背景：线上阿里云服务器部署的，mycat 一主三从（mysql），运行了一段时间突然发现这种异常；

Error querying database.  Cause: com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure

The last packet successfully received from the server was 65,331 milliseconds ago. The last packet sent successfully to the server was 65,332 milliseconds ago.
### The error may exist in com/zm/share/user/mapper/BrandMapper.xml
### The error may involve com.zm.share.user.mapper.BrandMapper.getAllBraName-Inline
### The error occurred while setting parameters
### SQL: SELECT bra_id, bra_name FROM by_crm_brand WHERE status = 1 AND group_id = ?
### Cause: com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure

The last packet successfully received from the server was 65,331 milliseconds ago. The last packet sent successfully to the server was 65,332 milliseconds ago.
; Communications link failure

The last packet successfully received from the server was 65,331 milliseconds ago. The last packet sent successfully to the server was 65,332 milliseconds ago.; nested exception is com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure
 

最终解决方案 ：

 对比dataSource 下的url 相关配置 ,开启重连配置   &autoReconnect=true  重启服务既可解决！！

url: jdbc:mysql://119.xx.xx.xx:3306/XXX?useSSL=false&useUnicode=true&characterEncoding=utf-8&zeroDateTimeBehavior=convertToNull&transformedBitIsBoolean=true&tinyInt1isBit=false&allowMultiQueries=true&serverTimezone=GMT%2B8&autoReconnect=true