Internal convenience method that returns the instance of the Memcached
Memcached
\RuntimeException
protected function getMemcached() {
  if (null === $this->memcached) {
    if (!preg_match('#^memcached://(?(?=\\[.*\\])\\[(.*)\\]|(.*)):(.*)$#', $this->dsn, $matches)) {
      throw new \RuntimeException(sprintf('Please check your configuration. You are trying to use Memcached with an invalid dsn "%s". The expected format is "memcached://[host]:port".', $this->dsn));
    }
    $host = $matches[1] ?: $matches[2];
    $port = $matches[3];
    $memcached = new Memcached();
    //disable compression to allow appending
    $memcached
      ->setOption(Memcached::OPT_COMPRESSION, false);
    $memcached
      ->addServer($host, $port);
    $this->memcached = $memcached;
  }
  return $this->memcached;
}