anchor.diff:      case start_bench_child(Params, State) of
           {ok, Id, NewState} ->
               {reply, {ok, #{id => Id, status => <<"pending">>}}, NewState};
  -        {error, Reason} ->
  -            {reply, {error, Reason}, State}
  +        {error, Reason, NewState} ->
  +            {reply, {error, Reason}, NewState}
       end;
   
   handle_call({start_bench, Params}, _From, #{status:= inactive} = State) ->
  
positive.code:             case start_bench_child(Params, State) of
                  {ok, Id, NewState} ->
                      {reply, {ok, #{id => Id, status => <<"pending">>}}, NewState};
                  {error, Reason} ->
                      {reply, {error, Reason}, State}
              end;
          {error, enoent} ->
              {reply, {error, not_found}, State};
  
negative.code:             NewState = State#{next_id => Id + 1, monitors => maps:put(Mon, Id, Mons)},
              {ok, Id, check_max_bench_num(NewState)};
          {error, Reason} ->
              {error, Reason, State#{next_id => Id + 1}}
      end.
  
  check_max_bench_num(#{max_bench_num:= MaxNum, next_id:= NextId, data_dir:= Dir} = State) ->
  