Node.js PM2 Process Manager

What is PM2 Process Manager in Node.js?

PM2 keeps a Node application running: it restarts on crash, runs one process per core, reloads with zero downtime, manages logs and restores the process list after a server reboot.

PM2 Process Manager example

pm2 start src/index.js --name api -i max   # one worker per core
pm2 list
pm2 logs api --lines 100
pm2 reload api          # zero-downtime restart
pm2 restart api         # hard restart
pm2 monit               # live CPU and memory
pm2 save && pm2 startup # survive a server reboot

ecosystem.config.cjs

module.exports = {
  apps: [{
    name: 'api',
    script: 'src/index.js',
    instances: 'max',
    exec_mode: 'cluster',
    max_memory_restart: '500M',
    env: { NODE_ENV: 'production', PORT: 5000 },
  }],
};

Key points to remember

• reload is zero-downtime in cluster mode; restart is not.
• max_memory_restart is a safety net for slow leaks, not a fix.
• pm2 save plus pm2 startup is what makes the app survive a reboot.
• Containerised deployments usually let the orchestrator do this instead.

Common mistakes with PM2 Process Manager

• Forgetting pm2 save, so nothing comes back after a reboot.
• Cluster mode with in-memory sessions, which breaks across workers.