How to properly automate autoscaling a cluster?

Hi,

Right now I’m on v3.3.5, a three-node cluster in AWS EC2, and I want to upgrade to v4.2.1.
In our system, everything is automated and we have autoscaling in place. On a button click we have three (or more) new EC2 instances built from scratch, Crate.IO CE installed on them, and they discover each other just fine.

Now, in v4.2.1 the new initial_master_nodes setting has been introduced and is required, and represents a problem for my current automation setup.
The problem is, EC2 instances are starting one-by-one, which means I don’t know all three IPs of my nodes.

So, what is the recommended way for scaling nodes that want to join a cluster?
Is there any way to avoid having to “change” the configuration on the first node, after the second node has been started?

The solution with v3.3.5 right now works very elegantly and nodes can be terminated or recreated at will, and they “just” join the cluster.
It seems somewhat cumbersome if I have to change yml config files on all nodes everytime I want to add a new node. I love the fact that I don’t have to think about my cluster, and which nodes are master and which are not. Is there a way to get there with v4.2.1?