test(perf): free-threaded decorated-call scaling bench and default-install GIL check (LAB-7060) by 27Bslash6 · Pull Request #424 · cachekit-io/cachekit-py

27Bslash6 · 2026-10-01T20:31:17Z

Adds a manual free-threading bench that times whole decorated calls, and a test for the GIL state a default install ends up in on CPython 3.14t. No CI change.

Why

tests/performance/gil_benchmark.py times StandardSerializer.serialize alone, so it never sees the shared state a decorated call touches: the L1 lock, per-function stats, metrics, the Rust ByteStorage and the backend client. The free-threaded CI lane installs without hiredis, so its GIL assertions never see what pip install cachekit gets on 3.14t, where hiredis is a default dependency.

What

tests/performance/ft_scaling_bench.py runs decorated L1-hit, L2-stub and loopback-CachekitIO cells at 1, 4 and 16 threads. Each arm runs in its own process, and every rep runs all arms in a seeded shuffled order: PYTHON_GIL=0, an A/A repeat of it, PYTHON_GIL=1 on the same binary, PYTHON_GIL unset, and an optional GIL build. The summary reports calls/s and scaling (N threads over 1 thread, same process) as the median and min-max over reps, plus each arm's difference from the no-GIL arm with a 95% bootstrap CI. It drops a process whose GIL state changed mid-run. It flags a cell TAINTED when a timed call was not a hit or a backend call raised, and SERVER-BOUND when a worker of the fake was over 80% busy. The driver stops when an arm ran under the wrong GIL state, and it refuses to append to an existing results file. No lock sits in the timed loop.
tests/performance/loopback_saas.py is the TLS fake for the CachekitIO cell. It serves HTTP/2 and HTTP/1.1 by ALPN, so it keeps working if the sync client's protocol changes, and it reports per-worker CPU time on /__stats. The cell measures client-side contention only, never service latency.
tests/unit/test_free_threading.py::test_default_install_keeps_gil_disabled_after_redis_backend runs a fresh interpreter with hiredis present and the [data]/[json] extras blocked. It imports cachekit, builds a RedisBackend, and asserts the GIL is still off. That fails today: hiredis_compat imports redis.connection to clear HIREDIS_AVAILABLE, the import loads hiredis, and the flag is inert anyway because redis-py binds its parser at import. So the test lands as xfail(strict=True, raises=AssertionError), and the strict mark turns it red once the GIL stays off. test_gil_stays_disabled_with_hiredis_blocked is its control: the same probe with hiredis blocked passes, which shows hiredis is the only blocker. Both tests find hiredis through package metadata, so a fix that blocks hiredis through sys.modules still runs them. They skip on GIL builds and where hiredis is not installed (the CI lane). They strip PYTHON_GIL, so they cannot pass vacuously.
docs/free-threading.md relabels the measured table as serializer throughput, because it never measured cache throughput. It also documents the new bench, the default-install gap, and the shared HTTP/2 client race the bench surfaces (encode/httpcore#1118).

Testing

The xfail test XFAILs on 3.14.7t with hiredis installed and skips on 3.14 and in a lane-shaped env without hiredis. It fails as XPASS(strict) when the probe blocks hiredis, including when the pytest process blocks it too. It still XFAILs with PYTHON_GIL=0 in the parent. The control passes.
The bench ran end to end on 3.14.7t and 3.14.7, with 5 arms and 7 reps.
The unit and critical suites pass on 3.14 (3835 passed). The unit suite passes on 3.14.7t in the lane's env shape (3157 passed).
ruff check, ruff format --check and basedpyright pass on the changed files.

Docs: docs/free-threading.md and tests/performance/README.md updated.

Closes LAB-7060

…install GIL check (LAB-7060) gil_benchmark.py times StandardSerializer.serialize alone, and the free-threaded CI lane installs without hiredis, so neither sees the shared state a decorated call touches nor the GIL state a default install ends up in. ft_scaling_bench.py runs decorated L1-hit, L2-stub and loopback-CachekitIO cells at 1/4/16 threads across interleaved, rotated arms (no-GIL, an A/A repeat, PYTHON_GIL=1 on the same binary, PYTHON_GIL unset, a GIL build). It reports scaling ratios with rep spreads and bootstrap CIs, drops processes whose GIL state flipped mid-run, and flags cells where a timed call was not a hit. loopback_saas.py is the TLS fake (HTTP/2 and HTTP/1.1 by ALPN). Manual only; no CI change. The default-install check runs in a fresh interpreter with hiredis present and the extras blocked. It fails today because hiredis_compat runs after redis has imported hiredis, so it lands as xfail(strict=True) and flips when that is fixed. It skips where hiredis is absent, as in the CI lane. docs/free-threading.md: the measured table is serializer throughput, not cache throughput; document the bench, the default-install gap and the shared HTTP/2 client race the bench surfaces.

