test(fault_tolerance): skip flaky sglang migration NATS combo, drop stale graceful_shutdown xfail by dmitry-tokarev-nv · Pull Request #8404 · ai-dynamo/dynamo

dmitry-tokarev-nv · 2026-04-20T20:41:08Z

Summary

Two small, related changes to tests/fault_tolerance/migration/test_sglang.py to stop the post-merge sglang / Test cuda* (amd64) job from failing on main:

Skip the single flaky parameter combination test_request_migration_sglang_aggregated[migration_enabled-max_seq_len_disabled-worker_failure-chat-stream-nats]. It has failed on every amd64 post-merge run this cycle — e.g. runs 24685348314, 24683926404, 24683166462, 24680832233, 24680530215. The adjacent TCP variant is stable. Failure signature:
```
AssertionError: Delay before response > 6 secs, got 13.050 secs
tests/fault_tolerance/migration/utils.py:417 in validate_response
```
Only the NATS transport is affected — first-token delay under migration lands around 13s where the 6s assertion trips.
Remove the xfail(reason="SGLang graceful shutdown not yet implemented") mark on the graceful_shutdown (immediate_kill=False) parameter. Every non-skipped graceful_shutdown[-chat-stream-*] combination (both nats and tcp, across all migration_limit × migration_max_seq_len values) has been XPASS in the same runs above, so the stated reason no longer holds.

The skip references a TODO(<LINEAR-ID>) placeholder — please swap in the real Linear ticket ID before merge. Last author on the file / the delay <= 6.0 assertion in utils.py:417 is @kthui, who should own the follow-up investigation.

Test plan

Post-merge sglang / Test cuda12.9 (amd64) passes with the skip in place
The previously-xfailed graceful_shutdown-chat-stream-{nats,tcp} combos run as regular passing cases (no XPASS, no XFAIL)
Swap <LINEAR-ID> placeholder for real Linear ticket ID before merge

🤖 Generated with Claude Code

Summary by CodeRabbit

Tests
- Re-enabled graceful shutdown test case previously marked as expected to fail.
- Added conditional skip for specific parameter combinations experiencing timing-related flakiness to improve test stability.

…tale graceful_shutdown xfail Skips the single parameter combination test_request_migration_sglang_aggregated[migration_enabled-max_seq_len_disabled-worker_failure-chat-stream-nats] which has failed on every amd64 post-merge run this cycle (e.g. runs 24685348314, 24683926404, 24683166462, 24680832233, 24680530215). The TCP sibling is stable. Skip references a TODO placeholder until the Linear ticket ID is filled in before merge. Also removes the xfail mark on the graceful_shutdown parameter: every non-skipped graceful_shutdown[-chat-stream-*] combination has been XPASS for the last several post-merge runs, so the "SGLang graceful shutdown not yet implemented" reason no longer holds. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> Signed-off-by: Dmitry Tokarev <dtokarev@nvidia.com>

coderabbitai · 2026-04-20T20:44:24Z

Walkthrough

Test file updated to remove an xfail wrapper from a graceful shutdown test parameter case and add a runtime conditional skip for a specific combination of test parameters related to flaky first-token delay behavior.

Changes

Cohort / File(s)	Summary
Test Parameter Updates `tests/fault_tolerance/migration/test_sglang.py`	Removed `pytest.mark.xfail` wrapper from `immediate_kill=False` test parameter case in `test_request_migration_sglang_aggregated`. Added runtime conditional skip for specific parameter combination: `migration_limit == 3`, `migration_max_seq_len is None`, `immediate_kill is True`, `request_api == "chat"`, `stream is True`, `request_plane == "nats"` to handle flaky first-token delay issue.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes both main changes: skipping a flaky test combo and removing a stale xfail mark.
Description check	✅ Passed	The description provides comprehensive details about changes, test failures, and a concrete test plan, though it lacks explicit linkage to specific related issues.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

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coderabbitai

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@tests/fault_tolerance/migration/test_sglang.py`:
- Around line 238-252: The TODO marker "TODO(<LINEAR-ID>)" in both the skip
message and the preceding comment should be replaced with the actual Linear
ticket ID (or a real issue identifier) so the flaky-test debt is trackable;
update the comment above the conditional and the pytest.skip(...) reason string
that guard the branch checking migration_limit, migration_max_seq_len,
immediate_kill, request_api, stream, and
request.getfixturevalue("request_plane") to include the real ticket ID (e.g.,
TODO(LINEAR-1234) or LINEAR-1234) or an actionable issue link and keep the
existing conditional logic unchanged.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

Push a commit to this branch (recommended)
Create a new PR with the fixes

ℹ️ Review info

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Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: d7af7411-7254-443e-8d53-399c5aa2204d

📥 Commits

Reviewing files that changed from the base of the PR and between cdb40ec and 8b869e4.

