Preview - Create and configure an Azure Kubernetes Services (AKS) cluster to use virtual nodes in the Azure portal
To quickly deploy workloads in an Azure Kubernetes Service (AKS) cluster, you can use virtual nodes. With virtual nodes, you have fast provisioning of pods, and only pay per second for their execution time. In a scaling scenario, you don't need to wait for the Kubernetes cluster autoscaler to deploy VM compute nodes to run the additional pods. This article shows you how to create and configure the virtual network resources and an AKS cluster with virtual nodes enabled.
AKS preview features are self-service and opt-in. Previews are provided to gather feedback and bugs from our community. However, they are not supported by Azure technical support. If you create a cluster, or add these features to existing clusters, that cluster is unsupported until the feature is no longer in preview and graduates to general availability (GA).
If you encounter issues with preview features, open an issue on the AKS GitHub repo with the name of the preview feature in the bug title.
The following regions are supported for virtual node deployments:
- Australia East (australiaeast)
- East US (eastus)
- West Central US (westcentralus)
- West Europe (westeurope)
- West US (westus)
Virtual Nodes functionality is heavily dependent on ACI's feature set. The following scenarios are not yet supported with Virtual Nodes
- Using service principal to pull ACR images. Workaround is to use Kubernetes secrets
- Virtual Network Limitations including VNet peering, Kubernetes network policies, and outbound traffic to the internet with network security groups.
- Init containers
- Host aliases
- Arguments for exec in ACI
- Daemonsets will not deploy pods to the virtual node
Sign in to Azure
Sign in to the Azure portal at https://portal.azure.com.
Create an AKS cluster
In the top left-hand corner of the Azure portal, select Create a resource > Kubernetes Service.
On the Basics page, configure the following options:
- PROJECT DETAILS: Select an Azure subscription, then select or create an Azure resource group, such as myResourceGroup. Enter a Kubernetes cluster name, such as myAKSCluster.
- CLUSTER DETAILS: Select a region, Kubernetes version, and DNS name prefix for the AKS cluster.
- SCALE: Select a VM size for the AKS nodes. The VM size cannot be changed once an AKS cluster has been deployed.
- Select the number of nodes to deploy into the cluster. For this article, set Node count to 1. Node count can be adjusted after the cluster has been deployed.
- Under Virtual nodes, select Enabled.
By default, an Azure Active Directory service principal is created. This service principal is used for cluster communication and integration with other Azure services.
The cluster is also configured for advanced networking. The virtual nodes are configured to use their own Azure virtual network subnet. This subnet has delegated permissions to connect Azure resources between the AKS cluster. If you don't already have delegated subnet, the Azure portal creates and configures the Azure virtual network and subnet for use with the virtual nodes.
Select Review + create. After the validation is complete, select Create.
It takes a few minutes to create the AKS cluster and to be ready for use.
Connect to the cluster
The Azure Cloud Shell is a free interactive shell that you can use to run the steps in this article. It has common Azure tools preinstalled and configured to use with your account. To manage a Kubernetes cluster, use kubectl, the Kubernetes command-line client. The
kubectl client is pre-installed in the Azure Cloud Shell.
To open the Cloud Shell, select Try it from the upper right corner of a code block. You can also launch Cloud Shell in a separate browser tab by going to https://shell.azure.com/bash. Select Copy to copy the blocks of code, paste it into the Cloud Shell, and press enter to run it.
Use the az aks get-credentials command to configure
kubectl to connect to your Kubernetes cluster. The following example gets credentials for the cluster name myAKSCluster in the resource group named myResourceGroup:
az aks get-credentials --resource-group myResourceGroup --name myAKSCluster
To verify the connection to your cluster, use the kubectl get command to return a list of the cluster nodes.
kubectl get nodes
The following example output shows the single VM node created and then the virtual node for Linux, virtual-node-aci-linux:
$ kubectl get nodes NAME STATUS ROLES AGE VERSION virtual-node-aci-linux Ready agent 28m v1.11.2 aks-agentpool-14693408-0 Ready agent 32m v1.11.2
Deploy a sample app
In the Azure Cloud Shell, create a file named
virtual-node.yaml and copy in the following YAML. To schedule the container on the node, a nodeSelector and toleration are defined. These settings allow the pod to be scheduled on the virtual node and confirm that the feature is successfully enabled.
apiVersion: apps/v1 kind: Deployment metadata: name: aci-helloworld spec: replicas: 1 selector: matchLabels: app: aci-helloworld template: metadata: labels: app: aci-helloworld spec: containers: - name: aci-helloworld image: microsoft/aci-helloworld ports: - containerPort: 80 nodeSelector: kubernetes.io/role: agent beta.kubernetes.io/os: linux type: virtual-kubelet tolerations: - key: virtual-kubelet.io/provider operator: Exists - key: azure.com/aci effect: NoSchedule
Run the application with the kubectl apply command.
kubectl apply -f virtual-node.yaml
Use the kubectl get pods command with the
-o wide argument to output a list of pods and the scheduled node. Notice that the
virtual-node-helloworld pod has been scheduled on the
$ kubectl get pods -o wide NAME READY STATUS RESTARTS AGE IP NODE virtual-node-helloworld-9b55975f-bnmfl 1/1 Running 0 4m 10.241.0.4 virtual-node-aci-linux
The pod is assigned an internal IP address from the Azure virtual network subnet delegated for use with virtual nodes.
If you use images stored in Azure Container Registry, configure and use a Kubernetes secret. A current limitation of the virtual nodes preview is that you can't use integrated Azure AD service principal authentication. If you don't use a secret, pods scheduled on virtual nodes fail to start and report the error
HTTP response status code 400 error code "InaccessibleImage".
Test the virtual node pod
To test the pod running on the virtual node, browse to the demo application with a web client. As the pod is assigned an internal IP address, you can quickly test this connectivity from another pod on the AKS cluster. Create a test pod and attach a terminal session to it:
kubectl run -it --rm virtual-node-test --image=debian
curl in the pod using
apt-get update && apt-get install -y curl
Now access the address of your pod using
curl, such as http://10.241.0.4. Provide your own internal IP address shown in the previous
kubectl get pods command:
curl -L http://10.241.0.4
The demo application is displayed, as shown in the following condensed example output:
$ curl -L 10.241.0.4 <html> <head> <title>Welcome to Azure Container Instances!</title> </head> [...]
Close the terminal session to your test pod with
exit. When your session is ended, the pod is the deleted.
In this article, a pod was scheduled on the virtual node and assigned a private, internal IP address. You could instead create a service deployment and route traffic to your pod through a load balancer or ingress controller. For more information, see Create a basic ingress controller in AKS.
Virtual nodes are one component of a scaling solution in AKS. For more information on scaling solutions, see the following articles:
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