IncomingMessage socket unref doesn't work

[cristianrgreco]

What version of Bun is running?

1.3.0+b0a6feca5

What platform is your computer?

Darwin 24.5.0 arm64 arm

What steps can reproduce the bug?

Pre-requisites:

• Have Docker installed
• Pull test image: docker pull testcontainers/ryuk:0.14.0

Create empty project with dockerode dependency:

mkdir incomingmessage-socket-unref-repro
cd $_
npm init -y
npm install dockerode

Create index.mjs file which starts a Docker container,

import Dockerode from "dockerode";

const dockerode = new Dockerode();

console.log("Creating container...");
const container = await dockerode.createContainer({
  Image: "testcontainers/ryuk:0.14.0",
  Env: ["RYUK_CONNECTION_TIMEOUT=10s"],
  ExposedPorts: { "8080/tcp": {} },
  HostConfig: {
    PortBindings: { "8080/tcp": [{ HostPort: "0" }] },
    Binds: [`/var/run/docker.sock:/var/run/docker.sock:rw`],
  },
});

console.log("Starting container...");
await container.start();

console.log("Fetching log stream...");
const logStream = await container.logs({
  follow: true,
  stdout: true,
  stderr: true,
});
logStream.socket.unref();

console.log("COMPLETE, EXIT NOW");

What is the expected behavior?

When run with node, we see the following output, followed by the process terminating immediately, even though the log stream has not ended:

❯ node index.mjs
Creating container...
Starting container...
Fetching log stream...
COMPLETE, EXIT NOW

❯

What do you see instead?

When run with bun, we see the same output, but the process does not terminate immediately. It will only terminate after 10 seconds, which is when the container exits and the log stream ends:

❯ bun index.mjs
Creating container...
Starting container...
Fetching log stream...
COMPLETE, EXIT NOW

Additional information

The logStream is of type IncomingMessage. The key code to let the process exit immediately is:

logStream.socket.unref();

Without it, both node and bun will wait for the stream to end before exiting. With it, node exits regardless of whether or not the stream is open, bun does not.

I am trying to add official bun support to testcontainers-node here testcontainers/testcontainers-node#1162.

Our use case is, we start a background container which manages containers created within the same session. When the session ends, the background container will clean up its managed containers after a timeout. We do not want the user's session to wait for this container's timeout, it should happen in the background.

[linear]

ENG-21048

[cristianrgreco]

I've potentially simplified the repro with the code below, and found some differences between node and bun, which may be contributing to my issue.

This code creates a socket and pushes a never ending stream of chunks at an interval. Everything is unref'd where possible:

import { IncomingMessage } from "node:http";
import { Socket } from "node:net";

function createNeverEndingIncomingMessage() {
  const socket = new Socket();
  socket.unref();

  const msg = new IncomingMessage(socket);
  msg.setEncoding("utf-8");

  let i = 0;
  const interval = setInterval(() => msg.push(`chunk ${i++}\n`), 100);
  interval.unref();

  return msg;
}

const msg = createNeverEndingIncomingMessage();
msg.on("data", (s) => console.log(s.trim()));

await new Promise((resolve) => setTimeout(resolve, 1000));

Output when running with node:

❯ node simple.mjs
chunk 0
chunk 1
chunk 2
chunk 3
chunk 4
chunk 5
chunk 6
chunk 7
chunk 8
# <PROCESS EXIT>

Output when running with bun:

❯ bun simple.mjs
chunk 0
# <PROCESS EXIT>

The behaviour is different, bun is not logging any chunks, but the process does exit.

What's also confusing is when we change the await new Promise(resolve => setTimeout(resolve, 1000)); to never resolve. If we change it to await new Promise(resolve => setTimeout(() => {}, 1000));, we get another difference in behaviour:

Node output:

✦ ❯ node simple.mjs
chunk 0
chunk 1
chunk 2
chunk 3
chunk 4
chunk 5
chunk 6
chunk 7
chunk 8
Warning: Detected unsettled top-level await at file:///Users/cristian/Desktop/bun-issue-repro/simple.mjs:25
await new Promise(resolve => setTimeout(() => {}, 1000));
^
# <PROCESS EXIT>

Bun output, no chunks logged, and the process hangs forever (I am not saying node's behaviour is right here, just pointing out that another behavioural difference is probably contributing to my issue):

❯ bun simple.mjs
chunk 0