Scaling EC2 ASGs with Cluster Autoscaler

Kubernetes CA is a core part of the K8s ecosystem and is used to scale worker nodes in or out based on two main conditions:

• If there is a Pod in the Kubernetes cluster in the Pending state due to an insufficient resources error
• If there is a worker node in the Kubernetes cluster that is identified as underutilized by Kubernetes CA

The following diagram illustrates the basic flow of a scale-out operation to support a single pod being placed in the Pending state and not being scheduled.

Figure 18.3 – High-level Cluster AutoScaler flow

In the preceding diagram, we can see the following:

1. The CA is actively looking for pods that cannot be scheduled for resource reasons and are in the Pending state.
2. The CA makes calls to the EC2 ASG API to increase the desired capacity, which in turn will add a new node to the ASG. A key aspect to note is that the nodes need tagging with k8s.io/cluster...