What is PM2 and how does it relate to Node.js clustering?

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PM2 is the most widely used tool for running Node.js applications in production. When you use cluster mode in PM2 (pm2 start app.js -i max), PM2 internally leverages the Node.js cluster module to fork multiple workers — one per CPU core. It adds enterprise-grade features on top that the raw cluster module does not provide out of the box. # Start app in cluster mode with max workers (= number of CPUs)
pm2 start app.js -i max

# Start with a specific number of workers
pm2 start app.js -i 4

# Zero-downtime reload (restarts workers one at a time)
pm2 reload app

# Real-time monitoring dashboard
pm2 monit

# View logs from all workers
pm2 logs

# List all running processes and status
pm2 list

# Stop the cluster
pm2 stop app

# Delete from PM2 registry
pm2 delete app module.exports = {
  apps: [{
    name: 'my-api',
    script: './src/server.js',
    instances: 'max',           // Use all CPU cores
    exec_mode: 'cluster',       // Enable cluster mode
    watch: false,
    max_memory_restart: '300M', // Restart if worker exceeds 300MB
    env: {
      NODE_ENV: 'production',
      PORT: 3000
    },
    error_file: './logs/err.log',
    out_file: './logs/out.log',
    log_date_format: 'YYYY-MM-DD HH:mm:ss'
  }]
};

// Run with: pm2 start ecosystem.config.js Auto-restart on crash — PM2 automatically restarts dead workers without any custom code Zero-downtime reload — pm2 reload restarts workers one-by-one, avoiding downtime Memory threshold restart — automatically restarts workers exceeding a configured memory limit Log aggregation — unified log management across all worker processes Startup scripts — pm2 startup generates OS init scripts so the cluster survives reboots Built-in metrics — CPU and memory dashboard with pm2 monit Ecosystem file — declarative configuration for complex multi-app production deployments

What is PM2 and how does it relate to Node.js clustering?

PM2 is a production-grade process manager for Node.js that internally uses the cluster module to spawn and manage multiple worker processes. It abstracts the complexity of manual clustering with built-in load balancing, auto-restart, monitoring, log management, and zero-downtime reloads.

What is PM2 and how does it relate to Node.js clustering?

PM2 is a production-grade process manager for Node.js that internally uses the cluster module to spawn and manage multiple worker processes. It abstracts the complexity of manual clustering with built-in load balancing, auto-restart, monitoring, log management, and zero-downtime reloads.

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