actually client side will throw an exception when any of the servers is down or unreachable instead like
Fatal error: Uncaught exception 'GearmanException' with message 'Failed to set exception option' in /var/www/ipao/Api/Q2/Test/gm-test.php:11
Stack trace:
#0 /var/www/ipao/Api/Q2/Test/gm-test.php(11): GearmanClient->addServer('xxx.xxx.xxx.xxx')
#1 {main}