diff --git a/weed/command/master.go b/weed/command/master.go
index 6ef511742..908299c8a 100644
--- a/weed/command/master.go
+++ b/weed/command/master.go
@@ -206,11 +206,13 @@ func startMaster(masterOption MasterOptions, masterWhiteList []string) {
 	if !*m.raftHashicorp {
 		go func() {
 			time.Sleep(timeSleep)
-			if ms.Topo.RaftServer.Leader() == "" && ms.Topo.RaftServer.IsLogEmpty() && isTheFirstOne(myMasterAddress, peers) {
-				if ms.MasterClient.FindLeaderFromOtherPeers(myMasterAddress) == "" {
-					raftServer.DoJoinCommand()
-				}
+
+			ms.Topo.RaftServerAccessLock.RLock()
+			isEmptyMaster := ms.Topo.RaftServer.Leader() == "" && ms.Topo.RaftServer.IsLogEmpty()
+			if isEmptyMaster && isTheFirstOne(myMasterAddress, peers) && ms.MasterClient.FindLeaderFromOtherPeers(myMasterAddress) == "" {
+				raftServer.DoJoinCommand()
 			}
+			ms.Topo.RaftServerAccessLock.RUnlock()
 		}()
 	}
 
diff --git a/weed/server/master_grpc_server_raft.go b/weed/server/master_grpc_server_raft.go
index 45a6c7a7e..7f8ad70df 100644
--- a/weed/server/master_grpc_server_raft.go
+++ b/weed/server/master_grpc_server_raft.go
@@ -3,7 +3,9 @@ package weed_server
 import (
 	"context"
 	"fmt"
+
 	"github.com/hashicorp/raft"
+
 	"github.com/seaweedfs/seaweedfs/weed/cluster"
 	"github.com/seaweedfs/seaweedfs/weed/pb/master_pb"
 )
@@ -11,11 +13,14 @@ import (
 func (ms *MasterServer) RaftListClusterServers(ctx context.Context, req *master_pb.RaftListClusterServersRequest) (*master_pb.RaftListClusterServersResponse, error) {
 	resp := &master_pb.RaftListClusterServersResponse{}
 
+	ms.Topo.RaftServerAccessLock.RLock()
 	if ms.Topo.HashicorpRaft == nil {
+		ms.Topo.RaftServerAccessLock.RUnlock()
 		return resp, nil
 	}
 
 	servers := ms.Topo.HashicorpRaft.GetConfiguration().Configuration().Servers
+	ms.Topo.RaftServerAccessLock.RUnlock()
 
 	for _, server := range servers {
 		resp.ClusterServers = append(resp.ClusterServers, &master_pb.RaftListClusterServersResponse_ClusterServers{
@@ -30,6 +35,9 @@ func (ms *MasterServer) RaftListClusterServers(ctx context.Context, req *master_
 func (ms *MasterServer) RaftAddServer(ctx context.Context, req *master_pb.RaftAddServerRequest) (*master_pb.RaftAddServerResponse, error) {
 	resp := &master_pb.RaftAddServerResponse{}
 
+	ms.Topo.RaftServerAccessLock.RLock()
+	defer ms.Topo.RaftServerAccessLock.RUnlock()
+
 	if ms.Topo.HashicorpRaft == nil {
 		return resp, nil
 	}
@@ -54,6 +62,9 @@ func (ms *MasterServer) RaftAddServer(ctx context.Context, req *master_pb.RaftAd
 func (ms *MasterServer) RaftRemoveServer(ctx context.Context, req *master_pb.RaftRemoveServerRequest) (*master_pb.RaftRemoveServerResponse, error) {
 	resp := &master_pb.RaftRemoveServerResponse{}
 
