github.com/prometheus/client_golang v1.19.1: prometheus.NewCounterVec

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 github.com/prometheus/client_golang/prometheus.NewCounterVec in 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
Demonstrate these symbols/APIs:
  - github.com/prometheus/client_golang/prometheus.NewCounterVec

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:e40e3feaacdc7982af60c942755cfba267de714b02913a95e8c1b35481272391","contract":["prometheus.NewCounterVec creates a non-nil CounterVec metric collector configured with CounterOpts and label names.","CounterVec.WithLabelValues and CounterVec.With return Counter metrics partitioned by label values.","CounterVec.GetMetricWithLabelValues validates label value counts against variable label names.","CounterVec.CurryWith binds a subset of labels returning a curried CounterVec referencing the same underlying metrics.","CounterVec.DeleteLabelValues and CounterVec.Delete remove metrics from the vector.","CounterVec.Reset deletes all metrics from the vector."],"goal":"verify github.com/prometheus/client_golang/prometheus.NewCounterVec in 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,"symbols":["github.com/prometheus/client_golang/prometheus.NewCounterVec"]},"contractCommand":["go","test","./..."],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"golang","executionContext":"go","language":"go","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"go","runtime":"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","symbols":["github.com/prometheus/client_golang/prometheus.NewCounterVec"],"verifierAdapter":"golang@1"}

module example.com/countervec

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 main

import (
	"fmt"

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

func main() {
	httpRequestsTotal := prometheus.NewCounterVec(
		prometheus.CounterOpts{
			Namespace: "http",
			Subsystem: "server",
			Name:      "requests_total",
			Help:      "Total number of HTTP requests processed, partitioned by method and status code.",
		},
		[]string{"method", "code"},
	)

	// Increment counter with label values
	httpRequestsTotal.WithLabelValues("POST", "200").Inc()
	httpRequestsTotal.WithLabelValues("POST", "200").Add(2)
	httpRequestsTotal.With(prometheus.Labels{"method": "GET", "code": "404"}).Inc()

	// Read metric value
	var metric dto.Metric
	if counter, err := httpRequestsTotal.GetMetricWithLabelValues("POST", "200"); err == nil {
		_ = counter.Write(&metric)
		fmt.Printf("POST 200 count: %f\n", metric.GetCounter().GetValue())
	}
}

{
  "schemaVersion": 1,
  "goal": "verify github.com/prometheus/client_golang/prometheus.NewCounterVec in pkg:golang/github.com/prometheus/client_golang@v1.19.1",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/prometheus/client_golang@v1.19.1"
  ],
  "symbols": [
    "github.com/prometheus/client_golang/prometheus.NewCounterVec"
  ]
}

package test

import (
	"testing"

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

func getCounterValue(t *testing.T, counter prometheus.Counter) float64 {
	t.Helper()
	var m dto.Metric
	if err := counter.Write(&m); err != nil {
		t.Fatalf("failed to write metric: %v", err)
	}
	if m.GetCounter() == nil {
		t.Fatal("expected counter metric, got nil")
	}
	return m.GetCounter().GetValue()
}

func TestNewCounterVecCreation(t *testing.T) {
	vec := prometheus.NewCounterVec(
		prometheus.CounterOpts{
			Namespace: "http",
			Subsystem: "server",
			Name:      "requests_total",
			Help:      "Total number of HTTP requests.",
		},
		[]string{"method", "code"},
	)
	if vec == nil {
		t.Fatal("expected non-nil CounterVec")
	}

	// Verify Describe emits a descriptor
	ch := make(chan *prometheus.Desc, 1)
	vec.Describe(ch)
	close(ch)

	desc := <-ch
	if desc == nil {
		t.Fatal("expected non-nil Desc from Describe")
	}
}

func TestCounterVecWithLabelValuesAndWith(t *testing.T) {
	vec := prometheus.NewCounterVec(
		prometheus.CounterOpts{
			Name: "test_counter",
			Help: "Test counter vector",
		},
		[]string{"service", "status"},
	)

