http: add V8 Fast API to http parser #61751

mcollina · 2026-02-09T13:57:22Z

Summary

Add V8 Fast API support for HTTP parser methods: free, remove, pause, resume, and unconsume
These methods bypass V8's argument marshaling overhead on the fast path
Provides modest performance improvements (2-3%) in HTTP client request body handling benchmarks

Implementation Details

Added *Impl() helper functions to share logic between slow and fast paths
Fast API functions use TRACK_V8_FAST_API_CALL for tracing
Methods registered on instance template using SetFastMethod
External references registered for snapshot support

Note: Close() and Consume() cannot use Fast API because:

Close() deletes the parser object (unsafe in fast path)
Consume() requires unwrapping StreamBase from JS object

Benchmark Results (10 runs, statistically significant)

Benchmark	Change	Confidence
`client-request-body.js method='end' len=1024 type='buf'`	+3.19%	**
`client-request-body.js method='write' len=256 type='utf'`	+3.56%	*
`client-request-body.js method='write' len=256 type='buf'`	+2.86%	*
`client-request-body.js method='end' len=256 type='buf'`	+2.67%	**
`headers.js group='fewHeaders' len=5 n=10`	+2.65%	*
`simple.js chunkedEnc=0 c=50 chunks=1 len=4 type='buffer'`	+2.27%	**

Test plan

All HTTP/HTTPS tests pass (730 tests)
Benchmark comparison with main branch

nodejs-github-bot · 2026-02-09T13:57:28Z

Review requested:

@nodejs/http
@nodejs/net

codecov · 2026-02-09T15:24:23Z

Codecov Report

❌ Patch coverage is 73.46939% with 13 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.72%. Comparing base (1e8a639) to head (b83b335).
⚠️ Report is 11 commits behind head on main.

Files with missing lines	Patch %	Lines
src/node_http_parser.cc	73.46%	12 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #61751      +/-   ##
==========================================
- Coverage   89.73%   89.72%   -0.01%     
==========================================
  Files         675      675              
  Lines      204525   204672     +147     
  Branches    39314    39320       +6     
==========================================
+ Hits       183523   183645     +122     
+ Misses      13300    13296       -4     
- Partials     7702     7731      +29

Files with missing lines	Coverage Δ
src/node_http_parser.cc	`83.96% <73.46%> (-0.77%)`	⬇️

... and 50 files with indirect coverage changes

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Copilot

Pull request overview

This PR adds V8 Fast API support to several HTTPParser instance methods in src/node_http_parser.cc to reduce argument marshaling overhead and improve HTTP client request body handling performance.

Changes:

Added Fast API variants for free, remove, pause, resume, and unconsume, with shared *Impl() helpers for slow/fast paths.
Registered Fast API methods via SetFastMethod(...) and added v8::CFunction external references for snapshot compatibility.
Added Fast API call tracing via TRACK_V8_FAST_API_CALL.

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Copilot · 2026-02-09T17:42:11Z

src/node_http_parser.cc

    // Since the Parser destructor isn't going to run the destroy() callbacks
    // it needs to be triggered manually.
    parser->EmitTraceEventDestroy();
    parser->EmitDestroy();
  }


FreeImpl() calls EmitTraceEventDestroy()/EmitDestroy(). AsyncWrap::EmitDestroy() can schedule SetImmediate / microtasks and touch V8 handles, which is not safe to run from a V8 Fast API callback. The fast path should either be removed for free, or FastFree should take FastApiCallbackOptions& and force a fallback to the slow callback whenever destroy hooks are enabled (or whenever it would call into V8).

Copilot · 2026-02-09T17:42:12Z

src/node_http_parser.cc

+  static void FastPause(Local<Object> receiver) {
+    if constexpr (should_pause) {
+      TRACK_V8_FAST_API_CALL("http_parser.pause");
+    } else {
+      TRACK_V8_FAST_API_CALL("http_parser.resume");


FastPause()/FastResume() bypass the context invariant enforced in the slow path (CHECK_EQ(env, parser->env())). That means cross-context usage would no longer be caught on the fast path, potentially masking bugs and diverging behavior. Consider adding a fast-path guard (e.g., obtain the current Environment* and CHECK_EQ, or use FastApiCallbackOptions& to fall back to the slow callback when the current context/Environment does not match).

Add V8 Fast API support for the following HTTP parser methods: - free(): triggers destroy callbacks - remove(): removes parser from connections list - pause(): pauses the HTTP parser - resume(): resumes the HTTP parser - unconsume(): removes parser as stream listener The following methods were intentionally not converted: - close(): deletes the parser object, unsafe in Fast API - consume(): requires unwrapping StreamBase from JS object This improves performance by bypassing V8's argument marshaling overhead for these frequently called methods.

gurgunday

Looks great! I tried doing this a few months ago and didn't get any performance improvements. But maybe I did something wrong. The code LGTM.

nodejs-github-bot added c++ Issues and PRs that require attention from people who are familiar with C++. http_parser Issues and PRs related to the HTTP Parser dependency or the http_parser binding. needs-ci PRs that need a full CI run. labels Feb 9, 2026

mcollina force-pushed the http-parser-fast-api branch from 2934b6f to a8e3a7f Compare February 9, 2026 17:35

mcollina requested review from addaleax, anonrig and Copilot February 9, 2026 17:35

Copilot started reviewing on behalf of mcollina February 9, 2026 17:36 View session

Copilot AI reviewed Feb 9, 2026

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mcollina force-pushed the http-parser-fast-api branch from a8e3a7f to b83b335 Compare February 9, 2026 17:58

gurgunday added the needs-benchmark-ci PR that need a benchmark CI run. label Feb 9, 2026

gurgunday approved these changes Feb 9, 2026

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http: add V8 Fast API to http parser #61751

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mcollina commented Feb 9, 2026 •

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mcollina commented Feb 9, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Summary

Implementation Details

Benchmark Results (10 runs, statistically significant)

Test plan

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