Update the Go struct field type

Oct 13, 2025 by talynt.org 117 views

Issue Overview

In this article, we will delve into a specific issue encountered while working with Gardener, a platform for managing and deploying Kubernetes clusters. The issue revolves around the clientIDPublic field in the oidcConfig section of the gardenerDashboard configuration. When a numeric value is assigned to this field, it results in a JSON unmarshalling error. However, when the value is quoted, it leads to authentication errors. We will explore the root cause of this issue, its implications, and potential solutions.

What Happened

The issue arises when attempting to declare a numeric value for the clientIDPublic field in the gardenerDashboard configuration. The following code snippet illustrates this:

clientIDPublic: 310585380464321630

Upon executing the kubectl edit command, the following error message is displayed:

Error from server: error when replacing "/tmp/kubectl-edit-4245896363.yaml": admission webhook "defaulting.operator.gardener.cloud" denied the request: json: cannot unmarshal number into Go struct field DashboardOIDC.spec.virtualCluster.gardener.gardenerDashboard.oidcConfig.clientIDPublic of type string

This error indicates that the admission webhook is denying the request due to a JSON unmarshalling issue. The error message specifically mentions that it cannot unmarshal the numeric value into a string.

What You Expected to Happen

The expected behavior is to be able to assign a numeric value to the clientIDPublic field without encountering any issues. However, the current implementation of the gardenerDashboard configuration does not support numeric values for this field.

How to Reproduce the Issue

To reproduce the issue, follow these steps:

Create a gardenerDashboard configuration with a numeric value assigned to the clientIDPublic field.
Execute the kubectl edit command to apply the changes.
Observe the JSON unmarshalling error message.

Anything Else We Need to Know?

To better understand and resolve this issue, it is essential to consider the following factors:

Gardener version: v1.113.1
Kubernetes version: v1.31.5
Cloud provider or hardware configuration: [Insert details]

Environment

The issue was encountered in the following environment:

Gardener version: v1.113.1
Kubernetes version: v1.31.5
Cloud provider or hardware configuration: [Insert details]

Conclusion

In conclusion, the issue of not being able to assign a numeric value to the clientIDPublic field in the gardenerDashboard configuration is a result of a JSON unmarshalling error. This error occurs due to the admission webhook denying the request. To resolve this issue, it is necessary to modify the gardenerDashboard configuration to support numeric values for the clientIDPublic field. This can be achieved by updating the Go struct field type to string or by implementing a custom unmarshalling function.

Potential Solutions

To address this issue, the following potential solutions can be explored:

Update the Go struct field type: Modify the clientIDPublic field type in the gardenerDashboard configuration to string. This will allow numeric values to be assigned to this field without encountering any issues.
Implement a custom unmarshalling function: Create a custom unmarshalling function to handle numeric values for the clientIDPublic field. This function can be used to convert the numeric value to a string before unmarshalling the JSON data.
Modify the admission webhook: Update the admission webhook to support numeric values for the clientIDPublic field. This can be achieved by modifying the webhook's configuration or by implementing a custom webhook.

Future Work

To further improve the gardenerDashboard configuration, the following tasks can be undertaken:

Enhance the clientIDPublic field type: Consider adding additional validation or constraints to the clientIDPublic field to ensure that it only accepts valid OIDC client IDs.
Implement support for multiple OIDC providers: Expand the gardenerDashboard configuration to support multiple OIDC providers. This can be achieved by adding additional fields or by implementing a custom OIDC provider configuration.
Improve the admission webhook: Update the admission webhook to support more advanced validation and constraints for the gardenerDashboard configuration.

By addressing these issues and implementing the proposed solutions, the gardenerDashboard configuration can be improved to provide a more robust and flexible OIDC authentication experience.

Q&A Overview

In this article, we will address the frequently asked questions related to the issue of not being able to assign a numeric value to the clientIDPublic field in the gardenerDashboard configuration. We will provide detailed answers to help users understand the root cause of the issue, its implications, and potential solutions.

Q1: What is the root cause of the issue?

A1: The root cause of the issue is a JSON unmarshalling error that occurs when attempting to assign a numeric value to the clientIDPublic field in the gardenerDashboard configuration. This error is due to the admission webhook denying the request.

Q2: Why is the admission webhook denying the request?

A2: The admission webhook is denying the request because it is expecting a string value for the clientIDPublic field, but a numeric value is being assigned instead.

Q3: What are the implications of this issue?

A3: The implications of this issue are that users cannot assign a numeric value to the clientIDPublic field in the gardenerDashboard configuration, which can lead to authentication errors.

Q4: How can I resolve this issue?

A4: To resolve this issue, you can modify the gardenerDashboard configuration to support numeric values for the clientIDPublic field. This can be achieved by updating the Go struct field type to string or by implementing a custom unmarshalling function.

Q5: What are the potential solutions to this issue?

A5: The potential solutions to this issue are:

Update the Go struct field type: Modify the clientIDPublic field type in the gardenerDashboard configuration to string.
Implement a custom unmarshalling function: Create a custom unmarshalling function to handle numeric values for the clientIDPublic field.
Modify the admission webhook: Update the admission webhook to support numeric values for the clientIDPublic field.

Q6: How can I implement a custom unmarshalling function?

A6: To implement a custom unmarshalling function, you can create a new function that takes the numeric value as input and returns a string value. This function can then be used to unmarshal the JSON data.

Q7: What are the benefits of implementing a custom unmarshalling function?

A7: The benefits of implementing a custom unmarshalling function are that it allows you to handle numeric values for the clientIDPublic field in a more flexible and robust way.

Q8: How can I modify the admission webhook?

A8: To modify the admission webhook, you can update the webhook's configuration or implement a custom webhook.

Q9: What are the benefits of modifying the admission webhook?

A9: The benefits of modifying the admission webhook are that it allows you to support numeric values for the clientIDPublic field in a more flexible and robust way.

Q10: What are the future work tasks related to this issue?

A10: The future work tasks related to this issue are:

Enhance the clientIDPublic field type: Consider adding additional validation or constraints to the clientIDPublic field to ensure that it only accepts valid OIDC client IDs.
Implement support for multiple OIDC providers: Expand the gardenerDashboard configuration to support multiple OIDC providers.
Improve the admission webhook: Update the admission webhook to support more advanced validation and constraints for the gardenerDashboard configuration.

By addressing these questions and providing detailed answers, we hope to have helped users understand the root cause of the issue, its implications, and potential solutions.