检查当前服务器的可用性,包括MySQL,MongoDB,Memcache等
null Core_Controller_RunTime::action_check_server( )
public function action_check_server()
{
    $config = array
    (
        'time'=>TIME,
    );
    $config['mysql'] = $this->check_mysql();
    if ( $this->save_runtime_config($config) )
    {
        $this->output('save runtime config success.');
    }
    else
    {
        $this->output('save runtime config fail.');
    }
}