Module Overview

What You’ll Learn

• Explain what happens to a running Express app when an unhandled error crashes it
• Use Node’s built-in cluster module to run multiple worker processes
• Shut a process down gracefully, and use PM2 to keep it running automatically

💡 Why this matters: node server.js, run directly in a terminal, dies the moment that terminal closes, or the moment an unhandled exception hits. Nothing in this course so far has needed to survive that, a production process does, every time, without a person watching it.

What’s Covered

• Why a single process isn’t enough, one uncaught exception, one crash, total downtime.
• The cluster module, running multiple worker processes on one machine, built into Node itself.
• Graceful shutdown, finishing in-flight requests before a process actually exits.
• PM2, a process manager that restarts a crashed application automatically, without a person intervening.

Hands-On

By the end of this module, you’ll have an application that survives a crash automatically, and makes use of more than one CPU core on the machine it runs on.

Next module: packaging that application into a container, so it runs identically anywhere.