code: protected function logSuccessfulRegistration(array $reg)
      {
          $this->getLogger()->info(
              "New registration: {name} ({email}) from {addr}",
              array(
                  "name" => $reg["username"],
                  "email" => $reg["email"],
                  "addr" => $_SERVER['REMOTE_ADDR']
              )
          );
          
          // Log the amount of users on each 10% of the maximum capacity
          $max = $this->config["maxUsers"];
          $count = $this->storage->getUsersCount()+1;
          if ($count % ceil($max/10) === 0) {
              $percent = intval($count/ceil($max/100));
              $this->getLogger()->warning(
                  "The amount of users has reached {percent} of the maximum capacity {max}.",
                  array(
                      "percent" => $percent,
                      "max" => $max
                  )
              );
          }
      }
docs: Logs successful registration
  
  @param array $reg Registration array