Before we dive into scaling Istio, we are going to explore scaling the cluster itself. It would be pointless to increase the number of replicas of Istio components, as a way to solve the problem of not being able to drain a node, if that is the only node in a cluster. We need the Gateway not only scaled but also distributed across different nodes of the cluster. Only then can we hope to drain a node successfully while the Gateway is running in it. We’ll assume that the experiment might shut down one replica, while others are still running somewhere else. Fortunately for us, Kubernetes always does its best to distribute instances of our apps across different nodes. As long as it can, it will not run multiple replicas on a single node.

So, our first action is to scale our cluster. However, scaling a cluster is not the same everywhere. Therefore, the commands to scale the cluster will differ depending on where you’re running it.