commit 1c0a9116416365dd42437a33963f088e1e00fc79 Author: Michael Stapelberg Date: Mon Oct 30 06:17:49 2017 -0700 Initial commit diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md new file mode 100644 index 0000000..ae319c7 --- /dev/null +++ b/CONTRIBUTING.md @@ -0,0 +1,23 @@ +# 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 +Agreement. You (or your employer) retain the copyright to your contribution, +this simply gives us permission to use and redistribute your contributions as +part of the project. 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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 , 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)) +} diff --git a/dnsmasq_exporter.service b/dnsmasq_exporter.service new file mode 100644 index 0000000..e962a1c --- /dev/null +++ b/dnsmasq_exporter.service @@ -0,0 +1,11 @@ +[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