Feature Description

Currently, a deployment of Vitess requires one of etcd, zk or consul for the topo. These are databases in their own right - and the contents have to be backed up and restorable.

I am proposing that mysql be supported as a new topo implementation. It has the required functionality to 'notify' subscribers, because they can connect as if they are replicas. The only requirement is that the binlog is row-based, which is pretty safe these days.

(I tested this out as a proof of concept, and it worked fine. Happy to submit a PR).

Use Case(s)

There are some advantages to using MySQL as a topo:

• Most Vitess deployments are probably already supporting MySQL; adding a new DB like etcd means it might not have the same understanding and support vs. adding one more small MySQL server to store the topo.
• a small managed MySQL server is available at low cost in most clouds.