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# How to Contribute
We'd love to accept your patches and contributions to this project. There are
just a few small guidelines you need to follow.
## Contributor License Agreement
Contributions to this project must be accompanied by a Contributor License
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You generally only need to submit a CLA once, so if you've already submitted one
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## Code reviews
All submissions, including submissions by project members, require review. We
use GitHub pull requests for this purpose. Consult
[GitHub Help](https://help.github.com/articles/about-pull-requests/) for more
information on using pull requests.

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# dnsmasq exporter
dnsmasq_exporter is an exporter for [Prometheus](https://prometheus.io/),
allowing you to monitor/alert on the number of DHCP leases and various DNS
statistics.
See also the “cache statistics” section in
https://manpages.debian.org/stretch/dnsmasq-base/dnsmasq.8.en.html#NOTES
This is not an official Google product.
## Installation
``` shell
go get -u github.com/google/dnsmasq_exporter
```
## Usage
Place `dnsmasq_exporter.service` in
`/etc/systemd/system/dnsmasq_exporter.service`, then enable and start the
service using:
```shell
systemctl daemon-reload
systemctl enable --now dnsmasq_exporter
```
Then, add the endpoint to your Prometheus configuration file:
```yaml
scrape_configs:
- job_name: dnsmasq
static_configs:
- targets: ['localhost:9153']
```

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dnsmasq.go Normal file
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// Copyright 2016 Google Inc. All Rights Reserved.
//
// 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.
// Binary dnsmasq_exporter is a Prometheus exporter for dnsmasq statistics.
package main
import (
"bufio"
"flag"
"fmt"
"log"
"net/http"
"os"
"strconv"
"golang.org/x/sync/errgroup"
"github.com/miekg/dns"
"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/client_golang/prometheus/promhttp"
)
var (
listen = flag.String("listen",
"localhost:9153",
"listen address")
leasesPath = flag.String("leases_path",
"/var/lib/misc/dnsmasq.leases",
"path to the dnsmasq leases file")
)
var (
// floatMetrics contains prometheus Gauges, keyed by the stats DNS record
// they correspond to.
floatMetrics = map[string]prometheus.Gauge{
"cachesize.bind.": prometheus.NewGauge(prometheus.GaugeOpts{
Name: "dnsmasq_cachesize",
Help: "configured size of the DNS cache",
}),
"insertions.bind.": prometheus.NewGauge(prometheus.GaugeOpts{
Name: "dnsmasq_insertions",
Help: "DNS cache insertions",
}),
"evictions.bind.": prometheus.NewGauge(prometheus.GaugeOpts{
Name: "dnsmasq_evictions",
Help: "DNS cache exictions: numbers of entries which replaced an unexpired cache entry",
}),
"misses.bind.": prometheus.NewGauge(prometheus.GaugeOpts{
Name: "dnsmasq_misses",
Help: "DNS cache misses: queries which had to be forwarded",
}),
"hits.bind.": prometheus.NewGauge(prometheus.GaugeOpts{
Name: "dnsmasq_hits",
Help: "DNS queries answered locally (cache hits)",
}),
"auth.bind.": prometheus.NewGauge(prometheus.GaugeOpts{
Name: "dnsmasq_auth",
Help: "DNS queries for authoritative zones",
}),
}
leases = prometheus.NewGauge(prometheus.GaugeOpts{
Name: "dnsmasq_leases",
Help: "Number of DHCP leases handed out",
})
)
func init() {
for _, g := range floatMetrics {
prometheus.MustRegister(g)
}
prometheus.MustRegister(leases)
}
// From https://manpages.debian.org/stretch/dnsmasq-base/dnsmasq.8.en.html:
// The cache statistics are also available in the DNS as answers to queries of
// class CHAOS and type TXT in domain bind. The domain names are cachesize.bind,
// insertions.bind, evictions.bind, misses.bind, hits.bind, auth.bind and
// servers.bind. An example command to query this, using the dig utility would
// be:
// dig +short chaos txt cachesize.bind
func main() {
flag.Parse()
promHandler := promhttp.Handler()
dnsClient := &dns.Client{
SingleInflight: true,
}
http.HandleFunc("/metrics", func(w http.ResponseWriter, r *http.Request) {
var eg errgroup.Group
eg.Go(func() error {
msg := &dns.Msg{
MsgHdr: dns.MsgHdr{
Id: dns.Id(),
},
Question: []dns.Question{
dns.Question{"cachesize.bind.", dns.TypeTXT, dns.ClassCHAOS},
dns.Question{"insertions.bind.", dns.TypeTXT, dns.ClassCHAOS},
dns.Question{"evictions.bind.", dns.TypeTXT, dns.ClassCHAOS},
dns.Question{"misses.bind.", dns.TypeTXT, dns.ClassCHAOS},
dns.Question{"hits.bind.", dns.TypeTXT, dns.ClassCHAOS},
dns.Question{"auth.bind.", dns.TypeTXT, dns.ClassCHAOS},
dns.Question{"servers.bind.", dns.TypeTXT, dns.ClassCHAOS},
},
}
in, _, err := dnsClient.Exchange(msg, "127.0.0.1:53")
if err != nil {
return err
}
for _, a := range in.Answer {
txt, ok := a.(*dns.TXT)
if !ok {
continue
}
switch txt.Hdr.Name {
case "servers.bind.":
// TODO: parse <server> <successes> <errors>, also with multiple upstreams
default:
g, ok := floatMetrics[txt.Hdr.Name]
if !ok {
continue // ignore unexpected answer from dnsmasq
}
if got, want := len(txt.Txt), 1; got != want {
return fmt.Errorf("stats DNS record %q: unexpected number of replies: got %d, want %d", txt.Hdr.Name, got, want)
}
f, err := strconv.ParseFloat(txt.Txt[0], 64)
if err != nil {
return err
}
g.Set(f)
}
}
return nil
})
eg.Go(func() error {
f, err := os.Open(*leasesPath)
if err != nil {
return err
}
defer f.Close()
scanner := bufio.NewScanner(f)
var lines float64
for scanner.Scan() {
lines++
}
if err := scanner.Err(); err != nil {
return err
}
leases.Set(lines)
return nil
})
if err := eg.Wait(); err != nil {
http.Error(w, err.Error(), http.StatusInternalServerError)
return
}
promHandler.ServeHTTP(w, r)
})
log.Fatal(http.ListenAndServe(*listen, nil))
}

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[Unit]
Description=dnsmasq exporter for Prometheus
Documentation=https://prometheus.io/docs/introduction/overview/
[Service]
Restart=always
User=prometheus
ExecStart=/usr/bin/dnsmasq_exporter
[Install]
WantedBy=multi-user.target