What exactly changed between Node.js 18 and Node.js 20 that's causing my API requests to fail?

[hrishikesh-k]

Hello!

My setup:

• I am using Node.js 20.9.0 inside WSL.
• WSL doesn't support IPv6 (it now supports that with an experimental feature)
• My Wi-Fi router also doesn't support IPv6

The reasons for mentioning all that will be evident in the rest of the message. I had the following piece of code (simplified for demonstration):

import axios from 'axios'
axios({
  url: 'https://answers.netlify.com/latest.json',
}).then(res => {
  console.log(res.data)
}, err => {
  console.log(err)
})

This was working fine until I was using Node.js 18 (last tested on 18.18.2 and 19.9.0). Since Node.js 20 went to LTS, I decided to upgrade and the code started to fail with this error:

Error: connect ETIMEDOUT 184.105.99.43:443
    at createConnectionError (node:net:1634:14)
    at Timeout.internalConnectMultipleTimeout (node:net:1685:38)
    at listOnTimeout (node:internal/timers:575:11)
    at processTimers (node:internal/timers:514:7) {
  errno: -110,
  code: 'ETIMEDOUT',
  syscall: 'connect',
  address: '184.105.99.43',
  port: 443
},
Error: connect ENETUNREACH 2602:fd3f:3:ff01::2b:443 - Local (:::0)
    at internalConnectMultiple (node:net:1176:40)
    at Timeout.internalConnectMultipleTimeout (node:net:1687:3)
    at listOnTimeout (node:internal/timers:575:11)
    at processTimers (node:internal/timers:514:7) {
  errno: -101,
  code: 'ENETUNREACH',
  syscall: 'connect',
  address: '2602:fd3f:3:ff01::2b',
  port: 443
}

It took me a long time to figure out what's going on here. I even reached out to Discourse: https://meta.discourse.org/t/285921 and the TL;DR was:

• IPv4 on Windows: Works
• IPv6 on Windows: Works
• IPv4 on WSL: Works
• IPv6 on WSL: Fails

This finally works on Node.js 20 by changing the above code to:

import {Agent} from 'node:https'
import axios from 'axios'
axios({
  url: 'https://answers.netlify.com/latest.json',
  httpsAgent: new Agent({
    family: 4
  })
}).then(res => {
  console.log(res.data)
}, err => {
  console.log(err)
})

I had to specify the family to force the connections through IPv4.

I have tried specifying --dns-result-order=ipv4first without success. I also checked the release notes: https://nodejs.org/en/blog/announcements/v20-release-announce which don't mention any related changes.

I simply wish to know what exactly has changed in Node.js causing this issue and how to adapt the application to work with it? I was trying to move away from Axios to Wretch which is a fetch based library and fetch doesn't provide any way to customise whether I can use IPv4 or IPv6.