startup probe failed: http probe failed with statuscode: 404

Guri Bee

3 min read

·

01-10-2024

12

0

Share

In the world of Kubernetes and container orchestration, maintaining application uptime and reliability is critical. One common error that developers encounter during application deployment is the “startup probe failed: http probe failed with status code: 404.” In this article, we'll explore what this error means, why it occurs, and how to effectively troubleshoot and resolve it.

What is a Startup Probe?

Before diving into the error, let's define what a startup probe is. In Kubernetes, a startup probe is a mechanism that checks whether an application within a container has started successfully. It allows Kubernetes to differentiate between the initialization of a container and its ongoing functionality. If the startup probe fails, Kubernetes will restart the container, assuming that the application has not started correctly.

Types of Probes

Kubernetes supports three types of probes:

1. Liveness Probes: Checks if the application is still running.
2. Readiness Probes: Determines if the application is ready to accept traffic.
3. Startup Probes: Ensures that the application has completed its startup phase before proceeding with regular probes.

What Does the Error Mean?

The error message “startup probe failed: http probe failed with status code: 404” indicates that the startup probe is sending HTTP requests to a defined endpoint, but the server responds with a 404 Not Found status. This means that the requested resource is not available at the specified URL.

Why Does This Happen?

There are several reasons why you might encounter this error:

1. Incorrect Endpoint Configuration: The URL specified for the probe does not correspond to an actual route in your application.
2. Application Not Ready: The application might not be fully initialized and ready to handle requests when the probe checks it.
3. Misconfigured Startup Probes: If the probe is set to check too early in the application lifecycle, it may not reach the expected endpoint.
4. Networking Issues: If there are networking issues within your Kubernetes cluster, it may also lead to probe failures.

Troubleshooting the 404 Error

Here are some practical steps you can take to diagnose and resolve this error:

Step 1: Verify the Probe Configuration

Check your Kubernetes YAML configuration for the startup probe. Ensure that the endpoint you are testing actually exists and is reachable:

livenessProbe:
  httpGet:
    path: /health
    port: 8080
  initialDelaySeconds: 5
  periodSeconds: 10

Step 2: Review Application Routes

Make sure that the application has correctly defined routes and is capable of serving the expected endpoint. You can test this locally or through the debugging pod:

kubectl exec -it <pod-name> -- curl http://localhost:8080/health

Step 3: Adjust Timing and Delays

If the application requires more time to initialize than what is configured in the probes, increase the initialDelaySeconds and timeoutSeconds values.

startupProbe:
  httpGet:
    path: /health
    port: 8080
  initialDelaySeconds: 30
  periodSeconds: 10

Step 4: Check Logs for Errors

Use the following command to view the application logs:

kubectl logs <pod-name>

Examine the logs for any errors during startup that may prevent the application from initializing correctly.

Step 5: Networking and Service Accessibility

Ensure that there are no network policies or firewall rules preventing access to the application. You can also troubleshoot potential issues using tools like kubectl port-forward.

kubectl port-forward <pod-name> 8080:8080

Then access the application via http://localhost:8080/health.

Conclusion

The error “startup probe failed: http probe failed with status code: 404” can be frustrating, but with a structured approach to troubleshooting, it can be resolved effectively. By understanding the nature of startup probes, examining your probe configurations, and reviewing your application routes and logs, you can identify the root cause and fix it.

Further Considerations

• Logging and Monitoring: Implement robust logging and monitoring to catch errors early in your application lifecycle.
• User Documentation: If you're deploying applications for users, ensure that proper documentation exists to help them troubleshoot similar issues.
• Test Early and Often: Integrate tests during development to catch potential configuration issues before reaching production.

By following these practices, you can enhance the reliability and resilience of your Kubernetes applications.

This article was inspired by community questions and responses on GitHub and is designed to provide additional insights and practical solutions for users facing the startup probe error.