anchor.diff:  -define(METRIC_AUTH_SUCCESS, [iorio, auth, success]).
   -define(METRIC_LISTEN_ONCE, [iorio, listen, active, once]).
   -define(METRIC_LISTEN_ACTIVE, [iorio, listen, active, active]).
  +-define(METRIC_LISTEN_FALSE, [iorio, listen, active, not_active]).
   -define(METRIC_HTTP_ACTIVE_REQS, [iorio, api, http, active_requests]).
   -define(METRIC_HTTP_REQ_TIME, [iorio, api, http, req_time]).
   
  
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:      {list_streams, unwrap_metric_value(?METRIC_CORE_LIST_STREAMS)},
       {truncate, unwrap_metric_value(?METRIC_CORE_TRUNCATE)},
       {msg_size, unwrap_metric_value(?METRIC_CORE_MSG_SIZE)}].
  
  to_string(V) when is_atom(V) -> atom_to_list(V);
  to_string(V) when is_integer(V) -> integer_to_list(V).
  