pass notifees to the mDNS constructor, add dedicated Start method

examples/chat-with-mdns/mdns.go

@@ -18,13 +18,14 @@ func (n *discoveryNotifee) HandlePeerFound(pi peer.AddrInfo) {
 
 //Initialize the MDNS service
 func initMDNS(peerhost host.Host, rendezvous string) chan peer.AddrInfo {
-	// An hour might be a long long period in practical applications. But this is fine for us
-	ser := mdns.NewMdnsService(peerhost, rendezvous)
-
-	//register with service so that we get notified about peer discovery
+	// register with service so that we get notified about peer discovery
 	n := &discoveryNotifee{}
 	n.PeerChan = make(chan peer.AddrInfo)
 
-	ser.RegisterNotifee(n)
+	// An hour might be a long long period in practical applications. But this is fine for us
+	ser := mdns.NewMdnsService(peerhost, rendezvous, n)
+	if err := ser.Start(); err != nil {
+		panic(err)
+	}
 	return n.PeerChan
 }

examples/ipfs-camp-2019/06-Pubsub/main.go

@@ -100,9 +100,11 @@ func main() {
 		fmt.Println("Connected to", targetInfo.ID)
 	}
 
-	mdns := mdns.NewMdnsService(host, "")
 	notifee := &discoveryNotifee{h: host, ctx: ctx}
-	mdns.RegisterNotifee(notifee)
+	mdns := mdns.NewMdnsService(host, "", notifee)
+	if err := mdns.Start(); err != nil {
+		panic(err)
+	}
 
 	err = dht.Bootstrap(ctx)
 	if err != nil {

examples/ipfs-camp-2019/07-Messaging/main.go

@@ -108,8 +108,10 @@ func main() {
 
 	fmt.Println("Connected to", targetInfo.ID)
 
-	mdns := mdns.NewMdnsService(host, "")
-	mdns.RegisterNotifee(&mdnsNotifee{h: host, ctx: ctx})
+	mdns := mdns.NewMdnsService(host, "", &mdnsNotifee{h: host, ctx: ctx})
+	if err := mdns.Start(); err != nil {
+		panic(err)
+	}
 
 	err = dht.Bootstrap(ctx)
 	if err != nil {

examples/ipfs-camp-2019/08-End/main.go

@@ -107,8 +107,10 @@ func main() {
 
 	fmt.Println("Connected to", targetInfo.ID)
 
-	mdns := mdns.NewMdnsService(host, "")
-	mdns.RegisterNotifee(&mdnsNotifee{h: host, ctx: ctx})
+	mdns := mdns.NewMdnsService(host, "", &mdnsNotifee{h: host, ctx: ctx})
+	if err := mdns.Start(); err != nil {
+		panic(err)
+	}
 
 	err = dht.Bootstrap(ctx)
 	if err != nil {

examples/pubsub/chat/main.go

@@ -41,8 +41,7 @@ func main() {
 	}
 
 	// setup local mDNS discovery
-	err = setupDiscovery(ctx, h)
-	if err != nil {
+	if err := setupDiscovery(h); err != nil {
 		panic(err)
 	}
 
@@ -103,11 +102,8 @@ func (n *discoveryNotifee) HandlePeerFound(pi peer.AddrInfo) {
 
 // setupDiscovery creates an mDNS discovery service and attaches it to the libp2p Host.
 // This lets us automatically discover peers on the same LAN and connect to them.
-func setupDiscovery(ctx context.Context, h host.Host) error {
+func setupDiscovery(h host.Host) error {
 	// setup mDNS discovery to find local peers
-	disc := mdns.NewMdnsService(h, DiscoveryServiceTag)
-
-	n := discoveryNotifee{h: h}
-	disc.RegisterNotifee(&n)
-	return nil
+	s := mdns.NewMdnsService(h, DiscoveryServiceTag, &discoveryNotifee{h: h})
+	return s.Start()
 }

p2p/discovery/mdns/mdns.go

@@ -26,9 +26,8 @@ const (
 var log = logging.Logger("mdns")
 
 type Service interface {
+	Start() error
 	io.Closer
-	RegisterNotifee(Notifee)
-	UnregisterNotifee(Notifee)
 }
 
 type Notifee interface {
@@ -40,30 +39,36 @@ type mdnsService struct {
 	serviceName string
 
