502 Bad Gateway troubleshooting in Nginx - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if the Nginx service is running.

Nginx

systemctl [1] nginx

Drag options to blanks, or click blank then click option'

Astatus

Bstop

Cstart

Drestart

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'start' instead of 'status' will try to start the service instead of checking it.

The systemctl status nginx command shows if the Nginx service is active and running.

2fill in blank

medium

Complete the code to test if the backend server is reachable on port 8080.

Nginx

curl -I http://localhost[1]

Drag options to blanks, or click blank then click option'

A:22

B:80

C:443

D:8080

Attempts:

3 left

💡 Hint

Common Mistakes

Using port 80 tests the frontend, not the backend server.

The backend server often listens on port 8080. Using curl -I http://localhost:8080 sends a HEAD request to check if it responds.

3fill in blank

hard

Fix the error in the Nginx config to correctly proxy requests to the backend.

Nginx

location / {
    proxy_pass http://127.0.0.1:8080[1];
}

Drag options to blanks, or click blank then click option'

A:8080

B8080

C/

Dhttp://localhost:8080

Attempts:

3 left

💡 Hint

Common Mistakes

Using just ':8080' or '8080' without protocol causes config errors.

The proxy_pass directive requires the backend URL with a trailing slash if you want to pass the URI correctly. So http://127.0.0.1:8080/ is correct.

4fill in blank

hard

Fill both blanks to reload Nginx and check its error log for recent 502 errors.

Nginx

sudo systemctl [1] nginx && tail -n 20 /var/log/nginx/[2]

Drag options to blanks, or click blank then click option'

Areload

Bstart

Cerror.log

Daccess.log

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'start' instead of 'reload' restarts the service unnecessarily.

Checking 'access.log' won't show error details.

Reloading Nginx applies config changes without downtime. Checking error.log shows recent errors like 502 Bad Gateway.

5fill in blank

hard

Fill all three blanks to create a dictionary of backend response times greater than 100ms from logs.

Nginx

response_times = { [1]: float(line.split()[2]) for line in logs if float(line.split()[2]) [2] [3] }

Drag options to blanks, or click blank then click option'

Aline.split()[0]

B>

C100

Dline.split()[1]

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong index for key or value.

Using '<' instead of '>' for filtering.

This comprehension extracts the first token as key and the third token as response time, filtering times greater than 100ms.