Table of contents:

• Features Overview
• Node Auto Provisioning (NAP) vs. Self-hosted
• Known limitations
• Installation (self-hosted)
  • Install utilities
  • Create a cluster
  • Configure Helm chart values
  • Install Karpenter
  • Create NodePool
  • Scale up deployment
  • Scale down deployment
  • Delete Karpenter nodes manually
  • Delete the cluster
• Source Attribution
• Community, discussion, contribution, and support

Features Overview

The AKS Karpenter Provider enables node autoprovisioning using Karpenter on your AKS cluster. Karpenter improves the efficiency and cost of running workloads on Kubernetes clusters by:

• Watching for pods that the Kubernetes scheduler has marked as unschedulable
• Evaluating scheduling constraints (resource requests, node selectors, affinities, tolerations, and topology-spread constraints) requested by the pods
• Provisioning nodes that meet the requirements of the pods
• Removing the nodes when they are no longer needed
• Consolidating existing nodes onto cheaper nodes with higher utilization per node

Node Auto Provisioning (NAP) vs. Self-hosted

Karpenter provider for AKS can be used in two modes:

• Node Auto Provisioning (NAP) mode (preview): Karpenter is run by AKS as a managed addon similar to managed Cluster Autoscaler. This is the recommended mode for most users. Follow the instructions in Node Auto Provisioning documentation to use Karpenter in that mode.
• Self-hosted mode: Karpenter is run as a standalone deployment in the cluster. This mode is useful for advanced users who want to customize or experiment with Karpenter's deployment. The rest of this page describes how to use Karpenter in self-hosted mode.

Known limitations

• Only AKS clusters with Azure CNI Overlay + Cilium networking are supported.
• Only Linux nodes are supported.

Installation (self-hosted)

This guide shows how to get started with Karpenter by creating an AKS cluster and installing Karpenter.

Install utilities

Install these tools before proceeding:

• Azure CLI
• kubectl
• Helm
• jq - used by some of the scripts below
• yq - used by some of the scripts below

Create a cluster

Create a new AKS cluster with the required configuration, and ready to run Karpenter using workload identity.

Note: You can use hack/deploy/create-cluster.sh <cluster-name> <resource-group> <namespace> to automate the following steps.

Set environment variables:

export CLUSTER_NAME=karpenter
export RG=karpenter
export LOCATION=eastus
export KARPENTER_NAMESPACE=kube-system

Create the resource group:

az group create --name ${RG} --location ${LOCATION}

Create the workload MSI that is the backing for the karpenter pod auth:

KMSI_JSON=$(az identity create --name karpentermsi --resource-group "${RG}" --location "${LOCATION}")

Create AKS cluster compatible with Karpenter, and with the workload identity enabled:

AKS_JSON=$(az aks create \
  --name "${CLUSTER_NAME}" --resource-group "${RG}" \
  --node-count 3 --generate-ssh-keys \
  --network-plugin azure --network-plugin-mode overlay --network-dataplane cilium \
  --enable-managed-identity \
  --enable-oidc-issuer --enable-workload-identity)
az aks get-credentials --name "${CLUSTER_NAME}" --resource-group "${RG}" --overwrite-existing

Create federated credential linked to the karpenter service account for auth usage:

az identity federated-credential create --name KARPENTER_FID --identity-name karpentermsi --resource-group "${RG}" \
  --issuer "$(jq -r ".oidcIssuerProfile.issuerUrl" <<< "$AKS_JSON")" \
  --subject system:serviceaccount:${KARPENTER_NAMESPACE}:karpenter-sa \
  --audience api://AzureADTokenExchange

Create role assignments to let Karpenter manage VMs and Network resources:

KARPENTER_USER_ASSIGNED_CLIENT_ID=$(jq -r '.principalId' <<< "$KMSI_JSON")
RG_MC=$(jq -r ".nodeResourceGroup" <<< "$AKS_JSON")
RG_MC_RES=$(az group show --name "${RG_MC}" --query "id" -otsv)
for role in "Virtual Machine Contributor" "Network Contributor" "Managed Identity Operator"; do
  az role assignment create --assignee "${KARPENTER_USER_ASSIGNED_CLIENT_ID}" --scope "${RG_MC_RES}" --role "$role"
done

Configure Helm chart values

The Karpenter Helm chart requires specific configuration values to work with an AKS cluster. While these values are documented within the Helm chart, you can use the configure-values.sh script to generate the karpenter-values.yaml file with the necessary configuration. This script queries the AKS cluster and creates the values file using karpenter-values-template.yaml as a template. Although the script automatically fetches the template from the main branch, inconsistencies may arise between the installed version of Karpenter and the repository code. Therefore, it is advisable to download the specific version of the template before running the script.

# Select version to install
export KARPENTER_VERSION=0.5.4

# Download the specific's version template
curl -sO https://raw.githubusercontent.com/Azure/karpenter/v${KARPENTER_VERSION}/karpenter-values-template.yaml

# use configure-values.sh to generate karpenter-values.yaml
# (in repo you can just do ./hack/deploy/configure-values.sh ${CLUSTER_NAME} ${RG})
curl -sO https://raw.githubusercontent.com/Azure/karpenter-provider-azure/v${KARPENTER_VERSION}/hack/deploy/configure-values.sh
chmod +x ./configure-values.sh && ./configure-values.sh ${CLUSTER_NAME} ${RG} karpenter-sa karpentermsi

