Internal network DNS propagation and new deployments

Questions / Help
3

Sure, this is what I am using:

upstream app {

    server my-node-app.internal:8080;

}

server {

    listen 443 ssl;
    listen [::]:443 ssl;

    ssl_certificate /etc/ssl/SSL_CERT.pem;
    ssl_certificate_key /etc/ssl/SSL_KEY.key;

    ssl_client_certificate /etc/nginx/certs/cloudflare.crt;
    ssl_verify_client on;

    # Catch all @see https://nginx.org/en/docs/http/server_names.html#miscellaneous_names
    server_name _;

    location / {
        proxy_pass http://app;
        proxy_set_header Host $host;
    }

}

So trying something like this should work?

- upstream app {
-
-    server my-node-app.internal:8080;
-
-}

server {

    listen 443 ssl;
    listen [::]:443 ssl;

    ssl_certificate /etc/ssl/SSL_CERT.pem;
    ssl_certificate_key /etc/ssl/SSL_KEY.key;

    ssl_client_certificate /etc/nginx/certs/cloudflare.crt;
    ssl_verify_client on;

    # Catch all @see https://nginx.org/en/docs/http/server_names.html#miscellaneous_names
    server_name _;

    location / {
-        proxy_pass http://app;
+        set $backend "http://my-node-app.internal:8080"
+        proxy_pass $backend;
        proxy_set_header Host $host;
    }

}

It mentions a resolver must be configured as well, e.G. resolver 127.0.0.1 [::1]:5353 valid=30s; - what would I set this to on fly.io?

And any idea why I see the app briefly unavailable during deployment even if I am not using cloudflare, a nginx proxy and the internal network but just a standard fly app?

Thanks!