Quick Guide: Troubleshooting Common Azure Kubernetes Service (AKS) Cluster Issues

Azure Kubernetes Service (AKS) simplifies container orchestration, but like any complex system, it can encounter issues. When problems arise, quick identification and resolution are key to maintaining application availability and performance. This guide provides straightforward steps to troubleshoot common AKS cluster issues efficiently.

Introduction

Managing AKS clusters involves monitoring various components such as nodes, pods, services, and network configurations. Recognizing symptoms early and understanding basic troubleshooting techniques can save time and reduce downtime. Here, we focus on common issues like cluster unavailability, pod failures, networking problems, and scaling challenges, along with practical solutions.

1. Verify Cluster and Node Status

Check Cluster Health

Start by ensuring your AKS cluster is operational:

az aks show --resource-group <ResourceGroupName> --name <ClusterName>

• Look for the provisioningState (should be Succeeded).
• Check the current Kubernetes version and node count.

Check Node Status

Ensure nodes are running:

kubectl get nodes

• Nodes should be in Ready state.
• If nodes are NotReady, investigate node logs and status.

Troubleshooting Tip

If nodes are unresponsive, consider cordoning and draining affected nodes:

kubectl cordon <NodeName>
kubectl drain <NodeName> --ignore-daemonsets --delete-emptydir-data

2. Investigate Pod and Deployment Issues

Check Pod Status

Identify failing pods:

kubectl get pods --all-namespaces

• Look for CrashLoopBackOff, Error, or Pending statuses.

Describe Problematic Pods

Get detailed info:

kubectl describe pod <PodName> -n <Namespace>

• Review events for clues, such as image pull errors, resource constraints, or crash reasons.

View Pod Logs

Access logs to diagnose issues:

kubectl logs <PodName> -n <Namespace>

• For multiple containers, specify container name:

kubectl logs <PodName> -c <ContainerName> -n <Namespace>

Troubleshooting Tip

Common pod issues include insufficient resources, image pull errors, or misconfiguration. Adjust resource requests/limits or correct image references as needed.

3. Check Networking and Service Connectivity

Validate Service Endpoints

Ensure services are correctly exposing pods:

kubectl get svc -n <Namespace>

• Confirm the service type (ClusterIP, LoadBalancer, NodePort) and external IPs.

Test Connectivity

Use kubectl port-forward or kubectl exec to test pod connectivity:

kubectl port-forward svc/<ServiceName> <LocalPort>:<TargetPort> -n <Namespace>

• Or access pods directly:

kubectl exec -it <PodName> -n <Namespace> -- /bin/bash

• Test network connectivity internally and externally.

Check Network Policies

Ensure network policies aren’t restricting traffic to or from pods.

4. Monitor Resource Utilization and Scaling

Review Resource Usage

Use Azure Monitor or kubectl top:

kubectl top nodes
kubectl top pods -n <Namespace>

• High CPU or memory usage may require scaling or resource adjustments.

Adjust Scaling

Scale the deployment as needed:

kubectl scale deployment/<DeploymentName> --replicas=<Number> -n <Namespace>

• Consider autoscaling with the Horizontal Pod Autoscaler (HPA).

5. Leverage AKS and Kubernetes Diagnostic Tools

Use Azure Portal Diagnostics

Azure Monitor provides insights into cluster health, node status, and logs.

Check the Kubernetes Dashboard

Deploy the dashboard for a visual overview:

az aks browse --resource-group <ResourceGroupName> --name <ClusterName>

Use kubectl Plugins

Tools like kubectl-debug can help attach debug containers or perform deep diagnostics.

Conclusion

Troubleshooting AKS clusters efficiently hinges on understanding core components and leveraging the right tools. Regular monitoring, timely log inspection, and strategic scaling help prevent issues from escalating. When problems do arise, the steps outlined here provide a quick reference to diagnose and resolve common AKS cluster issues, minimizing downtime and maintaining optimal performance.

Stay proactive, keep your tools updated, and document your troubleshooting procedures for faster resolutions in the future.