http: reduce per-request allocations in the server

Remove allocations and repeated work performed for every request:

- reuse a per-connection updateOutgoingData closure and a shared
  'finish' listener instead of binding two functions per request,
  reaching resOnFinish through the connection state stored on the
  response
- cache the ServerResponse options object per server (custom response
  classes keep receiving a fresh object)
- check for Host, Expect, Content-Length and Transfer-Encoding by
  scanning rawHeaders instead of materializing req.headers, which was
  built (with per-name toLowerCase calls) for every request even when
  the application never reads it
- cache the rendered status line per status code when the reason
  phrase is the default, skipping its character validation
- cache the complete 'Date: ...' header line in the utcDate cache and
  the keep-alive header pair for the current server settings
- compute the lenient-validation option chain once per message

Signed-off-by: Matteo Collina <hello@matteocollina.com>
PR-URL: #65802
Reviewed-By: Robert Nagy <ronagy@icloud.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Tim Perry <pimterry@gmail.com>
Reviewed-By: Gürgün Dayıoğlu <hey@gurgun.day>

Author: mcollina

lib/_http_incoming.js

@@ -536,6 +536,7 @@ function onError(self, error, cb) {
 module.exports = {
   IncomingMessage,
   kDetachAbortSignal,
+  kHeadersCount,
   readStart,
   readStop,
 };

lib/_http_outgoing.js

@@ -38,7 +38,7 @@ const { getDefaultHighWaterMark } = require('internal/streams/state');
 const assert = require('internal/assert');
 const EE = require('events');
 const Stream = require('stream');
-const { kOutHeaders, utcDate, kNeedDrain } = require('internal/http');
+const { kOutHeaders, utcDateHeader, kNeedDrain } = require('internal/http');
 const { Buffer } = require('buffer');
 const {
   _checkIsHttpToken: checkIsHttpToken,
@@ -86,6 +86,11 @@ const kChunkedLength = Symbol('kChunkedLength');
 const kUniqueHeaders = Symbol('kUniqueHeaders');
 const kBytesWritten = Symbol('kBytesWritten');
 const kErrored = Symbol('errored');
+const kLenientCache = Symbol('kLenientCache');
+
+let keepAliveTimeoutCache = -1;
+let keepAliveMaxCache = -1;
+let keepAliveHeaderCache = '';
 const kWritableFinished = Symbol('kWritableFinished');
 const kEndCallbacks = Symbol('kEndCallbacks');
 const kFlushError = Symbol('kFlushError');
@@ -162,6 +167,7 @@ function OutgoingMessage(options) {
   this[kFlushError] = null;
   this[kHighWaterMark] = options?.highWaterMark ?? getDefaultHighWaterMark();
   this[kRejectNonStandardBodyWrites] = options?.rejectNonStandardBodyWrites ?? false;
+  this[kLenientCache] = null;
 }
 ObjectSetPrototypeOf(OutgoingMessage.prototype, Stream.prototype);
 ObjectSetPrototypeOf(OutgoingMessage, Stream);
@@ -171,27 +177,34 @@ ObjectSetPrototypeOf(OutgoingMessage, Stream);
 // For ServerResponse: checks the server's httpValidation or insecureHTTPParser
 // Falls back to global --insecure-http-parser flag.
 OutgoingMessage.prototype._isLenientHeaderValidation = function() {
+  // The underlying options cannot change during the lifetime of a message:
+  // compute the lookup chain only once per message.
+  this[kLenientCache] ??= isLenientHeaderValidation(this);
+  return this[kLenientCache];
+};
+
+function isLenientHeaderValidation(msg) {
   // New httpValidation option takes priority (ClientRequest case)
-  if (this.httpValidation !== undefined) {
-    return this.httpValidation !== 'strict';
+  if (msg.httpValidation !== undefined) {
+    return msg.httpValidation !== 'strict';
   }
   // ServerResponse: check server's httpValidation option
-  const serverHttpValidation = this.req?.socket?.server?.httpValidation;
+  const serverHttpValidation = msg.req?.socket?.server?.httpValidation;
   if (serverHttpValidation !== undefined) {
     return serverHttpValidation !== 'strict';
   }
   // Legacy insecureHTTPParser - ClientRequest has it directly
-  if (typeof this.insecureHTTPParser === 'boolean') {
-    return this.insecureHTTPParser;
+  if (typeof msg.insecureHTTPParser === 'boolean') {
+    return msg.insecureHTTPParser;
   }
   // ServerResponse can access via req.socket.server
-  const serverOption = this.req?.socket?.server?.insecureHTTPParser;
+  const serverOption = msg.req?.socket?.server?.insecureHTTPParser;
   if (typeof serverOption === 'boolean') {
     return serverOption;
   }
   // Fall back to global option
   return isLenient();
-};
+}
 
 ObjectDefineProperty(OutgoingMessage.prototype, 'errored', {
   __proto__: null,
@@ -501,7 +514,7 @@ function _storeHeader(firstLine, headers) {
 
   // Date header
   if (this.sendDate && !state.date) {
-    header += 'Date: ' + utcDate() + '\r\n';
+    header += utcDateHeader();
   }
 
