doctrine:
  dbal:
    default_connection: default
    connections:
      default:
          driver:   pdo_mysql
          host:     "%database_host%"
          port:     "%database_port%"
          dbname:   "%database_name%"
          user:     "%database_user%"
          password: "%database_password%"
          charset:  UTF8
      dbsync:
          driver:   pdo_mysql
          host:     "%database_sync_host%"
          port:     "%database_sync_port%"
          dbname:   "%database_sync_name%"
          user:     "%database_sync_user%"
          password: "%database_sync_password%"
          charset:  UTF8

  orm:
    auto_generate_proxy_classes: "%kernel.debug%"
    naming_strategy: doctrine.orm.naming_strategy.underscore
    auto_mapping: true

...->getManager()->getConnection('dbsync');

<?php
namespace EntBundleService;

use DoctrineORMEntityManager;
use EntBundleEntityUserUser;

class MajUsers {

  private $em;

  /**
   * @param EntityManager $em
   */
  public function __construct(EntityManager $em)
  {
    $this->em = $em;
  }

  public function runUpdate()
  {
     $conn = $this->em->getManager('dbsync')->getConnection('dbsync');
     $personnels_sync =  $conn->fetchAll("SELECT * FROM xxxxx WHERE etat = 1 AND login !='' ORDER BY xxx, yyyyLIMIT 10");
     .....
     .....
  }
}

ent.maj_users:
    class: EntBundleServiceMajUsers
    arguments:
      - '@doctrine.orm.entity_manager'