go.opentelemetry.io/otel/metric v1.43.0: Float64ObservableGauge, Int64Counter, Meter

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 pkg:golang/go.opentelemetry.io/otel/metric@v1.43.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/go.opentelemetry.io/otel/metric@v1.43.0
Demonstrate these symbols/APIs:
  - go.opentelemetry.io/otel/metric.Float64ObservableGauge
  - go.opentelemetry.io/otel/metric.Int64Counter
  - go.opentelemetry.io/otel/metric.Meter
  - go.opentelemetry.io/otel/metric.MeterProvider

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:sha256:7aad2e27ca62f56eb712be301f65f6f415e3684035f763f2328dc5439ec4290a","contract":["MeterProvider creates Meter instances with instrumentation configuration","Meter creates Int64Counter and records measurements","Meter creates Float64ObservableGauge with description and unit","MetricManager manages instruments and callback lifecycle"],"goal":"verify pkg:golang/go.opentelemetry.io/otel/metric@v1.43.0","kind":"HOW","packages":["pkg:golang/go.opentelemetry.io/otel/metric@v1.43.0"],"schemaVersion":1,"symbols":["go.opentelemetry.io/otel/metric.Float64ObservableGauge","go.opentelemetry.io/otel/metric.Int64Counter","go.opentelemetry.io/otel/metric.Meter","go.opentelemetry.io/otel/metric.MeterProvider"]},"contractCommand":["go","test","./..."],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"golang","language":"go","libc":"glibc","libcVersion":"2.39","moduleSystem":"go.mod","os":"linux","osVersionBucket":"24","packageManager":"go","runtime":"go","runtimeVersion":"1.26","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/go.opentelemetry.io/otel/metric@v1.43.0"],"schemaVersion":1,"subject":"pkg:golang/go.opentelemetry.io/otel/metric@v1.43.0","symbols":["go.opentelemetry.io/otel/metric.Float64ObservableGauge","go.opentelemetry.io/otel/metric.Int64Counter","go.opentelemetry.io/otel/metric.Meter","go.opentelemetry.io/otel/metric.MeterProvider"],"verifierAdapter":"golang@1"}

module example.com/otel-metric-sample

go 1.25.0

require go.opentelemetry.io/otel/metric v1.43.0

require (
	github.com/cespare/xxhash/v2 v2.3.0 // indirect
	go.opentelemetry.io/otel v1.43.0 // indirect
)

github.com/cespare/xxhash/v2 v2.3.0 h1:UL815xU9SqsFlibzuggzjXhog7bL6oX9BbNZnL2UFvs=
github.com/cespare/xxhash/v2 v2.3.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
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 v1.4.3 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/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 v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
go.opentelemetry.io/auto/sdk v1.2.1 h1:jXsnJ4Lmnqd11kwkBV2LgLoFMZKizbCi5fNZ/ipaZ64=
go.opentelemetry.io/auto/sdk v1.2.1/go.mod h1:KRTj+aOaElaLi+wW1kO/DZRXwkF4C5xPbEe3ZiIhN7Y=
go.opentelemetry.io/otel v1.43.0 h1:mYIM03dnh5zfN7HautFE4ieIig9amkNANT+xcVxAj9I=
go.opentelemetry.io/otel v1.43.0/go.mod h1:JuG+u74mvjvcm8vj8pI5XiHy1zDeoCS2LB1spIq7Ay0=
go.opentelemetry.io/otel/metric v1.43.0 h1:d7638QeInOnuwOONPp4JAOGfbCEpYb+K6DVWvdxGzgM=
go.opentelemetry.io/otel/metric v1.43.0/go.mod h1:RDnPtIxvqlgO8GRW18W6Z/4P462ldprJtfxHxyKd2PY=
go.opentelemetry.io/otel/trace v1.43.0 h1:BkNrHpup+4k4w+ZZ86CZoHHEkohws8AY+WTX09nk+3A=
go.opentelemetry.io/otel/trace v1.43.0/go.mod h1:/QJhyVBUUswCphDVxq+8mld+AvhXZLhe+8WVFxiFff0=
gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

package sample

import (
	"context"
	"fmt"

	"go.opentelemetry.io/otel/metric"
	"go.opentelemetry.io/otel/metric/noop"
)

// MetricManager manages metric instruments created via OpenTelemetry Meter.
type MetricManager struct {
	meter        metric.Meter
	counter      metric.Int64Counter
	gauge        metric.Float64ObservableGauge
	registration metric.Registration
	gaugeValue   float64
}

