Connection marked as broken because of SQLSTATE(08S01), ErrorCode(0)；Communications link failure

Question：

springboot 2.X多数据源配置，一段时间后连接无效，不能进行有效性验证，提示：

Connection marked as broken because of SQLSTATE(08S01), ErrorCode(0);

Communications link failure

开始以为是HikariCP连接池配置的有问题，后面发现是程序的问题，使用EntityManager查询操作，debug hikari也发现查询后连接无法释放

Solution:

使用@PersistenceContext？

1. springboot data jpa中的entitymanager是transaction-scoped persistence contexts
2. http://yukinami.github.io/2016/02/15/Spring%20Data%20JPA%20&%20EntityManager/
3. https://stackoverflow.com/questions/10762974/should-jpa-entity-manager-be-closed
4. validationTimeout，refer: https://github.com/brettwooldridge/HikariCP