anchor.diff:  %% Messages sent and received of broker
   %%------------------------------------------------------------------------------
   -define(SYSTOP_MESSAGES, [
  -    'messages/received',    % Messages received
  -    'messages/sent',        % Messages sent
  -    'messages/retained',    % Messagea retained
  -    'messages/stored',      % Messages stored
  -    'messages/dropped'      % Messages dropped
  +    'messages/received',      % Messages received
  +    'messages/sent',          % Messages sent
  +    'messages/retained/count',% Messagea retained
  +    'messages/stored',        % Messages stored
  +    'messages/dropped'        % Messages dropped
   ]).
   
  -
  
positive.code: %%% SOFTWARE.
  %%%-----------------------------------------------------------------------------
  %%% @doc
  %%% emqtt system topics.
  %%%
  %%% @end
  %%%-----------------------------------------------------------------------------
  
negative.code:     version,      % Broker version
      uptime,       % Broker uptime
      datetime,     % Broker local datetime
      sysdescr      % Broker description
  ]).
  
  %%------------------------------------------------------------------------------
  %% $SYS Topics for Clients
  %%------------------------------------------------------------------------------
  -define(SYSTOP_CLIENTS, [
      'clients/count',         % clients connected current
      'clients/max'            % max clients connected
      %'clients/connected',     
      %'clients/disconnected',  
  ]).
  
  %%------------------------------------------------------------------------------
  %% $SYS Topics for Sessions
  %%------------------------------------------------------------------------------
  -define(SYSTOP_SESSIONS, [
      'sessions/count',
      'sessions/max'
  ]).
  
  %%------------------------------------------------------------------------------
  %% $SYS Topics for Subscribers
  %%------------------------------------------------------------------------------
  -define(SYSTOP_PUBSUB, [
      'topics/count',        % ...
      'subscribers/count',   % ...
      'subscribers/max'      % ...
  ]).
  
  %%------------------------------------------------------------------------------
  %% Bytes sent and received of Broker
  