What is PM2?

PM2 is a tool that helps you run and manage Node.js applications. It keeps your app alive forever, automatically restarts it if it crashes, and gives you simple ways to see how it’s performing.

Let's break it down

  • PM2: The name of the tool; “PM” stands for “Process Manager.”
  • Process Manager: A program that starts, stops, and watches other programs (processes).
  • Node.js applications: Programs written in JavaScript that run on the Node.js runtime, often used for web servers or APIs.
  • Keeps your app alive forever: Makes sure the program stays running even after you close the terminal.
  • Automatically restarts it if it crashes: Detects when the app stops unexpectedly and starts it again without you doing anything.
  • Gives you simple ways to see how it’s performing: Provides built-in logs and dashboards so you can check CPU usage, memory, and request stats.

Why does it matter?

If you want your website or service to be reliable, you need something that guarantees the code keeps running and lets you spot problems quickly. PM2 does this with just a few commands, saving you time and reducing downtime.

Where is it used?

  • Hosting a production web server that must stay online 24/7.
  • Running multiple micro-services that need to be balanced across CPU cores.
  • Managing background workers that process jobs from a queue.
  • Deploying Node.js code on IoT devices or small servers where manual restarts are impractical.

Good things about it

  • Auto-restart on crashes keeps services available.
  • Built-in clustering spreads load across all CPU cores.
  • Simple command-line interface (CLI) for start, stop, and monitor.
  • Centralized log handling and optional web dashboard.
  • Supports ecosystem files for managing many apps at once.

Not-so-good things

  • Adds extra memory and CPU overhead compared to running the app directly.
  • Primarily designed for Node.js; using it for other languages can be clunky.
  • Some errors may be hidden because PM2 restarts silently, making debugging harder.
  • Configuration files can become complex in large deployments.