How to install Cluster Autoscaler in AWS EKS?

A good start is to follow AWS documentations (https://docs.aws.amazon.com/eks/latest/userguide/autoscaling.html)

Pre-requisites

• eksctl (https://github.com/weaveworks/eksctl)
• Metrics Server (https://alexlogy.io/how-to-install-metrics-server-in-aws-eks/)

Create IAM Policy

Save the following content to a file.

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "VisualEditor0",
            "Effect": "Allow",
            "Action": [
                "autoscaling:SetDesiredCapacity",
                "autoscaling:TerminateInstanceInAutoScalingGroup"
            ],
            "Resource": "*",
            "Condition": {
                "StringEquals": {
                    "aws:ResourceTag/k8s.io/cluster-autoscaler/<my-cluster>": "owned"
                }
            }
        },
        {
            "Sid": "VisualEditor1",
            "Effect": "Allow",
            "Action": [
                "autoscaling:DescribeAutoScalingInstances",
                "autoscaling:DescribeAutoScalingGroups",
                "ec2:DescribeLaunchTemplateVersions",
                "autoscaling:DescribeTags",
                "autoscaling:DescribeLaunchConfigurations"
            ],
            "Resource": "*"
        }
    ]
}

Create IAM role and attach IAM policy

eksctl create iamserviceaccount \
  --cluster=<my-cluster> \
  --namespace=kube-system \
  --name=cluster-autoscaler \
  --attach-policy-arn=arn:aws:iam::<111122223333>:policy/<AmazonEKSClusterAutoscalerPolicy> \
  --override-existing-serviceaccounts \
  --approve

Download Cluster Autoscaler YAML

curl -o cluster-autoscaler-autodiscover.yaml https://raw.githubusercontent.com/kubernetes/autoscaler/master/cluster-autoscaler/cloudprovider/aws/examples/cluster-autoscaler-autodiscover.yaml

Apply the YAML

kubectl apply -f cluster-autoscaler-autodiscover.yaml

Annotate the Service Account

kubectl annotate serviceaccount cluster-autoscaler \
  -n kube-system \
  eks.amazonaws.com/role-arn=arn:aws:iam::<ACCOUNT_ID>:role/<AmazonEKSClusterAutoscalerRole>

Patch the deployment

kubectl patch deployment cluster-autoscaler \
  -n kube-system \
  -p '{"spec":{"template":{"metadata":{"annotations":{"cluster-autoscaler.kubernetes.io/safe-to-evict": "false"}}}}}'

Edit the Deployment

kubectl -n kube-system edit deployment.apps/cluster-autoscaler

Append the following under spec.containers.command:

• --balance-similar-node-groups
• --skip-nodes-with-system-pods=false

Save and close the file with ESC and then wq to apply the changes.

Upgrade to minor release

Find the latest minor release for your kubernetes cluster version from https://github.com/kubernetes/autoscaler/releases. For example, if your cluster is running 1.22, look for the highest minor version with 1.22.x.

Upgrade to minor release with the following command:

kubectl set image deployment cluster-autoscaler \
  -n kube-system \
  cluster-autoscaler=k8s.gcr.io/autoscaling/cluster-autoscaler:v<1.22.x>

View your Cluster Autoscaler logs

kubectl -n kube-system logs -f deployment.apps/cluster-autoscaler