Kube-probe HTTP probe failed with status code 403

The application is denying access to the probe due to insufficient permissions.

Understanding Kube-probe

Kube-probe is a diagnostic tool used within Kubernetes to monitor the health and readiness of applications running in a cluster. It helps ensure that applications are functioning correctly and can handle requests by periodically checking their status through HTTP, TCP, or command-based probes.

Identifying the Symptom

When using Kube-probe, you might encounter an error message stating: HTTP probe failed with status code 403. This indicates that the probe attempted to access the application endpoint but was denied permission.

What Does a 403 Status Code Mean?

The HTTP 403 Forbidden status code means that the server understands the request but refuses to authorize it. In the context of Kube-probe, this typically suggests that the probe lacks the necessary permissions to access the application endpoint.

Exploring the Issue

The root cause of receiving a 403 status code from a Kube-probe is often related to access control settings within the application. The application might have security measures that restrict access to certain endpoints, and the probe's request does not meet the criteria to bypass these restrictions.

Common Causes of Access Denial

  • Authentication requirements not met by the probe.
  • IP whitelisting that excludes the probe's IP address.
  • Role-based access control (RBAC) settings that do not permit probe access.

Steps to Fix the Issue

To resolve the 403 status code issue with Kube-probe, follow these steps:

1. Review Application Access Control Settings

Check the application's access control settings to ensure that the probe is allowed to access the required endpoint. This may involve:

  • Updating authentication credentials if the endpoint requires them.
  • Modifying IP whitelists to include the probe's IP address.
  • Adjusting RBAC settings to grant the probe necessary permissions.

2. Update Kubernetes Probe Configuration

Ensure that the probe configuration in your Kubernetes deployment is correct. This includes verifying the endpoint URL, HTTP method, and any headers required for authentication. For example:

livenessProbe:
httpGet:
path: /healthz
port: 8080
httpHeaders:
- name: Authorization
value: Bearer <token>

3. Test Access Manually

Use tools like curl to manually test access to the endpoint from within the cluster. This can help identify if the issue is specific to the probe or a broader access problem:

curl -I http://your-application/healthz

Further Reading and Resources

For more information on configuring probes in Kubernetes, refer to the official Kubernetes documentation on probes. Additionally, explore Kubernetes security concepts to better understand access control mechanisms.

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