The version of mysql provided with Ubuntu 16.04 is version 5.7, an upgrade from the previous version 5.6.
MySQL 5.7 has proven to be unstable and locks up periodically. I have spent several days trying to troubleshoot this, fixed a number of issues, and optimized the configuration. Still it locks up and dies from time to time.
I tried to upgrade to MariaDB 10. An in place upgrade failed, and dumping the old database and sourcing the resulting sql file in MariaDB also failed. It completes but the grant tables aren’t recognized which basically makes it useless. I have yet to find a fix for this. I apologize for this instability.
If anyone can find a clean path to migrate from MySQL 5.7 to MariaDB 10.0, please let me know (e-mail: email@example.com) or call me at 206-812-0051.