Mimic VirtualDocumentRoot with mod_rewrite

Question

In my apache setup I would like to have number of directories named after domain names that will be served based on subdomain hierarchy.

For example, given existent two directories:

1. company.com
2. shop.company.com

Apache will serve following directories based on request host:

1. www.company.com -> company.com
2. us.company.com -> company.com
3. shop.company.com -> shop.company.com
4. foo.bar.shop.company.com -> shop.company.com

mod_vhost_alias can't test existence of directories or manipulate request host as far as I know. Therefore it is not suitable for the task.

I was however successful with following mod_rewrite implementation:

<VirtualHost *:80>
    # Omitting this line produces strange behaviour, requesting company.com the
    # server will try to look up /var/www/test.localhost/var/www/test.localhost
    # Clarification on this issue is very welcome
    DocumentRoot /var/www

    RewriteEngine on

    # Full domain
    RewriteCond %{HTTP_HOST} ^(.*)$
    RewriteCond /var/www/%1 -d
    RewriteRule (.*) /var/www/%1/$1 [L]

    # -1 domain level
    RewriteCond %{HTTP_HOST} ^.+?\.(.*)$
    RewriteCond /var/www/%1 -d
    RewriteRule (.*) /var/www/%1/$1 [L]
</VirtualHost>

I would like to know if there is a better solution for this task and if my implementation has any pitfalls.

So far I only discovered that I need to specify "RewriteBase /" for scripts that rely on rewrite and supposed to be put on top level.

This is not intended for production and performance impact is neglectable.

Answer 1

I'd say it's quite a clever way to do it. The obvious pitfall is that it's not going to work for your fourth example - you only strip off the first subdomain part, so foo.bar.shop.company.com will be translated to bar.shop.company.com instead of shop.company.com

You could use an external program, such as a perl script, to do the rewriting, to catch more specialized cases, by using the RewriteMap directive. That'll bring in even more complications and decrease performance even more.