You’ve deployed automation, enabled automatic master failover and tested it many times: great, you can now sleep at night without being paged by a failing server. However, when you wake up in the morning, things might not have gone the way you expect. This talk will be about such a surprise.

Once upon a time, a failure brought down a master. Automation kicked in and fixed things. However, a fancy failure, combined with human errors, with an edge-case recovery, and a lack of oversight in automation, lead to a split-brain. This talk will go into details about the convoluted - but still real world - sequence of events that lead to this disaster. I will cover what could have avoided the split-brain and what could have make things easier to fix it.