开机自启动，PDO 连接报错的问题，请教

采用直接修改 /etc/rc.local 文件的方式实现开机启动。

系统报错，日志文件如下：

2017-08-15 18:30:35 pid:808 worker start in DAEMON mode
2017-08-15 18:30:35 pid:2437 exception 'PDOException' with message 'SQLSTATE  Connection refused' in /www/default/resheng/Gateway/vendor/workerman/gateway-worker/src/Lib/DbConnection.php:1697
Stack trace:
#0 /www/default/resheng/Gateway/vendor/workerman/gateway-worker/src/Lib/DbConnection.php(1697): PDO->__construct('mysql:dbname=re...', 'root', 'My201765', Array)
#1 /www/default/resheng/Gateway/vendor/workerman/gateway-worker/src/Lib/DbConnection.php(1683): GatewayWorker\Lib\DbConnection->connect()
#2 /www/default/resheng/Gateway/vendor/workerman/gateway-worker/src/Lib/Db.php(48): GatewayWorker\Lib\DbConnection->__construct('127.0.0.1', 3306, 'root', 'My201765', 'resheng')
#3 /www/default/resheng/Gateway/Applications/YourApp/Func.php(11): GatewayWorker\Lib\Db::instance('db1')

但是如果手工启动（php start.php start -d）则完全正常。

百思不得其解，难道是启动workerman的时候mysql等服务还未启动？？？