Cross-zone Azure Kubernetes Service (AKS) cluster

Overview: Azure Kubernetes Service (AKS) Cluster

Microsoft's Azure Kubernetes Service (AKS) is one of the better-known names in the world of cloud-based Kubernetes service providers. As of today, AKS users are presented with the option of over 50 availability regions. 11 of these regions offer different 'Availability Zones' within the same availability region. K8s cluster nodes in different availability zones are geographically set apart. In the event of a power outage, or any other form of failure in one of the data centers, cross-zone k8s clusters remain live with negligible down-time.

Multi-zone clusters are the next step in achieving high-availability in these failure scenarios, although they are quite rare. Here are some of the benefits of using one:

• With the use of pod-replication practices, there is minimal downtime in the event of a node failure. Your service remains live while being hosted in a remote location, away from the failure zone.
• With node-failure, there is always a risk of data-loss for stateful applications, databases, etc. This can be mitigated if your application supports data-replication. CAS solutions like OpenEBS use live replica containers spread across zones for your high-availability storage needs.

These steps are best done through the console at portal.azure.com. Alternatively, it may also be done through shell.azure.com.

You can check if the feature required to have nodes in separate zones is enabled by executing the following command:

az feature list -o table --query "[?contains(name, 'Microsoft.ContainerService/AvailabilityZonePreview')].{Name:name,State:properties.state}"

It should say, 'Registered.’

If it says 'NotRegistered,’ execute the following commands to enable the feature:

az extension add --name aks-preview

az extension update --name aks-preview

az feature register --name AvailabilityZonePreview --namespace Microsoft.ContainerService

az provider register --namespace Microsoft.ContainerService

To verify, execute:

az feature list -o table --query "[?contains(name, 'Microsoft.ContainerService/AvailabilityZonePreview')].{Name:name,State:properties.state}"

All Azure resources are grouped together into ‘Resource Groups.’ So, the first step towards creating our cluster is to create a Resource Group. AKS clusters can currently be created using availability zones in the following regions:

Australia East (australiaeast)
Central US (centralus)
East US 2 (eastus2)
East US (eastus)
France Central (francecentral)
Japan East (japaneast)
North Europe (northeurope)
Southeast Asia (southeastasia)
UK South (uksouth)
West Europe (westeurope)
West US 2 (westus2)

Let’s go with the ‘East US’ region.

az group create --name myResourceGroup --location eastus

Next, we’ll create the cluster. The cluster needs to have a load balancer of SKU type ‘Standard.’ We’ll use the az aks create command to create the cluster. We are using Standard_B2ms sized VMs. You can visit this page to check for the different VM sizes available in your region.

You can get the list of available Kubernetes versions using the following command. Substitute the region name for <region-name>.

az aks get-versions --output table --location <region-name>

az aks create \
	--resource-group myResourceGroup \
	--name myAKSCluster \
	--kubernetes-version 1.18.6 \
	--load-balancer-sku standard \
	--node-count 3 \
	--node-zones 1 2 3 \
	--node-vm-size Standard_B2ms \
	--node-osdisk-size 40 \
	--vm-set-type VirtualMachineScaleSets

Execute the az aks get-credentials command to get the kubeconfig for the cluster.

az aks get-credentials --name myAKSCluster --resource-group myResourceGroup

After doing that, we should be able to access the cluster.

Execute a ‘kubectl get nodes’ to check.

c8542d96-6801-47f2-bbfb-8c8116c9@Azure:~$ kubectl get nodes -o custom-columns=NAME:'{.metadata.name}',REGION:'{.metadata.labels.topology\.kubernetes\.io/region}',ZONE:'{metadata.labels.topology\.kubernetes\.io/zone}'
NAME                                REGION   ZONE
aks-nodepool1-12791571-vmss000000   eastus   eastus-1
aks-nodepool1-12791571-vmss000001   eastus   eastus-2
aks-nodepool1-12791571-vmss000002   eastus   eastus-3

Cross-zone HA is the first thing you’ll need in your quest for redundancy. Microsoft’s managed Kubernetes offering has come a long way, and a couple of bash commands is all it takes to set one of these up.