Zend Framework 2 - Session Memcached Configuration with Failover

Application\config\module.config.php

<?php
    'service_manager' => array(
        'factories' => [
            'Zend\Session\SessionManager' => 'Zend\Session\Service\SessionManagerFactory',
            'Zend\Session\Config\ConfigInterface' => 'Zend\Session\Service\SessionConfigFactory',
        ],
    ),
?>

Application\Service\MemcachedStorageFactory.php

<?php
namespace Application\Service;

use Zend\Cache\Storage\Adapter\MemcachedOptions;
use Zend\Cache\Storage\Adapter\MemcachedResourceManager;
use Zend\Cache\StorageFactory;
use Zend\ServiceManager\FactoryInterface;
use Zend\ServiceManager\ServiceLocatorInterface;
use Zend\Session\SaveHandler\Cache;

class MemcachedStorageFactory implements FactoryInterface
{
    /**
     * Create service
     *
     * @param ServiceLocatorInterface $serviceLocator
     * @return mixed
     */
    public function createService(ServiceLocatorInterface $serviceLocator)
    {
        $memcachedResourceManager = new MemcachedResourceManager();
        $memcachedResourceManager->addServers('default', $serviceLocator->get('Config')['memcached_session']['servers']);
        $memcachedResourceManager->setLibOptions('default', $serviceLocator->get('Config')['memcached_session']['lib_options']);

        $memcachedOptions = new MemcachedOptions();
        $memcachedOptions->setResourceManager($memcachedResourceManager);

        $adapter = StorageFactory::adapterFactory('memcached', $memcachedOptions);

        return new Cache($adapter);
    }

}

memcached.local.php

<?php
return [

    'session_storage' => [
        'type' => 'Zend\Session\Storage\SessionArrayStorage'
    ],

    'session_config' => [
        'use_cookies' => true,
        'hash_function' => 'sha1'
    ],

    'session_manager' => [

        'validators' => array(
            'Zend\Session\Validator\RemoteAddr',
            'Zend\Session\Validator\HttpUserAgent',
        ),
    ],

    'memcached_session' => [

        'enabled' => true,

        'servers' => [
            '127.0.0.1:11201',
            '127.0.0.1:11202',
            '127.0.0.1:12114',
            '127.0.0.1:11211',
            '127.0.0.1:11212',
            '127.0.0.1:11219',
        ],
        'lib_options' => [
            \Memcached::OPT_CONNECT_TIMEOUT => 10,
            \Memcached::OPT_REMOVE_FAILED_SERVERS => true,
            // set it to consistent hashing. If one memcached node is dead, its keys (and only its keys) will be evenly distributed to other nodes.
            // This is where the magic is done. This is really different from removing one server in your ->addServers() call.
            \Memcached::OPT_DISTRIBUTION => \Memcached::DISTRIBUTION_CONSISTENT,
            \Memcached::OPT_SERVER_FAILURE_LIMIT => 5,
            \Memcached::OPT_REMOVE_FAILED_SERVERS => true,
            \Memcached::OPT_RETRY_TIMEOUT => 1,
        ]
    ]


];

Module.php

<?php
/**
 * Zend Framework (http://framework.zend.com/)
 *
 * @link      http://github.com/zendframework/ZendSkeletonApplication for the canonical source repository
 * @copyright Copyright (c) 2005-2015 Zend Technologies USA Inc. (http://www.zend.com)
 * @license   http://framework.zend.com/license/new-bsd New BSD License
 */

namespace Application;

use Zend\ModuleManager\Listener\ConfigListener;
use Zend\ModuleManager\ModuleEvent;
use Zend\ModuleManager\ModuleManager;
use Zend\Mvc\ModuleRouteListener;
use Zend\Mvc\MvcEvent;

class Module
{

    public function init(ModuleManager $moduleManager)
    {
        $events = $moduleManager->getEventManager();
        $events->attach(ModuleEvent::EVENT_MERGE_CONFIG, array($this, 'onMergeConfig'));
    }

    public function onBootstrap(MvcEvent $e)
    {
        $eventManager        = $e->getApplication()->getEventManager();
        $moduleRouteListener = new ModuleRouteListener();
        $moduleRouteListener->attach($eventManager);


        $sessionManager = $e->getApplication()->getServiceManager()->get('Zend\Session\SessionManager');
        $sessionManager->start();
    }

    public function onMergeConfig($e)
    {
        $configListener = $e->getConfigListener();
        $config         = $configListener->getMergedConfig(false);

        // inject dependency for memcache factory interface, when memcached is enabled in config
        if ($config['memcached_session']['enabled'] == true) {
            $config['service_manager']['factories']['Zend\Session\SaveHandler\SaveHandlerInterface'] = 'Application\Service\MemcachedStorageFactory';
        }

        // Pass the changed configuration back to the listener:
        $configListener->setMergedConfig($config);
    }

    public function getConfig()
    {
        return include __DIR__ . '/config/module.config.php';
    }


    public function getAutoloaderConfig()
    {
        return array(
            'Zend\Loader\StandardAutoloader' => array(
                'namespaces' => array(
                    __NAMESPACE__ => __DIR__ . '/src/' . __NAMESPACE__,
                ),
            ),
        );
    }
}