Mysql database replication (failover solution)
Facebook's DBA YOSHINORI MATSUNOBU has developed MHA :


  A primary objective of MHA is automating master failover and slave promotion within short (usually 10-30 seconds) downtime, without suffering from replication consistency problems, without spending money for lots of new servers, without performance penalty, without complexity (easy-to-install), and without changing existing deployments.


The project link : http://code.google.com/p/mysql-master-ha/

Max.