How to rewrite / proxy an Apache URI to an application listening on a specific port / server?

Question

They say that Apache's mod_rewrite is the swiss-army knife of URL manipulation, but can it do this?

Lets say I want to add a new application to my Apache webserver, where the only configurable option of the app is a port number.

I want to use & give out URLs of the form "http://hostname.example.com/app" rather than "http://hostname.example.com:8080". This would ensure that clients would be getting through the institution's firewall as well, and it's generally tidier.

My application includes absolute URIs in php, javascript and css, so I want to prepend my own root location to the URI in the applications internal links. I have no access to DNS records and so can't create another name-based virtual server.

Using Apache's mod_rewrite and mod_proxy modules, I can transparently redirect a client to the correct home-page of the application. But links within that homepage don't point a client to links relative to the new base URL.

So, what's the best way of proxying a request to an application that is listening on a specific port?

For example, if I had an application listening on port 8080, I could put this in my Apache configuration:-

<VirtualHost *:80>
    SSLProxyEngine On
    ServerName myhost.example.com
    RewriteEngine On
    UseCanonicalName On
    ProxyVia On
    <Location "/application">
        RewriteRule ^/application/?(.*) http://localhost:8080/$1 [P,L]
    </Location>
</VirtualHost>

This would work fine if the application didn't use absolute URLs, but it does. What I need to do is rewrite URLs that are returned by the application's css, javascript and php.

I've looked at the ProxyPass and ReverseProxyPass documentation, but I don't think these would work..?

I've also come across Nick Kew's mod_proxy_html, but this isn't included in the standard Apache Distribution, and my institution's webserver seems to have been fine for years without it.. Other than trawling manually (or using a grep -r | sed type expression) through the application's source code, or using this 3rd party add-on, are there any other ways to go about this?

Could I perhaps use some of the internal server variables in a mod_rewrite rule? For example a rewrite rule based on ’HTTP_REFERER'?

Answer 1

Using mod_proxy would work just fine. For instance, I mapped https://localhost/yalla/ to point to a subdirectory of my webserver:

LoadModule proxy_module modules/mod_proxy.so
ProxyRequests On
<Proxy *>
      Order deny,allow
      Allow from localhost
</Proxy>
ProxyPass /yalla/ http://yalla.ynfonatic.de/tmp/

If you implement this, you'll note that the pictues of the directory-listing aren't visible; this is because they're below the /tmp/ directory on the remote server, hence not visible.

So, in your case you'd do:

LoadModule proxy_module modules/mod_proxy.so
ProxyRequests On
<Proxy *>
      Order deny,allow
      Allow from localhost # Or whatever your network is if you need an ACL
</Proxy>
ProxyPass /app/ http://hostname.example.com:8080/

Like with everything in Apache configuration, watch those trailing slashes when referring to directories.

Good luck! Alex.