Prozessverwaltung mit PM2

Welcome to process management with PM2! PM2 stands for Process Manager 2, and it's a powerful tool for Node.js applications.

In production, you need your application to run reliably, restart if it crashes, and utilize server resources efficiently. PM2 handles all of this.

• Keep Alive: Automatically restarts your app if it crashes.
• Monitoring: Provides insights into your app's performance.
• Scaling: Easily run multiple instances of your app for better performance.

Getting started with PM2 is straightforward. You install it globally using npm, so it's available as a command-line tool on your system.

Open your terminal and run the following command:

npm install -g pm2

This command installs the PM2 CLI (Command Line Interface) globally, allowing you to use pm2 commands from any directory.

Once installed, you can start any Node.js application with a simple command. PM2 will keep it running in the background, even if your terminal closes!

First, here's a basic Node.js server:

To start the server from the previous scene (let's say it's saved as app.js) with PM2, you'd run:

pm2 start app.js --name my-first-app

The --name flag gives your process a friendly identifier. PM2 will then list your running application, showing its status, uptime, and other details.

If your app crashes, PM2 will automatically restart it, ensuring high availability!

PM2 offers excellent tools to monitor your running applications. You can quickly see a list of all managed processes and their statuses.

• pm2 list: Shows a table of all your PM2-managed processes, including their ID, name, status, CPU usage, memory usage, and uptime.
• pm2 monit: Provides a dashboard-like view in your terminal, displaying real-time CPU, memory, and log data for all your applications. It's great for quick health checks.

Managing the lifecycle of your applications is simple with PM2. You can stop, restart, or delete processes using their name or ID.

• pm2 stop my-first-app: Stops the application named 'my-first-app'.
• pm2 restart my-first-app: Restarts the application. Useful after code changes.
• pm2 delete my-first-app: Stops the application and removes it from PM2's process list.
• pm2 stop all: Stops all running applications managed by PM2.

These commands give you full control over your deployed Node.js services.

For more complex setups or managing multiple applications, PM2 allows you to use a configuration file (e.g., ecosystem.config.js). This file defines your applications, environment variables, and other settings.

Here's a simple app for demonstration:

Now, let's define an ecosystem.config.js to manage this app:

module.exports = {
  apps : [{
    name: "my-config-app",
    script: "app-config-demo.js",
    instances: 1,
    exec_mode: "fork",
    env: {
      NODE_ENV: "development",
      PORT: 3001
    },
    env_production: {
      NODE_ENV: "production",
      PORT: 80
    }
  }]
};

To start this app using the config file, you'd run: pm2 start ecosystem.config.js. This is great for version control and consistent deployments.

Node.js is single-threaded, but modern servers have multiple CPU cores. PM2's clustering mode allows you to run multiple instances of your app, distributing the load across all available cores.

Here's a simple app that shows its process ID:

To start the app from the previous scene (e.g., app-cluster.js) in cluster mode, you can use:

pm2 start app-cluster.js -i max

The -i max flag tells PM2 to launch as many instances as your CPU has cores. PM2 will then act as a load balancer, distributing incoming requests among these instances. This significantly improves performance and resilience.

You've learned how to manage, monitor, and scale your Node.js applications with PM2. Let's test your understanding!

Great job! You've successfully learned the fundamentals of process management with PM2.

PM2 is an essential tool for deploying and maintaining Node.js applications in production, offering features like automatic restarts, monitoring, and easy scaling through clustering.

Keep exploring PM2's documentation for more advanced features, such as log management, startup scripts, and custom metrics. Happy deploying!