anchor.diff:  
   http_stats() ->
       [{listen, [{active, unwrap_metric_value(?METRIC_LISTEN_ACTIVE)},
  +               {not_active, unwrap_metric_value(?METRIC_LISTEN_FALSE)},
                  {once, unwrap_metric_value(?METRIC_LISTEN_ONCE)}]},
        {auth, [{error, unwrap_metric_value(?METRIC_AUTH_ERROR)},
                {success, unwrap_metric_value(?METRIC_AUTH_SUCCESS)}]},
  
positive.code: auth_error()    -> exometer:update(?METRIC_AUTH_ERROR, 1).
  auth_success() -> exometer:update(?METRIC_AUTH_SUCCESS, 1).
  
  listen_connect(once) -> exometer:update(?METRIC_LISTEN_ONCE, 1);
  listen_connect(true) -> exometer:update(?METRIC_LISTEN_ACTIVE, 1).
  
  listen_disconnect(once) -> exometer:update(?METRIC_LISTEN_ONCE, -1);
  listen_disconnect(true) -> exometer:update(?METRIC_LISTEN_ACTIVE, -1).
  
  core_ping()         -> exometer:update(?METRIC_CORE_PING, 1).
  core_put()          -> exometer:update(?METRIC_CORE_PUT, 1).
  
negative.code: 
      exometer:new(?METRIC_LISTEN_ONCE, counter, []),
      exometer:new(?METRIC_LISTEN_ACTIVE, counter, []),
      exometer:new(?METRIC_LISTEN_FALSE, counter, []),
  
      exometer:new(?METRIC_CORE_PING, spiral, [{time_span, 60000}]),
      exometer:new(?METRIC_CORE_PUT, spiral, [{time_span, 60000}]),
  