prometheus-latency-exporter/main.go

package main

import (
	"flag"
	"time"
	"github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/client_golang/prometheus/promhttp"
	"gopkg.in/yaml.v2"
	"io/ioutil"
	"log"
	"fmt"
	"net"
	"net/http"
)

type Service struct {
	Name string `yaml:"name"`
	Host string `yaml:"host"`
	Port string `yaml:"port"`
}

type Config struct {
	Services []Service `yaml:"services"`
}

var (
	latency = prometheus.NewGaugeVec(
		prometheus.GaugeOpts{
			Name: "service_latency_seconds",
			Help: "Latency of services.",
		},
		[]string{"service"},
	)
	addr	= flag.String("a", "0.0.0.0", "address to use")
	port	= flag.String("p", "9062", "port to run on")
	conf	= flag.String("c", "config.yml", "configuration file to use")
	inter	= flag.Int("i", 30, "time interval in seconds between two checks")
)

func init() {
	prometheus.MustRegister(latency)
}

func main() {
	flag.Parse()
	http.Handle("/metrics", promhttp.Handler())
	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "text/html")
		fmt.Fprintln(w, "Prometheus Latency Exporter: <a href='/metrics'>Metrics</a>")
	})
	go func() {
		for {
			checkLatency()
			time.Sleep(time.Duration(*inter) * time.Second)
		}
	}()
	log.Fatal(http.ListenAndServe(net.JoinHostPort(*addr, *port), nil))
}

func checkLatency() {
	var config Config
	source, err := ioutil.ReadFile(*conf)
	if err != nil {
		log.Fatalf("error: %v", err)
	}
	err = yaml.Unmarshal(source, &config)
	if err != nil {
		log.Fatalf("error: %v", err)
	}

	for _, service := range config.Services {
		start := time.Now()
		conn, err := net.Dial("tcp", net.JoinHostPort(service.Host, service.Port))
		if err != nil {
			log.Printf("Failed to check service: %s, error: %s", service.Name, err)
			continue
		}
		conn.Close()
		duration := time.Since(start)
		latency.With(prometheus.Labels{"service": service.Name}).Set(duration.Seconds())
	}
}