MySQL Connector/J lockup

Lately I have been working on a multi-threaded Java application that utilizes MySQL Connector/J 5.1.7

This is probably the easiest way to access a MySQL database from Java. Everything seemed to be fine until i recently ran a few days long test of the daemon application on one of our test servers. It did not like me in the long run, i am still not sure why and whether it really was a Conenctor/J problem or not.

In any case, the problem i have faced was CPU usage suddenly started raising to about 50% (in a period of one day) and it wasnt a spike – it was a steady raise. When i checked the log file there were no warnings except one i got a at the end of the day: MySQL connection link failure.

Now one may wonder – how is this related to MySQL Connector. Well, it seems to me that it was due to Statement cancellation timer lockup that it started causing problems. Right now i have modified the code of the application to cancel all statemnts explicitly as well as some forced Garbage Collection, just to make sure that nothing unwanted slips by. The new test has been deployed to the servers and we are about to see if it has any effect.

Another note about Java (not really MySQL related):
It seems to be smart using “-server” option when starting a VM if the application is supposed to run for a very long time. The performance optimization is huge: we are talking about almost 2x performance optimization compared to “-client” VM (default).