After upgrade to Community 201612 GA there are a lot of erros in connection to database
(log file attached)
This results in multiple failed transactions.
The error happens in all sorts of transactions, but can be triggered by uploading a new version where it needs to start creating thumbnails.
It also happens after the system has been used for a while (not immediately after a restart), and the number of active sessions is above 10.
It happens both with MariaDB and mySQL, both with mariadb and mysql jdbc driver.