Apache virtual host based on *source* IP

It wouldn't really be a different virtual host. But using something like mod_rewrite or mod_alias you can serve content out of any folder for which you have set the appropriate permissions. There's only one docroot, but you can effectively change that on the fly.

One way to do it might be:

<VirtualHost *.80>
    ServerName example.com
    ...
    DocumentRoot "/path/to/root"
    <Directory "/path/to/root">
       ...
    </Directory>
    <Directory "/path/to/not/root">
       Order allow,deny
       #replace with your IP
       Allow from 192.168.0.100 
       ...
    </Directory>
    RewriteEngine On
    #Rewrite to alternate path if IP address matches
    RewriteCond %{REMOTE_ADDR} ^192\.168\.0\.100$
    RewriteRule ^/(.*)$ /path/to/not/root/$1
<VirtualHost>

Do note though that it'd probably be a bit cleaner to handle this with a dev subdomain.

I don't know if that's possible (without mod_rewrite, anyway) in Apache level.

Here's another idea. What if you set up two Apache virtual hosts and then use iptables to transparently forward visitor to correct virtual host? Something like

iptables -A PREROUTING -t nat -i eth0 -p tcp -s your.ip.address -d your.server --dport 80 -j DNAT --to-destination your.actual.site:someport
iptables -A PREROUTING -t nat -i eth0 -p tcp ! -s your.ip.address -d your.server --dport 80 -j DNAT --to-destination your.holding.site:someport

Or something similar. :)

Apache 2.3 or later

With Apache 2.3 or later you can apparently do something like this (tested):

<VirtualHost *:80>
    ServerName www.example.com

    <If "-R '10.10.10.10'">
        # The next version of the website...
        Alias /favicon.ico /home/ubuntu/website-new/favicon.ico
        Alias /static/ /home/ubuntu/static/
        WSGIScriptAlias / /home/ubuntu/website-new/main/wsgi.py
    </If>
    <Else>
        # The standard version (e.g. holding page).
        Alias /favicon.ico /home/ubuntu/website/favicon.ico
        Alias /static/ /home/ubuntu/static/
        WSGIScriptAlias / /home/ubuntu/website/main/wsgi.py
    </Else>

    # and so on...

</VirtualHost>

Apache 2.2 or earlier

Update: This is not a good solution. See below.

You have to do a hack like this. Note the [PT] which stands for "passthrough". Without it, an actual HTTP redirect is sent back to the client, which probably isn't what you want. The [OR] thing (which stands for "or") shows how to match multiple addresses.

Alias /next/favicon.ico /home/ubuntu/website-new/favicon.ico
Alias /next/static/ /home/ubuntu/static/
WSGIScriptAlias /next /home/ubuntu/website-new/main/wsgi.py

Alias /favicon.ico /home/ubuntu/website/favicon.ico
Alias /static/ /home/ubuntu/static/
WSGIScriptAlias / /home/ubuntu/website/main/wsgi.py

# Rewrite for our IP.
RewriteEngine On
RewriteCond %{REMOTE_ADDR} ^80\.4\.170\.209$ [OR]
RewriteCond %{REMOTE_ADDR} ^94\.193\.52\.157$
RewriteRule ^/(.*) /next/$1 [PT]

You need to enable mod_rewrite which you can do on Debian/Ubuntu with this command:

sudo a2enmod rewrite

Note that this method doesn't completely ban other people from accessing your test site, so you will probably want to add some security, or just choose a more obscure prefix than next.

Update on the mod_rewrite method.

There are a couple of problems with this method. First, Django does not work with two sites in the same process like this, you need to follow the instructions in this answer.

Secondly mod_rewrite does not work with POST requests! All POSTs are silently changed to GET and the post data is discarded. Very frustrating! Therefore I recommend you use the...

iptables version

Simply run the servers on two different ports. This one includes the WSGI stuff to have two separate django sites.

<VirtualHost *:80>
    ServerName www.example.com

    Alias /favicon.ico /home/ubuntu/alpha/favicon.ico
    Alias /static/ /home/ubuntu/alpha/static/

    WSGIDaemonProcess alpha_wsgi user=www-data group=www-data
    WSGIScriptAlias / /home/ubuntu/alpha/alpha/wsgi.py
    WSGIProcessGroup alpha_wsgi

    ServerAdmin [email protected]

    ErrorLog ${APACHE_LOG_DIR}/error.log

    # Possible values include: debug, info, notice, warn, error, crit, alert, emerg.
    LogLevel warn

    CustomLog ${APACHE_LOG_DIR}/access.log combined
</VirtualHost>
<VirtualHost *:1222>
    ServerName www.example.com

    Alias /favicon.ico /home/ubuntu/main/favicon.ico
    Alias /static/ /home/ubuntu/main/static/

    WSGIDaemonProcess main_wsgi user=www-data group=www-data
    WSGIScriptAlias / /home/ubuntu/main/main/wsgi.py
    WSGIProcessGroup main_wsgi

    ServerAdmin [email protected]

    ErrorLog ${APACHE_LOG_DIR}/error.log

    # Possible values include: debug, info, notice, warn, error, crit, alert, emerg.
    LogLevel warn

    CustomLog ${APACHE_LOG_DIR}/access.log combined
</VirtualHost>

Then you can use this iptables command to route requests from your ip address on port 80 to port 1222:

sudo iptables -A PREROUTING -t nat -p tcp -s your.ip.address --dport 80 -j DNAT --to-destination :1222

Change -A to -D to remove the rule.

Note that the docs suggest you need to add additional Listen and NameVirtualHost commands, but I actually found that it works without them, and adding them made it break (at least in ubuntu).