CoreOS seems to do a decent job as the application layer for something operating in a larger cloud that provides database and file storage as services, like Amazon or OpenStack. However, I think Docker has the potential to eliminate the need for infrastructure-level "clouds" to be so complex. The basic unit can be the container instead of the instance, so you don't need fancy automated instance management and all that. It'd be nice if you could also obviate the need for the other external services, and just run everything in containers on metal.

I was really excited by CoreOS as a way to do this, but it seems to fighting me at every turn. It seems much easer to just wire together the REST APIs of several Ubuntu/CentOS nodes running Docker.

That is more likely what they'd have in mind than a single MySQL master container.

That explains how they chose to minimize deadlocks.

Yes, if you use it incorrectly and/or for the wrong problem space, you will have issues. It isn't a magical solution to all problems. It is, however, an effective solution for a specific problem space.

This is after configuring HAProxy to have a primary node which all connections go to.

OpenStack seems to be OK with it though, it chugs along without fully breaking down. I'm sure I would see a pretty big performance delta if I ran a benchmark against it with and without Galera.