fix(test): raise spawn-child join timeout in test_multi_process_visibility

[erichare]

Problem

Nightly run 27253229568 failed on Unit Tests - Python 3.12 - Group 5: test_flow_events_service.py::test_multi_process_visibility failed all 12 executions (5 pytest reruns × 2 step attempts) with AssertionError: Child process failed to append event.

The reruns failed exactly 10s apart — the proc.join(timeout=10) deadline, not a product bug. The test spawns a child via the multiprocessing spawn context, which cold-imports the full langflow package (plus coverage's multiprocessing hooks in CI) before appending a single event. On a loaded runner sharing 4 vCPUs with a second xdist worker that routinely exceeds 10s. This is a latent flake exposed by the test-group rebalance in #13583 (the test now runs alongside heavier neighbors).

Fix

• Raise the liveness bound to 60s — join returns as soon as the child exits, so the passing case is unaffected
• Kill the child if it's still alive at the deadline so a hung spawn can't leak into later tests

Test plan

• uv run pytest src/backend/tests/unit/test_flow_events_service.py — 16 passed in 5.3s locally
• Re-run nightly failed job after merge

Summary by CodeRabbit

• Tests
  • Improved robustness of process shutdown handling in tests with enhanced timeout management and force-termination logic.

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: 69f9420d-a342-4a57-afaa-bcc01690f37b

📥 Commits

Reviewing files that changed from the base of the PR and between 1744792 and 443f1fd.

📒 Files selected for processing (1)

• src/backend/tests/unit/test_flow_events_service.py

---

Walkthrough

The test test_multi_process_visibility is enhanced to handle child process shutdown more robustly. The initial join() timeout is increased to 60 seconds, and if the process has not terminated, it is force-killed via terminate() followed by an additional 5-second join to ensure cleanup.

Changes

Test process cleanup robustness

Layer / File(s)	Summary
Robust child process shutdown handling src/backend/tests/unit/test_flow_events_service.py	Extended proc.join() timeout from 10 to 60 seconds and added fallback force-kill with terminate() and additional 5-second join if the process remains alive after the initial timeout.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Suggested labels

ignore-for-release

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/multiprocess-test-spawn-timeout

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[github-actions]

✅ Test Coverage Advisor

No source changes detected without accompanying tests. Thanks for keeping coverage up! 🎉

Advisory check only — never blocks merge.