nginx why all routes works but one is "301 Moved Permanently "?

Question

I went to similar questions but without any success.

Let say I have two node.js app turning on a server:

// App GoodMorning
var express     = require('express');

app.post('/breakfast', function (req, res) {  
    console.log("Eating breakfast");
    res.sendStatus(200);
});

app.get('/', function (req, res) {
    res.send('GoodMorning');
});

app.listen(3000, function () {
  console.log('GoodMorning app listening on port 3000!');
});

and

// App GoodEvening
var express     = require('express');

app.post('/diner', function (req, res) {  
    console.log("Eating diner");
    res.sendStatus(200);
});

app.get('/', function (req, res) {
    res.send('GoodEvening');
});

app.listen(4000, function () {
  console.log('GoodEvening app listening on port 4000!');
});

And let's say Nginx is used as a reverse proxy server. So it has to send requests to the correct port, right ? So the "magic" file is like that:

# HTTP - redirect all requests to HTTPS:
server {
    listen 80;
    listen [::]:80 default_server ipv6only=on;
    return 301 https://$host$request_uri;
}


# HTTPS - proxy requests on to local Node.js app:
server {
    listen 443;
    server_name iamhungry.com;

    ssl on;
    # Use certificate and key provided by Let's Encrypt:
    ssl_certificate /etc/letsencrypt/live/iamhungry.com/fullchain.pem;
    ssl_certificate_key /etc/letsencrypt/live/iamhungry.com/privkey.pem;
    ssl_session_timeout 5m;
    ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
    ssl_prefer_server_ciphers on;
    ssl_ciphers 'EECDH+AESGCM:EDH+AESGCM:AES256+EECDH:AES256+EDH';

    # Pass requests for / to localhost:3000:
    location / {
            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header X-NginX-Proxy true;
            proxy_pass http://localhost:3000/;
            proxy_ssl_session_reuse off;
            proxy_set_header Host $http_host;
            proxy_cache_bypass $http_upgrade;
            proxy_redirect off;
    }

    # Pass requests for /homepageevening to localhost:4000:
    location /homepageevening {
            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header X-NginX-Proxy true;
            proxy_pass http://localhost:4000/;
            proxy_ssl_session_reuse off;
            proxy_set_header Host $http_host;
            proxy_cache_bypass $http_upgrade;
            proxy_redirect off;
    }

    # Pass requests for /diner to localhost/diner:4000:
    location /diner {
            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header X-NginX-Proxy true;
            proxy_pass http://localhost/diner:4000/;
            proxy_ssl_session_reuse off;
            proxy_set_header Host $http_host;
            proxy_cache_bypass $http_upgrade;
            proxy_redirect off;
    }

}

Then the following requests do the following results:

$ curl iamhungry.com 
$ GoodMorning // OK

$ curl -X POST iamhungry.com/breakfast
--> I see "Eating brakfast" in the log file of breakfast.js // OK


$ curl iamhungry.com/homepageevening
$ GoodEvening // OK

$ curl -X POST iamhungry.com/diner -I
HTTP/1.1 301 Moved Permanently // why ?!
--> And I see nothing in the log file of evening.js // why ?!

I am not at ease with these proxy concepts. I went through the documentation of nginx and I found no help about that. I wonder if my way of understanding the way it works is correct.

Answer 1

OK thank you @RichardSmith. I had to fix the configuration file:

  location /diner {
        ...
        proxy_pass http://localhost:4000/diner;

And do my tests with curl http://iamhungry.com -I -L instead of curl http://iamhungry.com -I to actually follow the rerouting.

Here is what I was missing:

1. A 301 is not an error. I was doing my test in the terminal using curl http://iamhungry.com -I but using the option -L curl http://iamhungry.com -I -L allowed me to follow the redirection and then get the end of the line ! So 301 is in fact normal using nginx because redirecting is its role.

2. Port number is attached to the domain name. Thanks @RichardSmith.

3. from @RichardSmith link: [...]the part of a normalized request URI matching the location is replaced by a URI specified in the directive.