What is PM2?

PM2 is a production process manager for Node.js applications. It keeps apps running 24/7 by:

Auto-restarting when apps crash
Starting on boot when servers restart
Clustering to use all CPU cores
Log management with rotation
Monitoring CPU and memory usage

Prerequisites

A VPS with Node.js installed
Node.js application to manage
SSH access with root or sudo privileges

Step 1: Install PM2

sudo npm install -g pm2
pm2 --version

Step 2: Start application

Navigate to application directory and start with PM2:

cd /home/youruser/myapp
pm2 start app.js --name myapp

The --name flag gives apps friendly names for management.

Step 3: Configure auto-restart on boot

pm2 startup

PM2 outputs a command to run. Copy and execute it:

sudo env PATH=$PATH:/usr/bin pm2 startup systemd -u youruser --hp /home/youruser

Save current process list:

pm2 save

Apps now start automatically when servers boot.

Step 4: Basic PM2 commands

# List all running applications
pm2 list

# Show detailed info
pm2 show myapp

# Restart application
pm2 restart myapp

# Stop application
pm2 stop myapp

# Delete from PM2
pm2 delete myapp

# View logs
pm2 logs myapp

# Monitor CPU/memory in real-time
pm2 monit

Step 5: Enable cluster mode

Node.js runs single-threaded by default. Cluster mode spawns multiple instances using all CPU cores:

pm2 start app.js --name myapp -i max

-i max spawns one instance per CPU core.

Scale already running apps:

pm2 scale myapp 4

Step 6: Use ecosystem file

For complex configurations:

pm2 ecosystem

Edit ecosystem.config.js:

module.exports = {
  apps: [{
    name: 'myapp',
    script: 'app.js',
    instances: 'max',
    exec_mode: 'cluster',
    env: {
      NODE_ENV: 'development',
      PORT: 3000
    },
    env_production: {
      NODE_ENV: 'production',
      PORT: 3000
    },
    max_memory_restart: '500M',
    log_date_format: 'YYYY-MM-DD HH:mm:ss'
  }]
}

Start with ecosystem file:

pm2 start ecosystem.config.js --env production

Step 7: Log management

Set up log rotation:

pm2 install pm2-logrotate
pm2 set pm2-logrotate:max_size 10M
pm2 set pm2-logrotate:retain 7
pm2 set pm2-logrotate:compress true

Step 8: Zero-downtime reloads

For deploying updates with zero downtime:

pm2 reload myapp

This restarts instances one by one, keeping apps available throughout.

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Managing Node.js applications with PM2