code: public function add(NodeConnectionInterface $connection)
      {
          $parameters = $connection->getParameters();
  
          if ('master' === $parameters->role) {
              $this->master = $connection;
          } else {
              // everything else is considered a slvave.
              $this->slaves[] = $connection;
          }
  
          if (isset($parameters->alias)) {
              $this->aliases[$parameters->alias] = $connection;
          }
  
          $this->pool[(string) $connection] = $connection;
  
          $this->reset();
      }
docs: {@inheritdoc}