fix(py-isolation-saga): document wait_for cancel semantics on timeout#2174
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imran-siddique merged 1 commit intoMay 12, 2026
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`SagaOrchestrator.execute_step` and `.compensate` both wrap their
callable in `asyncio.wait_for(callable, timeout=step.timeout_seconds)`.
The standing audit question was whether wait_for *awaits* the
cancellation it issues, or just signals it and moves on.
CPython's `asyncio.wait_for` does in fact wait for the cancellation to
complete before raising `TimeoutError`. Cooperative executors with
`await` points get a chance to release resources. But:
- Executors with no `await` points (synchronous CPU work inside an
`async def`) are not cancellable by Python at all — the timeout
only fires once the executor next yields control.
- Callers needing hard-kill semantics must run such executors in a
process or thread pool and arrange external termination.
Document this contract on `execute_step`; cross-reference from
`compensate`. No behaviour change — pure docstring clarification.
🤖 AI Agent: code-reviewer — View detailsNo issues found. Clean change. |
🤖 AI Agent: test-generator — View detailsTest coverage looks good. No gaps identified. |
🤖 AI Agent: security-scanner — View detailsNo security issues found. |
🤖 AI Agent: docs-sync-checker — Docs SyncDocs Sync
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🤖 AI Agent: breaking-change-detector — View detailsNo breaking changes detected. |
|
🟡 Contributor Check: MEDIUM
Automated check by AGT Contributor Check. |
PR Review Summary
Verdict: ✅ Ready for human review |
MohammadHaroonAbuomar
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Jun 1, 2026
…microsoft#2174) `SagaOrchestrator.execute_step` and `.compensate` both wrap their callable in `asyncio.wait_for(callable, timeout=step.timeout_seconds)`. The standing audit question was whether wait_for *awaits* the cancellation it issues, or just signals it and moves on. CPython's `asyncio.wait_for` does in fact wait for the cancellation to complete before raising `TimeoutError`. Cooperative executors with `await` points get a chance to release resources. But: - Executors with no `await` points (synchronous CPU work inside an `async def`) are not cancellable by Python at all — the timeout only fires once the executor next yields control. - Callers needing hard-kill semantics must run such executors in a process or thread pool and arrange external termination. Document this contract on `execute_step`; cross-reference from `compensate`. No behaviour change — pure docstring clarification.
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Summary
saga/orchestrator.py'sSagaOrchestrator.execute_stepand.compensateboth wrap their callable inasyncio.wait_for(callable, timeout=step.timeout_seconds). The standing audit question was whetherwait_forawaits the cancellation it issues, or just signals it and moves on.CPython's
asyncio.wait_fordoes wait for the cancellation to complete before raisingTimeoutError(see Python docs). Cooperative executors withawaitpoints get a chance to release resources. But:awaitpoints (synchronous CPU work inside anasync def) are not cancellable by Python at all — the timeout only fires once the executor next yields control.The behaviour is correct as-is; what's missing is the contract being documented for callers writing executors.
Change
Add a
Cancellation semantics on timeout:block toexecute_step's docstring naming the cooperative-cancel contract and the two failure modes. Cross-reference fromcompensate's docstring.Pure documentation change — no behaviour delta.
Tests
No new tests needed (documentation change).
Test plan
Surfaced during independent audit conducted by @finnoybu (Ken Tannenbaum, AEGIS Initiative); [LOW, Python Isolation].