'Cannot GET' on Express when using proxy pass in Nginx - node.js

Question

I'm running two websites on a DigitalOcean droplet, and now I've upgraded to https on both of them. On one of the sites I'm doing a request to a node server I'm running on there to send emails, but since I've enabled https it blocks this request because it isn't https (logically). So I tried to use the node mailserver as a proxy pass on one of the sites that has https enabled.
To test, my node server I want to proxy pass looks like this:
exports.start = () => {
app.use(bodyParser.json());
app.use(cors());
app.get('/', (req, res) => res.send('Hello World!'));
app.listen(4004, () => console.log('Server listening on port 4004'));
};
this.start();
My Nginx sites-enabled/default looks like this:
server {
server_name mywebsite.nl www.website.nl;
location / {
proxy_pass http://<PIVATE IP>:4000;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection 'upgrade';
proxy_set_header Host $host;
proxy_cache_bypass $http_upgrade;
}
location /ws {
proxy_pass http://<PIVATE IP>:4002;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection 'upgrade';
proxy_set_header Host $host;
}
location /mailmeister {
proxy_pass http://<PIVATE IP>:4004;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection 'upgrade';
proxy_set_header Host $host;
}
listen 443 ssl; # managed by Certbot
ssl_certificate /etc/letsencrypt/live/mywebsite.nl/fullchain.pem; # managed by Certbot
ssl_certificate_key /etc/letsencrypt/live/mywebsite.nl/privkey.pem; # managed by Certbot
include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot
}
So the /mailmeister is where I want to redirect all requests to the node server to.
When I run curl localhost:4004 or curl PRIVATE IP:4004 I get the expected
Hello World! response. But when I run curl https://mywebsite.nl/mailmeister It returns a webpage that says
Cannot GET /mailmeister
Anyone know how to fix this?

Answer 1

In a nutshell, since you have:
location /mailmeister {
proxy_pass http://<PIVATE IP>:4004;
}
It should be handled like so:
app.get('/mailmeister ', (req, res) => res.send('Hallo World!'));
Not tested this particular setup. There is a related answer where this is explained further. Once you get it, the documentation makes more sense.