Karpenter in AWS

Karpenter is an open-source Kubernetes node autoscaler developed by AWS. It automatically launches the right compute resources (EC2 instances) when your cluster needs them and shuts them down when they’re no longer needed.

Traditional autoscalers (like the Cluster Autoscaler) work well but can be slow and limited in flexibility. Karpenter is designed to be:

Faster: It reacts quickly to unschedulable pods. Smarter: It chooses the best instance types based on your workload needs. Cost-efficient: It can use spot instances and right-size nodes to save money. Flexible: It doesn’t require pre-defined node groups.

Installation Steps

Step 1: Create an IAM Role for Karpenter

Create an IAM role with the necessary policies for Karpenter to provision EC2 instances.

eksctl create iamserviceaccount \
  --cluster <your-cluster-name> \
  --namespace karpenter \
  --name karpenter \
  --attach-policy-arn arn:aws:iam::<account-id>:policy/KarpenterControllerPolicy \
  --approve

Step 2: Install Karpenter via Helm

Add the Karpenter Helm repository and install it:

helm repo add karpenter https://charts.karpenter.sh
helm repo update

helm install karpenter karpenter/karpenter \
  --namespace karpenter \
  --create-namespace \
  --set serviceAccount.create=false \
  --set serviceAccount.name=karpenter \
  --set controller.clusterName=<your-cluster-name> \
  --set controller.clusterEndpoint=<your-cluster-endpoint> \
  --set aws.defaultInstanceProfile=KarpenterNodeInstanceProfile

Configuration

Create a Provisioner resource to define how Karpenter should provision nodes:

apiVersion: karpenter.sh/v1alpha5
kind: Provisioner
metadata:
  name: default
spec:
  requirements:
    - key: "node.kubernetes.io/instance-type"
      operator: In
      values: ["t3.medium", "t3.large"]
  provider:
    subnetSelector:
      karpenter.sh/discovery: <your-cluster-name>
    securityGroupSelector:
      karpenter.sh/discovery: <your-cluster-name>
  ttlSecondsAfterEmpty: 30

Apply the configuration:

kubectl apply -f provisioner.yaml

Validation

To test Karpenter, deploy a pod that requires scheduling:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: inflate
spec:
  replicas: 5
  selector:
    matchLabels:
      app: inflate
  template:
    metadata:
      labels:
        app: inflate
    spec:
      containers:
        - name: inflate
          image: public.ecr.aws/eks-distro/kubernetes/pause:3.2
          resources:
            requests:
              cpu: 1

Apply the deployment and monitor Karpenter provisioning new nodes:

kubectl apply -f inflate.yaml
kubectl get nodes -w

Conclusion

Karpenter simplifies Kubernetes autoscaling by dynamically provisioning the right compute resources. With this setup, your EKS cluster can scale efficiently based on workload demands.