func startDNSServer(state *server.State, addr string, recursors []string) error {
dns := server.DNSServer{
UDPAddr: addr,
TCPAddr: addr,
Store: state,
Recursors: recursors,
}
return dns.ListenAndServe()
}
func main() {
defer shutdown.Exit()
httpAddr := flag.String("http-addr", ":1111", "address to serve HTTP API from")
dnsAddr := flag.String("dns-addr", ":53", "address to service DNS from")
resolvers := flag.String("recursors", "8.8.8.8,8.8.4.4", "upstream recursive DNS servers")
etcdAddrs := flag.String("etcd", "http://127.0.0.1:2379", "etcd servers (comma separated)")
notify := flag.String("notify", "", "url to send webhook to after starting listener")
flag.Parse()
etcdClient := etcd.NewClient(strings.Split(*etcdAddrs, ","))
// Check to make sure that etcd is online and accepting connections
// etcd takes a while to come online, so we attempt a GET multiple times
err := attempt.Strategy{
Min: 5,
Total: 10 * time.Minute,
Delay: 200 * time.Millisecond,
}.Run(func() (err error) {
_, err = etcdClient.Get("/", false, false)
if e, ok := err.(*etcd.EtcdError); ok && e.ErrorCode == 100 {
// Valid 404 from etcd (> v2.0)
err = nil
}
return
})
if err != nil {
log.Fatalf("Failed to connect to etcd at %v: %q", etcdAddrs, err)
}
state := server.NewState()
backend := server.NewEtcdBackend(etcdClient, "/discoverd", state)
if err := backend.StartSync(); err != nil {
log.Fatalf("Failed to perform initial etcd sync: %s", err)
}
dns := server.DNSServer{
UDPAddr: *dnsAddr,
TCPAddr: *dnsAddr,
Store: state,
}
if *resolvers != "" {
dns.Recursors = strings.Split(*resolvers, ",")
}
if err := dns.ListenAndServe(); err != nil {
log.Fatalf("Failed to start DNS server: %s", err)
}
l, err := net.Listen("tcp4", *httpAddr)
if err != nil {
log.Fatalf("Failed to start HTTP listener: %s", err)
}
log.Printf("discoverd listening for HTTP on %s and DNS on %s", *httpAddr, *dnsAddr)
if *notify != "" {
addr := l.Addr().String()
host, port, _ := net.SplitHostPort(addr)
if host == "0.0.0.0" {
// try to get real address from dns addr
if dnsHost, _, _ := net.SplitHostPort(*dnsAddr); dnsHost != "" {
addr = net.JoinHostPort(dnsHost, port)
}
}
data := struct {
URL string `json:"url"`
}{fmt.Sprintf("http://%s", addr)}
payload, _ := json.Marshal(data)
res, err := http.Post(*notify, "application/json", bytes.NewReader(payload))
if err != nil {
log.Printf("failed to notify: %s", err)
} else {
res.Body.Close()
}
}
http.Serve(l, server.NewHTTPHandler(server.NewBasicDatastore(state, backend)))
}