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fix(parity): contain fork-bombing tests in the node-suite harness - #6762

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proggeramlug merged 11 commits into
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fix/parity-harness-cluster-fork-bomb
Jul 30, 2026
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fix(parity): contain fork-bombing tests in the node-suite harness#6762
proggeramlug merged 11 commits into
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fix/parity-harness-cluster-fork-bomb

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@TheHypnoo

@TheHypnoo TheHypnoo commented Jul 22, 2026

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Problem

Running the full node-suite parity run locally (./run_parity_tests.sh --suite node-suite) kills the host machine. Two cluster tests (cluster/setup/validation-exec-args and cluster/setup/validation-serialization-inspect) fork-bomb under Perry: each forked worker re-execs itself and forks again. The harness's 10s timeout only kills the direct child, so the orphaned workers keep replicating until the macOS per-user process cap saturates — at which point the harness itself can no longer fork() and the suite dies mid-run. Reproduced twice: both runs died at the same spot with fork: Resource temporarily unavailable, leaving ~1,500 orphaned processes behind.

Fix (two layers, both in run_parity_tests.sh)

  1. Per-test fork budget. Each perry test binary now runs under /bin/sh -c 'ulimit -u <current user procs + 50>; exec …'. Legitimate multi-process tests (cluster/child_process spawn 2–4 workers) fit easily; a fork bomb stalls at ~50 orphans instead of starving the harness.
  2. Post-test orphan sweep. After every test, pkill -9 -f "$PARITY_TMP/" reaps anything still running from this run's tmp dir. Scoped to the per-run mktemp -d path, so concurrent suite runs are unaffected.

Note: a global ulimit -u around the whole suite does not work — the harness inherits the limit, the bomb pins the process count at the cap, and the cleanup pkill itself can no longer fork. (Tried; failed in practice.)

Validation

Full node-suite run (3,873 tests, Node 26.5.0) completes end-to-end with this fix: 3,815 run, 3,019 pass (79.1%), report generated. The two bombing tests are correctly classified as CRASH (timeout) and no orphan processes remain after the run (verified with ps). First 21 tests all pass under the wrapper, confirming it doesn't perturb normal execution.

The underlying Perry bug (cluster.fork re-exec loop) is a separate issue — this PR only makes the harness survive it.

Summary by CodeRabbit

  • Bug Fixes
    • Hardened the Node parity test runner to prevent runaway Perry processes that can lead to fork-bomb behavior, orphaned children, or resource starvation between tests.
    • Improved timed execution safeguards by applying stricter per-run process limits when system metrics are available.
    • Strengthened cleanup after test failures or timeouts to forcibly reap any leftover worker processes, improving stability for concurrent suite runs.

Two cluster/setup tests (validation-exec-args, validation-serialization-
inspect) re-exec themselves recursively under Perry. The harness's 10s
timeout only kills the direct child, so orphaned workers kept forking
until the macOS per-user process cap saturated and killed the suite
itself mid-run (twice), leaving ~1500 orphans behind.

Containment, two layers:
- Run each perry test binary under its own fork budget
  (current user procs + 50 via a /bin/sh ulimit wrapper): legit
  multi-process tests fit easily, a fork bomb stalls at ~50 orphans
  instead of starving the harness out of fork().
- Reap orphans after every test with pkill scoped to this run's
  PARITY_TMP dir, so concurrent suite runs are unaffected.

A global ulimit around the whole suite does not work: the harness
inherits it, the bomb pins the process count at the cap, and the
cleanup pkill itself can no longer fork.
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coderabbitai Bot commented Jul 22, 2026

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Review Change Stack

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Review failed

The pull request is closed.

ℹ️ Recent review info
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  • changelog.d/6762-parity-fork-containment.md
  • crates/perry-codegen/src/loop_purity.rs

📝 Walkthrough

Walkthrough

The parity runner now limits Perry’s per-test process usage and cleans up orphaned descendants. A changelog entry documents the fix, and an unrelated code-generation match arm is reformatted without behavioral changes.

