[outworlder]

There are several ways of bootstraping ETCD. The one I use is the one you mention: since they are brought up with Terraform, always on a brand new VPC, we can calculate what the IP addresses will be on Terraform itself and fill the initial node list that way. We can destroy an ETCD node if need be, and recreate. Granted, it is nowhere near close to being as convenient as an ASG.

The alternate method, and the method we used before, is to use an existing cluster, as you mention. If cattle self-healing is that important, perhaps you could afford a small cluster only for bootstrapping? Load will be very low unless you are bootstrapping a node somewhere. There are costs involved in keeping those instances 24/7, but they may be acceptable in your environment(and the instances can be small). Then the only thing you need is to store the discovery token and inject it with cloud init or some other mechanism.

That said, I just finish a task to automate our ELK clusters. For Elasticsearch I can just point to a load balancer which contains the masters and be done with it. I wish I could do the same for ETCD.