[gevent worker] prevent late monkey-patching in pytest

[ayubun]

🤖 summary

prevents gevent test modules from monkey-patching an already-running plain pytest process, while preserving the gevent worker's pre-patched integration runner and forced-exit workaround

related issues/tasks

• Bump grpcio to 1.82.1 #415
• [async worker] run unit tests in CI #467
• [ci] isolate compose test stack #469

changes made (˶ᵔ ᵕ ᵔ˶)

• avoid calling gevent.monkey.patch_all() after plain pytest has started
• tie the forced-exit workaround to pytest starting under the pre-patched gevent runner
• add subprocess regression coverage for every import-time monkey-patch site

models used

• anthropic/claude-opus-4-8: ~50%
• openai/gpt-5.6-sol: ~30%
• anthropic/claude-haiku-4-5: ~15%
• anthropic/claude-fable-5: ~5%

testing

• plain collection completed with 1,286 worker tests
• the pre-patched runner still collected all 5 discovery tests

Summary by CodeRabbit

• Bug Fixes

  • Improved test startup handling to prevent failures caused by late concurrency setup.
  • Prevented unnecessary process termination when tests modify concurrency behavior during execution.

• Tests

  • Added regression coverage confirming representative test modules collect successfully with standard pytest.
  • Verified collection completes without lock-release errors or collection failures.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro Plus

Run ID: f5f9602d-ded6-47f7-aa05-e2bf8c01c826

📥 Commits

Reviewing files that changed from the base of the PR and between 1cbf04b and 05ce29a.

📒 Files selected for processing (5)

• osprey_worker/conftest.py
• osprey_worker/src/osprey/worker/lib/discovery/tests/test_discovery.py
• osprey_worker/src/osprey/worker/lib/etcd/tests/conftest.py
• osprey_worker/src/osprey/worker/lib/instruments/tests/test_concurrency.py
• osprey_worker/tests/test_gevent_collection.py

Included review availability: Your plan provides up to 2 included reviews per hour; 0 remain after this review.

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📝 Walkthrough

Walkthrough

The changes prevent late gevent monkey-patching during plain pytest collection. Session finalization now uses the launch-time socket-patching state. New subprocess tests verify successful collection for representative modules.

Changes

Gevent collection behavior

Layer / File(s)	Summary
Launch-time session state osprey_worker/conftest.py	Records the initial socket-patching state and uses it during pytest_sessionfinish.
Conditional gevent patching osprey_worker/src/osprey/worker/lib/discovery/tests/test_discovery.py, osprey_worker/src/osprey/worker/lib/etcd/tests/conftest.py, osprey_worker/src/osprey/worker/lib/instruments/tests/test_concurrency.py	Applies gevent monkey-patching only when the socket module is already patched.
Plain collection regression coverage osprey_worker/tests/test_gevent_collection.py	Runs plain pytest --collect-only in child processes and checks exit status, error output, and collection summaries.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to 05ce2

This PR prevents late gevent monkey-patching in plain pytest while preserving the pre-patched worker path; no actionable merge-blocking risk remains beyond normal checks and review.

Suggested reviewers: exbreder

Sequence Diagram(s)

sequenceDiagram
  participant RegressionTest
  participant ChildPython
  participant Pytest
  participant TestModules
  RegressionTest->>ChildPython: Run pytest --collect-only
  ChildPython->>Pytest: Collect representative test module
  Pytest->>TestModules: Import test configuration
  TestModules-->>Pytest: Patch gevent only if socket is already patched
  Pytest-->>RegressionTest: Return collection status and output

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🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 75.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 4 functions across 5 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: preventing late gevent monkey-patching during pytest execution in the worker.
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.

✨ Finishing Touches 💡 1

📝 Generate docstrings 💡

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch ayu/pytest-gevent-collection

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[julietshen]

LGTM, tiny nit on a false green if there are zero tests

[julietshen]

i think this will also say this if it's empty, no?