fix(vllm): initialize synchronizer in KV warmup capacity test

[alec-flowers]

Summary

Fix the two test_kvwarm_does_not_build_a_stage_over_budget_at_the_depth_floor cases that fail with AttributeError: 'InstrumentedScheduler' object has no attribute '_bench_synchronizer' on current main, including the AMD64 CI job for #14981.

The test added in #14900 constructs its scheduler with __new__ and initializes the retired _kvwarm_stage_reported field. The stage-round implementation from #14728 reads _bench_synchronizer instead. Set that field to None so the existing capacity-fallback assertions exercise the intended single-rank path. This changes only the test setup.

Validation

• Before the fix: both parameter cases reproduce the CI AttributeError locally.
• After the fix: all 259 tests in components/src/dynamo/vllm/tests/test_vllm_instrumented_scheduler.py pass.
• Repository pre-commit checks pass for the changed file.

Local validation used Python 3.12.3, vLLM 0.29.0 and current checkout source in a cached container. The exact CI image could not be pulled because its ECR/SSO credentials had expired. No new tests were added; the existing failing cases cover the regression.

Summary by CodeRabbit

• Tests
  • Updated the KV-warmup planner test setup to use the correct scheduler synchronization state.

[coderabbitai]

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📥 Commits

Reviewing files that changed from the base of the PR and between 0951489 and e2461aa.

📒 Files selected for processing (1)

• components/src/dynamo/vllm/tests/test_vllm_instrumented_scheduler.py

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Walkthrough

Changes

KV warmup test setup

Layer / File(s)	Summary
Update test stub state components/src/dynamo/vllm/tests/test_vllm_instrumented_scheduler.py	The test stub replaces _kvwarm_stage_reported with _bench_synchronizer = None.

Priority: ⬇️ Low

Estimated code review effort: 1 (Trivial) | ~2 minutes

Merge Risk: ⚪ Minimal · up to e2461

This focused test-only change resolves the setup failure without introducing current merge-blocking risk.

🚥 Pre-merge checks | ✅ 3 | ❌ 2

❌ Failed checks (2 warnings)

Check name	Status	Explanation	Resolution
Description check	⚠️ Warning	The description provides a clear summary, technical details, and validation results. However, it omits the required Related Issues section and does not include the requested Where should the reviewer …	Add the required Related Issues section and explicitly choose the applicable issue-linking option, such as Relates to #14981 or Closes #14981. Add a Where should the reviewer start? section that identifies components/src/dynamo/vllm/tests/t…
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 1 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the test setup fix: initializing the synchronizer for the vLLM KV-warmup capacity test.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

Full details: Description check

Explanation

The description provides a clear summary, technical details, and validation results. However, it omits the required Related Issues section and does not include the requested Where should the reviewer start? section.

Resolution

Add the required Related Issues section and explicitly choose the applicable issue-linking option, such as Relates to #14981 or Closes #14981. Add a Where should the reviewer start? section that identifies components/src/dynamo/vllm/tests/test_vllm_instrumented_scheduler.py.

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