Django, subdomains and mod_rewrite. URLs messing up on deployment setups.

Question

I have a Django application being served of (say) example.com. It contains a number of sub-applications (say) strength, speed and skill. The URL scheme is something like http://example.com/strength, http://example.com/speed and http://example.com/skill. This is how I run my dev server (using runserver) and there are no problems whatsoever.

Now, during deployment, I need to have subdomains that map to these sub-applications. More specifically, I want http://x.example.com to map to http://example.com/x (for the above values of x) and then processing can go on.

I googled a little bit and found two ways of doing this.

• One is to get some middleware to get the subdomain part of the URL and keep it inside the request object passed to my view methods. I then do the whole thing inside my application logic.
• The other is to use Apache mod_rewrite to do the above URL translation and then let my app run as usual.

I chose the latter since it looked neater and I thought I wouldn't have to include deployment specific code inside my core application.

Now, I'm bitten by a problem which I can't really find a way out of. Inside the skill application, I have a named url skill_home. It's http://example.com/skill. However, once I deploy, the skill_home URL becomes http://skill.example.com/skill. Django appends the /skill to the top level domain and this is what I get. If I do a GET on this URL, mod_rewrite changes it to http://skill.example.com/skill/skill and it doesn't work.

My mod_rewrite snippets look like this

RewriteCond %{HTTP_HOST} !www.example.com$ [NC]
RewriteCond %{HTTP_HOST} ^(www.)?skill.example.com [NC]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule (.*) /skill/$1 

How do I fix this neatly?

Answer 1

For this answer I'm assuming that you're willing to do a mod_rewrite for each subdomain. I don't think this will work for any subdomain (i.e. the x you mention).

This will strip out the leading /skill/ so that your app will continue to work:

RewriteCond %{HTTP_HOST} !www.example.com$ [NC]
RewriteCond %{HTTP_HOST} ^(www.)?skill.example.com [NC]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule (/skill/)?(.*) /skill/$2

Update

Okay, so you want to strip out the leading part of the URL in the link itself.

Basically, that means you have to write a custom tag to replace the {% url %} tag, something like this:

import re
from django.template import Library
from django.template.defaulttags import URLNode, url

register = Library()

class SubdomainURLNode(URLNode):
    def render(self, context):
        domain = context['request'].get_host()
        subdomain = re.sub(r'^www\.','',domain).split('.')[0]
        path = super(SubdomainURLNode, self).render(context)
        return re.sub(r'^/%s/' % subdomain, '/', path)

@register.tag
def subdomainurl(parser, token, node_cls=SubdomainURLNode):
    """Just like {% url %} but checks for a subdomain."""
    node_instance = url(parser, token)
    return node_cls(view_name=node_instance.view_name,
        args=node_instance.args,
        kwargs=node_instance.kwargs,
        asvar=node_instance.asvar)

I've tested this on my server and it appears to work.