feat(concurrency): free-threaded CPython support — memory-ordering fixes, gil_used=false, CI lane (LAB-511) - #265
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…xes, gil_used=false, CI lane (LAB-511) Make cachekit-py provably race-free under free-threaded CPython and gate regressions in CI: - decorators/session.py: the lock-free fast path and in-lock double-check now gate on every published field (_session_start_ms included). Assignment order only guaranteed visibility order under the GIL; a GIL-free reader observing pid+id before start_ms hit the 'should never happen' RuntimeError and silently dropped session headers (the LAB-506 telemetry loss, resurfacing GIL-free). Regression tests pin the mid-publish state deterministically and fail pre-fix. - reliability/metrics_collection.py: AsyncMetricsCollector.flush polled Queue.empty(), which flips at dequeue — before processing finishes. Waits on unfinished_tasks now. Was a routine flake on the free-threaded lane. - rust/src/lib.rs: #[pymodule(gil_used = false)] — the PyO3 0.28+ default made explicit, justified by the LAB-511 audit (AtomicU64 nonce, Mutex metrics, &self-only pyclasses, Send+Sync compiler-enforced). - CI: new test-freethreaded job runs unit+critical on 3.14t, asserts the GIL stays disabled after importing cachekit (hiredis excluded — no Py_mod_gil declaration; redis-py falls back to pure-Python parser). - pyproject: dependency-groups split into test (free-threading-compatible core toolchain) + dev (includes test; adds the extras without free-threaded wheels: orjson, numpy, pandas, pyarrow). - tests: importorskip guards so the core suites honestly run without the [data]/[json] extras; full audit table in docs/free-threading.md. Free-threaded wheels/classifiers explicitly deferred: orjson (build rejects free-threaded), hiredis (no Py_mod_gil), numpy/pandas/pyarrow coverage.
…p encryption/protocol suites (LAB-511) Panel findings applied: - tests/conftest.py: autouse session-scoped fixture fails the run if the GIL got re-enabled on a free-threaded build — runs in EVERY xdist worker and both suites, covering lazily-imported extensions the single-process CI pre-flight and one-worker in-suite check missed (bug-hunter MAJ). - test_encryption_security_invariants.py / test_serializer_protocol.py: module-level importorskip narrowed to the 2+1 tests that actually need orjson/pyarrow — the encryption invariants and protocol-compliance suites now run on the free-threaded lane (craftsman MAJ x2; +35 tests). - README/docs: support claim narrowed to 3.14t — the only build the lane runs (craftsman MIN). Rejected: cutting test_session_headers_present_mid_publish as duplicate — it pins the get_session_headers fallback branch; the end-to-end test pins the info.session_id branch. Distinct paths, both stay.
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WalkthroughThe pull request adds Python 3.14 free-threaded CI coverage, declares the Rust extension as GIL-independent, hardens session and metrics concurrency behaviour, makes optional-dependency tests skip safely, and documents current support limits. ChangesFree-threaded CPython support
Estimated code review effort: 4 (Complex) | ~45 minutes Merge Risk: 🔵 Low · up to This change makes metrics flushing wait for in-flight work, but one regression-test failure path can leave its worker running and interfere with later tests. Address the cleanup ordering before merge. Sequence Diagram(s)sequenceDiagram
participant CPython314t
participant CacheKit
participant RustExtension
participant SessionState
CPython314t->>CacheKit: import CacheKit
CacheKit->>RustExtension: import Rust extension
RustExtension-->>CPython314t: declare GIL disabled
CacheKit->>SessionState: initialise session
SessionState-->>CacheKit: publish complete identity
🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
✨ Finishing Touches 💡 1📝 Generate docstrings 💡
🧪 Generate unit tests (beta)
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Inline comments:
In `@docs/free-threading.md`:
- Around line 68-72: Update the documented free-threaded installation command in
docs/free-threading.md to include --no-install-package hiredis, matching the CI
job and preventing redis[hiredis] from installing hiredis.
