JavaScript file executed twice when using pino/file transport with --import option

[richterich]

💬 Question

When using the pino/file transport with the --import option to include a JavaScript file, the file is executed twice instead of just once. This behavior looks as unexpected and can lead to issues such as duplicated log entries or other side effects from the script running twice. Should I report an issue or is there a solution for this problem?

To reproduce this issue, please, create fastify instance with following options:

// index.js
const app = fastify({
  logger: {
    level: 'debug',
    transport: {
      target: 'pino/file',
      options: { destination: './tmp/app.log', mkdir: true },
    },
  },
});

app.listen({ port: 8080, host: '127.0.0.1' }, (err, address) => {
  if (err) {
    instance.log.error({ err, address }, 'Server Start Error');
    process.exit(1);
  }
});

console.log("once");

Create another module with the following code:

// twice.js
console.log("twice");

Run application with command:

node --import=./twice.js index.js

Actual output:

twice
once
twice

Expected output:

twice
once

Please, see the repo to reproduce the problem.

Environment

• node version: 20.16.0
• fastify version: 4.28.1
• os: Linux 6.5.0-45-generic Ubuntu 22.04.1

Additional

As workaround it possible use true in logger options or don't use the transport option in logger options.

// use boolean value
const app = fastify({
  logger: true
});

// without transport option
const app = fastify({
  logger: {
    level: 'debug',
  },
});

[climba03003]

It is more like an issue from pino or node.js itself.

[jsumners]

Pino does not modify console.log. Nothing in the report is due to Fastify nor Pino. --import loads the designated script in a separate thread. There must be something omitted from index.js that shows where it is also importing twice.js.

[climba03003]

Here is the minimal repro with file creation.
The --import script will be run in every Worker creation. If that is not the desire behavior, you should file an issue to node repository.

import { spawn } from 'node:child_process';
import { rm, writeFile } from 'node:fs/promises';

await writeFile('main.mjs', `
import { rm, writeFile } from 'node:fs/promises';
import { Worker } from 'node:worker_threads';

await writeFile('worker.mjs', \`console.log('worker')\`)

const worker = new Worker('./worker.mjs')

process.once('beforeExit', () => {
  rm('worker.mjs')
})`)

await writeFile('import.mjs', `console.log('import')`)

spawn('node', ['--import', './import.mjs', 'main.mjs'], {
  stdio: 'inherit'
})

process.once('beforeExit', () => {
  rm('main.mjs')
  rm('import.mjs')
})

[richterich]

Thank you!