   // Force the connection to close when the response is a 204 No Content or
@@ -534,14 +547,21 @@ function _storeHeader(firstLine, headers) {
     if (shouldSendKeepAlive && this.maxRequestsOnConnectionReached) {
       header += 'Connection: close\r\n';
     } else if (shouldSendKeepAlive) {
-      header += 'Connection: keep-alive\r\n';
       if (this._keepAliveTimeout && this._defaultKeepAlive) {
-        const timeoutSeconds = MathFloor(this._keepAliveTimeout / 1000);
-        let max = '';
-        if (~~this._maxRequestsPerSocket > 0) {
-          max = `, max=${this._maxRequestsPerSocket}`;
+        // The keep-alive header lines are identical for every response of a
+        // given server: cache the last rendered value.
+        const timeout = this._keepAliveTimeout;
+        const max = ~~this._maxRequestsPerSocket;
+        if (timeout !== keepAliveTimeoutCache || max !== keepAliveMaxCache) {
+          keepAliveTimeoutCache = timeout;
+          keepAliveMaxCache = max;
+          keepAliveHeaderCache = 'Connection: keep-alive\r\n' +
+            `Keep-Alive: timeout=${MathFloor(timeout / 1000)}` +
+            (max > 0 ? `, max=${max}` : '') + '\r\n';
         }
-        header += `Keep-Alive: timeout=${timeoutSeconds}${max}\r\n`;
+        header += keepAliveHeaderCache;
+      } else {
+        header += 'Connection: keep-alive\r\n';
       }
     } else {
       this._last = true;

lib/_http_server.js

@@ -73,6 +73,7 @@ const {
 const {
   IncomingMessage,
   kDetachAbortSignal,
+  kHeadersCount,
 } = require('_http_incoming');
 const {
   ConnResetException,
@@ -116,6 +117,10 @@ const kServerResponseStatistics = Symbol('ServerResponseStatistics');
 const kUpgradeStream = Symbol('UpgradeStream');
 
 const kOptimizeEmptyRequests = Symbol('OptimizeEmptyRequestsOption');
+const kConnectionState = Symbol('ConnectionState');
+const kResponseOptions = Symbol('ResponseOptions');
+
+const statusLineCache = [];
 
 const {
   hasObserver,
@@ -470,10 +475,18 @@ function writeHead(statusCode, reason, obj) {
     headers = obj;
   }
 
-  if (checkInvalidHeaderChar(this.statusMessage))
-    throw new ERR_INVALID_CHAR('statusMessage');
+  let statusLine;
+  if (this.statusMessage === STATUS_CODES[statusCode]) {
+    // Default reason phrases contain no invalid characters and are shared
+    // across responses: cache the whole status line.
+    statusLine = statusLineCache[statusCode] ??=
+      `HTTP/1.1 ${statusCode} ${this.statusMessage}\r\n`;
+  } else {
+    if (checkInvalidHeaderChar(this.statusMessage))
+      throw new ERR_INVALID_CHAR('statusMessage');
 
-  const statusLine = `HTTP/1.1 ${statusCode} ${this.statusMessage}\r\n`;
+    statusLine = `HTTP/1.1 ${statusCode} ${this.statusMessage}\r\n`;
+  }
 
   if (statusCode === 204 || statusCode === 304 ||
       (statusCode >= 100 && statusCode <= 199)) {
@@ -820,7 +833,11 @@ function connectionListenerInternal(server, socket) {
     outgoingData: 0,
     requestsCount: 0,
     keepAliveTimeoutSet: false,
+    onPendingData: null,
+    server,
+    socket,
   };
+  state.onPendingData = updateOutgoingData.bind(undefined, socket, state);
   state.onData = socketOnData.bind(undefined,
                                    server, socket, parser, state);
   state.onEnd = socketOnEnd.bind(undefined,
@@ -1257,8 +1274,61 @@ function emitCloseNT(self) {
   }
 }
 
-function hasBodyHeaders(headers) {
-  return ('content-length' in headers) || ('transfer-encoding' in headers);
+// Check for the presence of a request header by scanning rawHeaders instead
+// of materializing the req.headers object. Only the first req[kHeadersCount]
+// entries are considered, matching what the req.headers getter exposes.
+function hasRequestHeader(req, length, lowerName) {
+  const rawHeaders = req.rawHeaders;
+  const count = req[kHeadersCount];
+  for (let i = 0; i < count; i += 2) {
+    const key = rawHeaders[i];
+    if (key.length === length &&
+        (key === lowerName || key.toLowerCase() === lowerName)) {
+      return true;
+    }
+  }
+  return false;
+}
+
+function hasBodyHeaders(req) {
+  const rawHeaders = req.rawHeaders;
+  const count = req[kHeadersCount];
+  for (let i = 0; i < count; i += 2) {
+    const length = rawHeaders[i].length;
+    if (length === 14 || length === 17) {
+      const key = rawHeaders[i].toLowerCase();
+      if (key === 'content-length' || key === 'transfer-encoding') {
+        return true;
+      }
+    }
+  }
+  return false;
+}
+
+// The options object passed to the ServerResponse constructor is identical
+// for every request of a given server: cache it. Custom response classes get
+// a fresh object since they may retain or mutate it.
+function getResponseOptions(server, socket) {
+  const highWaterMark = socket.writableHighWaterMark;
+  const rejectNonStandardBodyWrites = server.rejectNonStandardBodyWrites;
+  if (server[kServerResponse] !== ServerResponse) {
+    return { highWaterMark, rejectNonStandardBodyWrites };
+  }
+  let options = server[kResponseOptions];
+  if (options === undefined ||
+      options.highWaterMark !== highWaterMark ||
+      options.rejectNonStandardBodyWrites !== rejectNonStandardBodyWrites) {
+    options = server[kResponseOptions] =
+      { highWaterMark, rejectNonStandardBodyWrites };
+  }
+  return options;
+}
+
+// Shared 'finish' listener: everything resOnFinish needs is reachable from
+// the response, avoiding a bound function per request.
+function onResponseFinish() {
+  const state = this[kConnectionState];
+  resOnFinish(this.req, this, state.socket, state, state.server);
 }
 
