anchor.diff:  
           {graph, #{title => "Report interval",
                     units => "sec",
  -                  metrics => [{metric_name("interval", N), gauge} || N <- Nodes]}}]}].
  +                  metrics => [{metric_name("interval", N), gauge} || N <- Nodes]}}]},
  +     {group, "MZBench Internals", [
  +        {graph, #{title => "Mailbox messages",
  +                  metrics => [{metric_name("message_queue", N), gauge} || N <- Nodes]}}
  +        ]}].
   
   %% gen_server callbacks
   
   init([]) ->
       lager:info("~p started on node ~p", [?MODULE, node()]),
  +    _ = spawn_link(fun mailbox_len_reporter/0),
       erlang:send_after(interval(), self(), trigger),
       {ok, #state{last_rx_bytes = not_available,
           last_tx_bytes = not_available,
  
positive.code: 
  %% Internal functions
  
  metric_name(GaugeName) ->
      metric_name(GaugeName, atom_to_list(node())).
  
  
negative.code:         State
      end,
  
      ok = mzb_metrics:notify({metric_name("process_count"), gauge}, erlang:system_info(process_count)),
  
      %lager:info("System load at ~p: cpu ~p, la ~p, ram ~p", [node(), Cpu, La1, AllocatedMem / TotalMem]),
      erlang:send_after(interval(), self(), trigger),
      {noreply, NewState#state{last_trigger_timestamp = Now}};
  