The slides from last week’s talks I (co-)presented at Percona Live and Linuxcon Europe are now available from our web site.

• In my tutorial MySQL High Availability Sprint: Launch the Pacemaker, I gave a fast walk-through of Pacemaker high availability for MySQL. Tutorial presented at Percona Live UK 2011 in London, England.
• In Fencing and Maintaining Sanity in High Availability Clusters, Madison Kelly and I explored the importance of fencing in HA clusters, highlighted important considerations for fencing, and shared technical details and best practices. Talk presented at Linuxcon Europe 2011 in Prague, Czech Republic. …

I’ve been thinking recently about the failure scenarios of MySQL replication clusters, such as master-master pairs or master-master-with-slaves. There are a few tools that are designed to help manage failover and load balancing in such clusters, by moving virtual IP addresses around. The ones I’m familiar with don’t always do the right thing when an irregularity is detected. I’ve been debating what the best way to do replication clustering with automatic failover really is.

I’d like to hear your thoughts on the following question: what types of scenarios require what kind of response from such a tool?

I can think of a number of failures. Let me give just a few simple examples in a master-master pair:

Problem: Query overload on the writable master makes mysqld unresponsive

Do nothing. Moving the queries to another server will cause cascading failures.

Problem: The …