EADDRINUSE: Failed to start server. Is port 3000 in use?

[stefanos82]

What version of Bun is running?

1.0.33+9e91e137f

What platform is your computer?

Linux debian 6.6.15-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.6.15-2 (2024-02-04) x86_64 GNU/Linux

What steps can reproduce the bug?

Code directly taken from official website works as expected

spawn.tsx though with

import os from 'node:os';

// @ts-ignore
const numCPUs = os.availableParallelism();

for (let i = 0; i < numCPUs; i++) {
    Bun.spawn(['bun', 'src/index.tsx'], {
        stdio: ['inherit', 'inherit', 'inherit'],
        env: { ...process.env },
    });
}

produces EADDRINUSE: Failed to start server. Is port 3000 in use?.

Is it really a bug or am I doing something wrong here?

What is the expected behavior?

To see the same output as Elysia.js that works with spawn:

What do you see instead?

I see this

Additional information

No response

[ScribeSavant]

Can you check the port is already taken by another process sudo lsof -i :3000 if you see the port already taken or your program just working on background you can kill it with sudo kill -9 PID

[stefanos82]

Can you check the port is already taken by another process sudo lsof -i :3000 if you see the port already taken or your program just working on background you can kill it with sudo kill -9 PID

Only bun is reported:

The problem is, without the use of spawn, everything works as expected.

As soon as I execute the aforementioned example, it throws the message EADDRINUSE: Failed to start server. Is port 3000 in use? but if I run directly the src/index.tsx, it works just fine:

[ScribeSavant]

You can't run multi server on same port you should use different port for each server like 3000/3001/3002

This is not a bug, this is how TCP works

[stefanos82]

I have already tried this; still the same message about port 3000, even though I replaced it with 3300; it would still complain about port 3000 for some reason...

Where should I go to change the default port for Bun.spawn?

[ScribeSavant]

Here is an example

// file: index.ts

const port = parseInt(Bun.argv.slice(2)[0].split("=")[1]);

const server = Bun.serve({
  port: port,
  fetch(request) {
    return new Response("Welcome to Bun!");
  },
});

console.log(`Listening on localhost:${server.port}`);
process.once("SIGINT", () => {
  server.stop();
});
process.once("SIGTERM", () => {
  server.stop();
});

// file: spawn.ts

import os from "node:os";

// @ts-ignore
const numCPUs = os.availableParallelism();

for (let i = 0; i < numCPUs; i++) {
  Bun.spawn(["bun", "./index.ts", `--port=300${i + 1}`], {
    stdio: ["inherit", "inherit", "inherit"],
    env: { ...process.env },
  });
}

output

Do not use --watch otherwise you will get error after changes

[stefanos82]

These are your sub-processes; which one is your main / parent process that gets spawned? It should be the one that starts with port 3000; there's no reason to benchmark each sub-process separately, it cannot be done this way.

See how Elysia accomplishes the working output and compare it with your custom implementation, unless I'm missing something here which confuses me even further...

Here's node.js's example with Cluster:

import cluster from 'node:cluster';
import http from 'node:http';
import { availableParallelism } from 'node:os';
import process from 'node:process';

const numCPUs = availableParallelism();

if (cluster.isPrimary) {
  console.log(`Primary ${process.pid} is running`);

  // Fork workers.
  for (let i = 0; i < numCPUs; i++) {
    cluster.fork();
  }

  cluster.on('exit', (worker, code, signal) => {
    console.log(`worker ${worker.process.pid} died`);
  });
} else {
  // Workers can share any TCP connection
  // In this case it is an HTTP server
  http.createServer((req, res) => {
    res.writeHead(200);
    res.end('hello world\n');
  }).listen(3000); // Original example is `.listen(8000);`, I replaced it with port 3000

  console.log(`Worker ${process.pid} started`);
}

The execution:

The actual wrk benchmark:

[stefanos82]

Thanks to FrameworkBenchmarks I have found the cause of my problem: I should have added reusePort: true right after port: 3000 [1].

[1] https://github.com/TechEmpower/FrameworkBenchmarks/blob/master/frameworks/TypeScript/bun/src/index.ts#L4-L7