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fix(#1586): pin withPlanningLock liveness probe in perf-407 for determinism

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#1531/#1532 replaced withPlanningLock's mtime-staleness with PID-liveness
(process.kill(pid,0)). perf-407 plants pid: process.pid + 1 and relied on the
old mtime model to force the retry/sleep path; under the new model that pid's
liveness is environment-dependent, so the retry path was taken on some runners
and skipped on others (sleepCallCount: 0 precondition failure) — flaky CI red
on next that blocks the merge queue.

Pin the planted holder live via the _setLockProbes seam that #1532 added, and
_resetLockProbes() in afterEach. The retry/sleep path is now exercised
deterministically on every runner. No assertion weakened; no variable renamed.
perf-316 is unaffected (its worker writes the parent's own, always-live pid).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
This commit is contained in:
Tom Boucher
2026-06-22 12:33:13 -04:00
parent 5c8509cf7b
commit 7013406f0b
1 changed files with 22 additions and 1 deletions
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23
tests/perf-407-planning-lock-buffer-alloc.test.cjs
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@@ -93,6 +93,9 @@ function spySAB() {
describe('perf #407: withPlanningLock hoists sleep buffer — exactly one SAB per call', () => {
let tmpDir;
let lockPath;
// Keep a reference to the module so _setLockProbes/_resetLockProbes are
// accessible across beforeEach/afterEach boundaries.
let mod;
beforeEach(() => {
tmpDir = makeTempDir();
@@ -100,6 +103,12 @@ describe('perf #407: withPlanningLock hoists sleep buffer — exactly one SAB pe
});
afterEach(() => {
// Reset the liveness probe to the real implementation so other tests
// (or subsequent runs) are not affected by our deterministic override.
if (mod) {
mod._resetLockProbes();
mod = null;
}
try { fs.unlinkSync(lockPath); } catch { /* already gone */ }
removeTempDir(tmpDir);
// Purge module cache so each test gets a fresh require (and fresh SAB spy window).
@@ -119,12 +128,24 @@ describe('perf #407: withPlanningLock hoists sleep buffer — exactly one SAB pe
// Purge any previously cached versions so the spy catches module-level allocs.
delete require.cache[PLANNING_WORKSPACE_CJS_PATH];
delete require.cache[CLOCK_CJS_PATH];
withPlanningLock = require(PLANNING_WORKSPACE_CJS_PATH).withPlanningLock;
mod = require(PLANNING_WORKSPACE_CJS_PATH);
withPlanningLock = mod.withPlanningLock;
} finally {
spy.restore();
}
const sabCountAtLoad = spy.getCount();
// ── Inject deterministic liveness probe ───────────────────────────────
// PR #1532 replaced mtime-staleness with PID-liveness (process.kill(pid,0))
// to decide whether a contending lock holder should be waited on (live) or
// immediately stolen (dead). The test plants pid: process.pid + 1, which is
// environment-dependent: on some runners that pid is alive, on others it is
// not, making the retry/sleep path non-deterministic and causing CI flakiness
// (issue #1531). The _setLockProbes seam lets us pin the decision: treating
// the planted pid as LIVE deterministically forces the SUT into the retry path
// on every runner, which is exactly what the test intends to exercise.
mod._setLockProbes({ isPidAlive: (pid) => pid === process.pid + 1 });
// ── Step 2: pre-create the lock file (simulates a contending process) ──
// writing a valid lock JSON so withPlanningLock's stale-check doesn't
// delete it immediately (mtime is NOW, well within the 30s stale window).