balancer.py

#!/bin/env python

import cherrypy
import urlparse
import random
import re

class Balancer(object):
    http_url = re.compile(r"""^(?P<subdomain>[-\w]+)\.(?P<domain>[-\w]+\.\w+)$""")
    def __init__(self):
        #cherrypy.config.update({ "environment": "embedded" })
        pass

    def default(self):
        url = urlparse.urlparse(cherrypy.url())
        r = Balancer.http_url.match(url.hostname)
        if r == None:
            return 'Guru Meditation:  Bad Domain?'
        sub = r.group('subdomain')
        dom = r.group('domain')
        svr = str(random.randint(1,2))
        url_out = url.scheme + '://' + sub + svr + '.' + dom + url.path
        if url.query:
            url_out = url_out + '?' + url.query
        if url.fragment:
            url_out = url_out + '#' + url.fragment
        return url_out
        #raise cherrypy.HTTPRedirect(url_out, 302)
    default.exposed = True

cherrypy.server.socket_port = 3000

cherrypy.quickstart(Balancer())

I saw your question in #cherrypy.

Cherrypy can automatically parse segments for you when you use the default method and pass them as arguments to the method. For example:

class Example(object):
    @cherrypy.tools.json_out()
    def default(self, *args, **kw):
        return {
            'segments': args, 'params': kw,
        }
    default.exposed = True

cherrypy.quickstart(Example())

If you run this example you can visit http://localhost:8080/foo/bar/baz?hello=world and you should see a JSON response with {'segments': ['foo', 'bar', 'baz'], 'params': {'hello': 'world'}}.

As an aside, CherryPy also has a virtual hosts tool that might be helpful (http://tools.cherrypy.org/wiki/VirtualHosts).