Prometheus metrics code instrumentation in Golang

prometheus-metrics-golang.go

package main

import (
  "net/http"

  "github.com/prometheus/client_golang/prometheus"
  "github.com/prometheus/client_golang/prometheus/promhttp"
  "log"
  "time"
  "math/rand"
)

var (
  counter = prometheus.NewCounter(
     prometheus.CounterOpts{
        Namespace: "golang",
        Name:      "my_counter",
        Help:      "This is my counter",
     })

  gauge = prometheus.NewGauge(
     prometheus.GaugeOpts{
        Namespace: "golang",
        Name:      "my_gauge",
        Help:      "This is my gauge",
     })

  histogram = prometheus.NewHistogram(
     prometheus.HistogramOpts{
        Namespace: "golang",
        Name:      "my_histogram",
        Help:      "This is my histogram",
     })

  summary = prometheus.NewSummary(
     prometheus.SummaryOpts{
        Namespace: "golang",
        Name:      "my_summary",
        Help:      "This is my summary",
     })
)

func main() {
  rand.Seed(time.Now().Unix())

  http.Handle("/metrics", promhttp.Handler())

  prometheus.MustRegister(counter)
  prometheus.MustRegister(gauge)
  prometheus.MustRegister(histogram)
  prometheus.MustRegister(summary)

  go func() {
     for {
        counter.Add(rand.Float64() * 5)
        gauge.Add(rand.Float64()*15 - 5)
        histogram.Observe(rand.Float64() * 10)
        summary.Observe(rand.Float64() * 10)

        time.Sleep(time.Second)
     }
  }()

  log.Fatal(http.ListenAndServe(":8080", nil))
}