http: simplify drain()

Simplify and slightly optimize draining outgoing http streams. Avoid
extra event listener and inline with rest of the drain logic.

PR-URL: #29081
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

lib/_http_client.js

@@ -30,7 +30,6 @@ const {
   _checkIsHttpToken: checkIsHttpToken,
   debug,
   freeParser,
-  httpSocketSetup,
   parsers,
   HTTPParser,
   prepareError,
@@ -40,7 +39,7 @@ const Agent = require('_http_agent');
 const { Buffer } = require('buffer');
 const { defaultTriggerAsyncIdScope } = require('internal/async_hooks');
 const { URL, urlToOptions, searchParamsSymbol } = require('internal/url');
-const { kOutHeaders, ondrain } = require('internal/http');
+const { kOutHeaders, kNeedDrain } = require('internal/http');
 const { connResetException, codes } = require('internal/errors');
 const {
   ERR_HTTP_HEADERS_SENT,
@@ -335,6 +334,14 @@ function emitAbortNT() {
   this.emit('abort');
 }
 
+function ondrain() {
+  const msg = this._httpMessage;
+  if (msg && !msg.finished && msg[kNeedDrain]) {
+    msg[kNeedDrain] = false;
+    msg.emit('drain');
+  }
+}
+
 function socketCloseListener() {
   const socket = this;
   const req = socket._httpMessage;
@@ -649,9 +656,6 @@ function tickOnSocket(req, socket) {
   socket.parser = parser;
   socket._httpMessage = req;
 
-  // Setup "drain" propagation.
-  httpSocketSetup(socket);
-
   // Propagate headers limit from request object to parser
   if (typeof req.maxHeadersCount === 'number') {
     parser.maxHeaderPairs = req.maxHeadersCount << 1;
@@ -663,6 +667,7 @@ function tickOnSocket(req, socket) {
   socket.on('data', socketOnData);
   socket.on('end', socketOnEnd);
   socket.on('close', socketCloseListener);
+  socket.on('drain', ondrain);
 
   if (
     req.timeout !== undefined ||

lib/_http_common.js

@@ -31,7 +31,6 @@ const { methods, HTTPParser } =
     internalBinding('http_parser') : internalBinding('http_parser_llhttp');
 
 const FreeList = require('internal/freelist');
-const { ondrain } = require('internal/http');
 const incoming = require('_http_incoming');
 const {
   IncomingMessage,
@@ -201,12 +200,6 @@ function freeParser(parser, req, socket) {
   }
 }
 
-
-function httpSocketSetup(socket) {
-  socket.removeListener('drain', ondrain);
-  socket.on('drain', ondrain);
-}
-
 const tokenRegExp = /^[\^_`a-zA-Z\-0-9!#$%&'*+.|~]+$/;
 /**
  * Verifies that the given val is a valid HTTP token
@@ -253,7 +246,6 @@ module.exports = {
   CRLF: '\r\n',
   debug,
   freeParser,
-  httpSocketSetup,
   methods,
   parsers,
   kIncomingMessage,

lib/_http_outgoing.js

@@ -27,7 +27,7 @@ const { getDefaultHighWaterMark } = require('internal/streams/state');
 const assert = require('internal/assert');
 const Stream = require('stream');
 const internalUtil = require('internal/util');
-const { kOutHeaders, utcDate } = require('internal/http');
+const { kOutHeaders, utcDate, kNeedDrain } = require('internal/http');
 const { Buffer } = require('buffer');
 const common = require('_http_common');
 const checkIsHttpToken = common._checkIsHttpToken;
@@ -96,6 +96,7 @@ function OutgoingMessage() {
   this._contentLength = null;
   this._hasBody = true;
   this._trailer = '';
+  this[kNeedDrain] = false;
 
   this.finished = false;
   this._headerSent = false;
@@ -582,7 +583,10 @@ Object.defineProperty(OutgoingMessage.prototype, 'writableEnded', {
 
 const crlf_buf = Buffer.from('\r\n');
 OutgoingMessage.prototype.write = function write(chunk, encoding, callback) {
-  return write_(this, chunk, encoding, callback, false);
+  const ret = write_(this, chunk, encoding, callback, false);
+  if (!ret)
+    this[kNeedDrain] = true;
+  return ret;
 };
 
 function write_(msg, chunk, encoding, callback, fromEnd) {
@@ -782,8 +786,8 @@ OutgoingMessage.prototype._flush = function _flush() {
     if (this.finished) {
       // This is a queue to the server or client to bring in the next this.
       this._finish();
-    } else if (ret) {
-      // This is necessary to prevent https from breaking
+    } else if (ret && this[kNeedDrain]) {
+      this[kNeedDrain] = false;
       this.emit('drain');
     }
   }

lib/_http_server.js

@@ -32,7 +32,6 @@ const {
   CRLF,
   continueExpression,
   chunkExpression,
-  httpSocketSetup,
   kIncomingMessage,
   HTTPParser,
   _checkInvalidHeaderChar: checkInvalidHeaderChar,
@@ -41,7 +40,7 @@ const {
 const { OutgoingMessage } = require('_http_outgoing');
 const {
   kOutHeaders,
-  ondrain,
+  kNeedDrain,
   nowDate,
   emitStatistics
 } = require('internal/http');
@@ -363,8 +362,6 @@ function connectionListener(socket) {
 function connectionListenerInternal(server, socket) {
   debug('SERVER new http connection');
 
-  httpSocketSetup(socket);
-
   // Ensure that the server property of the socket is correctly set.
   // See https://github.com/nodejs/node/issues/13435
   if (socket.server === null)
@@ -459,6 +456,12 @@ function socketOnDrain(socket, state) {
       socket.parser.resume();
     socket.resume();
   }
+
+  const msg = socket._httpMessage;
+  if (msg && !msg.finished && msg[kNeedDrain]) {
+    msg[kNeedDrain] = false;
+    msg.emit('drain');
+  }
 }
 
 function socketOnTimeout() {
@@ -585,7 +588,6 @@ function onParserExecuteCommon(server, socket, parser, state, ret, d) {
     socket.removeListener('end', state.onEnd);
     socket.removeListener('close', state.onClose);
     socket.removeListener('drain', state.onDrain);
-    socket.removeListener('drain', ondrain);
     socket.removeListener('error', socketOnError);
     unconsume(parser, socket);
     parser.finish();

lib/internal/http.js

@@ -28,10 +28,6 @@ function resetCache() {
   utcCache = undefined;
 }
 
-function ondrain() {
-  if (this._httpMessage) this._httpMessage.emit('drain');
-}
-
 class HttpRequestTiming extends PerformanceEntry {
   constructor(statistics) {
     super();
@@ -50,7 +46,7 @@ function emitStatistics(statistics) {
 
 module.exports = {
   kOutHeaders: Symbol('kOutHeaders'),
-  ondrain,
+  kNeedDrain: Symbol('kNeedDrain'),
   nowDate,
   utcDate,
   emitStatistics