jest-worker breaks building the project with "write EPIPE" error on macOS

What version of Next.js are you using?

11.0.1

What version of Node.js are you using?

16.4.2

What browser are you using?

Firefox

What operating system are you using?

macOs Big Sur 11.4 (MacBook Pro 15" 2017)

How are you deploying your application?

next build

Describe the Bug

I’ve decided to move my project on to next@11.0.1, using macOS for development. When i try building it, i get the following lines:

info  - Loaded env from /Users/brrrrrr/.env
(node:99496) Warning: Setting the NODE_TLS_REJECT_UNAUTHORIZED environment variable to '0' makes TLS connections and HTTPS requests insecure by disabling certificate verification.
(Use `node --trace-warnings ...` to show where the warning was created)
info  - Checking validity of types
info  - Creating an optimized production build .node:events:371
      throw er; // Unhandled 'error' event
      ^

Error: write EPIPE
    at ChildProcess.target._send (node:internal/child_process:849:20)
    at ChildProcess.target.send (node:internal/child_process:722:19)
    at ChildProcessWorker.initialize (/Users/brrrrrr/.yarn/cache/jest-worker-npm-27.0.6-83200713fc-8d7ab8cdf6.zip/node_modules/jest-worker/build/workers/ChildProcessWorker.js:181:11)
    at ChildProcessWorker._onExit (/Users/brrrrrr/.yarn/cache/jest-worker-npm-27.0.6-83200713fc-8d7ab8cdf6.zip/node_modules/jest-worker/build/workers/ChildProcessWorker.js:277:12)
    at ChildProcess.emit (node:events:394:28)
    at Process.ChildProcess._handle.onexit (node:internal/child_process:290:12)
Emitted 'error' event on ChildProcess instance at:
    at node:internal/child_process:853:39
    at processTicksAndRejections (node:internal/process/task_queues:78:11) {
  errno: -32,
  code: 'EPIPE',
  syscall: 'write'
}

At some point, the error was gone, but i cannot reproduce the steps necessary to completely fix the issue. This issue is related to macOS and nextjs >11 versions only as this error doesn’t pop up on other machines/versions. Related: This project uses the pnp packaging system from yarn version berry

Expected Behavior

The project should build.

To Reproduce

Calling next build on macOS with next@11

[borekb]

This option in next.config.js seems to resolve the issue for us:

module.exports = {
  experimental: {
    cpus: 1,
  },
};

It affects how new Worker from jest-worker is created:

https://github.com/vercel/next.js/blob/d60c95cb57497396d534eb8dd6fce9a192fc22fe/packages/next/build/index.ts#L675

experimental.cpus is also used for other things like setting the parallelism for webpack build, see e.g. this full-text search:

Specifically for jest-worker, it sets numWorkers in jest-worker here:

const workerPoolOptions: WorkerPoolOptions = {
  numWorkers: this._options.numWorkers ?? Math.max(cpus().length - 1, 1),
  //...
};

On my machine which is MBP 16’’ 2019 with a 6-core Intel i7, cpus().length is 12 so jest-worker would then use 11 as numWorkers. For experimental.cpus, I can use the values 1, 2 and 3 for the build to succeed ✅. 4 and above lead to that EPIPE error 🚫.

[bhoodream]

The same problem! My build is running in docker and periodically crashes with this error!

Next.js: 11.0.1 Node.js: 14.17.3 Yarn: 2.4.2 (PnP)

events.js:352
#9 98.36       throw er; // Unhandled 'error' event
#9 98.36       ^
#9 98.36 
#9 98.36 Error: write EPIPE
#9 98.36     at ChildProcess.target._send (internal/child_process.js:839:20)
#9 98.36     at ChildProcess.target.send (internal/child_process.js:710:19)
#9 98.36     at ChildProcessWorker.initialize (/app/.yarn/cache/jest-worker-npm-27.0.0-next.5-6f53fab806-7564f4c78c.zip/node_modules/jest-worker/build/workers/ChildProcessWorker.js:181:11)
#9 98.36     at ChildProcessWorker._onExit (/app/.yarn/cache/jest-worker-npm-27.0.0-next.5-6f53fab806-7564f4c78c.zip/node_modules/jest-worker/build/workers/ChildProcessWorker.js:275:12)
#9 98.36     at ChildProcess.emit (events.js:375:28)
#9 98.36     at ChildProcess.emit (domain.js:470:12)
#9 98.36     at Process.ChildProcess._handle.onexit (internal/child_process.js:277:12)
#9 98.36 Emitted 'error' event on ChildProcess instance at:
#9 98.36     at internal/child_process.js:843:39
#9 98.36     at processTicksAndRejections (internal/process/task_queues.js:77:11) {
#9 98.36   errno: -32,
#9 98.36   code: 'EPIPE',
#9 98.36   syscall: 'write'
#9 98.36 }

Downgrading to version 10.2.3 solves the problem.

And yes, we’re on yarn 2 and PnP.