http: cache parser callbacks

[mcollina]

Cache the kOnHeadersComplete, kOnBody, and kOnMessageComplete lookups in internal fields on each parser’s JS object, rather than in strong v8::Global handles. This avoids an independent strong reference when a callback captures its parser.

The cache is cleared when the parser is initialized or freed. Callbacks replaced while a parser is active are picked up on its next initialization. Header names remain non-internalized because clients control them.

The new test covers repeated requests, callback replacement on reinitialization, and release of a cached callback on free(). The Release build, lint, formatting check, and focused tests passed. In the broader HTTP run, 500 tests passed and one timed out; the timed-out test passed when rerun alone.

[nodejs-github-bot]

Review requested:

• @nodejs/http
• @nodejs/net

[mcollina]

@nodejs/diagnostics ptal. Not sure if anyone is monkeypatching those callbacks on the fly.

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/77666/

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.37%. Comparing base (c0681e5) to head (2504fd1).
⚠️ Report is 12 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #66152   +/-   ##
=======================================
  Coverage   90.37%   90.37%           
=======================================
  Files         790      790           
  Lines      274514   274526   +12     
  Branches    52572    52576    +4     
=======================================
+ Hits       248102   248115   +13     
+ Misses      16889    16884    -5     
- Partials     9523     9527    +4     

Files with missing lines	Coverage Δ
src/node_http_parser.cc	85.33% <100.00%> (+0.45%)	⬆️

... and 24 files with indirect coverage changes

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[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/77790/

[Flarna]

Suggested change

	Local<Value> CachedCallback(uint32_t index, v8::Global<v8::Value>* cache) {
	Local<Value> CachedCallback(uint32_t index, v8::Global<v8::Value>& cache) {

maybe?
And change -> by . to access it.

[Flarna]

should this be done earlier, e.g. when parser is moved into freelist on managed side instead on next use?

[Flarna]

Is there a reason why kOnHeaders callback is not cached?
Are the two complete callbacks called more then once per HTTP request? I assume caching for single use would be not helpful.

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/77863/

[addaleax]

1. v8::Global referring to callbacks is a memory leak footgun, as any reference from the callback back to the parser will create an indefinite memory leak
2. If we do use v8::Globals, they need to be tracked in the Parser class's MemoryInfo method

If we do want to cache these methods, internal fields are likely a better choice (or, as a secondary option, weak v8::Globals, but I'd carefully evaluate the performance of that approach)

[github-actions]

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