fix(server): correct Kubernetes label key length validation

[zerone0x]

Summary

The _is_valid_label_key function in server/src/services/validators.py incorrectly rejected valid Kubernetes label keys when the total key length (prefix + / + name) exceeded 253 characters — even if the prefix alone was within the allowed 253-character limit.

Root Cause

The old guard condition:

if len(key) > 253 or "/" in key and len(key.split("/", 1)[0]) > 253:

was evaluated (due to Python operator precedence) as:

if (len(key) > 253) or ("/" in key and len(prefix) > 253):

The first clause len(key) > 253 applied to all keys, including prefixed ones. Because of this, a key whose prefix was valid (≤ 253 chars) but whose combined length exceeded 253 would be incorrectly rejected.

Fix

Per the Kubernetes label key specification:

• The prefix (DNS subdomain) may be at most 253 characters.
• The name segment may be at most 63 characters.
• The total combined key length has no specified upper bound (theoretical max: 253 + 1 + 63 = 317 chars).

The fix removes the total-length check and uses an explicit len(prefix) > 253 check instead.

Testing

All existing tests continue to pass. New regression tests are added for:

• A valid key with a 251-char prefix and total length > 253 (previously rejected — now correctly accepted).
• A prefix that exceeds 253 chars (correctly rejected).
• Other invalid key/value forms: invalid prefix format, name > 63 chars, value > 63 chars, non-string key, empty prefix.

uv run pytest tests/test_validators.py -v
# 54 passed

Checklist

• Bug fix (no breaking changes)
• Added regression tests
• All existing tests pass

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[Copilot]

Pull request overview

Fixes Kubernetes label key validation to correctly allow label keys whose combined prefix/name length exceeds 253 characters, while still enforcing the prefix (DNS subdomain) ≤ 253 and name ≤ 63.

Changes:

• Remove incorrect total-length guard from _is_valid_label_key and validate prefix length explicitly.
• Add regression tests covering long-but-valid prefixed keys and multiple invalid key/value cases.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
server/src/services/validators.py	Corrects label key validation logic to align with Kubernetes spec (prefix length vs total key length).
server/tests/test_validators.py	Adds regression tests for long prefix/name combinations and invalid metadata label inputs.

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[CLAassistant]

All committers have signed the CLA.

[Pangjiping]

Thanks for fixes. Please sign CLA and I will review and merge those changes as soon as possible.

[zerone0x]

@Pangjiping already signed!

[Pangjiping]

LGTM

[Generalwin]

LGTM