153 lines
3.7 KiB
Go
153 lines
3.7 KiB
Go
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package main
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import (
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"fmt"
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"io/ioutil"
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"net"
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"net/http"
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"net/http/httptest"
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"os"
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"os/exec"
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"strings"
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"testing"
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"time"
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"github.com/miekg/dns"
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"github.com/prometheus/client_golang/prometheus/promhttp"
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)
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func TestDnsmasqExporter(t *testing.T) {
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// NOTE(stapelberg): dnsmasq disables DNS operation upon --port=0 (as
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// opposed to picking a free port). Hence, we must pick one. This is
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// inherently prone to race conditions: another process could grab the port
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// between our ln.Close() and dnsmasq’s bind(). Ideally, dnsmasq would
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// support grabbing a free port and announcing it, or inheriting a listening
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// socket à la systemd socket activation.
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ln, err := net.Listen("tcp", "localhost:0")
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if err != nil {
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t.Fatal(err)
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}
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_, port, err := net.SplitHostPort(ln.Addr().String())
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if err != nil {
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t.Fatal(err)
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}
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ln.Close()
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dnsmasq := exec.Command(
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"dnsmasq",
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"--port="+port,
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"--no-daemon",
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"--cache-size=666",
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"--bind-interfaces",
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"--interface=lo")
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dnsmasq.Stderr = os.Stderr
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fmt.Printf("starting %v\n", dnsmasq.Args)
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if err := dnsmasq.Start(); err != nil {
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t.Fatal(err)
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}
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defer dnsmasq.Process.Kill()
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// Wait until dnsmasq started up
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resolver := &dns.Client{}
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for {
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// Cause a cache miss (dnsmasq must forward this query)
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var m dns.Msg
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m.SetQuestion("localhost.", dns.TypeA)
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if _, _, err := resolver.Exchange(&m, "localhost:"+port); err == nil {
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break
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}
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time.Sleep(10 * time.Millisecond) // do not hog the CPU
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}
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s := &server{
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promHandler: promhttp.Handler(),
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dnsClient: &dns.Client{
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SingleInflight: true,
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},
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dnsmasqAddr: "localhost:" + port,
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leasesPath: "testdata/dnsmasq.leases",
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}
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t.Run("first", func(t *testing.T) {
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metrics := fetchMetrics(t, s)
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want := map[string]string{
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"dnsmasq_leases": "2",
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"dnsmasq_cachesize": "666",
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"dnsmasq_hits": "1",
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"dnsmasq_misses": "0",
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}
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for key, val := range want {
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if got, want := metrics[key], val; got != want {
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t.Errorf("metric %q: got %q, want %q", key, got, want)
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}
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}
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})
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t.Run("second", func(t *testing.T) {
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metrics := fetchMetrics(t, s)
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want := map[string]string{
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"dnsmasq_leases": "2",
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"dnsmasq_cachesize": "666",
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"dnsmasq_hits": "2",
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"dnsmasq_misses": "0",
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}
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for key, val := range want {
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if got, want := metrics[key], val; got != want {
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t.Errorf("metric %q: got %q, want %q", key, got, want)
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}
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}
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})
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// Cause a cache miss (dnsmasq must forward this query)
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var m dns.Msg
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m.SetQuestion("no.such.domain.invalid.", dns.TypeA)
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if _, _, err := resolver.Exchange(&m, "localhost:"+port); err != nil {
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t.Fatal(err)
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}
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t.Run("after query", func(t *testing.T) {
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metrics := fetchMetrics(t, s)
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want := map[string]string{
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"dnsmasq_leases": "2",
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"dnsmasq_cachesize": "666",
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"dnsmasq_hits": "3",
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"dnsmasq_misses": "1",
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}
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for key, val := range want {
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if got, want := metrics[key], val; got != want {
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t.Errorf("metric %q: got %q, want %q", key, got, want)
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}
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}
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})
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}
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func fetchMetrics(t *testing.T, s *server) map[string]string {
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rec := httptest.NewRecorder()
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s.metrics(rec, httptest.NewRequest("GET", "/metrics", nil))
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resp := rec.Result()
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if got, want := resp.StatusCode, http.StatusOK; got != want {
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b, _ := ioutil.ReadAll(resp.Body)
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t.Fatalf("unexpected HTTP status: got %v (%v), want %v", resp.Status, string(b), want)
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}
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body, err := ioutil.ReadAll(resp.Body)
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if err != nil {
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t.Fatal(err)
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}
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metrics := make(map[string]string)
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for _, line := range strings.Split(strings.TrimSpace(string(body)), "\n") {
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if strings.HasPrefix(line, "#") {
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continue
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}
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parts := strings.Split(line, " ")
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if len(parts) < 2 {
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continue
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}
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if !strings.HasPrefix(parts[0], "dnsmasq_") {
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continue
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}
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metrics[parts[0]] = parts[1]
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}
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return metrics
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}
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