Changes

Parity process hardening

Layer / File(s) Summary
Process limiting and orphan cleanup
run_parity_tests.sh, changelog.d/6762-parity-fork-containment.md
Perry runs through a timed shell wrapper that measures the current user’s process count, applies ulimit -u with a 50-process allowance, aborts with exit code 125 if setup fails, and terminates matching orphaned processes after the run. The changelog records this containment behavior.

Codegen formatting

Layer / File(s) Summary
Buffer index match-arm formatting
crates/perry-codegen/src/loop_purity.rs
The Expr::BufferIndexGet branch is reformatted without changing its allocation analysis logic.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related issues

  • PerryTS/perry 6848 — Addresses orphaned parity-test processes exhausting the per-user process table.
🚥 Pre-merge checks | ✅ 5
✅ Passed checks (5 passed)
Check name Status Explanation
Title check ✅ Passed The title clearly summarizes the main change: containing fork-bombing parity tests in the node-suite harness.
Description check ✅ Passed The description covers the problem, fix, and validation clearly, though it does not follow the template headings exactly.
Docstring Coverage ✅ Passed No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
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.
✨ Finishing Touches
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  • Commit on current branch
🧪 Generate unit tests (beta)
  • Create PR with unit tests
  • Commit unit tests in branch fix/parity-harness-cluster-fork-bomb

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Actionable comments posted: 3

🤖 Prompt for all review comments with AI agents
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@run_parity_tests.sh`:
- Around line 760-761: Update the process-limit setup immediately before the
exec command to validate both the process-count calculation and the ulimit -u
application. Capture or check each operation’s status, abort with a nonzero
status if either fails, and only execute Perry after the limit has been
successfully established.
- Around line 760-761: Replace the per-process ulimit-based budget around the
Perry execution command with coordinated resource isolation: use a cgroup or
container PID limit scoped to this run, or serialize runs through a shared
budget mechanism. Ensure concurrent module runs and unrelated processes cannot
consume the run’s reserved process capacity, while preserving the existing exec
invocation and environment setup.
- Line 767: Replace the raw-path pkill invocation in the parity test cleanup
with targeted termination of the tracked test process group or PIDs. If
retaining pkill, escape the temporary path for literal matching and verify the
selector before sending SIGKILL, ensuring unrelated processes cannot be
terminated.
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Comment thread run_parity_tests.sh Outdated
Comment thread run_parity_tests.sh Outdated
TheHypnoo and others added 4 commits July 22, 2026 16:34
…kill pattern

CodeRabbit review of #6762:
- If ps can't measure the current process count, skip the cap entirely
  (fail open, commented why) instead of computing ulimit -u 50 from a
  zero count — a bogus low cap would silently break every legitimate
  multi-process test. The cap is containment, not a correctness gate;
  the post-test reap still runs either way.
- pkill -f treats its pattern as an ERE, so escape the tmp-dir path's
  metacharacters (the mktemp component contains a dot) before matching.

Validated: node-suite path module runs end-to-end through the updated
wrapper (97.8%, same 2 known mismatches as the 2026-07-22 baseline,
0 crashes).

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Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@run_parity_tests.sh`:
- Around line 765-780: Update the process-counting logic before the ulimit call
in the run_with_timeout block to count all current user tasks/threads rather
than only process leaders returned by ps -u -o pid=. Use a Linux-compatible
task-level count, preserve the existing validation and failure handling, and
continue setting the limit relative to that count.
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Fix all unresolved CodeRabbit comments on this PR:

  • Push a commit to this branch (recommended)
  • Create a new PR with the fixes

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📒 Files selected for processing (1)
  • run_parity_tests.sh

Comment thread run_parity_tests.sh Outdated
@TheHypnoo TheHypnoo added bug Confirmed defect or regression parity Compatibility gap with Node.js, ECMAScript, or the supported ecosystem tooling Developer tooling, CI, tests, or release infrastructure labels Jul 26, 2026
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