This is awesome! Also, I was at MySql event at Oracle two days ago and I overheard MySql guys talking with the pinterest folks about their sharding and how MySql team was going to announce something soon and wanted to get the pinterest's team feedback.
MySql is doing their scripting on Python. So for a python shop, their release might be more interesting.
Cool, looking forward to seeing that! I love Python too, and readily admit it's perhaps a more frequent choice for this type of automation.
That said, I really grew to love Ruby over the course of this project, which is actually my first in the language. Ruby's open classes allowed me to write a pretty flexible plugin/callback system with very little code. Jetpants allows you to hook arbitrary methods in before or after any method in any Jetpants class, and these callbacks "stack" (with support for different priorities) so multiple plugins can hook-in to the same place.
Because every large site seems to tackle sharding slightly differently, I figured a nice plugin system was pretty important in order for anyone else to be able to use this :)
