test(anr): Use pure-JS busy work so ANR stack samples capture longWork#22133
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test(anr): Use pure-JS busy work so ANR stack samples capture longWork#22133mydea wants to merge 1 commit into
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The ANR tests intermittently failed because the captured stacktrace was missing the required `longWork` frame — the sample showed only `node:internal/timers` frames instead. Root cause: `longWork` blocked the event loop via `crypto.pbkdf2Sync`, a native addon call. The ANR worker samples the main thread through the inspector, which can only pause at a JS safepoint — V8 cannot pause inside a native call, so the pause resolves only after `pbkdf2Sync` returns. When ANR fired near the tail of `longWork`, the pause landed after the call returned and control had popped back to the timer dispatch, so the sampled stack missed `longWork` entirely. Replace the native crypto busy-work with a pure-JS CPU loop in every ANR scenario (both node-core and node integration tests). V8 can now sample inside `longWork`, so it reliably appears on the captured stack. `longWork` stays defined locally in each scenario to preserve the per-file `filename` assertions. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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isaacs
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LGTM. The math seems kind of unnecessary, but harmless.
| const start = Date.now(); | ||
| let n = 1; | ||
| while (Date.now() - start < 1000) { | ||
| n = (n * 1103515245 + 12345) % 2147483648; |
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This math seems kind of silly? It's not significantly different than just n++, since it's going to run about 35M times in a second, regardless. The more costly work is just the Date.now() check.
timfish
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The ANR integration tests intermittently failed because the captured stacktrace was missing the required
longWorkframe — the sample showed onlynode:internal/timersframes (processTimers/listOnTimeout/insert) instead, anddebug_metawas absent.Root cause:
longWorkblocked the event loop viacrypto.pbkdf2Sync, a native addon call. The ANR worker samples the main thread through the inspector, which can only pause at a JS safepoint — V8 cannot pause inside a native call, so the pause resolves only afterpbkdf2Syncreturns. When ANR fired near the tail oflongWork, the pause landed after the call had returned and control had popped back to the timer dispatch, so the sampled stack missedlongWorkentirely.longWorkblocks ~880ms locally (well over the 100ms threshold), so this was a sampling-boundary race, not a too-short block.This replaces the native crypto busy-work with a pure-JS CPU loop in every ANR scenario, across both the node-core and node integration test suites. V8 can now sample inside
longWork, so it reliably appears on the captured stack.longWorkstays defined locally in each scenario to preserve the per-filefilenameassertions (e.g.isolated.mjs).Verified locally: both suites pass 12/12 across repeated runs.
Fixes #21702
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