github.com/prometheus/client_golang v1.19.1

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/github.com/prometheus/client_golang@v1.19.1
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/github.com/prometheus/client_golang@v1.19.1
Constraints:
  - executionContext: node
Required runtime conditions:
  - ecosystem: npm
  - language: javascript
  - moduleSystem: cjs
  - packageManager: npm@10.9.8
  - runtime: node@22.23.2

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:sha256:2e08c96909016ff89cb8a562437d0dca52a1be6972513646c71e5a4730575336","contract":["prometheus.NewRegistry creates a distinct non-nil metric registry","prometheus.NewCounterVec increments labeled counter metrics and gathers them","prometheus.NewGauge records and updates gauge values in the registry","prometheus.NewHistogram records observations with bucket counts and sum"],"goal":"verify pkg:golang/github.com/prometheus/client_golang@v1.19.1","kind":"HOW","packages":["pkg:golang/github.com/prometheus/client_golang@v1.19.1"],"schemaVersion":1},"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/github.com/prometheus/client_golang@v1.19.1"],"schemaVersion":1,"subject":"pkg:golang/github.com/prometheus/client_golang@v1.19.1","verifierAdapter":"golang@1"}

module sample

go 1.26.6

require (
	github.com/prometheus/client_golang v1.19.1
	github.com/prometheus/client_model v0.5.0
)

require (
	github.com/beorn7/perks v1.0.1 // indirect
	github.com/cespare/xxhash/v2 v2.2.0 // indirect
	github.com/prometheus/common v0.48.0 // indirect
	github.com/prometheus/procfs v0.12.0 // indirect
	golang.org/x/sys v0.17.0 // indirect
	google.golang.org/protobuf v1.33.0 // indirect
)

github.com/beorn7/perks v1.0.1 h1:VlbKKnNfV8bJzeqoa4cOKqO6bYr3WgKZxO8Z16+hsOM=
github.com/beorn7/perks v1.0.1/go.mod h1:G2ZrVWU2WbWT9wwq4/hrbKbnv/1ERSJQ0ibhJ6rlkpw=
github.com/cespare/xxhash/v2 v2.2.0 h1:DC2CZ1Ep5Y4k3ZQ899DldepgrayRUGE6BBZ/cd9Cj44=
github.com/cespare/xxhash/v2 v2.2.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
github.com/prometheus/client_golang v1.19.1 h1:wZWJDwK+NameRJuPGDhlnFgx8e8HN3XHQeLaYJFJBOE=
github.com/prometheus/client_golang v1.19.1/go.mod h1:mP78NwGzrVks5S2H6ab8+ZZGJLZUq1hoULYBAYBw1Ho=
github.com/prometheus/client_model v0.5.0 h1:VQw1hfvPvk3Uv6Qf29VrPF32JB6rtbgI6cYPYQjL0Qw=
github.com/prometheus/client_model v0.5.0/go.mod h1:dTiFglRmd66nLR9Pv9f0mZi7B7fk5Pm3gvsjB5tr+kI=
github.com/prometheus/common v0.48.0 h1:QO8U2CdOzSn1BBsmXJXduaaW+dY/5QLjfB8svtSzKKE=
github.com/prometheus/common v0.48.0/go.mod h1:0/KsvlIEfPQCQ5I2iNSAWKPZziNCvRs5EC6ILDTlAPc=
github.com/prometheus/procfs v0.12.0 h1:jluTpSng7V9hY0O2R9DzzJHYb2xULk9VTR1V1R/k6Bo=
github.com/prometheus/procfs v0.12.0/go.mod h1:pcuDEFsWDnvcgNzo4EEweacyhjeA9Zk3cnaOZAZEfOo=
golang.org/x/sys v0.17.0 h1:25cE3gD+tdBA7lp7QfhuV+rJiE9YXTcS3VG1SqssI/Y=
golang.org/x/sys v0.17.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
google.golang.org/protobuf v1.33.0 h1:uNO2rsAINq/JlFpSdYEKIZ0uKD/R9cpdv0T+yoGwGmI=
google.golang.org/protobuf v1.33.0/go.mod h1:c6P6GXX6sHbq/GpV6MGZEdwhWPcYBgnhAHhKbcUYpos=

package sample

import (
	"github.com/prometheus/client_golang/prometheus"
)

// Metrics holds prometheus collectors registered to a custom registry.
type Metrics struct {
	Registry       *prometheus.Registry
	RequestCounter *prometheus.CounterVec
	ActiveGauge    prometheus.Gauge
	DurationHist   prometheus.Histogram
}

