django-hosts 0.1.1

Overview

This middleware routes requests to specific hosts to different URL schemes (“hostconf”).

For example, if you own example.com but want to serve specific content at api.example.com and beta.example.com, add the following to your hosts.py:

from hosts import patterns, host

host_patterns = patterns('path.to',
    host(r'api', 'api.urls', name='api'),
    host(r'beta', 'beta.urls', name='beta'),
)

This causes requests to {api,beta}.example.com to be routed to their corresponding URLconf. You can use your urls.py as a template for these URLconfs.

Patterns are evaluated in order. If no pattern matches, the request is processed in the usual way, ie. using settings.ROOT_URLCONF.

Installation

• Install the app with your favorite package manager, e.g.:

  pip install django-hosts

• Add 'hosts' to your INSTALLED_APPS setting.

• Add 'hosts.middleware.HostsMiddleware' to your MIDDLEWARE_CLASSES setting.

• Create a module containing your default host patterns, e.g. in the hosts.py file next to your urls.py.

• Set the ROOT_HOSTCONF setting to the dotted Python import path of the module containing your default host patterns, e.g.:

  ROOT_HOSTCONF = 'mysite.hosts'

• Set the DEFAULT_HOST setting to the name of the host pattern you want to refer to as the default pattern. It’ll be used if no other pattern matches or you don’t give a name to the host_url template tag (see below).

Pattern format

The patterns on the left-hand side are regular expressions. For example, the following settings.ROOT_HOSTCONF will route foo.example.com and bar.example.com to the same URLconf.

from hosts import patterns, host

host_patterns = patterns('',
    host(r'(foo|bar)', 'path.to.urls', name='foo-or-bar'),
)

Dynamic hosts using regular expressions

Patterns being regular expressions allows setups to feature dynamic (or “wildcard”) host schemes:

from django.conf import settings
from hosts import patterns, host

host_patterns = patterns('',
    host(r'www', settings.ROOT_URLCONF, name='www'),
    host(r'(\w+)', 'path.to.custom_urls', name='wildcard'),
)

Here, requests to www.example.com will be routed as normal but a request to lamby.example.com is routed to path.to.custom_urls.

As patterns are matched in order, we placed www first as it otherwise would have matched against \w+ and thus routed to the wrong destination.

Alternatively, we could have used negative lookahead:

from hosts import patterns, host

host_patterns = patterns('',
    host(r'(?!www)\w+', 'path.to.custom_urls', name='wildcard'),
)

Callback methods to simplify dynamic hosts

The previous section outlined using regular expressions to implement dynamic hosts.

However, inside every view referenced by the target URLconf we would have to parse the host from request.get_host() and lookup its corresponding object instance, violating DRY. If these dynamic hosts had a lot of views this would become particularly unwieldy.

To remedy this, you can optionally specify a callback method to be called if your host matches:

from django.conf import settings
from hosts import patterns, host

host_patterns = patterns('',
    host(r'www', settings.ROOT_URLCONF, name='www'),
    host(r'(?P<username>\w+)', 'path.to.custom_urls',
         callback='path.to.custom_fn', name='with-callback'),
)

[..]

from django.shortcuts import get_object_or_404
from django.contrib.auth.models import User

def custom_fn(request, username):
    request.viewing_user = get_object_or_404(User, username=username)

This example avoids the duplicated work in every view by attaching a viewing_user instance to the request object. Views referenced by the “dynamic” URLconf can now assume that this object exists.

The custom method is called with the request object and any named captured arguments, similar to regular Django url processing.

Callbacks may return either None or an HttpResponse object. If it returns None, the request continues to be processed and the appropriate view is eventually called. If a callback returns an HttpResponse object, that HttpResponse is returned to the client without any further processing.

Template tags

Now if you want to actually refer to the full URLs in your templates you can use the included host_url template tag. So imagine having a host pattern of:

from django.conf import settings
from hosts import patterns, host

host_patterns = patterns('',
    host(r'admin', settings.ROOT_URLCONF, name='our-admin'),
)

and a ROOT_URLCONF of:

from django.conf.urls.defaults import patterns, url

urlpatterns = patterns('mysite.admin',
    url(r'^dashboard/$', 'dashboard', name='dashboard'),
)

then this example will create a link to the admin dashboard:

{% load hosts %}

<a href="{% host_url dashboard on our-admin %}">Admin dashboard</a>

which will be rendered as:

<a href="//admin/dashboard/">Admin dashboard</a>

In case you want to append a default domain name to the domain part of the rendered URL you can simply set the PARENT_HOST, e.g:

PARENT_HOST = 'example.com'

This would render the link above as:

<a href="//admin.example.com/dashboard/">Admin dashboard</a>

Alternatively – in case you don’t want to append this parent domain to all URLs you can also spell out the domain in the host pattern:

from django.conf import settings
from hosts import patterns, host

host_patterns = patterns('',
    host(r'admin\.example\.com', settings.ROOT_URLCONF, name='admin'),
)

If your host pattern contains an argument (or key argument), like:

from django.conf import settings
from hosts import patterns, host

host_patterns = patterns('',
    host(r'www', settings.ROOT_URLCONF, name='homepage'),
    host(r'(\w+)', 'path.to.support_urls', name='wildcard'),
    host(r'(?P<username>\w+)', 'path.to.user_urls', name='user-area'),
)

you can also easily pass arguments to the host_url template tag:

{% load hosts %}

<a href="{% host_url user-dashboard on user-area username='johndoe' %}">John's dashboard</a>
<a href="{% host_url faq-index on wildcard 'help' %}">FAQ</a>

Which will be rendered (with a PARENT_HOST of 'example.com') as:

<a href="//johndoe.example.com/">John's dashboard</a>
<a href="//help.example.com/faq/">FAQ</a>

Notes

• When using dynamic hosts based on user input, ensure users cannot specify names that conflict with static subdomains such as “www” or their subdomain will not be accessible.

• Don’t forget to add handler404 and handler500 entries for your custom URLconfs.

Changelog

Thanks

Many thanks to the folks at playfire for releasing their django-dynamic-subdomains app, which was the inspiration for django-hosts.