+	ms.Topo.RaftServerAccessLock.RLock()
+	defer ms.Topo.RaftServerAccessLock.RUnlock()
+
 	if ms.Topo.HashicorpRaft == nil {
 		return resp, nil
 	}
diff --git a/weed/server/master_server.go b/weed/server/master_server.go
index feee59455..ecbfd64af 100644
--- a/weed/server/master_server.go
+++ b/weed/server/master_server.go
@@ -166,6 +166,8 @@ func NewMasterServer(r *mux.Router, option *MasterOption, peers map[string]pb.Se
 
 func (ms *MasterServer) SetRaftServer(raftServer *RaftServer) {
 	var raftServerName string
+
+	ms.Topo.RaftServerAccessLock.Lock()
 	if raftServer.raftServer != nil {
 		ms.Topo.RaftServer = raftServer.raftServer
 		ms.Topo.RaftServer.AddEventListener(raft.LeaderChangeEventType, func(e raft.Event) {
@@ -193,14 +195,18 @@ func (ms *MasterServer) SetRaftServer(raftServer *RaftServer) {
 		}()
 		raftServerName = ms.Topo.HashicorpRaft.String()
 	}
+	ms.Topo.RaftServerAccessLock.Unlock()
+
 	if ms.Topo.IsLeader() {
 		glog.V(0).Infoln("[", raftServerName, "]", "I am the leader!")
 	} else {
+		ms.Topo.RaftServerAccessLock.RLock()
 		if ms.Topo.RaftServer != nil && ms.Topo.RaftServer.Leader() != "" {
 			glog.V(0).Infoln("[", ms.Topo.RaftServer.Name(), "]", ms.Topo.RaftServer.Leader(), "is the leader.")
 		} else if ms.Topo.HashicorpRaft != nil && ms.Topo.HashicorpRaft.Leader() != "" {
 			glog.V(0).Infoln("[", ms.Topo.HashicorpRaft.String(), "]", ms.Topo.HashicorpRaft.Leader(), "is the leader.")
 		}
+		ms.Topo.RaftServerAccessLock.RUnlock()
 	}
 }
 
@@ -210,16 +216,15 @@ func (ms *MasterServer) proxyToLeader(f http.HandlerFunc) http.HandlerFunc {
 			f(w, r)
 			return
 		}
-		var raftServerLeader string
-		if ms.Topo.RaftServer != nil && ms.Topo.RaftServer.Leader() != "" {
-			raftServerLeader = ms.Topo.RaftServer.Leader()
-		} else if ms.Topo.HashicorpRaft != nil && ms.Topo.HashicorpRaft.Leader() != "" {
-			raftServerLeader = string(ms.Topo.HashicorpRaft.Leader())
-		}
+
+		// get the current raft leader
+		leaderAddr, _ := ms.Topo.MaybeLeader()
+		raftServerLeader := string(leaderAddr)
 		if raftServerLeader == "" {
 			f(w, r)
 			return
 		}
+
 		ms.boundedLeaderChan <- 1
 		defer func() { <-ms.boundedLeaderChan }()
 		targetUrl, err := url.Parse("http://" + raftServerLeader)
@@ -228,6 +233,8 @@ func (ms *MasterServer) proxyToLeader(f http.HandlerFunc) http.HandlerFunc {
 				fmt.Errorf("Leader URL http://%s Parse Error: %v", raftServerLeader, err))
 			return
 		}
+
+		// proxy to leader
 		glog.V(4).Infoln("proxying to leader", raftServerLeader)
 		proxy := httputil.NewSingleHostReverseProxy(targetUrl)
 		director := proxy.Director
@@ -336,6 +343,9 @@ func (ms *MasterServer) createSequencer(option *MasterOption) sequence.Sequencer
 }
 
