Kubernetes Ingress Error 403: Content-Length too long

The Problem

Encountering a 403 error with a complaint about ‘Content-Length too long’ when working with Kubernetes Ingress can be perplexing. The issue generally arises due to misconfigured limits in your ingress controller or policy enforcement that doesn’t agree with your service’s expectations.

What does the ‘HTTP 403 Error’ Mean?

The HTTP 403 Forbidden response status code indicates that the server understands the request but refuses to authorize it. When the error mentions ‘Content-Length too long,’ it’s likely referring to either the body of the request being larger than the server is willing to process, or a miscommunication between the client and server about allowable message sizes.

Solution 1: Increase Body Size Limit in Ingress

The Ingress resource may be set with a lower max-body-size than required by the service. You might need to increase this limit to accommodate larger request payloads.

1. Identify the ingress resource that is handling traffic for the affected service.
2. Edit the ingress resource to include a larger body size using the nginx.ingress.kubernetes.io/proxy-body-size annotation.
3. Apply the changes to your cluster.

Example:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: example-ingress
  annotations:
    nginx.ingress.kubernetes.io/proxy-body-size: "64m"
spec: [...]

Output: After applying the above manifest, the Ingress resource will allow HTTP requests with a body size up to 64 megabytes.

Notes: This solution only applies to NGINX Ingress Controller. It is straightforward to apply but raises the limit for all traffic flowing through the Ingress, which might not be ideal in all situations. Additionally, if you have multiple replicas of the Ingress controller, ensure that the modification is consistent across all instances.

Solution 2: Adjusting the Kubernetes Client Configuration

If the content-length error persists, it is possible that the client attempting to communicate with the service is sending improperly formatted headers or that expectations around the message size are not clearly defined. Adjust the client configuration to ensure compliance with the Kubernetes Ingress.

1. Determine if the client is setting a content-length header manually and ensure that it is reflective of the actual payload size.
2. Ensure that the client and the Kubernetes cluster agree on the message sizes that are permissible.
3. As needed, adjust the header configurations in the client to resolve discrepancies.

Notes: This is a more complex solution that requires an understanding of the client behaviour and how it interacts with the Kubernetes Ingress. There might also be limitations imposed by the consumer of your service that you need to consider.

Conclusion

The above solutions offer a starting point when diagnosing and resolving the ‘Kubernetes Ingress Error 403: Content-Length too long’. Remember to apply changes sensibly and test thoroughly to avoid introducing security vulnerabilities or performance bottlenecks.