Kubernetes AutoScaler Not Scaling: Troubleshooting HPA Showing Target <unknown>

When working with Kubernetes, one of the most powerful features is the Horizontal Pod Autoscaler (HPA). It allows your applications to scale based on metrics like CPU usage, memory, or custom metrics. However, sometimes you might encounter a situation where the Kubernetes AutoScaler is not scaling, and the HPA shows the target as . This blog post will guide you through the steps to troubleshoot and resolve this issue.

By Saturn Cloud | Tuesday, August 08, 2023 | Miscellaneous

Kubernetes AutoScaler Not Scaling: Troubleshooting HPA Showing Target

When working with Kubernetes, one of the most powerful features is the Horizontal Pod Autoscaler (HPA). It allows your applications to scale based on metrics like CPU usage, memory, or custom metrics. However, sometimes you might encounter a situation where the Kubernetes AutoScaler is not scaling, and the HPA shows the target as <unknown>. This blog post will guide you through the steps to troubleshoot and resolve this issue.

Understanding the Problem

Before we dive into the solution, let’s understand the problem. When you describe the HPA, you might see something like this:

$ kubectl describe hpa <hpa-name>
Name:                           <hpa-name>
Namespace:                      default
Labels:                         <none>
Annotations:                    <none>
CreationTimestamp:              Thu, 10 Jul 2023 16:20:38 +0000
Reference:                      Deployment/<deployment-name>
Metrics:                        ( current / target )
  resource cpu on pods  (as a percentage of request):  <unknown> / 50%
Events:                         <none>

The <unknown> value indicates that the HPA is unable to retrieve the metrics it needs to make scaling decisions. This could be due to several reasons, such as issues with the metrics server, incorrect HPA configuration, or problems with the pods themselves.

Checking the Metrics Server

The first step in troubleshooting is to check the metrics server. Kubernetes uses the metrics server to gather information about the resource usage of pods and nodes. If the metrics server is not running or not correctly configured, the HPA will not be able to retrieve the necessary metrics.

$ kubectl get pods -n kube-system | grep metrics-server

If the metrics server is not running, you will need to install it. If it’s running but not correctly configured, you might need to check its logs for any errors.

Verifying HPA Configuration

The next step is to verify the HPA configuration. The HPA uses the metrics from the metrics server to make scaling decisions. If the HPA is not correctly configured, it might not be able to retrieve or interpret these metrics.

$ kubectl describe hpa <hpa-name>

Check the Metrics and Target fields. The Metrics field should specify the metric that the HPA uses to make scaling decisions, and the Target field should specify the target value for that metric.

Checking the Pods

If the metrics server and HPA configuration are correct, the issue might be with the pods themselves. The HPA needs to retrieve metrics from the pods to make scaling decisions. If the pods are not correctly configured to provide these metrics, the HPA will show the target as <unknown>.

$ kubectl describe pod <pod-name>

Check the Resources field. It should specify the resource requests and limits for the pod. If these are not set, the HPA will not be able to retrieve the necessary metrics.

Conclusion

Troubleshooting Kubernetes AutoScaler not scaling and HPA showing target <unknown> can be a complex task. However, by checking the metrics server, verifying the HPA configuration, and checking the pods, you can identify and resolve the issue.

Remember, Kubernetes is a powerful tool for managing and scaling your applications, but it requires careful configuration and monitoring to ensure it operates correctly. Always keep an eye on your metrics and logs to catch any potential issues early.

If you found this blog post helpful, please share it with your colleagues and friends. If you have any questions or comments, feel free to leave them below. Happy scaling!

Keywords: Kubernetes, AutoScaler, HPA, Scaling, Metrics Server, Troubleshooting, Data Science, DevOps, Kubernetes Configuration, Kubernetes Troubleshooting, Kubernetes Scaling, Kubernetes Metrics Server, Kubernetes HPA

About Saturn Cloud

Saturn Cloud is your all-in-one solution for data science & ML development, deployment, and data pipelines in the cloud. Spin up a notebook with 4TB of RAM, add a GPU, connect to a distributed cluster of workers, and more. Join today and get 150 hours of free compute per month.

Try Saturn Cloud Now