What is PM2 and how to use it? | Node.js Interview Questions

What You'll Learn

What PM2 is
Key commands
Configuration options

What is PM2?

PM2 is a production process manager for Node.js with load balancing, monitoring, and zero-downtime deployments.

Installation & Basic Commands

$ terminalBash

npm install -g pm2

# Start app
pm2 start app.js

# With name
pm2 start app.js --name "my-app"

# Cluster mode (use all CPUs)
pm2 start app.js -i max

# List processes
pm2 list

# Monitor
pm2 monit

# Logs
pm2 logs
pm2 logs my-app

# Restart/Stop/Delete
pm2 restart my-app
pm2 stop my-app
pm2 delete my-app

# Restart all
pm2 restart all

Ecosystem File

code.jsJavaScript

// ecosystem.config.js
module.exports = {
  apps: [{
    name: 'my-app',
    script: './app.js',
    instances: 'max',
    exec_mode: 'cluster',
    env: {
      NODE_ENV: 'development'
    },
    env_production: {
      NODE_ENV: 'production'
    }
  }]
};

$ terminalBash

# Start with ecosystem file
pm2 start ecosystem.config.js --env production

# Save process list for startup
pm2 save
pm2 startup

Zero-Downtime Reload

$ terminalBash

pm2 reload my-app