How to make nginx rewrite URIs in HTTP body content

After continued investigation and testing of different combinations and ordering of directives, adding proxy_redirect after the proxy_pass directive seems to fix the URI translation issue:

 proxy_redirect https://10.0.0.22/ https://domain.com/my/web/app/;

After some more tinkering, it seems that setting proxy_redirect to default does the same thing implicitly:

 proxy_redirect default;

The full location block then looked like this:

location ^~ /my/web/app/
{
        proxy_buffering   off;
        rewrite           /my/web/app/(.*) /$1 break;
        proxy_pass        https://10.0.0.22/;
        #proxy_redirect    https://10.0.0.22/ https://domain.com/my/web/app/;
        proxy_redirect    default;
}

Images were still broken, however, because they point to /images on the local server. I'm not sure of how to get nginx to translate those (because they're embedded in the HTML body) but to work around the problem for now, I was able to add a dedicated location block for /images before the location block for /my/web/app, like this:

    location ^~ /images/
    {
            proxy_pass https://10.0.0.22/images/;
            proxy_redirect default;
    } 

The location blocks have nothing similar, so combining them with a regex is a bit time consuming and complicated.

Instead, we can just route all the requests to the DSM.

There are three methods to have multiple DSM servers without clashing.

Method #1: Virtual Hosts

You will need to configure your DNS to point your chosen virtual host at the NGINX server.

http {
    #DSM 1 Standard DSM setup
    upstream dsm1 {
        server 1.1.1.1:5000;
    }
    #DSM 2 - DSM has different Port, same IP Address
    upstream dsm2 {
        server 1.1.1.1:6000;
    }
    #DSM 3 - DSM has different IP Address
    upstream dsm3 {
        server 2.1.1.1:5000;
    }
    #DSM 1 Standard DSM setup
    server {
        listen       80;
        server_name dsm1.mydomain.com;
        location / {
            include proxy_headers;
            proxy_pass http://dsm1/;
    }
    #DSM 2 - DSM has different Port, same IP Address
    server {
        listen       80;
        server_name dsm2.mydomain.com;
        location / {
            include proxy_headers;
            proxy_pass http://dsm2/;
    }
    #DSM 3 - DSM has different IP Address
    server {
        listen       80;
        server_name dsm3.mydomain.com;
        location / {
            include proxy_headers;
            proxy_pass http://dsm3/;
    }

Method #2, Different NGINX ports

Each server can be accessed on it's own port on the NGINX server

http {
    #DSM 1 Standard DSM setup
    upstream dsm1 {
        server 1.1.1.1:5000;
    }
    #DSM 2 - DSM has different Port, same IP Address
    upstream dsm2 {
        server 1.1.1.1:6000;
    }
    #DSM 3 - DSM has different IP Address
    upstream dsm3 {
        server 2.1.1.1:5000;
    }
    #DSM 1 Standard DSM setup
    server {
        listen       80;
        location / {
            include proxy_headers;
            proxy_pass http://dsm1/;
    }
    #DSM 2 This DSM server is available on another port (8081). Access using http://nginx_ip:8081
    server {
        listen       81;
        location / {
            include proxy_headers;
            proxy_pass http://dsm1/;
    }
}

Method #3: Rewrites

Each server can be accessed via a sub-url on the NGINX server. May not work depending on the DSM webpage configuration, and whether or not it has relative instead of absolute URLs.

http {
    #DSM 1
    upstream dsm1 {
      server 1.1.1.1:5000
    }
    #DSM 2
    upstream dsm2 {
      server: 1.1.1.2:5000
    }
    server {
      listen 80;
      location /dsm1/(?<dsmurl>.*) {
        include proxy_headers;
        proxy_pass http://dsm1/$dsmurl
      }
      location /dsm2/(?<dsmurl>.*) {
        include proxy_headers;
        proxy_pass http://dsm2/$dsmurl
      }
     }
}