Helm template validation

When working with Kubernetes and Helm, input validation is automatically performed by the Kubernetes API server when a new resource is created. This means that if an invalid resource is created by Helm, an error message will be returned by the API server, resulting in a failed installation. Although Kubernetes performs input validation, there may still be cases in which chart developers will want to perform validation before the resources reach the API server, such as to return a simple error message or to limit the range of possibilities to the user.

In Helm, input validation refers to validating user-provided values to ensure that users have provided a proper set of values. You can perform this validation in three different ways (or a combination of these three), as follows:

• Using the fail function
• Using the required function
• Using a values.schema.json file

Let’s begin exploring input validation by first looking at the fail...