'redis' => array(
    'cluster' => true,
    'default' => array(
      'host'   => '172.21.107.247',
      'port'   => 6379,
    ),
   'redis1' => array(
      'host'   => '172.21.107.248',
      'port'   => 6379,
    ),

Session::put('test', 124);

IlluminateSupportFacadesSession
IlluminateSupportFacadesFacade
IlluminateSessionFacade::app['session']->put
IlluminateSessionFacade::app['session']为IlluminateSessionSessionManager
IlluminateSupportManager::__call

$this->app['config']['session.driver']

IlluminateSessionSessionManager::IlluminateSessionSessionManager

public function __construct(array $servers = array())
{
    if (isset($servers['cluster']) && $servers['cluster'])
    {
      $this->clients = $this->createAggregateClient($servers);
    }
    else
    {
      $this->clients = $this->createSingleClients($servers);
    }
}

protected function createAggregateClient(array $servers)
{
    $servers = array_except($servers, array('cluster'));
    return array('default' => new Client(array_values($servers)));
}

protected function addNodeToRing(&$ring, $node, $totalNodes, $replicas, $weightRatio)
{
    $nodeObject = $node['object'];
    $nodeHash = $this->getNodeHash($nodeObject);
    $replicas = (int) round($weightRatio * $totalNodes * $replicas);
    for ($i = 0; $i < $replicas; $i++) {
      $key = crc32("$nodeHash:$i");
      $ring[$key] = $nodeObject;
    }
}