This same issue was encountered over at the
jHipster project. It took a long time to troubleshoot (as you can see from that bug), and lots of fingers were pointed at HikariCP, but ultimately it turned out to be a
bug in Hibernate 4.3.1. Updating to Hibernate 4.3.2 should fix it. At this point the HikariCP 1.3.8 release has proven to be ridiculously solid.