PM2: The Superhero Sidekick for Your Node.js Apps (Auto-Restarts & Zero-Downtime)

What the Heck is PM2 (And Why Should You Care)?

Picture this: You've built an awesome Node.js app. You run it with node app.js, high-five your cat, and call it a day. Next morning... "Connection refused". Your app crashed overnight!

Enter PM2 – the trusty sidekick that:

• 🦸 Keeps your app alive forever (auto-restarts if it crashes)

• ⚡ Makes scaling apps as easy as snapping fingers

• 🔍 Gives you X-ray vision into your app's performance

• ⏰ Enables zero-downtime deployments

Getting Started: PM2 in 60 Seconds

Install PM2 globally (you'll only do this once):

Bash

npm install pm2 -g

Now start your Node app like a pro:

Bash

pm2 start app.js

Boom! Your app is now:

• 🛡️ Protected from crashes (PM2 auto-restarts it)

• 📊 Logged (view logs with pm2 logs)

• 🔧 Managed (stop/restart easily)

Local Setup (On Your Computer – Perfect for Development)

1. Install PM2 (if not done):

   Bash

   npm install pm2 -g

2. Go to your project folder:

   Bash

   cd your-project-folder

3. Start your app:

   Bash

   pm2 start dist/main.js --name my-app  # or app.js

4. Check status and logs:

   Bash

   pm2 status
   pm2 logs my-app

blog.appsignal.com

stackoverflow.com

Production Setup (Real Server – With SSH)

In real projects, your app runs on a remote server.

1. Connect via SSH (from your laptop terminal):

   Bash

   ssh pachhai@192.168.1.100  # replace with your username & IP

   (First time? Type "yes" to accept.)

tech.nicolonsky.ch

docs.bytemark.co.uk

2. Go to backend folder (common pattern: project-name → backend):

   Bash

   cd myproject/backend

3. Install PM2 (only once on server):

   Bash

   npm install pm2 -g

Real-World PM2 Usage: From Development to Production

In actual workflows (like my recent project), PM2 manages different environments safely.

Multi-Environment Management

Check running processes:

Bash

pm2 status

Typical output (dev for testing, prod for live users):

blog.appsignal.com

blog.appsignal.com

stackoverflow.com

Critical Rule: Always work on dev (usually higher ID) and never touch prod (usually ID 0) during development. This prevents downtime!

The Development Workflow

1. After code changes, build:

   Bash

   yarn build  # or npm run build

2. Reload dev:

   Bash

   pm2 reload dev  # or pm2 reload 1

3. Monitor logs:

   Bash

   pm2 logs dev  # or pm2 logs 1

stackoverflow.com

github.com

When ready, deploy to prod:

Bash

pm2 reload prod

Live Monitoring Dashboard

Bash

pm2 monit

pm2.io

pm2.keymetrics.io

PM2 Cheat Sheet: Must-Know Commands

Bash

pm2 list              # Same as status
pm2 stop app_name
pm2 restart app_name
pm2 reload app_name   # Zero downtime!
pm2 logs app_name --lines 100
pm2 monit
pm2 save              # Save processes
pm2 show app_name

Supercharge Your Setup: Pro Tips

1. The Magic Configuration File

Create ecosystem.config.js for pro setups:

stackoverflow.com

node.js - dockerizing a nodejs application - should pm2 ls work ...

JavaScript

module.exports = {
  apps: [{
    name: "My Awesome App",
    script: "./dist/main.js",
    instances: 2,
    autorestart: true,
    watch: false,
    max_memory_restart: "1G",
    env: { NODE_ENV: "development", PORT: 3000 },
    env_production: { NODE_ENV: "production", PORT: 80 }
  }]
};

Start:

Bash

pm2 start ecosystem.config.js --env production

2. Log Management for Debugging

Bash

pm2 logs --lines 50
pm2 logs --raw
pm2 logs --err
pm2 logs --out
pm2 logs --timestamp

3. Startup Scripts (Survive Reboots!)

Bash

pm2 startup
pm2 save

Real-World PM2 Superpowers in Action

Scenario 1: 10x Traffic

Bash

pm2 scale app_name 4

Scenario 2: Zero-Downtime Update

Bash

git pull origin main
npm install
npm run build
pm2 reload app_name

Scenario 3: Debugging Issues

Bash

pm2 status
pm2 logs app_name --err --lines 100
pm2 monit
pm2 reload app_name

Scenario 4: Multiple Environments

Bash

pm2 start ecosystem.config.js --env development
pm2 start ecosystem.config.js --env production --name "app-prod"
pm2 list
pm2 reload app-dev

Your PM2 Action Plan

1. Install today: npm i pm2 -g

2. Replace node app.js with PM2

3. Create ecosystem.config.js

4. Try pm2 monit

5. Run pm2 startup && pm2 save

Lessons from the Trenches

• Always reload, not restart

• Check logs after every deploy

• Separate dev/prod

• Run pm2 save on warnings

• Watch memory leaks!

PM2 isn't just a tool – it's your app's insurance policy. Happy coding, and may your servers stay forever online! 🚀