In `@src/cachekit/reliability/metrics_collection.py`:
- Line 303: Update flush around the metric queue wait to avoid accessing Queue
internals such as unfinished_tasks or all_tasks_done. Use a collector-owned
condition or event to track completion while preserving the bounded timeout
behavior, and signal it whenever queued metric processing finishes so completion
is observed without the current polling delay.
In `@tests/critical/test_production_data_patterns.py`:
- Line 34: Move the module-level pandas import skip into
test_pandas_dataframe_enterprise_scenarios, keeping pandas imported or skipped
only within that test. Ensure the other tests in the module remain runnable
without pandas installed.
In `@tests/unit/test_serializer_integrity.py`:
- Around line 12-14: Move the pyarrow and orjson dependency guards from module
scope into their respective serializer test groups in
tests/unit/test_serializer_integrity.py, keeping each lazy serializer import
guarded only by the dependencies it requires. Ensure a missing optional backend
skips only that backend’s tests while allowing the other group to be collected;
leave the existing pandas setup and cache_serializer_compat.py behavior
unchanged.
In `@tests/unit/test_xxhash_integrity.py`:
- Around line 20-22: Move optional-dependency guards out of module scope in
tests/unit/test_xxhash_integrity.py: apply pandas and PyArrow skips only to the
Arrow tests, orjson only to the Orjson tests, and NumPy only to the two
NumPy-specific tests. Update the related guard in
tests/unit/test_key_generator_blake2b.py similarly so missing optional packages
skip only the tests that use them; leave unrelated tests runnable.
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.github/workflows/ci.ymlREADME.mddocs/README.mddocs/free-threading.mdpyproject.tomlrust/src/lib.rssrc/cachekit/decorators/session.pysrc/cachekit/reliability/metrics_collection.pytests/conftest.pytests/critical/test_cache_serializer_compression.pytests/critical/test_cache_serializer_patterns.pytests/critical/test_encryption_integration.pytests/critical/test_production_data_patterns.pytests/unit/test_arrow_serializer.pytests/unit/test_auto_serializer_mutation_and_corruption.pytests/unit/test_auto_serializer_new_types.pytests/unit/test_auto_serializer_numpy_integrity.pytests/unit/test_docs_conftest_no_key_leak.pytests/unit/test_encryption_security_invariants.pytests/unit/test_free_threading.pytests/unit/test_key_generator_blake2b.pytests/unit/test_mmap_read_path.pytests/unit/test_orjson_serializer.pytests/unit/test_saas_observability.pytests/unit/test_serializer_integrity.pytests/unit/test_serializer_lazy_loading.pytests/unit/test_serializer_protocol.pytests/unit/test_xxhash_integrity.py
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…nambiguous (LAB-511) CodeRabbit flagged docs/free-threading.md:72 as omitting --no-install-package hiredis from the documented free-threaded install command. The flag was already-present-but-wrapped: the inline command spanned two markdown lines and the reviewer read only the first. Moved it into a one-line fenced block so it cannot be misread or half-copied, and matches ci.yml byte-for-byte. Also (Review Panel non-blocking note on 0234dab): the audit-table row for AsyncMetricsCollector.flush said the pending-work condition is 'signaled after task_done()'; the real signal is notify_all() when the collector-owned pending counter reaches zero. Reworded to describe the shipped mechanism. CodeRabbit-Resolved: docs/free-threading.md:72:Match the documented ins
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Inline comments:
In `@src/cachekit/reliability/metrics_collection.py`:
- Line 301: Update the worker-thread handling around _worker_thread to return
immediately when it is absent or not alive, then keep the existing timeout logic
at the top level without unnecessary nesting.
In `@tests/unit/test_metrics_collection.py`:
- Around line 176-182: Wrap the assertions after starting the flush thread in a
finally block that always sets allow_processing, performs a bounded thread.join,
and calls collector.shutdown. Preserve the existing timing assertions while
ensuring cleanup runs when either assertion fails.