📒 Files selected for processing (1)

tests/fault_tolerance/migration/test_sglang.py

coderabbitai · 2026-04-20T20:44:27Z

+    # TODO(<LINEAR-ID>): Flaky on NATS transport — first-token delay routinely
+    # exceeds the 6s threshold in utils.validate_response. Other parameter
+    # combinations (including the TCP variant) are stable.
+    if (
+        migration_limit == 3
+        and migration_max_seq_len is None
+        and immediate_kill is True
+        and request_api == "chat"
+        and stream is True
+        and request.getfixturevalue("request_plane") == "nats"
+    ):
+        pytest.skip(
+            "Flaky on NATS transport: first-token delay > 6s threshold. "
+            "TODO(<LINEAR-ID>)"
+        )


⚠️ Potential issue | 🟡 Minor

Replace the Linear placeholder before merge.

The skip is targeted correctly, but both the comment and skip reason still contain TODO(<LINEAR-ID>), which makes the tracked flaky-test debt unactionable once merged.

If helpful, I can update this once you provide the real Linear ticket ID.

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed. In `@tests/fault_tolerance/migration/test_sglang.py` around lines 238 - 252, The TODO marker "TODO(<LINEAR-ID>)" in both the skip message and the preceding comment should be replaced with the actual Linear ticket ID (or a real issue identifier) so the flaky-test debt is trackable; update the comment above the conditional and the pytest.skip(...) reason string that guard the branch checking migration_limit, migration_max_seq_len, immediate_kill, request_api, stream, and request.getfixturevalue("request_plane") to include the real ticket ID (e.g., TODO(LINEAR-1234) or LINEAR-1234) or an actionable issue link and keep the existing conditional logic unchanged.

sara4dev

better to create linear ticket so we don't forget later to investigate the root cause & fix

Signed-off-by: Dmitry Tokarev <dtokarev@nvidia.com>

…(OPS-4446) PR #8404 skipped only the NATS variant of test_request_migration_sglang_aggregated[migration_enabled-max_seq_len_disabled-worker_failure-chat-stream-*] because the TCP variant was stable at the time. Starting from the first post-merge run after that skip landed, the TCP variant began failing with the same symptom (AssertionError: Delay before response > 6 secs, got ~13 secs at utils.py:417) in every run: 24733651809, 24733908729, 24734216001, 24735128282, and onwards. The cause is ordering: when NATS ran first, it warmed the path; with NATS skipped, TCP now pays the cold-start cost itself. Drop the request_plane == "nats" clause so both transports skip, and also replace the stale TODO(<LINEAR-ID>) comment with the OPS-4446 reference that the skip reason string already uses. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> Signed-off-by: Dmitry Tokarev <dtokarev@nvidia.com>

dmitry-tokarev-nv requested review from a team as code owners April 20, 2026 20:41

pull-request-size Bot added the size/S label Apr 20, 2026

github-actions Bot added the test label Apr 20, 2026

coderabbitai Bot reviewed Apr 20, 2026

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sara4dev approved these changes Apr 20, 2026

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dmitry-tokarev-nv commented Apr 21, 2026

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Comment thread tests/fault_tolerance/migration/test_sglang.py Outdated

Apply suggestion from @dmitry-tokarev-nv

9d88a2e

Signed-off-by: Dmitry Tokarev <dtokarev@nvidia.com>

copy-pr-bot Bot temporarily deployed to GITLAB April 21, 2026 16:19 Inactive

dmitry-tokarev-nv merged commit e6ce4db into main Apr 21, 2026
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dmitry-tokarev-nv deleted the dtokarev/skip-flaky-migration-nats-test branch April 21, 2026 16:20

copy-pr-bot Bot had a problem deploying to GITLAB April 21, 2026 17:20 Failure

dmitry-tokarev-nv mentioned this pull request Apr 21, 2026

test: stabilize nightly — skip engine-init failures, convert xfails to skips, fix http URL validation regression #8443

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test(fault_tolerance): skip flaky sglang migration NATS combo, drop stale graceful_shutdown xfail - #8404

test(fault_tolerance): skip flaky sglang migration NATS combo, drop stale graceful_shutdown xfail#8404
dmitry-tokarev-nv merged 2 commits into
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dtokarev/skip-flaky-migration-nats-test

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