func (s *EtcdServer) AddMember(ctx context.Context, memb membership.Member) ([]*membership.Member, error) {
    if err := s.checkMembershipOperationPermission(ctx); err != nil {
        return nil, err
    }

    if s.Cfg.StrictReconfigCheck {
        // by default StrictReconfigCheck is enabled; reject new members if unhealthy
        if !s.cluster.IsReadyToAddNewMember() {
            if lg := s.getLogger(); lg != nil {
                lg.Warn(
                    "rejecting member add request; not enough healthy members",
                    zap.String("local-member-id", s.ID().String()),
                    zap.String("requested-member-add", fmt.Sprintf("%+v", memb)),
                    zap.Error(ErrNotEnoughStartedMembers),
                )
            } else {
                plog.Warningf("not enough started members, rejecting member add %+v", memb)
            }
            return nil, ErrNotEnoughStartedMembers
        }

        if !isConnectedFullySince(s.r.transport, time.Now().Add(-HealthInterval), s.ID(), s.cluster.Members()) {
            if lg := s.getLogger(); lg != nil {
                lg.Warn(
                    "rejecting member add request; local member has not been connected to all peers, reconfigure breaks active quorum",
                    zap.String("local-member-id", s.ID().String()),
                    zap.String("requested-member-add", fmt.Sprintf("%+v", memb)),
                    zap.Error(ErrUnhealthy),
                )
            } else {
                plog.Warningf("not healthy for reconfigure, rejecting member add %+v", memb)
            }
            return nil, ErrUnhealthy
        }
    }

    // TODO: move Member to protobuf type
    b, err := json.Marshal(memb)
    if err != nil {
        return nil, err
    }
    cc := raftpb.ConfChange{
        Type:    raftpb.ConfChangeAddNode,
        NodeID:  uint64(memb.ID),
        Context: b,
    }
    return s.configure(ctx, cc)
}