base db router

gistfile1.py

class BaseRouter(object):
    """
    Base class for routers allowing several apps to be grouped in a shard group.
    Subclasses need to define a list of app names and a prefix for the db names of the shard group.
    e.g.,
    app_list = ('my_app1', )
    db_names_prefix = 'my_shard_'
    """

    app_list = tuple()
    db_name_prefix = None

    def db_for_read(self, model, **hints):
        if model._meta.app_label in self.app_list:
            instance = hints.get('instance')
            if instance:
                return instance.get_shard()
        return None

    def db_for_write(self, model, **hints):
        if model._meta.app_label in self.app_list:
            instance = hints.get('instance')
            if instance:
                return instance.get_shard()
        return None

    def allow_syncdb(self, db, model):
        if model._meta.app_label in ['south']:
            return True

        # This logic was pulled from: https://github.com/malcolmt/django-multidb-patterns/blob/master/sharding/reviews/router.py#L22
        # and is correct, but very ugly.
        this_app = (model._meta.app_label in self.app_list)
        _db = db.startswith(self.db_names_prefix)
        if this_app:
            return _db
        if _db:
            return False
        return None