1. volume server now sends master server its max file key, so that

master server does not need to store the sequence on disk any more
2. fix raft server's failure to init cluster during bootstrapping

go/storage/store.go

@@ -44,6 +44,9 @@ func (mn *MasterNodes) findMaster() (string, error) {
 	if mn.lastNode < 0 {
 		for _, m := range mn.nodes {
 			if masters, e := operation.ListMasters(m); e == nil {
+				if len(masters) == 0 {
+					continue
+				}
 				mn.nodes = masters
 				mn.lastNode = rand.Intn(len(mn.nodes))
 				glog.V(2).Info("current master node is :", mn.nodes[mn.lastNode])
@@ -268,6 +271,7 @@ func (s *Store) Join() error {
 	}
 	stats := new([]*VolumeInfo)
 	maxVolumeCount := 0
+	var maxFileKey uint64
 	for _, location := range s.Locations {
 		maxVolumeCount = maxVolumeCount + location.MaxVolumeCount
 		for k, v := range location.volumes {
@@ -280,6 +284,9 @@ func (s *Store) Join() error {
 				DeletedByteCount: v.nm.DeletedSize(),
 				ReadOnly:         v.readOnly}
 			*stats = append(*stats, s)
+			if maxFileKey < v.nm.MaxFileKey() {
+				maxFileKey = v.nm.MaxFileKey()
+			}
 		}
 	}
 	bytes, _ := json.Marshal(stats)
@@ -292,6 +299,7 @@ func (s *Store) Join() error {
 	values.Add("publicUrl", s.PublicUrl)
 	values.Add("volumes", string(bytes))
 	values.Add("maxVolumeCount", strconv.Itoa(maxVolumeCount))
+	values.Add("maxFileKey", strconv.FormatUint(maxFileKey, 10))
 	values.Add("dataCenter", s.dataCenter)
 	values.Add("rack", s.rack)
 	jsonBlob, err := util.Post("http://"+masterNode+"/dir/join", values)