Details
Major Description
MySQL graphs stopped working a few days ago without any change in configuration or software.
Turns out there's some typecasting done in includes/polling/applications/mysql.inc.php which converts large values into their scientific notation and rrd doesn't like it:
app-mysql-5.rrd: not a simple integer: '1.47191921045E+12'
I'm not sure if there's any other implication, but simply disabling the typecasting fixed data collection for us.