// NewMetrics creates and registers custom Prometheus metrics with a dedicated registry.
func NewMetrics() *Metrics {
	reg := prometheus.NewRegistry()

	counter := prometheus.NewCounterVec(
		prometheus.CounterOpts{
			Name: "http_requests_total",
			Help: "Total number of HTTP requests processed.",
		},
		[]string{"method", "status"},
	)

	gauge := prometheus.NewGauge(
		prometheus.GaugeOpts{
			Name: "current_active_workers",
			Help: "Current number of active workers.",
		},
	)

	hist := prometheus.NewHistogram(
		prometheus.HistogramOpts{
			Name:    "task_duration_seconds",
			Help:    "Duration of tasks in seconds.",
			Buckets: []float64{0.1, 0.5, 1.0, 5.0},
		},
	)

	reg.MustRegister(counter, gauge, hist)

	return &Metrics{
		Registry:       reg,
		RequestCounter: counter,
		ActiveGauge:    gauge,
		DurationHist:   hist,
	}
}

{
  "schemaVersion": 1,
  "goal": "verify pkg:golang/github.com/prometheus/client_golang@v1.19.1",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/prometheus/client_golang@v1.19.1"
  ],
  "constraints": {
    "executionContext": "node"
  },
  "runtimeConditions": {
    "ecosystem": "npm",
    "language": "javascript",
    "moduleSystem": "cjs",
    "packageManager": "npm@10.9.8",
    "runtime": "node@22.23.2"
  }
}

package main

import (
	"fmt"
	"os"

	"sample"
	dto "github.com/prometheus/client_model/go"
)

func main() {
	m := sample.NewMetrics()
	if m == nil || m.Registry == nil {
		fmt.Fprintf(os.Stderr, "failed to initialize metrics registry\n")
		os.Exit(1)
	}

	// 1. Record metric values
	m.RequestCounter.WithLabelValues("GET", "200").Inc()
	m.RequestCounter.WithLabelValues("POST", "201").Add(2)
	m.ActiveGauge.Set(42)
	m.DurationHist.Observe(0.35)

	// 2. Gather metrics from the registry
	mfs, err := m.Registry.Gather()
	if err != nil {
		fmt.Fprintf(os.Stderr, "registry.Gather failed: %v\n", err)
		os.Exit(1)
	}

	if len(mfs) != 3 {
		fmt.Fprintf(os.Stderr, "expected 3 metric families, got %d\n", len(mfs))
		os.Exit(1)
	}

	foundMap := make(map[string]*dto.MetricFamily)
	for _, mf := range mfs {
		foundMap[mf.GetName()] = mf
	}

	// 3. Verify counter family
	counterMF, ok := foundMap["http_requests_total"]
	if !ok {
		fmt.Fprintf(os.Stderr, "missing http_requests_total metric\n")
		os.Exit(1)
	}
	if counterMF.GetType() != dto.MetricType_COUNTER {
		fmt.Fprintf(os.Stderr, "expected COUNTER type, got %v\n", counterMF.GetType())
		os.Exit(1)
	}
	if len(counterMF.GetMetric()) != 2 {
		fmt.Fprintf(os.Stderr, "expected 2 counter metric instances, got %d\n", len(counterMF.GetMetric()))
		os.Exit(1)
	}

	// 4. Verify gauge family
	gaugeMF, ok := foundMap["current_active_workers"]
	if !ok {
		fmt.Fprintf(os.Stderr, "missing current_active_workers metric\n")
		os.Exit(1)
	}
	if gaugeMF.GetType() != dto.MetricType_GAUGE {
		fmt.Fprintf(os.Stderr, "expected GAUGE type, got %v\n", gaugeMF.GetType())
		os.Exit(1)
	}
	if len(gaugeMF.GetMetric()) != 1 || gaugeMF.GetMetric()[0].GetGauge().GetValue() != 42 {
		fmt.Fprintf(os.Stderr, "expected gauge value 42\n")
		os.Exit(1)
	}

	// 5. Verify histogram family
	histMF, ok := foundMap["task_duration_seconds"]
	if !ok {
		fmt.Fprintf(os.Stderr, "missing task_duration_seconds metric\n")
		os.Exit(1)
	}
	if histMF.GetType() != dto.MetricType_HISTOGRAM {
		fmt.Fprintf(os.Stderr, "expected HISTOGRAM type, got %v\n", histMF.GetType())
		os.Exit(1)
	}
	hist := histMF.GetMetric()[0].GetHistogram()
	if hist.GetSampleCount() != 1 || hist.GetSampleSum() != 0.35 {
		fmt.Fprintf(os.Stderr, "expected sample count 1 and sum 0.35, got %d, %f\n", hist.GetSampleCount(), hist.GetSampleSum())
		os.Exit(1)
	}

	fmt.Println("All prometheus client_golang contract assertions passed.")
}