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This is a series called Save Intern Ruby, where you help Ruby debug her program.
Ruby is an intern and a fresh graduate.
Ruby wrote this compose.yaml file
services:
web:
image: nginx
ports:
- "3000:80"
demo-tools:
image: busybox
# This keeps the container running so you can exec into it
command: sleep infinity
She started the containers docker compose up -d, Both are running properly.
✔ Container web-1 Started
✔ Container demo-tools-1 Started
She wants to send a GET request from the busybox container to the nginx container like this:
docker compose exec demo-tools wget http:// web:3000
(This runs wget in the busybox container shell)
Ruby expects an output like this:
<title>Welcome to nginx!</title>But instead, she got this:
wget: can't connect to remote host (172.18.0.3): Connection refused What went wrong?
Help her fix the problem.
Solution
It's a networking issue.
The reason why it didn't work is because how exposing ports work.
When you expose a port like this:
ports:
- "3000:80"You are forwarding the container's port 80 to the host's port 3000.
There's nothing running on the Nginx container's port 3000. That's why this request doesn't work:
docker compose exec demo-tools wget http:// web:3000
Because we're trying to send a request to the container directly, not to the host, we should be querying port 80:
docker compose exec demo-tools wget http:// web:80
