Kube-probe HTTP probe failed with status code 408

What is Kube-probe HTTP probe failed with status code 408

Understanding Kube-probe

Kube-probe is a diagnostic tool used within Kubernetes to monitor the health of applications running in pods. It ensures that applications are running smoothly by sending periodic requests to the application and checking the responses. If an application fails to respond correctly, Kube-probe can trigger actions such as restarting the pod to maintain the desired state of the application.

Identifying the Symptom

When using Kube-probe, you might encounter an error message stating: HTTP probe failed with status code 408. This indicates that the probe request sent to the application did not receive a timely response, leading to a timeout.

What is a 408 Status Code?

The HTTP 408 Request Timeout status code means that the server did not receive a complete request message within the time that it was prepared to wait. In the context of Kube-probe, this suggests that the application is not responding quickly enough to the health check requests.

Exploring the Issue

The primary cause of a 408 status code in Kube-probe is that the application is taking too long to respond to the probe's HTTP request. This can be due to various factors, such as high server load, inefficient application code, or network latency.

Impact on Application Health

If the application consistently fails to respond within the expected time, Kubernetes may consider the pod unhealthy and take corrective actions, such as restarting the pod. This can lead to application downtime and affect the overall reliability of your services.

Steps to Fix the Issue

To resolve the HTTP probe failure with status code 408, you can take the following steps:

1. Increase the Timeout Value

One immediate solution is to increase the timeout value in the probe configuration. This allows the application more time to respond before the probe times out. You can modify the timeoutSeconds field in your probe configuration:

livenessProbe: httpGet: path: /healthz port: 8080 initialDelaySeconds: 3 periodSeconds: 5 timeoutSeconds: 10

For more details on configuring probes, refer to the Kubernetes documentation.

2. Optimize Application Performance

Review your application code to identify any performance bottlenecks that might be causing delays. Consider optimizing database queries, reducing resource-intensive operations, or improving caching strategies.

3. Monitor Server Load

Check the server's resource usage to ensure it has sufficient CPU and memory to handle incoming requests. You can use tools like Prometheus and Grafana for monitoring and visualizing server metrics.

Conclusion

Addressing the HTTP probe failure with status code 408 involves both configuration adjustments and application optimizations. By increasing the timeout and improving application performance, you can enhance the reliability and responsiveness of your services within Kubernetes.