AppEngine flexible environment memcached handling for sessions and doctrine cache

config_prod.yml

# .....
framework:
    validation:
        cache: validator.mapping.cache.doctrine.apc
    serializer:
        cache: serializer.mapping.cache.doctrine.apc
    session:
        handler_id: session.handler.memcached

# Doctrine Configuration
doctrine:
    dbal:
        driver:   pdo_mysql
        charset:  UTF8
    orm:
        metadata_cache_driver:
            type: service
            id: doctrine.cache.memcached
        result_cache_driver:
            type: service
            id: doctrine.cache.memcached
        query_cache_driver:
            type: service
            id: doctrine.cache.memcached

monolog:
    handlers:
        main:
            type: service
            id: vendor_infra.logging.handler.appengine

MemcachedFactory.php

<?php

namespace Vendor\InfraBundle\Cache;

use Memcached;
use Symfony\Component\DependencyInjection\ContainerAwareInterface;
use Symfony\Component\DependencyInjection\ContainerInterface;

/**
 * @package Vendor\InfraBundle\Cache
 */
class MemcachedFactory implements ContainerAwareInterface
{
    /**
     * @var ContainerInterface
     */
    protected $container;

    /**
     * @return Memcached
     */
    public function getInstance()
    {
        $host = getenv('MEMCACHE_PORT_11211_TCP_ADDR');
        $port = getenv('MEMCACHE_PORT_11211_TCP_PORT');

        $cache = new Memcached($this->container->getParameter('session_memcached_prefix'));
        $cache->addServer($host, $port);

        return $cache;
    }

    /**
     * @param ContainerInterface|null $container A ContainerInterface instance or null
     */
    public function setContainer(ContainerInterface $container = null)
    {
        $this->container = $container;
    }
}

services.yml

parameters:
    doctrine.cache.memcached.prefix: dqc
services:
    ##
    # Memcached factory
    ##
    vendor_infra.cache.memcached_factory:
        class: Vendor\InfraBundle\Cache\MemcachedFactory
        calls:
            - [ setContainer, [ '@service_container' ]]
    ##
    # Memcached Session
    ##
    session.memcached:
        class: Memcached
        factory: ['@vendor_infra.cache.memcached_factory', getInstance]
        arguments:
            persistent_id: '%session_memcached_prefix%'
    ##
    # Memcached Session Handler
    ##
    session.handler.memcached:
        class:     Symfony\Component\HttpFoundation\Session\Storage\Handler\MemcachedSessionHandler
        arguments: ['@session.memcached', { prefix: '%session_memcached_prefix%', expiretime: '%session_memcached_expire%' }]

    ##
    # Memcached Doctrine cache instance
    ##
    doctrine.cache.query.memcached:
        class: Memcached
        factory: ['@vendor_infra.cache.memcached_factory', getInstance]
        arguments:
            persistent_id: '%doctrine.cache.memcached.prefix%'

    ##
    # Memcached Doctrine cache
    ##
    doctrine.cache.memcached:
        class: Doctrine\Common\Cache\MemcachedCache
        calls:
            - [ setMemcached, [ '@doctrine.cache.query.memcached' ] ]