PM2 for process management in Express - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

What does PM2 do when you run pm2 start app.js?

When you use PM2 to start an Express app with pm2 start app.js, what is the main behavior PM2 provides?

A It compiles the app code before running it.

B It only runs the app once and stops monitoring it.

C It runs the app and automatically restarts it if it crashes or stops.

D It runs the app but disables all network connections.

💡 Hint

Think about what process managers do to keep apps running smoothly.

PM2 runs your app and watches it. If the app crashes or stops, PM2 restarts it automatically to keep it running.

❓ component_behavior

intermediate

What is the output of pm2 list after starting two apps?

You started two Express apps with PM2: pm2 start app1.js and pm2 start app2.js. What will pm2 list show?

A An error saying no apps are running.

B A table showing both apps with their status as online and their process IDs.

C Only the first app listed with status online.

D A list of all files in the current directory.

💡 Hint

PM2 keeps track of all running apps and shows their status.

The pm2 list command displays all apps PM2 manages, showing their names, IDs, and if they are online.

📝 Syntax

advanced

Which PM2 command syntax correctly restarts an app named server?

Choose the correct PM2 command to restart an app named server.

A pm2 reload-server

B pm2 start --restart server

C pm2 reset server

D pm2 restart server

💡 Hint

Look for the PM2 command that explicitly restarts an app by name.

pm2 restart server is the correct syntax to restart an app named server. Other options are invalid or do different things.

🔧 Debug

advanced

Why does pm2 logs show no output after starting an app?

You started your Express app with PM2 using pm2 start app.js, but pm2 logs shows no output even when you make requests. What is a likely cause?

A The app does not print anything to the console; logs are empty.

B PM2 logs command only shows errors, not normal output.

C PM2 was not installed correctly and cannot show logs.

D The app crashed immediately and stopped logging.

💡 Hint

Think about what your app prints to the console and what PM2 captures.

If the app does not use console.log or similar, PM2 logs will be empty because there is no output to capture.

❓ lifecycle

expert

What happens when you run pm2 save and then reboot the server?

After starting your Express app with PM2, you run pm2 save and then reboot your server. What is the expected behavior after reboot?

A PM2 automatically restarts all saved apps on reboot without manual commands.

B PM2 forgets all apps and you must start them again manually.

C PM2 deletes the saved list and stops running after reboot.

D PM2 restarts apps but only if you run <code>pm2 resurrect</code> manually.

💡 Hint

Consider what pm2 save does and how PM2 integrates with system startup.

pm2 save saves the current process list. If PM2 startup scripts are configured, it will auto-restart saved apps on reboot.