This is related to common issue with tomcat connection pool.
The db connections in the tomcat jdbc connection pool have timed out which cause persistent exceptions.
We can add commented connection pool properties to the configuration in order to remind the users what is need it for production setup.

For example:

<!-- Consider these properties for production setup
              testOnBorrow="true"
              validationQuery="SELECT 1" -->

Tomcat properties link: https://tomcat.apache.org/tomcat-8.0-doc/jdbc-pool.html#Attributes