proxying relative urls with nginx

Question

My question is similar to Nginx Relative URL to Absolute Rewrite Rule? - but with an added twist.

I have nginx acting as a proxy server, which proxies for multiple apps, similar to this (simplified) config:

server {
  listen 80;
  server_name example.com;

  location /app1 {
    proxy_pass   http://app1.com;
  }
  location /app2 {
    proxy_pass http://app2.com;
  }
}

This works fine, but as in the other question, these applications (app1 and app2) use relative urls such as /css/foo.css, or /js/bar.js. Also it's a big problem to ask all applications to change to something like /app1/css/foo.css.

Is it possible for nginx to intelligently figure out which application should handle the request? FTR, users would be accessing these applications like this:

http://example.com/app1/fooaction or http://example.com/app2/baraction.

If it matters, all applications are Java/Tomcat based apps.

TIA!

Answer 1

Based on your updated comments; if the upstream backend sends the referer header, you could do something like this:

location ~* ^/(css|js)/.+\.(css|js)$ {            
        #checking if referer is from app1            
        if ($http_referer ~ "^.*/app1"){
            return 417;
        }    

        #checking if referer is from app2
        if ($http_referer ~ "^.*/app2"){
            return 418;
        }    
    }
    error_page   417  /app1$request_uri;
    error_page   418  /app2$request_uri;


    location /app1 {        
         proxy_pass  http://app1.com;
    }

    location /app2 {
        proxy_pass http://app2.com;
    }

For example, if the backend on app2.com, requests the test.css like this:

curl 'http://example.com/css/test.css' -H 'Referer: http://app2.com/app2/some/api'

The request land here:

/app2/css/test.css