node_exporter/collector/ntp.go

// +build !nontp

package collector

import (
	"flag"
	"fmt"
	"time"

	"github.com/beevik/ntp"
	"github.com/golang/glog"
	"github.com/prometheus/client_golang/prometheus"
)

var (
	ntpServer = flag.String("ntpServer", "", "NTP server to use for ntp collector.")
	ntpDrift  = prometheus.NewGauge(prometheus.GaugeOpts{
		Namespace: Namespace,
		Name:      "ntp_drift_seconds",
		Help:      "Time between system time and ntp time.",
	})
)

type ntpCollector struct {
}

func init() {
	Factories["ntp"] = NewNtpCollector
}

// Takes a config struct and prometheus registry and returns a new Collector exposing
// the offset between ntp and the current system time.
func NewNtpCollector(config Config) (Collector, error) {
	if *ntpServer == "" {
		return nil, fmt.Errorf("No NTP server specifies, see --ntpServer")
	}
	c := ntpCollector{}

	if _, err := prometheus.RegisterOrGet(ntpDrift); err != nil {
		return nil, err
	}
	return &c, nil
}

func (c *ntpCollector) Update() (updates int, err error) {
	t, err := ntp.Time(*ntpServer)
	if err != nil {
		return updates, fmt.Errorf("Couldn't get ntp drift: %s", err)
	}
	drift := t.Sub(time.Now())
	updates++
	glog.V(1).Infof("Set ntp_drift_seconds: %f", drift.Seconds())
	ntpDrift.Set(drift.Seconds())

	return updates, err
}