Monitoring WhatsApp WebSockets with PM2

Once you've deployed your Node.js WhatsApp bot to a VPS, you need a way to keep it running 24/7. PM2 is the industry standard process manager for Node.js, but using its default settings with a WebSocket-heavy, file-state-dependent library like @whiskeysockets/baileys will lead to disaster.

In this guide, we'll cover the exact PM2 configuration required to run a WhatsApp gateway reliably.

1. The Golden Rule: No Cluster Mode

PM2's most famous feature is cluster mode (pm2 start app.js -i max), which spawns multiple instances of your app to utilize all CPU cores.

You cannot use cluster mode with Baileys.

Baileys maintains its session via cryptographic keys saved in a local folder (e.g., ./auth_info). If multiple PM2 instances run simultaneously, they will race to overwrite these files. Your session will corrupt, WhatsApp will disconnect, and you will be forced to rescan the QR code.

You must run a single fork instance.

2. The Ecosystem Configuration

Instead of running PM2 directly from the CLI, create an ecosystem.config.js file in your project root. This ensures your configuration is version-controlled and reproducible.

// ecosystem.config.js
module.exports = {
  apps: [
    {
      name: "whatsapp-gateway",
      script: "index.js",
      instances: 1,           // Strictly 1 instance
      exec_mode: "fork",      // Use fork, not cluster
      autorestart: true,      // Restart if the app crashes
      watch: false,           // NEVER watch in production (causes infinite restart loops on auth file writes)
      max_memory_restart: "500M", // Hard limit: Restart if memory leaks beyond 500MB
      restart_delay: 5000,    // Wait 5 seconds before restarting to prevent rapid crash loops
      env: {
        NODE_ENV: "production",
      }
    }
  ]
}

Why watch: false is Critical

If you enable PM2's watch feature, it restarts your app every time a file in the directory changes. Because Baileys updates the ./auth_info files every few seconds, PM2 will restart your bot infinitely, getting you banned from WhatsApp instantly.

3. Starting and Saving the Process

Start the application using the ecosystem file:

pm2 start ecosystem.config.js

To ensure PM2 boots up automatically if your VPS restarts (e.g., due to a host reboot):

pm2 startup
# Run the command PM2 outputs to the console, then:
pm2 save

4. Taming the Logs with Logrotate

Baileys is a chatty library. Even if you silence the internal logger, your console.log statements for incoming messages will add up. A 24/7 bot can generate gigabytes of logs, eventually crashing your VPS with a "Disk Full" error.

You must install PM2's log rotation module:

pm2 install pm2-logrotate

Configure it to compress logs daily and keep only the last 7 days:

pm2 set pm2-logrotate:max_size 50M
pm2 set pm2-logrotate:retain 7
pm2 set pm2-logrotate:compress true

Summary

A WhatsApp bot is not a standard REST API. It is a stateful WebSocket connection tied to local cryptographic files. By restricting PM2 to a single instance, setting memory boundaries, and rotating logs, you isolate the fragility of the protocol and ensure your bot stays online for months without manual intervention.