undici: Multiple parallel long fetches with overridden, non-zero, timeouts fails all the time

Bug Description

When running multiple LONG running fetches in parallel, some of them seem to just die and hit a timeout that doesnt really seem relevant

name: HeadersTimeoutError
    message: Headers Timeout Error
    stack: >-
      HeadersTimeoutError: Headers Timeout Error
          at onParserTimeout (/src/archive/undici/lib/client.js:908:28)
          at callTimer (/src/archive/undici/node_modules/@sinonjs/fake-timer
  s/src/fake-timers-src.js:743:24)
          at doTickInner (/src/archive/undici/node_modules/@sinonjs/fake-tim
  ers/src/fake-timers-src.js:1311:29)
          at doTick (/src/archive/undici/node_modules/@sinonjs/fake-timers/s
  rc/fake-timers-src.js:1392:20)
          at Object.tick (/src/archive/undici/node_modules/@sinonjs/fake-tim
  ers/src/fake-timers-src.js:1400:20)
          at Server.<anonymous>
  (/src/archive/undici/test/fetch/fetch-timeouts.js:32:11)
          at Server.emit (node:events:513:28)
          at parserOnIncoming (node:_http_server:1065:12)
          at HTTPParser.parserOnHeadersComplete (node:_http_common:117:17)
    code: UND_ERR_HEADERS_TIMEOUT

Reproducible By

Tweaking minutesPerRequest, numParallelRequests, and timeout here makes for some pretty confusing results. When timeout is 0, everything seems to work correctly. I suspect there are a few timers that are overlapping eachother or getting shared somehow.

Simply set timeout to 0 and see that the test passes, and set timeout to 30 minutes and see that it fails

"use strict";

const { test } = require("tap");

const { fetch, Agent } = require("../..");
const { createServer } = require("http");
const FakeTimers = require("@sinonjs/fake-timers");

// Tweaking request length can have an impact too potentially (Setting to 1 seems to pass, and setting it to 10 min fails on my machine)
const minutesPerRequest = 10;

// On my machine setting this to 0 passes, and setting it to something very high fails with a UND_ERR_HEADERS_TIMEOUT
const timeout = 1000 * 60 * (minutesPerRequest + 5);
// const timeout = 0;

// Tweaking num requests to either 1 or multiple has different impacts
const numParallelRequests = 5;

test("Fetch very long parallel requests, timeout overridden", (t) => {
  const msToDelay = 1000 * 60 * minutesPerRequest;

  t.setTimeout(undefined);
  t.plan(numParallelRequests);

  const clock = FakeTimers.install();
  t.teardown(clock.uninstall.bind(clock));

  const server = createServer((req, res) => {
    setTimeout(() => {
      res.end("hello");
    }, msToDelay);
    clock.tick(msToDelay + 1);
  });
  t.teardown(server.close.bind(server));

  server.listen(0, () => {
    for (let i = 0; i < numParallelRequests; i++) {
      fetch(`http://localhost:${server.address().port}`, {
        path: "/",
        method: "GET",
        dispatcher: new Agent({
          headersTimeout: timeout,
          connectTimeout: timeout,
          bodyTimeout: timeout,
        }),
      })
        .then((response) => response.text())
        .then((response) => {
          t.equal("hello", response);
        })
        .catch((err) => {
          // This should not happen, a timeout error should not occur
          t.error(err);
        });
    }

    clock.tick(msToDelay - 1);
  });
});

Expected Behavior

The fetches to succeed

Logs & Screenshots

Environment

Node v18.13.0

Additional context