fix(trainer): validate polling_interval is strictly less than timeout

[prabindersinghh]

Summary

Fixes a silent validation bug in KubernetesBackend.wait_for_job_status()
where polling_interval == timeout passed the guard but produced only
1 poll iteration with no retry window.

The Bug

# Before — allows equal values silently
if polling_interval > timeout:
    raise ValueError(...)

# When equal: round(10/10) == 1 → only 1 poll, then TimeoutError

The error message says "must be less than timeout" but the code
allowed equal values — a direct contradiction.

The Fix

# After — matches documented constraint exactly
if polling_interval >= timeout:
    raise ValueError(...)

One character change. No logic impact for valid inputs.

Validation

make verify → PASSED
backend_test.py → 48/48 PASSED (1 new test case added)

New test case: polling_interval equal to timeout raises ValueError

Related

• Fixes bug(trainer): wait_for_job_status silently allows polling_interval == timeout #400

[google-oss-prow]

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[Copilot]

Pull request overview

This PR fixes a validation edge case in the Kubernetes runtime backend so wait_for_job_status() enforces the documented constraint that polling_interval must be strictly less than timeout, and adds a regression test to cover the equality case.

Changes:

• Update KubernetesBackend.wait_for_job_status() validation to reject polling_interval >= timeout.
• Add a new unit test asserting polling_interval == timeout raises ValueError.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
kubeflow/trainer/backends/kubernetes/backend.py	Tightens polling_interval vs timeout validation to match the documented contract.
kubeflow/trainer/backends/kubernetes/backend_test.py	Adds a regression test for the polling_interval == timeout invalid-input case.