anchor.diff:  %% <p>
   %% gen_server callback - Module:handle_info(Info, State) -> Result.
   %% </p>
  -handle_info(Info, #state{cur  = #ring_info{ring_group_list = CurRing },
  -                         prev = #ring_info{ring_group_list = PrevRing}} = State) ->
  -    case Info of
  -        {mnesia_table_event, {write, El,_}} ->
  -            NodeStatus = erlang:element(8, El),
  -            case NodeStatus of
  -                ?STATE_RUNNING when CurRing  == [];
  -                                    CurRing  == undefined;
  -                                    PrevRing == [];
  -                                    PrevRing == undefined ->
  -                    ok;
  -                ?STATE_RUNNING ->
  -                    %% exists an attached node in ring?
  -                    Table = erlang:element(1, El),
  -                    Node  = erlang:element(2, El),
  -                    VNodeList = get_vnode_list(Table, CurRing, PrevRing),
  -                    case find_node_from_ring(VNodeList, Node) of
  -                        ok ->
  -                            void;
  -                        not_found ->
  -                            timer:apply_after(100, leo_redundant_manager_api, create, [])
  -                    end;
  -                _ ->
  -                    ok
  -            end;
  -        {mnesia_table_event, {delete, El,_}} ->
  -            case (CurRing  == [] orelse
  -                  PrevRing == [] orelse
  -                  CurRing  == undefined orelse
  -                  PrevRing == undefined) of
  -                true ->
  -                    timer:apply_after(100, leo_redundant_manager_api, create, []),
  -                    ok;
  -                false ->
  -                    %% exists a detached node in ring?
  -                    Table = erlang:element(1, El),
  -                    Node  = erlang:element(2, El),
  -                    VNodeList = get_vnode_list(Table, CurRing, PrevRing),
  -                    case find_node_from_ring(VNodeList, Node) of
  -                        ok ->
  -                            timer:apply_after(100, leo_redundant_manager_api, create, []);
  -                        not_found ->
  -                            ok
  -                    end
  -            end;
  -        _ ->
  -            ok
  -    end,
  +handle_info(_Info, State) ->
       {noreply, State}.
   
   %% @doc This function is called by a gen_server when it is about to
  
positive.code:     {reply, ok, State};
  
  handle_call(subscribe,_From, State) ->
      mnesia:subscribe({table, ?MEMBER_TBL_CUR,  simple}),
      mnesia:subscribe({table, ?MEMBER_TBL_PREV, simple}),
      {reply, ok, State};
  
  handle_call(_Handle, _From, State) ->
  
negative.code:     State#state.prev;
  ring_info(_,_) ->
      {error, invalid_table}.
  