Lets django find certain models on a certain database. Cross DB joins will still probably fail.

stickyrouter.py

from django.conf import settings

#STICKY_DB_DEFAULT=None
#STICKY_DB_ALLOW_CROSS_DB_RELATIONS=False

#STICKY_DB_MODELS = {
#    ('app', 'model'): 'dbalias',
#    ('app', 'model'): 'dbalias',
#    ('app', 'model'): 'dbalias',
#}

class StickyRouter(object):
    """A router to stick models to particular databases"""
    def _find_db(self, model):

        STICKY_DB_MODELS = getattr(settings, 'STICKY_DB_MODELS', {})

        search = (model._meta.app_label, model.__name__)
        return STICKY_DB_MODELS.get(search, getattr(settings, 'STICKY_DB_DEFAULT', None))

    def db_for_read(self, model, **hints):
        return self._find_db(model)

    def db_for_write(self, model, **hints):
        return self._find_db(model)

    def allow_relation(self, obj1, obj2, **hints):
        if getattr(settings, 'STICKY_DB_ALLOW_CROSS_DB_RELATIONS', False):
            return True #Allow scary cross DB foreign keys
        opts = [self._find_db(obj1.__class__), self._find_db(obj2.__class__)]
        if opts == [None, None]:
            return None #No opinion
        if opts[0] == opts[1]:
            return True #Both using the same DB
        return False #Different DBs

    def allow_syncdb(self, db, model):
        opinion = self._find_db(model)
        care = opinion is not None
        if care and opinion == db:
            return True
        elif care:
            return False
        else:
            return None