 // The following callback is issued after the headers have been read on a
@@ -1291,15 +1361,11 @@ function parserOnIncoming(server, socket, state, req, keepAlive) {
     }
   }
 
-  const res = new server[kServerResponse](req,
-                                          {
-                                            highWaterMark: socket.writableHighWaterMark,
-                                            rejectNonStandardBodyWrites: server.rejectNonStandardBodyWrites,
-                                          });
+  const res = new server[kServerResponse](req, getResponseOptions(server, socket));
   res._keepAliveTimeout = server.keepAliveTimeout;
   res._maxRequestsPerSocket = server.maxRequestsPerSocket;
-  res._onPendingData = updateOutgoingData.bind(undefined,
-                                               socket, state);
+  res._onPendingData = state.onPendingData;
+  res[kConnectionState] = state;
 
   res.shouldKeepAlive = keepAlive;
   res[kUniqueHeaders] = server[kUniqueHeaders];
@@ -1314,7 +1380,7 @@ function parserOnIncoming(server, socket, state, req, keepAlive) {
   }
 
   // Check if we should optimize empty requests (those without Content-Length or Transfer-Encoding headers)
-  const shouldOptimize = server[kOptimizeEmptyRequests] === true && !hasBodyHeaders(req.headers);
+  const shouldOptimize = server[kOptimizeEmptyRequests] === true && !hasBodyHeaders(req);
 
   if (shouldOptimize) {
     // Fast processing where emitting 'data', 'end' and 'close' events is
@@ -1335,9 +1401,7 @@ function parserOnIncoming(server, socket, state, req, keepAlive) {
 
   // When we're finished writing the response, check if this is the last
   // response, if so destroy the socket.
-  res.on('finish',
-         resOnFinish.bind(undefined,
-                          req, res, socket, state, server));
+  res.on('finish', onResponseFinish);
 
   let handled = false;
 
@@ -1347,7 +1411,7 @@ function parserOnIncoming(server, socket, state, req, keepAlive) {
     // From RFC 7230 5.4 https://datatracker.ietf.org/doc/html/rfc7230#section-5.4
     // A server MUST respond with a 400 (Bad Request) status code to any
     // HTTP/1.1 request message that lacks a Host header field
-    if (server.requireHostHeader && req.headers.host === undefined) {
+    if (server.requireHostHeader && !hasRequestHeader(req, 4, 'host')) {
       res.writeHead(400, ['Connection', 'close']);
       res.end();
       return 0;
@@ -1370,7 +1434,7 @@ function parserOnIncoming(server, socket, state, req, keepAlive) {
       server.emit('dropRequest', req, socket);
       res.writeHead(503);
       res.end();
-    } else if (req.headers.expect !== undefined) {
+    } else if (hasRequestHeader(req, 6, 'expect')) {
       handled = true;
 
       if (continueExpression.test(req.headers.expect)) {

lib/internal/http.js

@@ -22,12 +22,20 @@ const { Buffer } = require('buffer');
 const { isIPv4 } = require('internal/net');
 const { ERR_PROXY_INVALID_CONFIG } = require('internal/errors').codes;
 let utcCache;
+let utcHeaderCache;
 
 function utcDate() {
   if (!utcCache) cache();
   return utcCache;
 }
 
+// The complete `Date: ...\r\n` header line, cached alongside utcDate() so
+// that the serializer does not re-concatenate it for every response.
+function utcDateHeader() {
+  utcHeaderCache ||= 'Date: ' + utcDate() + '\r\n';
+  return utcHeaderCache;
+}
+
 function cache() {
   const d = new Date();
   utcCache = d.toUTCString();
@@ -36,6 +44,7 @@ function cache() {
 
 function resetCache() {
   utcCache = undefined;
+  utcHeaderCache = undefined;
 }
 
 let traceEventId = 0;
@@ -273,6 +282,7 @@ module.exports = {
   checkShouldUseProxy,
   parseProxyConfigFromEnv,
   utcDate,
+  utcDateHeader,
   traceBegin,
   traceEnd,
   getNextTraceEventId,