lib: defer AbortSignal.any() following

[Han5991]

Summary

• defer following source signals for AbortSignal.any() until the composite is observed
• keep composite state in sync via lazy refresh and follow paths
• unregister fired timeout signals from clearTimeoutRegistry to reduce timeout churn retention
• add regression coverage for long-lived and timeout churn cases

Problem

AbortSignal.any() eagerly registered listener-less composites as dependants of their source signals. With a long-lived source, repeated AbortSignal.any([source]) calls accumulated in kDependantSignals and retained memory (#62363).

While investigating broader AbortSignal churn, timeout-only churn also kept timeout finalization registry entries alive after timers had fired, which delayed cleanup.

What Changed

AbortSignal.any()

• listener-less composites no longer follow source signals eagerly
• composites follow their sources only when observed
• composite state is refreshed lazily when reading aborted, reason, or throwIfAborted()

AbortSignal.timeout()

• fired timeout signals now unregister themselves from clearTimeoutRegistry
• this releases timeout churn bookkeeping sooner after the timer has fired

Results

#62363 repro

• out/Release/node stayed flat through 2,000,000 iterations
• kDependantSignals stayed at 0

Timeout churn

Repro	Before patch	With patch
AbortSignal.timeout(1) after GC	rss 164.55 MiB, heap 23.15 MiB	rss 67.19 MiB, heap 3.96 MiB
AbortSignal.any([AbortSignal.timeout(1)]) after GC	rss 135.30 MiB, heap 7.85 MiB	rss 74.22 MiB, heap 4.01 MiB

Timeout churn logs

Before patch

AbortSignal.timeout(1)
start {"rss":"45.67","heap":"3.49"}
before-gc {"rss":"153.39","heap":"79.54"}
after-gc {"rss":"164.55","heap":"23.15"}
after-1-immediate {"rss":"160.23","heap":"6.28"}
after-50ms {"rss":"158.67","heap":"6.26"}

AbortSignal.any([AbortSignal.timeout(1)])
start {"rss":"45.72","heap":"3.49","handles":0}
before-gc {"rss":"133.58","heap":"32.48","handles":2}
after-gc {"rss":"135.30","heap":"7.85","handles":2}
after-1-immediate {"rss":"135.31","heap":"5.06","handles":2}
after-50ms {"rss":"135.31","heap":"5.04","handles":2}

With patch

AbortSignal.timeout(1)
start {"rss":"45.52","heap":"3.49"}
before-gc {"rss":"66.55","heap":"6.84"}
after-gc {"rss":"67.19","heap":"3.96"}
after-1-immediate {"rss":"67.20","heap":"3.88"}
after-50ms {"rss":"67.23","heap":"3.87"}

AbortSignal.any([AbortSignal.timeout(1)])
start {"rss":"45.58","heap":"3.49","handles":0}
before-gc {"rss":"73.52","heap":"9.82","handles":2}
after-gc {"rss":"74.22","heap":"4.01","handles":2}
after-1-immediate {"rss":"74.22","heap":"3.91","handles":2}
after-50ms {"rss":"74.22","heap":"3.90","handles":2}

Notes

The same-tick fresh AbortController microbenchmark from #54614 still shows heap growth until the next turn. That appears to be due to WeakRef cleanup semantics rather than long-lived source retention: the heap drops back after a setImmediate() and the weak references clear on the next turn.

Testing

• python3 tools/test.py test/parallel/test-abortsignal-any.mjs test/parallel/test-abort-controller-any-timeout.js test/parallel/test-abortsignal-drop-settled-signals.mjs test/parallel/test-abortsignal-timeout-memory.js test/parallel/test-abortcontroller.js

Fixes: #62363
Refs: #54614

[codecov]

Codecov Report

❌ Patch coverage is 76.74419% with 20 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.68%. Comparing base (7547e79) to head (f7a442c).
⚠️ Report is 89 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/internal/abort_controller.js	76.74%	20 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #62367      +/-   ##
==========================================
- Coverage   91.60%   89.68%   -1.92%     
==========================================
  Files         337      676     +339     
  Lines      140745   206752   +66007     
  Branches    21802    39593   +17791     
==========================================
+ Hits       128925   185433   +56508     
- Misses      11595    13465    +1870     
- Partials      225     7854    +7629     

Files with missing lines	Coverage Δ
lib/internal/abort_controller.js	95.29% <76.74%> (-2.98%)	⬇️

... and 459 files with indirect coverage changes

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[geeksilva97]

cc @atlowChemi

[Han5991]

@geeksilva97

Could you please rerun the failed CI jobs? Thank you!

[geeksilva97]

@geeksilva97

Could you please rerun the failed CI jobs? Thank you!

done

[Han5991]

@geeksilva97

I've been failing a lot lately. I'm asking you to try again.

parallel.test-http-expect-continue
parallel.test-http-dont-set-default-headers-with-setHost
parallel.test-http2-connect-method-extended-cant-turn-off

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/72391/ 💚

[geeksilva97]

CI is beating us

[Han5991]

@geeksilva97

The CI has finally been approved! Please merge it.

[geeksilva97]

@geeksilva97

The CI has finally been approved! Please merge it.

That's great! Thanks for such a nice PR. Added the tags, the bot will merge it soon

[nodejs-github-bot]

Landed in a9ac9b1