Install Karpenter

Usinge the generated karpenter-values.yaml file, install Karpenter using Helm:

helm upgrade --install karpenter oci://mcr.microsoft.com/aks/karpenter/karpenter \
  --version "${KARPENTER_VERSION}" \
  --namespace "${KARPENTER_NAMESPACE}" --create-namespace \
  --values karpenter-values.yaml \
  --set controller.resources.requests.cpu=1 \
  --set controller.resources.requests.memory=1Gi \
  --set controller.resources.limits.cpu=1 \
  --set controller.resources.limits.memory=1Gi \
  --wait

kubectl logs -f -n "${KARPENTER_NAMESPACE}" -l app.kubernetes.io/name=karpenter -c controller

Snapshot versions can be installed in a similar way for development:

export KARPENTER_NAMESPACE=kube-system
export KARPENTER_VERSION=0-f83fadf2c99ffc2b7429cb40a316fcefc0c4752a

helm upgrade --install karpenter oci://ksnap.azurecr.io/karpenter/snapshot/karpenter \
  --version "${KARPENTER_VERSION}" \
  --namespace "${KARPENTER_NAMESPACE}" --create-namespace \
  --values karpenter-values.yaml \
  --set controller.resources.requests.cpu=1 \
  --set controller.resources.requests.memory=1Gi \
  --set controller.resources.limits.cpu=1 \
  --set controller.resources.limits.memory=1Gi \
  --wait

kubectl logs -f -n "${KARPENTER_NAMESPACE}" -l app.kubernetes.io/name=karpenter -c controller

Create NodePool

A single Karpenter NodePool is capable of handling many different pod shapes. Karpenter makes scheduling and provisioning decisions based on pod attributes such as labels and affinity. In other words, Karpenter eliminates the need to manage many different node groups.

Create a default NodePool using the command below. (Additional examples available in the repository under examples/v1beta1.) The consolidationPolicy set to WhenUnderutilized in the disruption block configures Karpenter to reduce cluster cost by removing and replacing nodes. As a result, consolidation will terminate any empty nodes on the cluster. This behavior can be disabled by setting consolidateAfter to Never, telling Karpenter that it should never consolidate nodes.

Note: This NodePool will create capacity as long as the sum of all created capacity is less than the specified limit.

cat <<EOF | kubectl apply -f -
---
apiVersion: karpenter.sh/v1beta1
kind: NodePool
metadata:
  name: general-purpose
  annotations:
    kubernetes.io/description: "General purpose NodePool for generic workloads"
spec:
  template:
    spec:
      requirements:
        - key: kubernetes.io/arch
          operator: In
          values: ["amd64"]
        - key: kubernetes.io/os
          operator: In
          values: ["linux"]
        - key: karpenter.sh/capacity-type
          operator: In
          values: ["on-demand"]
        - key: karpenter.azure.com/sku-family
          operator: In
          values: [D]
      nodeClassRef:
        name: default
  limits:
    cpu: 100
  disruption:
    consolidationPolicy: WhenUnderutilized
    expireAfter: Never
---
apiVersion: karpenter.azure.com/v1alpha2
kind: AKSNodeClass
metadata:
  name: default
  annotations:
    kubernetes.io/description: "General purpose AKSNodeClass for running Ubuntu2204 nodes"
spec:
  imageFamily: Ubuntu2204
EOF

Karpenter is now active and ready to begin provisioning nodes.

Scale up deployment

This deployment uses the pause image and starts with zero replicas.

cat <<EOF | kubectl apply -f -
apiVersion: apps/v1
kind: Deployment
metadata:
  name: inflate
spec:
  replicas: 0
  selector:
    matchLabels:
      app: inflate
  template:
    metadata:
      labels:
        app: inflate
    spec:
      terminationGracePeriodSeconds: 0
      containers:
        - name: inflate
          image: mcr.microsoft.com/oss/kubernetes/pause:3.6
          resources:
            requests:
              cpu: 1
EOF

kubectl scale deployment inflate --replicas 5
kubectl logs -f -n "${KARPENTER_NAMESPACE}" -l app.kubernetes.io/name=karpenter -c controller

Scale down deployment

Now, delete the deployment. After a short amount of time, Karpenter should terminate the empty nodes due to consolidation.

kubectl delete deployment inflate
kubectl logs -f -n "${KARPENTER_NAMESPACE}" -l app.kubernetes.io/name=karpenter -c controller

Delete Karpenter nodes manually

If you delete a node with kubectl, Karpenter will gracefully cordon, drain, and shutdown the corresponding instance. Under the hood, Karpenter adds a finalizer to the node object, which blocks deletion until all pods are drained and the instance is terminated. Keep in mind, this only works for nodes provisioned by Karpenter.

kubectl delete node $NODE_NAME

Delete the cluster

To avoid additional charges, remove the demo infrastructure from your AKS account.

helm uninstall karpenter --namespace "${KARPENTER_NAMESPACE}"
az aks delete --name "${CLUSTER_NAME}" --resource-group "${RG}"

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Source Attribution

Notice: Files in this source code originated from a fork of https://github.com/aws/karpenter which is under an Apache 2.0 license. Those files have been modified to reflect environmental requirements in AKS and Azure.

Many thanks to @ellistarn, @jonathan-innis, @tzneal, @bwagner5, @njtran, and many other developers active in the Karpenter community for laying the foundations of a Karpenter provider ecosystem!

Many thanks to @Bryce-Soghigian, @rakechill, @charliedmcb, @jackfrancis, @comtalyst, @aagusuab, @matthchr, @gandhipr, @dtzar for contributing to AKS Karpenter Provider!

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Community, discussion, contribution, and support

This project has adopted the Microsoft Open Source Code of Conduct. For more information see the Code of Conduct FAQ or contact [email protected] with any additional questions or comments.

Come discuss Karpenter in the #karpenter channel in the Kubernetes slack!

Check out the Docs to learn more.

Check out our contributing guide.