You can use this w/mysql to enable automatic recovery when a master fails.

Quoted: Heartbeat works like this: you tell Heartbeat which computer owns a particular resource (which computer is the primary server), and the other computer will automatically be the backup server. You then configure the Heartbeat daemon running on the backup server to listen to the “heartbeats” coming from the primary server. If the backup server does not hear the primary server’s heartbeat, it initiates a failover and takes ownership of the resource.