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…leanup (LAB-511) - AsyncMetricsCollector.flush: early-return when the worker is absent or dead instead of nesting the wait under the liveness check (repo rule: guard clauses over nesting). Behaviour unchanged. - test_flush_waits_for_inflight_processing: release the blocked worker, bounded-join the flush thread and shut the collector down in a finally, so a failed assertion cannot leave a daemon thread parked in process_metric for the rest of the test process. Verified on 3.13 (GIL) and 3.14t (GIL disabled): metrics tests 6/6 stable runs each, full unit suite 2038 / 1784 passed. CodeRabbit-Resolved: src/cachekit/reliability/metrics_collection.py:301:Return early when _worker CodeRabbit-Resolved: tests/unit/test_metrics_collection.py:182:Always release the blocked
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Inline comments:
In `@tests/unit/test_metrics_collection.py`:
- Line 178: Update the test cleanup flow around processing_started.wait and the
collector worker: initialize thread to None, move the readiness assertion inside
the try block, and ensure allow_processing is set and collector shutdown runs in
finally even when readiness times out. Join the worker only when it has
successfully started.
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…adiness timeout (LAB-511) The readiness assertion (processing_started.wait) sat before the try, so a timeout there skipped the finally: allow_processing never set, collector never shut down, daemon worker left running for the rest of the process. Hoisted the enqueue + readiness wait into the try; thread starts as None and is joined only once started. Verified 3.13 (GIL) and 3.14t (GIL disabled): 6/6 stable runs. CodeRabbit-Resolved: tests/unit/test_metrics_collection.py:178:Move the cleanup block befor
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Closes LAB-511.
Makes cachekit-py provably race-free under free-threaded CPython, with a CI lane that gates regressions. No wire/format change; crypto surfaces untouched.
The defect (LAB-506 panel, comment b80e0145)
decorators/session.py::_ensure_session_initializedpublished three module globals and relied on assignment order for its lock-free fast path — a guarantee only the GIL provides. A GIL-free reader observingpid+idbefore_session_start_mssailed intoget_session_start_ms()'s "should never happen"RuntimeError, whichbackend.pycatches and turns into silently dropped session headers — the exact telemetry loss LAB-506 eliminated, resurfacing GIL-free. The fast path and in-lock double-check now gate on every published field. Regression tests pin the mid-publish state deterministically (fail pre-fix, pass post-fix) and an 8-thread hammer races first-touch init for real on the free-threaded lane.What the free-threaded lane surfaced
Running the suites on 3.14t found a second real bug:
AsyncMetricsCollector.flush()polledQueue.empty(), which flips at dequeue — before processing finishes. Routine flake under true concurrency, invisible under the GIL. Now waits onunfinished_tasks(zeroed bytask_done()after processing).Changes
decorators/session.pyfull-field gate; regression tests intest_saas_observability.py::TestMidPublishMemoryOrdering+test_free_threading.py.docs/free-threading.md(stats registry + fork handlers,_FunctionStats, session identity, header cache, L1/L2 SWR single-flight,ObjectCache,_cached_keys, metrics singleton, Rust extension).#[pymodule(gil_used = false)](the 0.28+ default made explicit); justified by audit:&self-only pyclasses,AtomicU64nonce,Mutexmetrics,Send + Synccompiler-enforced.test-freethreadedjob:uv sync --python 3.14t --no-default-groups --group test --no-install-package hiredis(hiredis has noPy_mod_gildeclaration; redis-py falls back to its pure-Python parser), asserts the GIL stays disabled after importing cachekit, runs unit + critical. Wired intoci-success. An autouse session fixture re-asserts GIL state at teardown in every xdist worker.test(free-threading-compatible core toolchain) split out ofdev(which includes it viainclude-group);devresolves identically to before.pytest.importorskipso the core suites honestly run without the[data]/[json]extras; narrowed to per-test scope where a module-level skip would have dropped extra-free coverage (encryption invariants, protocol compliance).docs/free-threading.md(support status, audit table, deferral), README thread-safety section.Deferred (per acceptance criteria, explicitly)
Free-threaded wheels / declared support blocked on upstream: orjson (build script rejects free-threaded interpreters, no FT wheels through 3.12.0), hiredis (no
Py_mod_gil), numpy/pandas/pyarrow ([data]extra coverage incomplete). When they clear: add-i python3.14tto thebuild-wheelsmatrix.Verification
Summary by CodeRabbit
Bug Fixes
Compatibility
Documentation
Tests