Securely scale your applications using the KEDA add-on and workload identity on Azure Kubernetes Service (AKS)

Article
08/01/2024

This article shows you how to securely scale your applications with the Kubernetes Event-driven Autoscaling (KEDA) add-on and workload identity on Azure Kubernetes Service (AKS).

Important

Your cluster Kubernetes version determines what KEDA version will be installed on your AKS cluster. To see which KEDA version maps to each AKS version, see the AKS managed add-ons column of the Kubernetes component version table.

For GA Kubernetes versions, AKS offers full support of the corresponding KEDA minor version in the table. Kubernetes preview versions and the latest KEDA patch are partially covered by customer support on a best-effort basis. As such, these features aren't meant for production use. For more information, see the following support articles:

Before you begin

You need an Azure subscription. If you don't have an Azure subscription, you can create a free account.
You need the Azure CLI installed.
Ensure you have firewall rules configured to allow access to the Kubernetes API server. For more information, see Outbound network and FQDN rules for Azure Kubernetes Service (AKS) clusters.

Create a resource group

Create a resource group using the az group create command. Make sure you replace the placeholder values with your own values.
```
LOCATION=<azure-region>
RG_NAME=<resource-group-name>

az group create --name $RG_NAME --location $LOCATION
```

Create an AKS cluster

Create an AKS cluster with the KEDA add-on, workload identity, and OIDC issuer enabled using the az aks create command with the --enable-workload-identity, --enable-keda, and --enable-oidc-issuer flags. Make sure you replace the placeholder value with your own value.
```
AKS_NAME=<cluster-name>

az aks create \
    --name $AKS_NAME \
    --resource-group $RG_NAME \
    --enable-workload-identity \
    --enable-oidc-issuer \
    --enable-keda \
    --generate-ssh-keys 
```
Validate the deployment was successful and make sure the cluster has KEDA, workload identity, and OIDC issuer enabled using the az aks show command with the --query flag set to "[workloadAutoScalerProfile, securityProfile, oidcIssuerProfile]".
```
az aks show \
    --name $AKS_NAME \
    --resource-group $RG_NAME \
    --query "[workloadAutoScalerProfile, securityProfile, oidcIssuerProfile]"
```

Connect to the cluster using the az aks get-credentials command.

az aks get-credentials \
    --name $AKS_NAME \
    --resource-group $RG_NAME \
    --overwrite-existing

Create an Azure Service Bus

Create an Azure Service Bus namespace using the az servicebus namespace create command. Make sure to replace the placeholder value with your own value.

SB_NAME=<service-bus-name>
SB_HOSTNAME="${SB_NAME}.servicebus.windows.net"

az servicebus namespace create \
    --name $SB_NAME \
    --resource-group $RG_NAME \
    --disable-local-auth

Create an Azure Service Bus queue using the az servicebus queue create command. Make sure to replace the placeholder value with your own value.

SB_QUEUE_NAME=<service-bus-queue-name>

az servicebus queue create \
    --name $SB_QUEUE_NAME \
    --namespace $SB_NAME \
    --resource-group $RG_NAME

Create a managed identity

Create a managed identity using the az identity create command. Make sure to replace the placeholder value with your own value.

MI_NAME=<managed-identity-name>

MI_CLIENT_ID=$(az identity create \
    --name $MI_NAME \
    --resource-group $RG_NAME \
    --query "clientId" \
    --output tsv)

Get the OIDC issuer URL using the az aks show command with the --query flag set to oidcIssuerProfile.issuerUrl.

AKS_OIDC_ISSUER=$(az aks show \
    --name $AKS_NAME \
    --resource-group $RG_NAME \
    --query oidcIssuerProfile.issuerUrl \
    --output tsv)

Create a federated credential between the managed identity and the namespace and service account used by the workload using the az identity federated-credential create command. Make sure to replace the placeholder value with your own value.

FED_WORKLOAD=<federated-credential-workload-name>

az identity federated-credential create \
    --name $FED_WORKLOAD \
    --identity-name $MI_NAME \
    --resource-group $RG_NAME \
    --issuer $AKS_OIDC_ISSUER \
    --subject system:serviceaccount:default:$MI_NAME \
    --audience api://AzureADTokenExchange

Create a second federated credential between the managed identity and the namespace and service account used by the keda-operator using the az identity federated-credential create command. Make sure to replace the placeholder value with your own value.

FED_KEDA=<federated-credential-keda-name>

az identity federated-credential create \
    --name $FED_KEDA \
    --identity-name $MI_NAME \
    --resource-group $RG_NAME \
    --issuer $AKS_OIDC_ISSUER \
    --subject system:serviceaccount:kube-system:keda-operator \
    --audience api://AzureADTokenExchange

Create role assignments

Get the object ID for the managed identity using the az identity show command with the --query flag set to "principalId".

MI_OBJECT_ID=$(az identity show \
    --name $MI_NAME \
    --resource-group $RG_NAME \
    --query "principalId" \
    --output tsv)

Get the Service Bus namespace resource ID using the az servicebus namespace show command with the --query flag set to "id".

