fix: XD cold-start scenario races JVM startup on CI runners#13
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The XD ``test_cold_start_scenario`` introduced in #12 used a blind ``time.sleep(0.25)`` followed by a direct ``JavaGateway()`` connect attempt. On CodSpeed CI runners (and any host slower than a modern laptop) the JVM hadn't yet bound its listen socket when the connect fired, surfacing as ``ConnectionRefusedError: [Errno 111] Connection refused`` and failing the whole codspeed workflow. Switch XD's body to the existing ``fresh_jvm`` context manager with ``readiness_retries=5``. ``fresh_jvm`` polls connection readiness with ``check_connection`` and only proceeds once the JVM is actually accepting calls — same convention the rest of the test suite uses. This also drops a bunch of try/finally boilerplate since ``fresh_jvm`` handles spawn/shutdown. Locally on M-series + JDK 21: XD median ~355 ms (unchanged from post-#12 baseline). The variance is higher in cold-start measurement by nature; what matters is the elimination of hard failures on slower hosts. Co-authored-by: Isaac
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py4j#557) (py4j#595) Adds four CodSpeed scenarios mapping 1:1 to py4j cold-start improvement work areas, plus tightens the perf-framework JVM readiness check so slow scenarios get enough samples per benchmark budget. Pure measurement infrastructure — zero behavior change in py4j proper. Touches only the perf testing subtree. New scenarios: * XA-3 — attribute_walk_jvm_java_lang_System 1 000 walks of ``gateway.jvm.java.lang.System``. Each walk re-issues 3 reflection round-trips today because JVMView / JavaPackage / JavaClass __getattr__ don't memoize. Cache canary for the upcoming Python attribute-cache PR. * XB — gateway_reconnect_against_running_jvm 50 fresh ``JavaGateway()`` against the fixture JVM per round. Measures per-connection setup cost — Java accept() loop allocates 14 command class instances per connection (GatewayConnection.java:196-208), Python runs _create_connection + socket setup. * XC — callback_infra_overhead_unused X1-1 workload with ``CallbackServer`` started, but no callbacks actually invoked. Delta vs X1-1 = the steady-state cost of running callback infrastructure alongside the main gateway. * XD — full_cold_start_subprocess_first_call subprocess.Popen -> first call -> shutdown, one cycle per round. Slow per-iteration; CodSpeed adapts iteration count. Target of the JVM-flag work (AppCDS, -XX:TieredStopAtLevel=1, CRaC). XA/XB/XC share the long-running fixture JVM (``test_macro_scenario``). XD owns its full JVM lifecycle inside ``measure()`` and is dispatched via a separate ``test_cold_start_scenario`` test function — it can't share the fixture because both default to port 25333. Readiness model overhaul in ``perf.jvm.fresh_jvm``: before: 0.25 s sleep + 1 retry x 2.0 s = 2.25 s ceiling after: 0 s sleep + 300 retries x 0.05 s = 15 s ceiling Tight polling matters for XD on CodSpeed: under the old model each XD iteration cost ~2.7 s and CodSpeed could fit only one sample per benchmark budget, making variance and regression detection impossible. Under the new model XD per-iteration finishes in ~500-1100 ms — enough for 2-5 samples per budget. The unconditional 0.25 s startup_sleep's original rationale ("let the OS reuse the listen port") no longer applies: GatewayServer.startSocket() already uses SO_REUSEADDR, so bind() succeeds immediately even over TIME_WAIT. Backwards compatibility preserved — callers can pass ``startup_sleep=0.25`` to restore the old wait pattern. Validated on #12, #13, #16 (where these changes originated as 3 iterative PRs; bundled here for a clean single upstream review surface). Full 56-cell CI matrix green on each byteoak iteration. CodSpeed scenarios surface real cold-start work on subsequent PRs — issue py4j#557. Co-authored-by: Isaac
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Summary
PR-0 (#12) introduced XD as a CodSpeed cold-start scenario, but its body used
time.sleep(0.25)+ directJavaGateway()connect — on CI runners the JVM hadn't bound its listen socket yet, surfacing asConnectionRefusedError: [Errno 111]and failing the whole codspeed workflow on the merged commit.Switch XD to the existing
fresh_jvm(readiness_retries=5)context manager so connection readiness is polled rather than blind-slept.Diff
macro.py: -24 / +10 — replaced inline spawn/sleep/try-finally withfresh_jvmdelegation.Local verification
Variance is higher in cold-start measurement by nature — what matters is the elimination of hard CI failures.
Test plan
pytest src/py4j/tests/perf/scenarios/codspeed_macros.py::test_cold_start_scenario -vpasses locally