fix: Ensure NillableDuration can round-trip with unstructured

[adammw]

Description
Ensure NillableDuration can round-trip with default unstructured converter.

Previously this failed with "invalid duration" and a base64-encoded duration.

How was this change tested?

Test added to round-trip through the default unstructured converter.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

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[coveralls]

Pull Request Test Coverage Report for Build 14830014839

Details

• 5 of 7 (71.43%) changed or added relevant lines in 1 file are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.05%) to 82.044%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pkg/apis/v1/duration.go	5	7	71.43%

Files with Coverage Reduction	New Missed Lines	%
pkg/controllers/disruption/drift.go	2	89.66%

Totals
Change from base Build 14806030316:	0.05%
Covered Lines:	10084
Relevant Lines:	12291

---

💛 - Coveralls

[rschalo]

Maybe I'm missing something but when does this actually happen?

[adammw]

We encounter this problem using any of the Karpenter API types that include the NIllableDuration in our internal project that manages the nodepool resources for us. Since the API type claims to support the FromUnstructured/ToUnstructured interface, the suggestion was that the fix should live upstream where those methods are defined.

[engedaam]

/assign @rschalo

[rschalo]

Can you please give an example? Is it something that is being set by the client managing the NodePool? What does the duration and NodePool look like when it fails?

[adammw]

An example from the test case which will fail with the following without the implementation changes:

runtime.DefaultUnstructuredConverter.FromUnstructured(u, nodePool)

returns error

time: invalid duration "IjMwcyI="

with a valid duration of 30s set.

Unstructured conversions are used often to write generic helper methods, we use them to detect and save changes back to Kubernetes in our controller. However without custom handling of UnmarshalJSON, the above error occurs from the byte array being marshalled to base64 and therefore cannot be unmashalled as a time duration.

[jonathan-innis]

Is the issue that we need to do a base64 decode here or that we just need to return the string representation of the byte array on L82 -- or maybe better yet, just store the string representation in Raw?

[adammw]

Happy to try alternative implementations - my understanding was that FromUnstructured is hard coded to call MarshalJSON on the []byte (rather than it being on string) which causes the base64 encoding.