// NewMetricManager creates a new MetricManager using the provided MeterProvider.
// If provider is nil, a no-op MeterProvider is used.
func NewMetricManager(provider metric.MeterProvider, meterName string) (*MetricManager, error) {
	if provider == nil {
		provider = noop.NewMeterProvider()
	}

	meter := provider.Meter(
		meterName,
		metric.WithInstrumentationVersion("v1.43.0"),
	)

	counter, err := meter.Int64Counter(
		"sample_requests_total",
		metric.WithDescription("Total number of processed sample requests"),
		metric.WithUnit("{request}"),
	)
	if err != nil {
		return nil, fmt.Errorf("failed to create counter: %w", err)
	}

	gauge, err := meter.Float64ObservableGauge(
		"sample_memory_utilization",
		metric.WithDescription("Current memory utilization ratio between 0 and 1"),
		metric.WithUnit("1"),
	)
	if err != nil {
		return nil, fmt.Errorf("failed to create observable gauge: %w", err)
	}

	mm := &MetricManager{
		meter:      meter,
		counter:    counter,
		gauge:      gauge,
		gaugeValue: 0.0,
	}

	reg, err := meter.RegisterCallback(
		func(ctx context.Context, obs metric.Observer) error {
			obs.ObserveFloat64(mm.gauge, mm.gaugeValue)
			return nil
		},
		gauge,
	)
	if err != nil {
		return nil, fmt.Errorf("failed to register callback: %w", err)
	}
	mm.registration = reg

	return mm, nil
}

// RecordRequest adds the given delta to the Int64Counter.
func (m *MetricManager) RecordRequest(ctx context.Context, delta int64) {
	if m.counter != nil {
		m.counter.Add(ctx, delta)
	}
}

// SetGaugeValue updates the internal value observed by the Float64ObservableGauge callback.
func (m *MetricManager) SetGaugeValue(val float64) {
	m.gaugeValue = val
}

// Close unregisters the callback.
func (m *MetricManager) Close() error {
	if m.registration != nil {
		return m.registration.Unregister()
	}
	return nil
}

{
  "schemaVersion": 1,
  "goal": "verify pkg:golang/go.opentelemetry.io/otel/metric@v1.43.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/go.opentelemetry.io/otel/metric@v1.43.0"
  ],
  "symbols": [
    "go.opentelemetry.io/otel/metric.Float64ObservableGauge",
    "go.opentelemetry.io/otel/metric.Int64Counter",
    "go.opentelemetry.io/otel/metric.Meter",
    "go.opentelemetry.io/otel/metric.MeterProvider"
  ]
}

package test

import (
	"context"
	"testing"

	sample "example.com/otel-metric-sample"
	"go.opentelemetry.io/otel/metric"
	"go.opentelemetry.io/otel/metric/noop"
)

func TestMetricContract(t *testing.T) {
	ctx := context.Background()

	// 1. MeterProvider creates Meter instances with instrumentation configuration
	mp := noop.NewMeterProvider()
	meter := mp.Meter(
		"example.com/test-meter",
		metric.WithInstrumentationVersion("v1.43.0"),
	)
	if meter == nil {
		t.Fatal("expected non-nil Meter from MeterProvider")
	}

	// 2. Meter creates Int64Counter and records measurements
	counter, err := meter.Int64Counter(
		"test_requests_total",
		metric.WithDescription("Total test requests"),
		metric.WithUnit("{request}"),
	)
	if err != nil {
		t.Fatalf("unexpected error creating Int64Counter: %v", err)
	}
	if counter == nil {
		t.Fatal("expected non-nil Int64Counter")
	}
	counter.Add(ctx, 1)
	counter.Add(ctx, 10)

	// 3. Meter creates Float64ObservableGauge with description and unit
	gauge, err := meter.Float64ObservableGauge(
		"test_memory_ratio",
		metric.WithDescription("Memory usage ratio"),
		metric.WithUnit("1"),
	)
	if err != nil {
		t.Fatalf("unexpected error creating Float64ObservableGauge: %v", err)
	}
	if gauge == nil {
		t.Fatal("expected non-nil Float64ObservableGauge")
	}

	// 4. MetricManager manages instruments and callback lifecycle
	manager, err := sample.NewMetricManager(mp, "example.com/sample-manager")
	if err != nil {
		t.Fatalf("unexpected error creating MetricManager: %v", err)
	}
	if manager == nil {
		t.Fatal("expected non-nil MetricManager")
	}

	manager.RecordRequest(ctx, 5)
	manager.SetGaugeValue(0.75)

	if err := manager.Close(); err != nil {
		t.Fatalf("unexpected error closing manager registration: %v", err)
	}
}