[yissachar]

To expand on the sibling comment by nrmitchi, in Kubernetes you don't scale your worker nodes by CPU or memory. Instead you scale your pods by CPU or memory. Running the cluster autoscaler ensures that when you run out of space to schedule a new pod new worker nodes are brought up. It also works the other way; when your nodes are being underutilized for a while, the autoscaler will kill some nodes (and the scheduler will automatically handle placing any pods on those nodes onto other nodes).

[djb_hackernews]

Right, I see that in the CA docs. This doesn't work with our business requirements since our workloads are spikey and we don't want to wait around for pods not being able to be scheduled to start more nodes.

A contrived example is imagine if for every gmail user that logs into gmail google spins up a pod for the user. No imagine if there wasn't any capacity to schedule a pod for a user that is logging in. That user would either be denied or have to wait for an instance to come up and then the pod to be scheduled. Not ideal.

[yissachar]

Yes, this is my biggest problem with the autoscaler as well. I opened an issue about this almost a year ago, looks like they're finally getting around to addressing it: https://github.com/kubernetes/autoscaler/pull/77