master: disconnect only the phantom volume server

fix https://github.com/chrislusf/seaweedfs/issues/2311

weed/server/master_grpc_server.go

@@ -22,7 +22,11 @@ func (ms *MasterServer) SendHeartbeat(stream master_pb.Seaweed_SendHeartbeatServ
 
 	defer func() {
 		if dn != nil {
-
+			dn.Counter--
+			if dn.Counter >  0 {
+				glog.V(0).Infof("disconnect phantom volume server %s:%d remaining %d", dn.Counter, dn.Ip, dn.Port)
+				return
+			}
 			// if the volume server disconnects and reconnects quickly
 			//  the unregister and register can race with each other
 			ms.Topo.UnRegisterDataNode(dn)
@@ -68,6 +72,7 @@ func (ms *MasterServer) SendHeartbeat(stream master_pb.Seaweed_SendHeartbeatServ
 			dc := ms.Topo.GetOrCreateDataCenter(dcName)
 			rack := dc.GetOrCreateRack(rackName)
 			dn = rack.GetOrCreateDataNode(heartbeat.Ip, int(heartbeat.Port), heartbeat.PublicUrl, heartbeat.MaxVolumeCounts)
+			dn.Counter++
 			glog.V(0).Infof("added volume server %v:%d", heartbeat.GetIp(), heartbeat.GetPort())
 			if err := stream.Send(&master_pb.HeartbeatResponse{
 				VolumeSizeLimit: uint64(ms.option.VolumeSizeLimitMB) * 1024 * 1024,

weed/topology/data_node.go

@@ -18,6 +18,7 @@ type DataNode struct {
 	Port      int
 	PublicUrl string
 	LastSeen  int64 // unix time in seconds
+	Counter   int   // in race condition, the previous dataNode was not dead
 }
 
 func NewDataNode(id string) *DataNode {