code: function onerror(err) {
      if (!err) {
        return;
      }
      debug('[%s] [cfork:master:%s] master uncaughtException: %s', Date(), process.pid, err.stack);
      debug(err);
      debug('(total %d disconnect, %d unexpected exit)', disconnectCount, unexpectedCount);
    }
docs: uncaughtException default handler