…w (LAB-7060) The xfail check now finds hiredis by package metadata, so a fix that blocks hiredis through sys.modules still runs it; harness failures are pytest.fail and the xfail only accepts AssertionError; a control test proves hiredis is the only thing re-enabling the GIL. The bench counts CachekitIO get/set errors as well as misses, flags cells where a fake worker is over 80% busy, shuffles arm order, refuses to append to an existing results file, checks each arm ran under the GIL state it claims, times out a hung arm, and fails a cell whose thread raised. Docs give the real hiredis_compat mechanism.

…LAB-7060) The sync decorated path reads through get_with_freshness, not get, so the error counter missed every read failure; misses still flagged those cells.

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docs/free-threading.md
tests/performance/ft_scaling_bench.py
tests/performance/loopback_saas.py

Summary by CodeRabbit

Documentation
- Expanded the free-threading guide with details on how optional hiredis availability affects GIL behaviour and how to interpret related test results.
- Clarified what the serializer benchmark measures and documented decorated-call scaling workloads, measurement methods and exclusions.
- Noted that CachekitIO no-GIL results may be affected by concurrent HTTP/2 request failures.
New Features
- Added a benchmark for comparing decorated cache-call throughput across GIL-enabled and free-threaded interpreters, with results and scaling summaries.

Walkthrough

The change adds fresh-interpreter tests for hiredis-related GIL behaviour and a benchmark for decorated cache calls across GIL modes and thread counts. It also adds a TLS loopback fake and updates the free-threading and performance documentation.

Changes

Hiredis free-threading probe

Layer / File(s)	Summary
Probe, assertions and documentation `tests/unit/test_free_threading.py`, `docs/free-threading.md`	The tests check GIL state after Redis backend initialisation, both with hiredis blocked and with the default installation. The documentation describes the cases and how to run them.

Decorated-call scaling benchmark

Layer / File(s)	Summary
TLS loopback fake `tests/performance/loopback_saas.py`	The fake serves GET, HEAD, PUT and DELETE requests over HTTP/2 or HTTP/1.1. It also exposes worker CPU statistics.
Benchmark workloads and cell measurement `tests/performance/ft_scaling_bench.py`, `tests/performance/README.md`, `docs/free-threading.md`	The benchmark measures decorated L1, in-process L2 and CachekitIO calls across thread counts. The documentation describes the workloads and clarifies the separate serializer benchmark measurement.
Benchmark execution and summary `tests/performance/ft_scaling_bench.py`, `docs/free-threading.md`	The driver validates interpreter arms, runs repetitions and records results. The summary filters tainted cells and reports throughput, scaling and paired comparisons.

Priority: ⬇️ Low

Estimated code review effort: 4 (Complex) | ~45 minutes

Change: Other

Sequence Diagram(s)

sequenceDiagram
  participant Driver as ft_scaling_bench.py
  participant Interpreter as Interpreter process
  participant Cache as Decorated cache calls
  participant Fake as loopback_saas.py
  participant Results as JSONL results
  Driver->>Interpreter: Run benchmark cell
  Interpreter->>Cache: Measure L1 and in-process L2 calls
  Interpreter->>Fake: Send CachekitIO requests
  Fake-->>Interpreter: Return responses and worker CPU totals
  Interpreter-->>Driver: Return cell measurements
  Driver->>Results: Append process results

Merge Risk: 🟡 Moderate · up to f9562

Reject free-threaded binaries for the standard-build control before relying on benchmark comparisons, and align the scripts with repository requirements before merging. These changes do not establish a new production-runtime failure.

Security Architecture Review

Security architecture risk: 🔵 Low · up to f9562

The benchmark uses synthetic data, an explicit test credential, and a loopback-only endpoint. Its security overrides are confined to benchmark subprocesses. Remaining exposure is local, including a startup-interruption cleanup gap; no introduced production security issue was established.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

inferred — A local client can read, replace, or delete fake cache entries and request worker statistics without authentication. The demonstrated scope is synthetic state and resources in the benchmark server process; the inspected request handler has no production tenant-data, credential, or persistent-store sink.

Trust Boundaries and Controls

observed — Loopback binding limits network reachability but does not authenticate other local clients. Client-side certificate trust remains explicit, and the SSRF-check relaxation is process-local rather than a production policy change.

Resilience and Maintainability Implications

inferred — Post-start failures enter a finally block that terminates and waits for the fake. Readiness acquisition occurs before that block, so interruption during startup can leave the unauthenticated loopback process alive. This is a local test-resource containment limitation, not established production corruption or a verified security vulnerability.

Hardening Proposals

proposed — Extend fake-process cleanup ownership across startup and readiness acquisition, with bounded readiness and termination waits and a kill fallback, to keep the local listener short-lived on interruption.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 22.50% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 40 functions across 3 files. (2 skipped: …	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the free-threaded decorated-call benchmark and the default-install GIL check. It is concise and directly related to the main changes.
Description check	✅ Passed	The description clearly covers the changes, motivation, testing, documentation updates, and issue reference. It does not use all template headings or record the security, change type, and backward-com…
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.

Full details: Docstring Coverage

Explanation

Docstring coverage is 22.50% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 40 functions across 3 files. (2 skipped: 2 unsupported.)

