How to handle relative urls correctly with a nginx reverse proxy

Question

Sure I'm not the first one that tried to serve a domain example.com from a example.net/bbb, but I haven't found a solution yet.

My NGINX configuration follows the guidelines and looks something like this:

server {
    listen 80;
    server_name example.net;
    root /path/to/aaa;

    location /bbb/ {
        proxy_pass http://example.com/;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
    }

    location / {
        try_files $uri $uri/ /index.html;
    }
    location ~ \.(svg|ttf|js|css|svgz|eot|otf|woff|jpg|jpeg|gif|png|ico)$ {
        access_log off;
        log_not_found off;
        expires max;
    }
}

I can manage to render the root of example.com in example.net/bbb but:

ISSUE 1

example.net/bbb/some/path doesn't work as expected and the index.html of example.net is rendered.

ISSUE 2

Any asset in example.com/assets gives 404 because the browser look for example.net/assets. Be great if I could solve this without placing absolute paths everywhere.

Solution

The problem is basically that using a proxy_pass directive won't rewrite HTML code and therefor relative URL's to for instance a img src="/assets/image.png" won't magically change to img src="/bbb/assets/image.png".

I wrote about potential strategies to address that in Apache httpd here and similar solutions are possible for nginx as well:

• If you have control over example.com and the how the application/content is deployed there, deploy in the same base URI you want to use on example.net for the reverse proxy
  --> deploy your code in example.com/bbb and then your proxy_pass will become quite an easy as /assets/image.png will have been moved to /bbb/assets/image.png:

  location /bbb/ {
       proxy_pass http://example.com/bbb/; 
  

• If you have control over example.com and the how the application/content is deployed:
  change to relative paths, i.e. rather than img src="/assets/image.png"
  refer to img src="./assets/image.png" from a page example.com/index.html
  and to img src="../../assets/image.png"from a page example.com/some/path/index.html

• Maybe you're lucky and example.com only uses a few URI paths in the root and non of those are used by example.net, then simply reverse proxy every necessary subdirectory:

  location /bbb/ {
       proxy_pass http://example.com/; 
  }
  location /assets/ {
       proxy_pass http://example.com/assets/; 
  }
  location /styles/ {
       proxy_pass http://example.com/styles/; 
  

• give up using a example.com as subdirectory on example.net and instead host it on a subdomain of example.net:

  server { 
    server_name bbb.example.net 
    location / {
       proxy_pass http://example.com/; 
    }
  }
  

• rewrite the (HTML) content by enabling the nginx ngx_http_sub_module. That will also allow you to rewrite absolute URL's with something similar to:

  location /bbb/ {
       sub_filter 'src="/assets/'  'src="/bbb/assets/';
       sub_filter 'src="http://example.com/js/' 'src="http://www.example.net/bbb/js/' ;
       sub_filter_once off;
       proxy_pass http://example.com/; 
  }
  

Comments

[a.barbieri]

I can definitely do the first option. The last one is pretty extreme but it's good to know there's such an alternative.

[Sammy]

Excellent explanation of the implementation options. I've been looking for a breakdown like this for quite some time, happy I finally found it. Thank you.