perf: Add an option to skip OpenAPI schema initialization

[iliakonnov]

This PR introduces a new skip field to the openapi map in the kustomization file.

Problem

When using Kustomize as a library, Kustomizer.Run calls openapi.SetSchema on every execution. In high-frequency scenarios where the same schema is used repeatedly, this leads to a significant performance bottleneck due to redundant schema compilation.

In our use case, we call Kustomizer.Run thousands of times. Flame graph analysis showed that schema compilation was a major contributor to the overall execution time.

Solution

By setting openapi.skip to true, users can now bypass the call to openapi.SetSchema inside Kustomizer.Run. This allows library consumers to initialize the schema once at application startup and reuse it for all subsequent runs.

Example workflow:

1. Initialize the schema manually once when your application starts: openapi.SetSchema(...).
2. In your kustomization.yaml, add the skip field:

openapi:
  skip: true

3. Call kustomizer.Run() as usual.

Result

This change dramatically improves performance in our scenario, reducing the total processing time from 30 minutes to 9 minutes.

Next Steps and Design Alternatives

I've submitted this patch as a minimal implementation to start a discussion and validate the approach. I'm keen to hear your feedback and I'm ready to make adjustments.

Here are a few alternatives I've considered:

1. Instead of modifying the public kustomization.yaml format, we could add a new field directly to the Kustomizer struct (e.g., Kustomizer.SkipOpenAPISchema). This would make the feature available only when Kustomize is used as a library, which is the primary use case for this optimization. I'm happy to implement it this way if you prefer.
2. The field name skip is a placeholder. A more descriptive name like usePreconfiguredSchema or built-in might be better. I don't have a strong preference and am open to suggestions.

My main goal is to get early feedback on whether this direction for performance improvement is welcome before investing more time.

[linux-foundation-easycla]

• ✅login: iliakonnov / (c108924)

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