I am the core developer. It's not abandoned at all. There are updates that haven't been pushed upstream, but no new features. Was going to support replication via an external consensus service (etc, consul, etc) -- but looks like implementing Raft directly into Tank for interfacing with other cluster nodes is a better idea, all things considering (no external deps., simplicity).
The reason this hasn't happened yet is that, other than lack of free time to pursue it, we(work) haven't really needed that feature yet. We run a few instances and they are very idle and we can also mirror to other nodes (via tank-cli).
Can you please please please use the etcd implementation[1] of raft and not the normal go-raft or consul raft implementations? They've done some serious business fault injection and integration testing with etcd as part of google's hosted kubernetes (GKE). There are still some lingering issues with consul at scale that make me a bit gunshy. Mesosphere did some of this work themselves: https://mesosphere.com/blog/2015/10/26/etcd-mesos-kubernetes... , but I know that Google engineers have done tons of work on this as well.
