mysql问题：‘The last packet successfully received from the server was xxx milliseconds ago‘

1.springboot + druid + mysql 在查询某些比较耗时的sql会报错
2.问题说明
查询数据量较小时不会报错，数据量大时会报错，报错信息如下：

com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure

The last packet successfully received from the server was **10,010** milliseconds ago. The last packet sent successfully to the server was 10,010 milliseconds ago.
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3.问题解决：
（1）sql上增加分页限制不会报错；
（2）从报错信息来看，这里设置的超时是10000毫秒，debug mysql-connector源码，发现有socketTimeout参数的值正好是10000，于是在datasource.url后面socketTimeout参数配置，重启测试发现能被正确识别，正常。
我的参考示例，最后两个参数：

url: jdbc:mysql://127.0.0.1:3306/${spring.datasource.dynamic.datasource.master.name}?useUnicode=true&characterEncoding=utf8&zeroDateTimeBehavior=convertToNull&useSSL=false&serverTimezone=Asia/Shanghai&allowPublicKeyRetrieval=true&nullCatalogMeansCurrent=true&connectTimeout=10000&socketTimeout=30000
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