Install Karpenter

In this section we will install Karpenter and learn how to configure a default Provisioner CRD to set the configuration. Karpenter is installed in clusters with a helm chart. Karpenter follows best practices for kubernetes controllers for its configuration. Karpenter uses Custom Resource Definition(CRD) to declare its configuration. Custom Resources are extensions of the Kubernetes API. One of the premises of Kubernetes is the declarative aspect of its APIs. Karpenter simplifies its configuration by adhering to that principle.

Install Karpenter Helm Chart

We will use helm to deploy Karpenter to the cluster.

export KARPENTER_IAM_ROLE_ARN="arn:aws:iam::${AWS_ACCOUNT_ID}:role/${CLUSTER_NAME}-karpenter"
export CLUSTER_ENDPOINT="$(aws eks describe-cluster --name ${CLUSTER_NAME} --query "cluster.endpoint" --output text)"
echo "export KARPENTER_IAM_ROLE_ARN=${KARPENTER_IAM_ROLE_ARN}" >> ~/.bash_profile
echo "export CLUSTER_ENDPOINT=${CLUSTER_ENDPOINT}" >> ~/.bash_profile
helm upgrade --install --namespace karpenter --create-namespace \
  karpenter oci://public.ecr.aws/karpenter/karpenter \
  --version ${KARPENTER_VERSION}\
  --set serviceAccount.annotations."eks\.amazonaws\.com/role-arn"=${KARPENTER_IAM_ROLE_ARN} \
  --set settings.aws.clusterName=${CLUSTER_NAME} \
  --set settings.aws.clusterEndpoint=${CLUSTER_ENDPOINT} \
  --set settings.aws.defaultInstanceProfile=KarpenterNodeInstanceProfile-${CLUSTER_NAME} \
  --set settings.aws.interruptionQueueName=${CLUSTER_NAME} \
  --set nodeSelector.intent=control-apps \
  --wait

The command above:

  • uses both the CLUSTER_NAME and the CLUSTER_ENDPOINT so that Karpenter controller can contact the Cluster API Server.

  • uses the argument --set nodeSelector.intent=control-apps to deploy the controllers in the On-Demand managed node group that was created with the cluster.

  • uses the argument --set settings.aws.defaultInstanceProfile=KarpenterNodeInstanceProfile-${CLUSTER_NAME} to use the instance profile we created before to grant permissions necessary to instances to run containers and configure networking.

  • uses the argument --set settings.aws.interruptionQueueName=${CLUSTER_NAME} to use the SQS queue created in the previous CloudFormation stack to handle Spot interruption notifications and AWS Health events.

  • Karpenter configuration is provided through a Custom Resource Definition (CRD). We will be learning about Provisioners in the next section, the --wait notifies the webhook controller to wait until the Provisioner Controller has been deployed.

To check Karpenter is running you can check the Pods, Deployment and Service are Running.

To check running pods run the command below. There should be at least one pod karpenter

kubectl get pods --namespace karpenter

You should see an output similar to the one below.

NAME                         READY   STATUS    RESTARTS   AGE
karpenter-75f6596894-pgrsd   1/1     Running   0          48s
karpenter-75f6596894-t4mrx   1/1     Running   0          48s

To check the deployment. Like with the pods, there should be one deployment karpenter

kubectl get deployment -n karpenter

Since v0.16.0 Karpenter deploys 2 replicas. One of the replicas is elected as a Leader while the other stays in standby mode. The karpenter deployment also uses topologySpreadConstraints to spread each replica in a different AZ.

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