My web application is running on Tomcat8.
And it used Amazon Aurora with MariaDB Connector/J failover setting (jdbc:mysql:aurora//...).
Tomcat is now not shut down since I updated MariaDB Connector/J to 1.3.4
Please see the attachment.
It seems the failover additional threads are not shut down.
I think it is following changes effects.
Calling ExecutorService#shutdown has removed.