PM2 for process management in Express - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is PM2 in the context of Node.js applications?

PM2 is a process manager for Node.js applications that helps keep apps running continuously, restarts them if they crash, and manages multiple processes easily.

beginner

How do you start an Express app using PM2?

You use the command pm2 start app.js where app.js is your Express app's main file. PM2 will run and monitor the app.

beginner

What command shows the list of running processes managed by PM2?

The command pm2 list displays all running processes with their status, CPU, and memory usage.

intermediate

How does PM2 help with zero-downtime reloads in production?

PM2 can reload your app without stopping it completely using pm2 reload app_name, which restarts processes one by one to avoid downtime.

intermediate

What is the purpose of the ecosystem.config.js file in PM2?

It is a configuration file where you define how PM2 should run your app(s), including environment variables, number of instances, and script paths.

Which PM2 command starts your Express app?

A pm2 start app.js

B pm2 run app.js

C pm2 execute app.js

D pm2 launch app.js

The correct command to start an app with PM2 is pm2 start app.js.

What does pm2 list show?

A All installed npm packages

B Running processes managed by PM2

C System CPU usage

D Network connections

pm2 list shows all processes PM2 is managing, including their status.

How can PM2 help avoid downtime when updating your app?

A By disabling the app temporarily

B By stopping all processes before restart

C By running a backup server

D By reloading processes one by one

PM2 reloads processes one at a time to keep the app available during updates.

What is the role of ecosystem.config.js in PM2?

A It stores app logs

B It is a database file

C It defines app start settings and environment

D It contains user credentials

ecosystem.config.js configures how PM2 runs your app, including environment variables and instances.

Which of these is NOT a feature of PM2?

A Compiling JavaScript to machine code

B Load balancing across CPU cores

C Monitoring CPU and memory usage

D Automatic app restarts on crash

PM2 manages processes but does not compile JavaScript to machine code.

Explain how PM2 helps keep an Express app running smoothly in production.

Think about what happens if your app crashes or needs updating.

Describe the purpose and typical contents of the PM2 ecosystem.config.js file.

It's a setup file that tells PM2 how to run your app.