from MeterProvider.
	{
		var reader *metric.ManualReader = metric.NewManualReader()
		if reader == nil {
			fmt.Fprintln(os.Stderr, "FAIL: NewManualReader returned nil")
			os.Exit(1)
		}

		var _ metric.Reader = reader

		mp := metric.NewMeterProvider(metric.WithReader(reader))
		meter := mp.Meter("test.example.com")
		counter, err := meter.Int64Counter("contract_counter")
		if err != nil {
			fmt.Fprintf(os.Stderr, "FAIL: failed to create counter: %v\n", err)
			os.Exit(1)
		}

		counter.Add(ctx, 42)

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

		if len(rm.ScopeMetrics) == 0 {
			fmt.Fprintln(os.Stderr, "FAIL: expected non-empty ScopeMetrics")
			os.Exit(1)
		}

		found := false
		for _, sm := range rm.ScopeMetrics {
			for _, m := range sm.Metrics {
				if m.Name == "contract_counter" {
					if sumData, ok := m.Data.(metricdata.Sum[int64]); ok {
						for _, dp := range sumData.DataPoints {
							if dp.Value == 42 {
								found = true
								break
							}
						}
					}
				}
			}
		}
		if !found {
			fmt.Fprintln(os.Stderr, "FAIL: recorded metric value not found in collected data")
			os.Exit(1)
		}
		_ = mp.Shutdown(ctx)
	}

	// 2. Collect returns ErrReaderNotRegistered before ManualReader is registered with a MeterProvider.
	{
		unregistered := metric.NewManualReader()
		var rm metricdata.ResourceMetrics
		if err := unregistered.Collect(ctx, &rm); !errors.Is(err, metric.ErrReaderNotRegistered) {
			fmt.Fprintf(os.Stderr, "FAIL: expected ErrReaderNotRegistered on Collect, got: %v\n", err)
			os.Exit(1)
		}
	}

	// 3. ManualReader accepts WithTemporalitySelector to configure aggregation temporality such as DeltaTemporality.
	{
		deltaSelector := func(metric.InstrumentKind) metricdata.Temporality {
			return metricdata.DeltaTemporality
		}
		reader := metric.NewManualReader(metric.WithTemporalitySelector(deltaSelector))
		if reader == nil {
			fmt.Fprintln(os.Stderr, "FAIL: NewManualReader with temporality selector returned nil")
			os.Exit(1)
		}

		mp := metric.NewMeterProvider(metric.WithReader(reader))
		meter := mp.Meter("test.temporality")
		counter, err := meter.Int64Counter("delta_counter")
		if err != nil {
			fmt.Fprintf(os.Stderr, "FAIL: failed to create counter: %v\n", err)
			os.Exit(1)
		}

		counter.Add(ctx, 15)

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

		foundDelta := false
		for _, sm := range rm.ScopeMetrics {
			for _, m := range sm.Metrics {
				if m.Name == "delta_counter" {
					if sumData, ok := m.Data.(metricdata.Sum[int64]); ok {
						if sumData.Temporality == metricdata.DeltaTemporality {
							foundDelta = true
						}
					}
				}
			}
		}
		if !foundDelta {
			fmt.Fprintln(os.Stderr, "FAIL: expected DeltaTemporality in metric data")
			os.Exit(1)
		}
		_ = mp.Shutdown(ctx)
	}

	// 4. Collect and Shutdown return ErrReaderShutdown after ManualReader has been shut down once.
	{
		reader := metric.NewManualReader()
		mp := metric.NewMeterProvider(metric.WithReader(reader))
		_ = mp

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

		var rm metricdata.ResourceMetrics
		if err := reader.Collect(ctx, &rm); !errors.Is(err, metric.ErrReaderShutdown) {
			fmt.Fprintf(os.Stderr, "FAIL: expected ErrReaderShutdown on Collect, got: %v\n", err)
			os.Exit(1)
		}

		if err := reader.Shutdown(ctx); !errors.Is(err, metric.ErrReaderShutdown) {
			fmt.Fprintf(os.Stderr, "FAIL: expected ErrReaderShutdown on subsequent Shutdown, got: %v\n", err)
			os.Exit(1)
		}
	}

	// 5. ManualReader accepts WithAggregationSelector to configure aggregation such as AggregationDrop.
	{
		reader := metric.NewManualReader(metric.WithAggregationSelector(func(ik metric.InstrumentKind) metric.Aggregation {
			return metric.AggregationDrop{}
		}))
		mp := metric.NewMeterProvider(metric.WithReader(reader))
		meter := mp.Meter("test.drop")
		counter, err := meter.Int64Counter("dropped_counter")
		if err != nil {
			fmt.Fprintf(os.Stderr, "FAIL: failed to create counter: %v\n", err)
			os.Exit(1)
		}
		counter.Add(ctx, 100)

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

		for _, sm := range rm.ScopeMetrics {
			for _, m := range sm.Metrics {
				if m.Name == "dropped_counter" {
					fmt.Fprintln(os.Stderr, "FAIL: dropped_counter should have been dropped by AggregationDrop")
					os.Exit(1)
				}
			}
		}
		_ = mp.Shutdown(ctx)
	}

	fmt.Println("PASS: ManualReader contract verified")
}