public function getCluster($name, $db = 0, $replicas = 128, $selectRandomSlave = true, $writeOnly = false)
{
if (!isset($this->_cluster[$name])) {
$this->_cluster[$name] = $this->createCluster($name, $db, $replicas, $selectRandomSlave, $writeOnly);
}
return $this->_cluster[$name];
}