	// 1. WithLabelValues
	c1 := vec.WithLabelValues("auth", "200")
	if c1 == nil {
		t.Fatal("expected non-nil Counter from WithLabelValues")
	}
	c1.Inc()
	c1.Add(4.5)

	if got := getCounterValue(t, c1); got != 5.5 {
		t.Errorf("expected counter value 5.5, got %v", got)
	}

	// 2. With
	c2 := vec.With(prometheus.Labels{"service": "api", "status": "500"})
	if c2 == nil {
		t.Fatal("expected non-nil Counter from With")
	}
	c2.Add(2.0)

	if got := getCounterValue(t, c2); got != 2.0 {
		t.Errorf("expected counter value 2.0, got %v", got)
	}

	// Ensure c1 and c2 are separate metrics
	if got := getCounterValue(t, c1); got != 5.5 {
		t.Errorf("expected c1 to remain 5.5, got %v", got)
	}
}

func TestCounterVecGetMetricValidation(t *testing.T) {
	vec := prometheus.NewCounterVec(
		prometheus.CounterOpts{
			Name: "validation_counter",
			Help: "Counter for validation tests",
		},
		[]string{"zone", "tier"},
	)

	// Wrong number of label values
	if _, err := vec.GetMetricWithLabelValues("us-east"); err == nil {
		t.Error("expected error when label values length is less than label names")
	}
	if _, err := vec.GetMetricWithLabelValues("us-east", "web", "extra"); err == nil {
		t.Error("expected error when label values length exceeds label names")
	}

	// Wrong label names in map
	if _, err := vec.GetMetricWith(prometheus.Labels{"invalid": "val", "tier": "web"}); err == nil {
		t.Error("expected error when invalid label names are provided")
	}

	// Correct label values
	c, err := vec.GetMetricWithLabelValues("us-east", "web")
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	c.Inc()
	if got := getCounterValue(t, c); got != 1.0 {
		t.Errorf("expected counter value 1.0, got %v", got)
	}
}

func TestCounterVecCurryWith(t *testing.T) {
	vec := prometheus.NewCounterVec(
		prometheus.CounterOpts{
			Name: "curried_counter",
			Help: "Counter for currying tests",
		},
		[]string{"region", "cluster", "endpoint"},
	)

	// Curry with subset of labels
	curriedVec, err := vec.CurryWith(prometheus.Labels{"region": "us-west", "cluster": "alpha"})
	if err != nil {
		t.Fatalf("CurryWith failed: %v", err)
	}

	// Use remaining variable label
	c := curriedVec.WithLabelValues("/health")
	c.Add(3.0)

	// Fetch from original vec to ensure shared underlying metric
	origCounter, err := vec.GetMetricWithLabelValues("us-west", "alpha", "/health")
	if err != nil {
		t.Fatalf("GetMetricWithLabelValues on original vec failed: %v", err)
	}
	if got := getCounterValue(t, origCounter); got != 3.0 {
		t.Errorf("expected value 3.0 in original metric, got %v", got)
	}

	// Currying with non-existent label returns error
	if _, err := vec.CurryWith(prometheus.Labels{"nonexistent": "value"}); err == nil {
		t.Error("expected error when currying with unknown label name")
	}
}

func TestCounterVecDeleteAndReset(t *testing.T) {
	vec := prometheus.NewCounterVec(
		prometheus.CounterOpts{
			Name: "lifecycle_counter",
			Help: "Counter for delete and reset tests",
		},
		[]string{"tenant"},
	)

	vec.WithLabelValues("tenant-a").Inc()
	vec.WithLabelValues("tenant-b").Inc()

	// Delete existing
	deleted := vec.DeleteLabelValues("tenant-a")
	if !deleted {
		t.Error("expected DeleteLabelValues to return true for existing label")
	}

	// Delete non-existing
	deletedAgain := vec.DeleteLabelValues("tenant-a")
	if deletedAgain {
		t.Error("expected DeleteLabelValues to return false for already deleted label")
	}

	// Reset clears everything
	vec.Reset()
	deletedAfterReset := vec.DeleteLabelValues("tenant-b")
	if deletedAfterReset {
		t.Error("expected DeleteLabelValues to return false after Reset")
	}
}