How to: change etcd cluster size

The etcd cluster size is determined by counting the number of ip addresses in the variable etcd-ips. etcd-ips is used to create the etcd discovery dns entries and those ips are statically assigned to the etcd instances.

To run, say, 5 etcd instance for example, update etcd-ips in /io.tf to:

variable "etcd-ips" { default = "10.0.0.10,10.0.0.11,10.0.0.12,10.0.0.13,10.0.0.14" }

Changing this after a cluster is running is not recommended as it will destroy existing etcd cluster resulting in data loss.

Interestingly changing the third octet of the ip addresses (in the default configuration) will change the subnet for that etcd instance. It is not clear what the implications of running raft (etcd) across AZs is - due to increased latency - so the default tack configuration is to run etcd in one AZ.