Solving the "Punycode Module is Deprecated" Issue in Node.js

Hi everyone, my name is Asim Khan, and I am currently a full stack developer at Meta Melon. Recently, I encountered a frustrating issue while working on a project for Naseebi.com, a matrimonial mobile and web application. The issue involved the deprecation of the punycode module in Node.js, and I want to share my experience and solution with you.

Punycode

Punycode is a way to convert international characters in domain names (like 你好.com) into a format compatible with the Domain Name System (DNS), which only understands ASCII characters. It ensures global accessibility for non-English domain names.

Example:
Original (Unicode): müller.de
Punycode (ASCII): xn--mller-kva.de
When a user types müller.de, the browser converts it to xn--mller-kva.de so DNS can handle it.

The Issue

While working on the profile creation feature in the application, I encountered a 502 Bad Gateway error. After checking my server logs on AWS EC2, I found this warning:

The punycode module is deprecated. Please use a userland alternative instead. (Use node --trace-deprecation ... to show where the warning was created)

This was strange because I hadn't used punycode directly in my code. However, after inspecting my package-lock.json file, I found that it was included as a dependency somewhere in the project. My Node.js version at the time was v22.0.0. I tried downgrading to v20.9.0 and even v18.18.0, but the warning persisted.

Understanding the Problem

The punycode module was deprecated in Node.js version 21. To resolve this, I needed to replace it with the recommended userland alternative, punycode.js. However, simply installing the userland module didn't seem to help.

Solutions and Workarounds

Here are the steps I took to finally resolve the issue:

1. Downgrade Node.js Version

If you're not particular about using the latest Node.js version, a quick fix is to downgrade to a version before 21.

nvm install 20.5.1
nvm use 20.5.1

2. Identify the Problematic Dependencies

You can run npm ls punycode to identify which dependencies are still using punycode.

npm ls punycode

In my case, the culprits were ajv and whatwg-url-without-unicode. I found these through the following steps:

Updating ajv: I updated ajv in my package.json file.

"overrides": {
  "ajv": "^8.17.1"
}

Updating whatwg-url: I updated whatwg-url as well.

"overrides": {
  "ajv": "^8.17.1",
  "whatwg-url": "^14.0.0"
}

After these updates, the warning was gone. However, if the issue persists, you can use the following steps.

3. Suppress the Warning (Temporary Fix)

You can suppress the warning in your package.json scripts:

"scripts": {
  "start": "NODE_NO_WARNINGS=1 vite"
}

This will remove the deprecation warnings from your console output.

4. Use pm2 to Manage Your Application (Horizontal Scaling)

Finally, I realized that one of my two clusters was down(horizontal Scale) so I added a ecosystem.config.js file in the project root to manage my application with pm2.

module.exports = {
  apps: [
    {
      name: "my-app",
      script: "npm",
      args: "run start",
      instances: "max",
      exec_mode: "cluster",
      max_memory_restart: "1G",
      watch: false,
      autorestart: true,
      restart_delay: 5000,
    },
  ],
};

After pushing the code and pulling it on EC2, I restarted the pm2 server, and everything started working smoothly.

Conclusion

This issue taught me a lot about managing dependencies and dealing with deprecated modules. While the punycode module is deprecated, you can still use it temporarily, but it's better to address the issue now to avoid problems in the future. I hope this guide helps you if you encounter a similar issue.