get_instance

获取SwooleDistributedServer的实例。

Common.php中也有get_instance，效果和这个等同。

例子:

    public function __construct()
    {
        if (!empty(get_instance())) {
            $this->loader = get_instance()->loader;
            $this->logger = get_instance()->log;
            $this->server = get_instance()->server;
            $this->config = get_instance()->config;
            $this->pack = get_instance()->pack;
        }
    }