ping and pong

synced-pool.go

@@ -162,6 +162,8 @@ const (
 	RemoteGrainChanged = uint16(4)
 	AckChange          = uint16(5)
 	AckError           = uint16(6)
+	Ping               = uint16(7)
+	Pong               = uint16(8)
 )
 
 func (p *SyncedPool) handleConnection(conn net.Conn) {
@@ -180,6 +182,13 @@ func (p *SyncedPool) handleConnection(conn net.Conn) {
 		// 	return
 		// }
 		switch packet.MessageType {
+		case Ping:
+			err = SendPacket(conn, Pong, func(w io.Writer) error {
+				return nil
+			})
+			if err != nil {
+				log.Printf("Error sending pong: %v\n", err)
+			}
 		case RemoteNegotiate:
 			negotiationCount.Inc()
 			data := make([]byte, packet.DataLength)
@@ -318,6 +327,20 @@ func (p *SyncedPool) AddRemoteWithConnection(address string, connection net.Conn
 	return p.addRemoteHost(address, remote)
 }
 
+func DoPing(connection net.Conn) error {
+	SendPacket(connection, Ping, func(w io.Writer) error {
+		return nil
+	})
+	t, _, err := ReceivePacket(connection)
+	if err != nil {
+		return err
+	}
+	if t != Pong {
+		return fmt.Errorf("unexpected message type %d", t)
+	}
+	return nil
+}
+
 func (p *SyncedPool) addRemoteHost(address string, remote RemoteHost) error {
 	for _, r := range p.remotes {
 		if r.Host == address {
@@ -326,6 +349,11 @@ func (p *SyncedPool) addRemoteHost(address string, remote RemoteHost) error {
 		}
 	}
 
+	err := DoPing(remote.connection)
+	if err != nil {
+		log.Printf("Error pinging remote %s: %v\n", address, err)
+	}
+
 	p.remotes = append(p.remotes, remote)
 	connectedRemotes.Set(float64(len(p.remotes)))
 	log.Printf("Added remote %s\n", remote.Host)