code: public function add(NodeConnectionInterface $connection)
      {
          $parameters = $connection->getParameters();
  
          if ('master' === $role = $parameters->role) {
              $this->master = $connection;
          } elseif ('sentinel' === $role) {
              $this->sentinels[] = $connection;
              // sentinels are not considered part of the pool.
              return;
          } else {
              // everything else is considered a slave.
              $this->slaves[] = $connection;
          }
  
          $this->pool[(string) $connection] = $connection;
  
          $this->reset();
      }
docs: {@inheritdoc}