使用阿里云上的mysql数据库，就出现这个问题了，之前在本地没有出现过。

网上说要修改连接池的配置，

不过 content-center 、user-center中都没有使用连接池呀

请问大目老师，应该怎么设置？

10:15:44.052 ERROR 8883 --- [nio-8020-exec-8] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.exceptions.PersistenceException: 

### Error updating database.  Cause: org.springframework.jdbc.CannotGetJdbcConnectionException: Failed to obtain JDBC Connection; nested exception is java.sql.SQLTransientConnectionException: HikariPool-1 - Connection is not available, request timed out after 30051ms.

### Cause: org.springframework.jdbc.CannotGetJdbcConnectionException: Failed to obtain JDBC Connection; nested exception is java.sql.SQLTransientConnectionException: HikariPool-1 - Connection is not available, request timed out after 30051ms.] with root cause

com.mysql.cj.exceptions.ConnectionIsClosedException: No operations allowed after connection closed.

at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.8.0_65]

at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) ~[na:1.8.0_65]

at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[na:1.8.0_65]

at java.lang.reflect.Constructor.newInstance(Constructor.java:422) ~[na:1.8.0_65]