node_exporter/collector/ntp.go
Chris Batey 387c64424b Use the offset calculation that includes round trip time in the ntp collector
Previously the raw time difference was used which includes the network trip time
between the node and the ntp server. This makes setting alerts off the value
troublesome as it depends on the latency as well as the clock offset.
2016-06-01 08:56:20 +01:00

70 lines
2.0 KiB
Go

// Copyright 2015 The Prometheus Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// +build !nontp
package collector
import (
"flag"
"fmt"
"github.com/beevik/ntp"
"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/common/log"
)
var (
ntpServer = flag.String("collector.ntp.server", "", "NTP server to use for ntp collector.")
ntpProtocolVersion = flag.Int("collector.ntp.protocol-version", 4, "NTP protocol version")
)
type ntpCollector struct {
drift prometheus.Gauge
}
func init() {
Factories["ntp"] = NewNtpCollector
}
// Takes a prometheus registry and returns a new Collector exposing
// the offset between ntp and the current system time.
func NewNtpCollector() (Collector, error) {
if *ntpServer == "" {
return nil, fmt.Errorf("no NTP server specified, see -collector.ntp.server")
}
if *ntpProtocolVersion < 2 || *ntpProtocolVersion > 4 {
return nil, fmt.Errorf("invalid NTP protocol version %d; must be 2, 3, or 4", *ntpProtocolVersion)
}
return &ntpCollector{
drift: prometheus.NewGauge(prometheus.GaugeOpts{
Namespace: Namespace,
Name: "ntp_drift_seconds",
Help: "Time between system time and ntp time.",
}),
}, nil
}
func (c *ntpCollector) Update(ch chan<- prometheus.Metric) (err error) {
resp, err := ntp.Query(*ntpServer, *ntpProtocolVersion)
if err != nil {
return fmt.Errorf("couldn't get NTP drift: %s", err)
}
driftSeconds := resp.ClockOffset.Seconds()
log.Debugf("Set ntp_drift_seconds: %f", driftSeconds)
c.drift.Set(driftSeconds)
c.drift.Collect(ch)
return err
}