 	// The context is canceled when Close() is called.
+	ctx       context.Context
 	ctxCancel context.CancelFunc
 
 	resolverWG sync.WaitGroup
 	server     *zeroconf.Server
 
-	mutex    sync.Mutex
-	notifees []Notifee
+	notifee Notifee
 }
 
-func NewMdnsService(host host.Host, serviceName string) *mdnsService {
-	ctx, cancel := context.WithCancel(context.Background())
+func NewMdnsService(host host.Host, serviceName string, notifee Notifee) *mdnsService {
 	if serviceName == "" {
 		serviceName = ServiceName
 	}
 	s := &mdnsService{
-		ctxCancel:   cancel,
 		host:        host,
 		serviceName: serviceName,
+		notifee:     notifee,
 	}
-	s.startServer()
-	s.startResolver(ctx)
+	s.ctx, s.ctxCancel = context.WithCancel(context.Background())
 	return s
 }
 
+func (s *mdnsService) Start() error {
+	if err := s.startServer(); err != nil {
+		return err
+	}
+	s.startResolver(s.ctx)
+	return nil
+}
+
 func (s *mdnsService) Close() error {
 	s.ctxCancel()
 	if s.server != nil {
@@ -176,13 +181,9 @@ func (s *mdnsService) startResolver(ctx context.Context) {
 				log.Debugf("failed to get peer info: %s", err)
 				continue
 			}
-			s.mutex.Lock()
 			for _, info := range infos {
-				for _, notif := range s.notifees {
-					go notif.HandlePeerFound(info)
-				}
+				go s.notifee.HandlePeerFound(info)
 			}
-			s.mutex.Unlock()
 		}
 	}()
 	go func() {
@@ -192,25 +193,3 @@ func (s *mdnsService) startResolver(ctx context.Context) {
 		}
 	}()
 }
-
-func (s *mdnsService) RegisterNotifee(n Notifee) {
-	s.mutex.Lock()
-	s.notifees = append(s.notifees, n)
-	s.mutex.Unlock()
-}
-
-func (s *mdnsService) UnregisterNotifee(n Notifee) {
-	s.mutex.Lock()
-	defer s.mutex.Unlock()
-
-	found := -1
-	for i, notif := range s.notifees {
-		if notif == n {
-			found = i
-			break
-		}
-	}
-	if found != -1 {
-		s.notifees = append(s.notifees[:found], s.notifees[found+1:]...)
-	}
-}

p2p/discovery/mdns/mdns_test.go

@@ -16,8 +16,8 @@ func setupMDNS(t *testing.T, notifee Notifee) peer.ID {
 	t.Helper()
 	host, err := libp2p.New(libp2p.ListenAddrStrings("/ip4/127.0.0.1/tcp/0"))
 	require.NoError(t, err)
-	s := NewMdnsService(host, "")
-	s.RegisterNotifee(notifee)
+	s := NewMdnsService(host, "", notifee)
+	require.NoError(t, s.Start())
 	t.Cleanup(func() {
 		host.Close()
 		s.Close()

p2p/discovery/mdns_legacy/mdns.go

@@ -3,6 +3,7 @@ package mdns_legacy
 import (
 	"context"
 	"errors"
+	"io"
 	"net"
 	"sync"
 	"time"
@@ -26,7 +27,12 @@ var log = logging.Logger("mdns_legacy")
 
 const ServiceTag = "_ipfs-discovery._udp"
 
-type Service = mdnsnew.Service
+type Service interface {
+	io.Closer
+	RegisterNotifee(Notifee)
+	UnregisterNotifee(Notifee)
+}
+
 type Notifee = mdnsnew.Notifee
 
 type mdnsService struct {