 func (ms *MasterServer) OnPeerUpdate(update *master_pb.ClusterNodeUpdate, startFrom time.Time) {
+	ms.Topo.RaftServerAccessLock.RLock()
+	defer ms.Topo.RaftServerAccessLock.RUnlock()
+
 	if update.NodeType != cluster.MasterType || ms.Topo.HashicorpRaft == nil {
 		return
 	}
diff --git a/weed/server/master_server_handlers_ui.go b/weed/server/master_server_handlers_ui.go
index e377a0e19..2c6fa3474 100644
--- a/weed/server/master_server_handlers_ui.go
+++ b/weed/server/master_server_handlers_ui.go
@@ -16,6 +16,10 @@ func (ms *MasterServer) uiStatusHandler(w http.ResponseWriter, r *http.Request)
 	infos := make(map[string]interface{})
 	infos["Up Time"] = time.Now().Sub(startTime).String()
 	infos["Max Volume Id"] = ms.Topo.GetMaxVolumeId()
+
+	ms.Topo.RaftServerAccessLock.RLock()
+	defer ms.Topo.RaftServerAccessLock.RUnlock()
+
 	if ms.Topo.RaftServer != nil {
 		args := struct {
 			Version           string
diff --git a/weed/topology/topology.go b/weed/topology/topology.go
index 546642841..35224d280 100644
--- a/weed/topology/topology.go
+++ b/weed/topology/topology.go
@@ -43,10 +43,11 @@ type Topology struct {
 
 	Configuration *Configuration
 
-	RaftServer     raft.Server
-	HashicorpRaft  *hashicorpRaft.Raft
-	UuidAccessLock sync.RWMutex
-	UuidMap        map[string][]string
+	RaftServer           raft.Server
+	RaftServerAccessLock sync.RWMutex
+	HashicorpRaft        *hashicorpRaft.Raft
+	UuidAccessLock       sync.RWMutex
+	UuidMap              map[string][]string
 }
 
 func NewTopology(id string, seq sequence.Sequencer, volumeSizeLimit uint64, pulse int, replicationAsMin bool) *Topology {
@@ -73,6 +74,9 @@ func NewTopology(id string, seq sequence.Sequencer, volumeSizeLimit uint64, puls
 }
 
 func (t *Topology) IsLeader() bool {
+	t.RaftServerAccessLock.RLock()
+	defer t.RaftServerAccessLock.RUnlock()
+
 	if t.RaftServer != nil {
 		if t.RaftServer.State() == raft.Leader {
 			return true
@@ -90,23 +94,35 @@ func (t *Topology) IsLeader() bool {
 	return false
 }
 
-func (t *Topology) Leader() (pb.ServerAddress, error) {
-	var l pb.ServerAddress
+func (t *Topology) Leader() (l pb.ServerAddress, err error) {
 	for count := 0; count < 3; count++ {
-		if t.RaftServer != nil {
-			l = pb.ServerAddress(t.RaftServer.Leader())
-		} else if t.HashicorpRaft != nil {
-			l = pb.ServerAddress(t.HashicorpRaft.Leader())
-		} else {
-			return "", errors.New("Raft Server not ready yet!")
+		l, err = t.MaybeLeader()
+		if err != nil {
+			return
 		}
 		if l != "" {
 			break
-		} else {
-			time.Sleep(time.Duration(5+count) * time.Second)
 		}
+
+		time.Sleep(time.Duration(5+count) * time.Second)
+	}
+
+	return
+}
+
+func (t *Topology) MaybeLeader() (l pb.ServerAddress, err error) {
+	t.RaftServerAccessLock.RLock()
+	defer t.RaftServerAccessLock.RUnlock()
+
+	if t.RaftServer != nil {
+		l = pb.ServerAddress(t.RaftServer.Leader())
+	} else if t.HashicorpRaft != nil {
+		l = pb.ServerAddress(t.HashicorpRaft.Leader())
+	} else {
+		err = errors.New("Raft Server not ready yet!")
 	}
-	return l, nil
+
+	return
 }
 
 func (t *Topology) Lookup(collection string, vid needle.VolumeId) (dataNodes []*DataNode) {
@@ -136,6 +152,10 @@ func (t *Topology) Lookup(collection string, vid needle.VolumeId) (dataNodes []*
 func (t *Topology) NextVolumeId() (needle.VolumeId, error) {
 	vid := t.GetMaxVolumeId()
 	next := vid.Next()
+
+	t.RaftServerAccessLock.RLock()
+	defer t.RaftServerAccessLock.RUnlock()
+
 	if t.RaftServer != nil {
 		if _, err := t.RaftServer.Do(NewMaxVolumeIdCommand(next)); err != nil {
 			return 0, err