Using PM2 for Node.js Process Management
PM2 is a production-level process manager for Node.js applications. It ensures your app stays running, restarts automatically if it crashes, handles logs, and can scale across CPU cores — all with simple commands.
Think of PM2 as a tool that keeps your Node.js backend alive, stable, and scalable.
🔹 1. What PM2 Does
PM2 helps with:
✔ Keeping the app always running (auto-restart)
✔ Monitoring CPU & RAM usage
✔ Load balancing across multiple CPU cores (“cluster mode”)
✔ Easy logs & error tracking
✔ Zero-downtime deployments
✔ Startup scripts so PM2 launches at boot
✔ Built-in dashboard (pm2 monit)
🔹 2. Install PM2
Install globally:
npm install -g pm2
Check version:
pm2 -v
🔹 3. Starting a Node.js App with PM2
Start an app:
pm2 start app.js
Start with a name:
pm2 start app.js --name api-server
Start with environment variables:
pm2 start app.js --name api-server --env production
🔹 4. Managing Processes
List running apps:
pm2 list
View detailed info:
pm2 describe api-server
Stop an app:
pm2 stop api-server
Restart an app:
pm2 restart api-server
Delete an app:
pm2 delete api-server
🔹 5. Watching for Code Changes (Dev Mode)
Automatically restart when files change:
pm2 start app.js --watch
PM2 watches all files in the folder by default.
🔹 6. Running Multiple Instances (Cluster Mode)
Cluster mode automatically uses all CPU cores:
pm2 start app.js -i max
Or specify a number:
pm2 start app.js -i 4
Cluster mode gives:
Load balancing
Fault tolerance
Better performance in production
🔹 7. Viewing Logs
See logs:
pm2 logs
Real-time logs of one app:
pm2 logs api-server
Error logs only:
pm2 logs --err
🔹 8. Monitoring Apps
CPU and memory dashboard:
pm2 monit
JSON dump of status:
pm2 status
🔹 9. Zero-Downtime Deployment
If you modify your code, restart smoothly:
pm2 reload api-server
Reload = no downtime, cluster mode friendly.
🔹 10. Autostart on System Boot
Generate startup script:
pm2 startup
It will give you a command to run next.
Save the current process list:
pm2 save
Now PM2 will restart your apps automatically after a reboot.
🔹 11. Managing Configurations with Ecosystem File
You can create an ecosystem.config.js for multiple apps:
module.exports = {
apps: [
{
name: "api",
script: "./app.js",
instances: "max",
exec_mode: "cluster",
watch: false,
env: {
NODE_ENV: "development",
},
env_production: {
NODE_ENV: "production",
}
}
]
};
Run it:
pm2 start ecosystem.config.js
🔹 12. Common Use Cases
✔ Hosting APIs
✔ Long-running workers
✔ Cron/queue processors
✔ IoT + edge scripts
✔ Multi-core scaling
✔ High availability Node.js apps
✔ Zero-downtime updates
🎯 Summary
PM2 makes running Node.js apps in production easier by providing:
Process monitoring
Auto-restart on crashes
CPU load balancing
Log management
Zero-downtime reloads
Startup scripts
It is one of the most popular and reliable tools for managing Node.js services.
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