anchor.diff:  
   %% @doc add an appender into the ets
   %%
  --spec add_appender(atom(), atom()) ->
  -             ok.
  +-spec(add_appender(atom(), atom()) ->
  +             ok).
   add_appender(GroupId, LoggerId) ->
       catch ets:insert(?ETS_LOGGER_GROUP, {GroupId, LoggerId}),
       ok.
  
positive.code:     case supervisor:start_child(leo_logger_sup, ChildSpec) of
          {ok, _Pid} ->
              start_child_1(Id);
          {error, {already_started, _Pid}} ->
              start_child_1(Id);
          Error ->
              Error
      end.
  
  %% @private
  -spec start_child_1(atom()) ->
       'ok' | {'error',_} | {'ok','undefined' | pid(),_}.
  start_child_1(Id)->
      RotatorId = list_to_atom(lists:append([atom_to_list(Id),"_rotator"])),
      ChildSpec = {RotatorId,
  
negative.code: %%--------------------------------------------------------------------
  %% @doc Start object storage application.
  %%
  -spec(start_app() ->
               ok | {error, any()}).
  start_app() ->
      Module = leo_logger,
      case whereis(leo_logger_sup) of
          undefined ->
              case application:start(Module) of
                  ok ->
                      ?ETS_LOGGER_GROUP = ets:new(?ETS_LOGGER_GROUP,
                                                  [named_table, bag, public, {read_concurrency,true}]),
                      ok;
                  {error,{{already_started,_},_}} ->
                      ?debugVal(already_started),
                      ok;
                  {error, {already_started,_}} ->
                      ?debugVal(already_started),
                      ok;
                  Error ->
                      ?debugVal(Error),
                      Error
              end;
          _ ->
              ok
      end.
  
  
  %% @doc Launch a child worker
  %% @private
  -spec(start_child(atom(), log_appender(), atom(), [_]) ->
               ok | {error, any()}).
  start_child(Id, Appender, Callback, Props) ->
      ChildSpec = {Id,
                   {leo_logger_server, start_link,
  