http: move invariant IncomingMessage defaults to the prototype

anonrig · anonrig · commit af61c79edb69 · 2026-07-07T18:30:10.000-04:00
Fields the parser (or the client/server glue) assigns before user code
can observe the message (httpVersion*, url, method, statusCode,
statusMessage, upgrade) become prototype defaults instead of nine
per-request own-property stores.

Note: for messages that never get these fields assigned (bare
IncomingMessage construction outside the parser path), they disappear
from Object.keys()/spread results, though property reads are unchanged.
Kept as a separate commit so it can be dropped independently if that
tradeoff is unwanted.

Together with the previous commit this measures +8.46% requests per
CPU-second (p=2.2e-11, 15x600k-request interleaved samples) over the
pre-series baseline.

Assisted-by: Grok
Signed-off-by: Yagiz Nizipli &lt;yagiz@nizipli.com&gt;
diff --git a/lib/_http_incoming.js b/lib/_http_incoming.js
@@ -65,9 +65,6 @@ function IncomingMessage(socket) {
 
   this.socket = socket;
 
-  this.httpVersionMajor = null;
-  this.httpVersionMinor = null;
-  this.httpVersion = null;
   this.complete = false;
   this[kHeaders] = null;
   this[kHeadersCount] = 0;
@@ -78,15 +75,6 @@ function IncomingMessage(socket) {
   this.joinDuplicateHeaders = false;
   this.aborted = false;
 
-  this.upgrade = null;
-
-  // request (server) only
-  this.url = '';
-  this.method = null;
-
-  // response (client) only
-  this.statusCode = null;
-  this.statusMessage = null;
   this.client = socket;
 
   this._consuming = false;
@@ -98,6 +86,20 @@ function IncomingMessage(socket) {
 ObjectSetPrototypeOf(IncomingMessage.prototype, Readable.prototype);
 ObjectSetPrototypeOf(IncomingMessage, Readable);
 
+// Fields the parser (or the client/server glue) assigns before user code
+// can observe the message live on the prototype as defaults instead of
+// being written per instance: ~9 fewer own-property stores per request.
+IncomingMessage.prototype.httpVersionMajor = null;
+IncomingMessage.prototype.httpVersionMinor = null;
+IncomingMessage.prototype.httpVersion = null;
+IncomingMessage.prototype.upgrade = null;
+// Request (server) only.
+IncomingMessage.prototype.url = '';
+IncomingMessage.prototype.method = null;
+// Response (client) only.
+IncomingMessage.prototype.statusCode = null;
+IncomingMessage.prototype.statusMessage = null;
+
 ObjectDefineProperty(IncomingMessage.prototype, 'connection', {
   __proto__: null,
   get: function() {
