nodejs / nodejs/node

Buffer is not transferable in Node 21/22

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buffer web-standards
Dominant language
JavaScript
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Description

Version

v21.7.3, v22.11.0

Platform
Linux nweiz1 6.9.10-1rodete5-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.9.10-1rodete5 (2024-09-04) x86_64 GNU/Linux
Subsystem

worker_threads

What steps will reproduce the bug?
import {MessageChannel, Worker} from 'worker_threads';

const channel = new MessageChannel();
const buffer = Buffer.from('some text');
channel.port1.postMessage(buffer, [buffer.buffer]);
channel.port2.on('message', (e) => {
  console.log(Buffer.from(e).toString());
  channel.port1.close();
  channel.port2.close();
});

This worked in v20 and fails in v21 and v22.

How often does it reproduce? Is there a required condition?

It always reproduces.

What is the expected behavior? Why is that the expected behavior?

The buffer should be transferred through the message channel.

What do you see instead?
node:internal/per_context/domexception:53
    ErrorCaptureStackTrace(this);
    ^
DOMException [DataCloneError]: Cannot transfer object of unsupported type.
    at new DOMException (node:internal/per_context/domexception:53:5)
    at file:///.../test.mjs:5:15
    at ModuleJob.run (node:internal/modules/esm/module_job:268:25)
    at async onImport.tracePromise.__proto__ (node:internal/modules/esm/loader:543:26)
    at async asyncRunEntryPointWithESMLoader (node:internal/modules/run_main:116:5)

Node.js v22.11.0
Additional information

I didn't see anything in the v21 or v22 changelogs about buffers becoming untransferable, and transferring it worked in v20, so I'm assuming this is unintentional. If it's intentional, I would have expected at least a deprecation message indicating that this was going to start breaking.

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by running the provided worker_threads MessageChannel reproduction on the listed Node versions and compare the transfer behavior. Trace the Buffer transfer path from postMessage in the worker_threads subsystem; done means the reproduction transfers the Buffer successfully, with regression coverage for the reported behavior.

Written by the indexing model from the issue text.

Assessment

Tech stack
javascript, node.js
Domain
backend
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Quiet
Clarity
Clearly specified
Newbie friendliness
48/100

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