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[withmask]

My fastfiy instance does not use the body returned by my custom error handler for request timeouts.

Specifically ones with fake content-length.

import fastify from 'fastify';
import axios from 'axios';

const instance = fastify({
  requestTimeout: 1000
});

instance.setErrorHandler((err, req, res) => {
  console.log(err);
  //This still logs.
  return {
    status: false,
    message: 'should be overwitten'
  };
});

instance.post('/', (req, res) => {
  console.log(req.body);
});

await instance.listen({
  host: '0.0.0.0',
  port: 8000
});
console.log('listened');

const x = await axios({
  method: 'POST',
  url: 'http://0.0.0.0:8000',
  headers: {
    'Content-Length': 16,
    'Content-Type': 'application/json'
  },
  data: 'a',
  validateStatus: () => true
});

console.log(x.data);
//Received body
/**
 * {
  error: 'Request Timeout',
  message: 'Client Timeout',
  statusCode: 408
}
 */

The logs from the instance are as follows.

listened
{
  error: 'Request Timeout',
  message: 'Client Timeout',
  statusCode: 408
}
Error: aborted
    at abortIncoming (node:_http_server:809:17)
    at socketOnClose (node:_http_server:803:3)
    at Socket.emit (node:events:536:35)
    at TCP.<anonymous> (node:net:350:12) {
  code: 'ECONNRESET',
  statusCode: 400
}

Your Environment

• node version: 22.10.0
• fastify version: 5.2.1
• os: Linux
• Running in a docker container.