func membersFromStore(st store.Store) (map[types.ID]*Member, map[types.ID]bool) {
	members := make(map[types.ID]*Member)
	removed := make(map[types.ID]bool)
	e, err := st.Get(storeMembersPrefix, true, true)
	if err != nil {
		if isKeyNotFound(err) {
			return members, removed
		}
		plog.Panicf("get storeMembers should never fail: %v", err)
	}
	for _, n := range e.Node.Nodes {
		var m *Member
		m, err = nodeToMember(n)
		if err != nil {
			plog.Panicf("nodeToMember should never fail: %v", err)
		}
		members[m.ID] = m
	}

	e, err = st.Get(storeRemovedMembersPrefix, true, true)
	if err != nil {
		if isKeyNotFound(err) {
			return members, removed
		}
		plog.Panicf("get storeRemovedMembers should never fail: %v", err)
	}
	for _, n := range e.Node.Nodes {
		removed[mustParseMemberIDFromKey(n.Key)] = true
	}
	return members, removed
}

func mustDeleteMemberFromStore(s store.Store, id types.ID) {
	if _, err := s.Delete(MemberStoreKey(id), true, true); err != nil {
		plog.Panicf("delete member should never fail: %v", err)
	}
	if _, err := s.Create(RemovedMemberStoreKey(id), false, "", false, store.TTLOptionSet{ExpireTime: store.Permanent}); err != nil {
		plog.Panicf("create removedMember should never fail: %v", err)
	}
}

func clusterVersionFromStore(st store.Store) *semver.Version {
	e, err := st.Get(path.Join(StoreClusterPrefix, "version"), false, false)
	if err != nil {
		if isKeyNotFound(err) {
			return nil
		}
		plog.Panicf("unexpected error (%v) when getting cluster version from store", err)
	}
	return semver.Must(semver.NewVersion(*e.Node.Value))
}

func mustUpdateMemberInStore(s store.Store, m *Member) {
	b, err := json.Marshal(m.RaftAttributes)
	if err != nil {
		plog.Panicf("marshal raftAttributes should never fail: %v", err)
	}
	p := path.Join(MemberStoreKey(m.ID), raftAttributesSuffix)
	if _, err := s.Update(p, string(b), store.TTLOptionSet{ExpireTime: store.Permanent}); err != nil {
		plog.Panicf("update raftAttributes should never fail: %v", err)
	}
}

func writeStore(w io.Writer, st store.Store) uint64 {
	all, err := st.Get("/1", true, true)
	if err != nil {
		if eerr, ok := err.(*etcdErr.Error); ok && eerr.ErrorCode == etcdErr.EcodeKeyNotFound {
			fmt.Println("no v2 keys to migrate")
			os.Exit(0)
		}
		ExitWithError(ExitError, err)
	}
	return writeKeys(w, all.Node)
}

func traverseAndDeleteEmptyDir(st store.Store, dir string) error {
	e, err := st.Get(dir, true, false)
	if err != nil {
		return err
	}
	if len(e.Node.Nodes) == 0 {
		st.Delete(dir, true, true)
		return nil
	}
	for _, node := range e.Node.Nodes {
		if !node.Dir {
			glog.V(2).Infof("key: %s", node.Key[len(etcdserver.StoreKeysPrefix):])
		} else {
			err := traverseAndDeleteEmptyDir(st, node.Key)
			if err != nil {
				return err
			}
		}
	}
	return nil
}

func mustSaveClusterVersionToStore(s store.Store, ver *semver.Version) {
	if _, err := s.Set(StoreClusterVersionKey(), false, ver.String(), store.TTLOptionSet{ExpireTime: store.Permanent}); err != nil {
		plog.Panicf("save cluster version should never fail: %v", err)
	}
}