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kodus-27b · 2026-10-01T20:31:33Z

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A code review identified the following issues in this pull request.
Each section describes what was found and includes a reference implementation where available.

Files involved:
- tests/performance/ft_scaling_bench.py:103
- tests/performance/ft_scaling_bench.py:187
- tests/performance/ft_scaling_bench.py:243
- tests/performance/loopback_saas.py:34
- tests/performance/loopback_saas.py:134

---

### [1/5] tests/performance/ft_scaling_bench.py:103
Issue identified during code review:
Violates team rule 'Add specific exception handling': Catch and handle only the exceptions you expect (e.g., KeyError, ValueError, TimeoutError); let unknown ones bubble.

---

### [2/5] tests/performance/ft_scaling_bench.py:187
Issue identified during code review:
Violates team rule 'No hardcoded API key/token literal in credential-named variable': WHAT: Flag a string literal assigned to a variable, constant, struct field, or default value whose name indicates a credential (api_key, token, secret, password, access_key, client_secret) in non-test source code.
HOW: In ADDED lines, look for `let/const/static <credential-ish name> = "..."` or `credential_field: "..."` where the right-hand side is a literal instead of an env/secret lookup.

---

### [3/5] tests/performance/ft_scaling_bench.py:243
Issue identified during code review:
Violates team rule 'Replace print statements with logging framework': Use the standard logging module (or your app's logger) instead of print() in committed code.

---

### [4/5] tests/performance/loopback_saas.py:34
Issue identified during code review:
WHAT: `STORE` is a module-level mutable dict that `handle()` mutates from every worker thread.
WHY: Global mutable state shared across threads behaves unpredictably and makes the fake hard to reset or reuse in tests.
HOW: Put the store in a small class (e.g. `class Store` holding a dict, plus a lock if needed). Create one instance in `main()` and pass it to `handle` and `_Protocol`, for example via a protocol factory.

---

### [5/5] tests/performance/loopback_saas.py:134
Issue identified during code review:
Missing argument validation in loopback_saas.py main(): `sys.argv[1]` through `sys.argv[3]` are indexed and `port` and `workers` are converted with `int()` without any length or range checks. Running the script with fewer than three arguments, such as only a port, crashes with a bare `IndexError` instead of printing usage. Fix: check `len(sys.argv) >= 4` and print the usage string if it fails, and reject `port` outside `0..65535` or `workers < 1` with a clear message, or switch to argparse.

---

Review each issue in context, use the reference implementations as guidance, and apply fixes that are consistent with the surrounding codebase.

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…he CI by rep (LAB-7060) A tainted cell measures fallback throughput, not cache-hit scaling, yet it still fed the medians and the bootstrap, so an all-tainted arm could print a conclusive difference. Tainted cells are now excluded everywhere, a ratio needs a clean 1-thread cell, and the table shows how many clean reps remain. Each rep is a session block holding every arm, so the difference from ft-nogil is now the median of per-rep paired differences, its CI resamples whole reps, and fewer than five clean pairs prints "insufficient clean reps" instead of a CI. Independent resampling per arm threw away that session control.

kodus-27b · 2026-10-01T20:42:06Z

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Actionable comments posted: 3

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Inline comments:
Review comments at @tests/performance/ft_scaling_bench.py:
- Around line 295-296: Update the build validation in the benchmark flow around
ARMS so the gil-build arm rejects interpreters with free_threaded_build=True,
while preserving the existing check that FT arms require a free-threaded build.
- Line 81: Update the public run_cell signature to annotate make_op as
Callable[[int], Callable[[], object]], importing Callable from collections.abc.
- Line 437: Replace direct argparse configuration in ft_scaling_bench.py at
lines 437-437 with typed pydantic-settings loaded before benchmark dispatch, and
load loopback_saas.py’s port, certificate paths, and worker count through typed
pydantic-settings at lines 133-134. Route both entrypoints’ configuration
exclusively through pydantic-settings while retaining their existing options and
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docs/free-threading.md
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tests/performance/loopback_saas.py
tests/unit/test_free_threading.py

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…LAB-7060) gil-build checked only the runtime GIL state, so a free-threaded --gil-python whose imports switched the GIL back on (hiredis does) was recorded as the GIL-build control. The driver now also checks the build. summarise keyed results by rep alone, and reps restart at 0 each session, so a file that pooled two sessions silently overwrote half its rows and paired one session's arm with another's ft-nogil. It now refuses a file that repeats an (arm, rep). loopback_saas.py parses its argv with argparse, so a short or bad command line prints usage instead of an IndexError, and it rejects a port outside 0-65535 or fewer than one worker. run_cell's make_op is typed.

kodus-27b · 2026-10-01T21:04:20Z

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27Bslash6 · 2026-10-01T21:04:26Z

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27Bslash6 added 3 commits October 2, 2026 06:03

test(perf): count CachekitIO get_with_freshness errors in the bench (…

1611a0d

…LAB-7060) The sync decorated path reads through get_with_freshness, not get, so the error counter missed every read failure; misses still flagged those cells.