On a fresh project, two requests coming in resolve sequentially and not in parallel when waiting on a setTimeout in a service

Bug Report

Current behavior

Generate fresh project run yarn Change the app.service.ts file run yarn start Create latency using a timeout send two almost simultaneous requests one returned in ~6 seconds, and the other returns in ~12 seconds repeated with yarn build and yarn start:prod with a similar result

Input Code

I generated a fresh Nest project (typescript) and changed the app.service.ts file to the below and fixed the TS error in app.controller.ts

import { Injectable } from '@nestjs/common';

@Injectable()
export class AppService {
  async getHello(): Promise<string> {
         // await 5 seconds
	  await new Promise<void>((res) => {
		  setTimeout(() => {res()}, 5000);
	  });

    return 'Hello World!';
  }
}

Expected behavior

I would expect the calls to resolve in parallel, even on a single core given that the promises would be put off into worker threads

Possible Solution

I’m pretty stumped as to why this is happening

Environment

Nest version: 8.0.6 (happened on 7.x as well)

For Tooling issues:

• Node version: v14.15.1
• Platform: Mac 6 core

[jmcdo29]

I’m not able to replicate this using curl. I can take your service code and do

sendTwoRequests() {
curl http://localhost:3000 &
curl http://localhost:3000 &
}
sendTwoRequests

And I get a response back from the background processes after about 5 seconds.

[jmcdo29]

I think that would be an issue of the active window. Browsers sometimes seem to put requests on hold momentarily if windows are switched. That’s really my only guess. If you send two requests from the browser console, they’d probably come back around the same time