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

[Varun-39]

Summary

ContainerBackend.wait_for_job_status was missing input validation that both the kubernetes and localprocess backends already have.

The Bug

When polling_interval >= timeout, the time-based while loop exits before the first time.sleep() completes — job status is checked zero times — and a TimeoutError fires immediately with a misleading message. No error is raised for clearly invalid input.

The Fix

Added a ValueError guard matching the established pattern in the other two backends.

Validation

• Added unit test for polling_interval == timeout
• 43/43 tests pass

Fixes #411
Related: #402

[google-oss-prow]

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[Copilot]

Pull request overview

This PR addresses a missing input validation in ContainerBackend.wait_for_job_status() by adding a guard that raises ValueError when polling_interval >= timeout, preventing scenarios where the polling loop would not adequately check job status. The fix is intended to match the established pattern in the kubernetes and localprocess backends.

Changes:

• Add validation at the start of ContainerBackend.wait_for_job_status() to check that polling_interval is less than timeout
• Add a new test case to verify the validation raises ValueError when polling_interval equals timeout

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
kubeflow/trainer/backends/container/backend.py	Adds input validation for polling_interval/timeout constraint
kubeflow/trainer/backends/container/backend_test.py	Adds test case for polling_interval=timeout scenario

[Copilot]

The validation uses polling_interval >= timeout but the kubernetes backend (line 463) and localprocess backend (line 229) both use polling_interval > timeout. This inconsistency means the container backend will reject valid inputs that the other two backends accept (when polling_interval equals timeout). Align this validation with the other backends by changing >= to >.

Suggested change

	if polling_interval >= timeout:
	if polling_interval > timeout: