fix: allow ClientRequest responses to be throttled (#25531)

* fix: allow net streams to be throttled [WIP]

* fix: handle resume throttling within IncomingMessage [WIP]

* fix: fix urlLoader typing, add throttle test

* fix: fix lint and increase test timeout for Linux

* fix: increase test chunk limit to 20 and timeout to 2000

Co-authored-by: Jeremy Rose <nornagon@nornagon.net>

lib/browser/api/net.ts

@@ -38,12 +38,14 @@ class IncomingMessage extends Readable {
   _shouldPush: boolean;
   _data: (Buffer | null)[];
   _responseHead: NodeJS.ResponseHead;
+  _resume: (() => void) | null;
 
   constructor (responseHead: NodeJS.ResponseHead) {
     super();
     this._shouldPush = false;
     this._data = [];
     this._responseHead = responseHead;
+    this._resume = null;
   }
 
   get statusCode () {
@@ -103,7 +105,9 @@ class IncomingMessage extends Readable {
     throw new Error('HTTP trailers are not supported');
   }
 
-  _storeInternalData (chunk: Buffer | null) {
+  _storeInternalData (chunk: Buffer | null, resume: (() => void) | null) {
+    // save the network callback for use in _pushInternalData
+    this._resume = resume;
     this._data.push(chunk);
     this._pushInternalData();
   }
@@ -113,6 +117,12 @@ class IncomingMessage extends Readable {
       const chunk = this._data.shift();
       this._shouldPush = this.push(chunk);
     }
+    if (this._shouldPush && this._resume) {
+      this._resume();
+      // Reset the callback, so that a new one is used for each
+      // batch of throttled data
+      this._resume = null;
+    }
   }
 
   _read () {
@@ -404,11 +414,11 @@ export class ClientRequest extends Writable implements Electron.ClientRequest {
       const response = this._response = new IncomingMessage(responseHead);
       this.emit('response', response);
     });
-    this._urlLoader.on('data', (event, data) => {
-      this._response!._storeInternalData(Buffer.from(data));
+    this._urlLoader.on('data', (event, data, resume) => {
+      this._response!._storeInternalData(Buffer.from(data), resume);
     });
     this._urlLoader.on('complete', () => {
-      if (this._response) { this._response._storeInternalData(null); }
+      if (this._response) { this._response._storeInternalData(null, null); }
     });
     this._urlLoader.on('error', (event, netErrorString) => {
       const error = new Error(netErrorString);

shell/browser/api/electron_api_url_loader.cc

@@ -458,8 +458,8 @@ void SimpleURLLoaderWrapper::OnDataReceived(base::StringPiece string_piece,
   auto array_buffer = v8::ArrayBuffer::New(isolate, string_piece.size());
   auto backing_store = array_buffer->GetBackingStore();
   memcpy(backing_store->Data(), string_piece.data(), string_piece.size());
-  Emit("data", array_buffer);
-  std::move(resume).Run();
+  Emit("data", array_buffer,
+       base::AdaptCallbackForRepeating(std::move(resume)));
 }
 
 void SimpleURLLoaderWrapper::OnComplete(bool success) {

spec-main/api-net-spec.ts

@@ -4,7 +4,7 @@ import * as http from 'http';
 import * as url from 'url';
 import { AddressInfo, Socket } from 'net';
 import { emittedOnce } from './events-helpers';
-import { defer } from './spec-helpers';
+import { defer, delay } from './spec-helpers';
 
 const kOneKiloByte = 1024;
 const kOneMegaByte = kOneKiloByte * kOneKiloByte;
@@ -1476,6 +1476,28 @@ describe('net module', () => {
       await collectStreamBody(nodeResponse);
       expect(nodeRequestProcessed).to.equal(true);
     });
+
+    it('should correctly throttle an incoming stream', async () => {
+      let numChunksSent = 0;
+      const serverUrl = await respondOnce.toSingleURL((request, response) => {
+        const data = randomString(kOneMegaByte);
+        const write = () => {
+          let ok = true;
+          do {
+            numChunksSent++;
+            if (numChunksSent > 30) return;
+            ok = response.write(data);
+          } while (ok);
+          response.once('drain', write);
+        };
+        write();
+      });
+      const urlRequest = net.request(serverUrl);
+      urlRequest.on('response', () => {});
+      urlRequest.end();
+      await delay(2000);
+      expect(numChunksSent).to.be.at.most(20);
+    });
   });
 
   describe('Stability and performance', () => {

typings/internal-ambient.d.ts

@@ -120,7 +120,7 @@ declare namespace NodeJS {
 
   interface URLLoader extends EventEmitter {
     cancel(): void;
-    on(eventName: 'data', listener: (event: any, data: ArrayBuffer) => void): this;
+    on(eventName: 'data', listener: (event: any, data: ArrayBuffer, resume: () => void) => void): this;
     on(eventName: 'response-started', listener: (event: any, finalUrl: string, responseHead: ResponseHead) => void): this;
     on(eventName: 'complete', listener: (event: any) => void): this;
     on(eventName: 'error', listener: (event: any, netErrorString: string) => void): this;