fix: support string duration values in JSON/YAML config files

[crawfordxx]

Summary

• Fix watch-progress-notify-interval and all other time.Duration config fields failing to unmarshal from string values (e.g. "1m", "500ms") in JSON/YAML config files
• Add preprocessDurationFields() that converts string duration values to nanosecond integers before unmarshaling, matching the behavior of command-line flags
• Applies to all 11 duration fields: backend-batch-interval, grpc-keepalive-min-time, grpc-keepalive-interval, grpc-keepalive-timeout, corrupt-check-time, compact-hash-check-time, compaction-sleep-interval, watch-progress-notify-interval, warning-apply-duration, warning-unary-request-duration, downgrade-check-time

Fixes #20342

Root Cause

time.Duration is an int64 in Go and does not implement json.Unmarshaler. When sigs.k8s.io/yaml converts YAML to JSON then uses encoding/json, string values like "1m" cannot be unmarshaled into time.Duration fields. Only raw nanosecond integers work, which is not user-friendly.

Solution

Before passing config bytes to yaml.Unmarshal, pre-process known duration field keys: if the value is a string, parse it with time.ParseDuration and replace it with the equivalent nanosecond integer. Numeric values pass through unchanged.

This approach is minimally invasive - it does not change the Config struct's public API or field types, and follows the existing pattern of translating config file values in configFromFile (similar to how URL string fields are handled).

Test plan

• Unit test: string duration value for watch-progress-notify-interval parses correctly
• Unit test: numeric duration value (nanoseconds) still works
• Unit test: all 11 duration fields parse correctly from strings
• Unit test: invalid duration string returns error
• Unit test: preprocessDurationFields handles string, numeric, non-duration, and invalid inputs
• All existing embed package tests pass

[k8s-ci-robot]

Hi @crawfordxx. Thanks for your PR.

I'm waiting for a etcd-io member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work.

Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

Details

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: crawfordxx
Once this PR has been reviewed and has the lgtm label, please assign ahrtr for approval. For more information see the Code Review Process.

The full list of commands accepted by this bot can be found here.

Details

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment