prometheus counter example

main.go

package main

import (
	"net/http"

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

var (
	cpuTemp = prometheus.NewGauge(prometheus.GaugeOpts{
		Name:        "cpu_temperature_celsius",
		Help:        "Current temperature of the CPU.",
		ConstLabels: prometheus.Labels{"version": "1234"},
	})
	hdFailures = prometheus.NewCounter(prometheus.CounterOpts{
		Name:        "hd_errors_total",
		Help:        "Number of hard-disk errors.",
		ConstLabels: prometheus.Labels{"version": "1234"},
	})
)

func init() {
	prometheus.MustRegister(cpuTemp)
	prometheus.MustRegister(hdFailures)
}

func main() {
	cpuTemp.Set(65.3)
	hdFailures.Inc()

	http.Handle("/metrics", prometheus.Handler())
	http.ListenAndServe(":8080", nil)
}

out

# HELP cpu_temperature_celsius Current temperature of the CPU.
# TYPE cpu_temperature_celsius gauge
cpu_temperature_celsius{version="1234"} 65.3
# HELP hd_errors_total Number of hard-disk errors.
# TYPE hd_errors_total counter
hd_errors_total 1
# HELP http_request_duration_microseconds The HTTP request latencies in microseconds.
# TYPE http_request_duration_microseconds summary
http_request_duration_microseconds{handler="prometheus",quantile="0.5"} 0
http_request_duration_microseconds{handler="prometheus",quantile="0.9"} 0
http_request_duration_microseconds{handler="prometheus",quantile="0.99"} 0
http_request_duration_microseconds_sum{handler="prometheus"} 0
http_request_duration_microseconds_count{handler="prometheus"} 0
# HELP http_request_size_bytes The HTTP request sizes in bytes.
# TYPE http_request_size_bytes summary
http_request_size_bytes{handler="prometheus",quantile="0.5"} 0
http_request_size_bytes{handler="prometheus",quantile="0.9"} 0
http_request_size_bytes{handler="prometheus",quantile="0.99"} 0
http_request_size_bytes_sum{handler="prometheus"} 0
http_request_size_bytes_count{handler="prometheus"} 0
# HELP http_response_size_bytes The HTTP response sizes in bytes.
# TYPE http_response_size_bytes summary
http_response_size_bytes{handler="prometheus",quantile="0.5"} 0
http_response_size_bytes{handler="prometheus",quantile="0.9"} 0
http_response_size_bytes{handler="prometheus",quantile="0.99"} 0
http_response_size_bytes_sum{handler="prometheus"} 0
http_response_size_bytes_count{handler="prometheus"} 0
# HELP process_goroutines Number of goroutines that currently exist.
# TYPE process_goroutines gauge
process_goroutines 10