Leap Second on 6/30/2015 Caused mysqld Process To Consume CPU

This morning I got a notification that mysqld was consuming on average 35% of the CPU on one my servers. This was strange because this particular server doesn’t even use MySQL regularly. It’s there only to serve a rarely used legacy table. A quick look with “show processlist” confirmed that there were no queries running. After a bit of search, I found the solution here:

https://blog.mozilla.org/it/2012/06/30/mysql-and-the-leap-second-high-cpu-and-the-fix/

The solution is to run a short script that sets the correct time. Basically, the cause was the leapsecond that was added at midnight UTC. Here is a screenshot showing when mysqld starting consuming CPU – exactly at midnight UTC.

Screen Shot 2015-07-01 at 8.11.15 AM