SB_ID=$(az servicebus namespace show \
    --name $SB_NAME \
    --resource-group $RG_NAME \
    --query "id" \
    --output tsv)

Assign the Azure Service Bus Data Owner role to the managed identity using the az role assignment create command.

az role assignment create \
    --role "Azure Service Bus Data Owner" \
    --assignee-object-id $MI_OBJECT_ID \
    --assignee-principal-type ServicePrincipal \
    --scope $SB_ID

Enable Workload Identity on KEDA operator

After creating the federated credential for the keda-operator ServiceAccount, you will need to manually restart the keda-operator pods to ensure Workload Identity environment variables are injected into the pod.
```
kubectl rollout restart deploy keda-operator -n kube-system
```

Confirm the keda-operator pods restart

kubectl get pod -n kube-system -lapp=keda-operator -w

Once you've confirmed the keda-operator pods have finished rolling hit Ctrl+c to break the previous watch command then confirm the Workload Identity environment variables have been injected.
```
KEDA_POD_ID=$(kubectl get po -n kube-system -l app.kubernetes.io/name=keda-operator -ojsonpath='{.items[0].metadata.name}')
kubectl describe po $KEDA_POD_ID -n kube-system
```

You should see output similar to the following under Environment.

---
AZURE_CLIENT_ID:
AZURE_TENANT_ID:               xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxx
AZURE_FEDERATED_TOKEN_FILE:    /var/run/secrets/azure/tokens/azure-identity-token
AZURE_AUTHORITY_HOST:          https://login.microsoftonline.com/
---

Deploy a KEDA TriggerAuthentication resource that includes the User-Assigned Managed Identity's Client ID.
```
kubectl apply -f - <<EOF
apiVersion: keda.sh/v1alpha1
kind: TriggerAuthentication
metadata:
  name: azure-servicebus-auth
  namespace: default  # this must be same namespace as the ScaledObject/ScaledJob that will use it
spec:
  podIdentity:
    provider:  azure-workload
    identityId: $MI_CLIENT_ID
EOF
```
Note

With the TriggerAuthentication in place, KEDA will be able to authenticate via workload identity. The keda-operator Pods use the identityId to authenticate against Azure resources when evaluating scaling triggers.

Publish messages to Azure Service Bus

At this point everything is configured for scaling with KEDA and Microsoft Entra Workload Identity. We will test this by deploying producer and consumer workloads.

Create a new ServiceAccount for the workloads.

kubectl apply -f - <<EOF
apiVersion: v1
kind: ServiceAccount
metadata:
  annotations:
    azure.workload.identity/client-id: $MI_CLIENT_ID
  name: $MI_NAME
EOF

Deploy a Job to publish 100 messages.

kubectl apply -f - <<EOF
apiVersion: batch/v1
kind: Job
metadata:
  name: myproducer
spec:
  template:
    metadata:
      labels:
        azure.workload.identity/use: "true"
    spec:
      serviceAccountName: $MI_NAME
      containers:
      - image: ghcr.io/azure-samples/aks-app-samples/servicebusdemo:latest
        name: myproducer
        resources: {}
        env:
        - name: OPERATION_MODE
          value: "producer"
        - name: MESSAGE_COUNT
          value: "100"
        - name: AZURE_SERVICEBUS_QUEUE_NAME
          value: $SB_QUEUE_NAME
        - name: AZURE_SERVICEBUS_HOSTNAME
          value: $SB_HOSTNAME
      restartPolicy: Never
EOF

Consume messages from Azure Service Bus

Now that we have published messages to the Azure Service Bus queue, we will deploy a ScaledJob to consume the messages. This ScaledJob will use the KEDA TriggerAuthentication resource to authenticate against the Azure Service Bus queue using the workload identity and scale out every 10 messages.

Deploy a ScaledJob resource to consume the messages. The scale trigger will be configured to scale out every 10 messages. The KEDA scaler will create 10 jobs to consume the 100 messages.

kubectl apply -f - <<EOF
apiVersion: keda.sh/v1alpha1
kind: ScaledJob
metadata:
  name: myconsumer-scaledjob
spec:
  jobTargetRef:
    template:
      metadata:
        labels:
          azure.workload.identity/use: "true"
      spec:
        serviceAccountName: $MI_NAME
        containers:
        - image: ghcr.io/azure-samples/aks-app-samples/servicebusdemo:latest
          name: myconsumer
          env:
          - name: OPERATION_MODE
            value: "consumer"
          - name: MESSAGE_COUNT
            value: "10"
          - name: AZURE_SERVICEBUS_QUEUE_NAME
            value: $SB_QUEUE_NAME
          - name: AZURE_SERVICEBUS_HOSTNAME
            value: $SB_HOSTNAME
        restartPolicy: Never
  triggers:
  - type: azure-servicebus
    metadata:
      queueName: $SB_QUEUE_NAME
      namespace: $SB_NAME
      messageCount: "10"
    authenticationRef:
      name: azure-servicebus-auth
EOF

Note

ScaledJob creates a Kubernetes Job resource whenever a scaling event occurs and thus a Job template needs to be passed in when creating the resource. As new Jobs are created, Pods will be deployed with workload identity bits to consume messages.

Verify the KEDA scaler worked as intended.

kubectl describe scaledjob myconsumer-scaledjob

You should see events similar to the following.

Events:
Type     Reason              Age   From           Message
----     ------              ----  ----           -------
Normal   KEDAScalersStarted  10m   scale-handler  Started scalers watch
Normal   ScaledJobReady      10m   keda-operator  ScaledJob is ready for scaling
Warning  KEDAScalerFailed    10m   scale-handler  context canceled
Normal   KEDAJobsCreated     10m   scale-handler  Created 10 jobs

Clean up resources

After you verify that the deployment is successful, you can clean up the resources to avoid incurring Azure costs.

Delete the Azure resource group and all resources in it using the [az group delete][az-group-delete] command.
```
az group delete --name $RG_NAME --yes --no-wait
```

Next steps

This article showed you how to securely scale your applications using the KEDA add-on and workload identity in AKS.

For information on KEDA troubleshooting, see Troubleshoot the Kubernetes Event-driven Autoscaling (KEDA) add-on.

To learn more about KEDA, see the upstream KEDA docs.

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