doctrine 2 master slave connection (switch connection)

<?php

$conn = \Doctrine\DBAL\DriverManager::getConnection(array(
        'wrapperClass' => 'Doctrine\DBAL\Connections\MasterSlaveConnection',
        'driver' => 'pdo_mysql',
        'keepSlave' => true,
        'master' => array(
            'user'     => 'ideato',
            'password' => 'ideato',
            'dbname'   => 'db_ideato'
        ),
        'slaves' => array(
            array(
                'user' => 'ideato',
                'password' => 'ideato',
                'dbname' => 'db_ideato_slave'
            )
        )
    )
);
$entityManager = EntityManager::create($conn, $config);

//read on slave
$productRepository = $entityManager->getRepository('Product');
$products = $productRepository->findAll();

//write on master
$product = new Product();
$product->setName("nuovo_prod1");
$product->setCategory("oeeooeoe");
$entityManager->persist($product);
$entityManager->flush();
echo "Created Product with ID " . $product->getId() . "\n";
//now connection remains on master

//get masterslave connection
$masterSlaveConn = $entityManager->getConnection();
$masterSlaveConn->getWrappedConnection();

//switch connection on slave
$masterSlaveConn->connect('slave');
var_dump($masterSlaveConn->isConnectedToMaster()); //false

//read on slave
$productRepository = $entityManager->getRepository('Product');
$products = $productRepository->findAll();
foreach ($products as $product) {
    echo sprintf("-%s\n", $product->getName());
}

//switch connection on master
$masterSlaveConn->connect('master');
//read on master
$productRepository = $entityManager->getRepository('Product');
$products = $productRepository->findAll();
foreach ($products as $product) {
    echo sprintf("-%s\n", $product->getName());
}
var_dump($masterSlaveConn->isConnectedToMaster()) ;//true

//switch connection on slave
$masterSlaveConn->connect('slave');
//read on slave
$productRepository = $entityManager->getRepository('Product');
$products = $productRepository->findAll();
foreach ($products as $product) {
//    echo sprintf("-%s\n", $product->getName());
}
var_dump($masterSlaveConn->isConnectedToMaster()); //false