Fix https://github.com/chrislusf/seaweedfs/issues/830

weed/server/master_grpc_server.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"net"
 	"strings"
+	"time"
 
 	"github.com/chrislusf/raft"
 	"github.com/chrislusf/seaweedfs/weed/glog"
@@ -172,6 +173,7 @@ func (ms *MasterServer) KeepConnected(stream master_pb.Seaweed_KeepConnectedServ
 		}
 	}()
 
+	ticker := time.NewTicker(5 * time.Second)
 	for {
 		select {
 		case message := <-messageChan:
@@ -179,6 +181,10 @@ func (ms *MasterServer) KeepConnected(stream master_pb.Seaweed_KeepConnectedServ
 				glog.V(0).Infof("=> client %v: %+v", clientName, message)
 				return err
 			}
+		case <-ticker.C:
+			if !ms.Topo.IsLeader() {
+				return raft.NotLeaderError
+			}
 		case <-stopChan:
 			return nil
 		}