API timeout issues

The API returns a 504 Gateway Timeout error when accessed through the nginx reverse proxy.

About this task

Symptom

Direct access to the FastAPI backend works, but external access through the nginx proxy returns a 504 Gateway Timeout error.

Cause

The nginx configuration uses the hostname metaltank to proxy requests to the FastAPI backend, but this hostname is not resolvable via DNS or /etc/hosts on the Provisioner server itself, causing nginx to fail connecting to the backend.

Procedure

Verify that the FastAPI backend is running and listening on port 8000.
```
curl http://localhost:8000/login
ss -tlnp | grep 8000
```

Verify that nginx is running.

systemctl status metaltank-webserver.service

Test hostname resolution for metaltank on the Provisioner server.
```
ping -c 1 metaltank
```
If the hostname cannot be resolved, add it to /etc/hosts:
```
echo "127.0.0.1   metaltank" | sudo tee -a /etc/hosts
```

Restart the nginx service to apply the fix.

systemctl restart metaltank-webserver.service

Verify that external API access is restored.
```
curl -k https://provisioner-ip:443/api/
```

Results

The nginx proxy can resolve the metaltank hostname and API requests are no longer timing out.