urls.py

#!/usr/bin/env python

import logging, sys, webapp2

from google.appengine.api import memcache

# the apps we are using
INSTALLED_APPS = [
    'emailreminder',
    'homepage',
]

# our intelligent uri router

old_len = 0
new_len = 0
reload_uris = memcache.get('reload_uris')
import_error = False

try:
    combined_uris = memcache.get('combined_uris')
except:
    reload_uris   = True
    combined_uris = False

if reload_uris or not combined_uris:
    # if we have no uris, or if we are rewriting
    logging.info('reloading uris %s %s' % (reload_uris, combined_uris))
    combined_uris = []
    for app in INSTALLED_APPS: # INSTALLED_APPS came from consts.py
        try:
            import_str = 'apps.%s.urls' % app
            __import__(import_str, globals(), locals(), [], -1)
            app_urls = sys.modules[import_str]
            combined_uris.extend(app_urls.urlpatterns)

            old_len = new_len
            new_len = len(combined_uris)

            if old_len + len(app_urls.urlpatterns) > new_len:
                # we clobbered some urls
                raise Exception('url route conflict with %s' % app)
        except Exception, e:
            logging.error('error importing %s: %s' % (app, e), exc_info=True)
            import_error = True

    if import_error:
        reload_uris = True
    else:
        reload_uris = False

    memcache.set('combined_uris', combined_uris)
    memcache.set('reload_uris', reload_uris)
else:
    logging.warn('using memcached uris!')

logging.info('running application with patterns: %s' % combined_uris)

try:
    app = webapp2.WSGIApplication( routes=combined_uris, debug=True )
except:
    logging.error('There was an error running the application', exc_info=True)
    raise Exception('we need to fix something')