class DiscourseRouter:

    def db_for_read(self, model, **hints):
        if model._meta.app_label == 'discourse':
            return 'discourse'
        elif model._meta.app_label == 'blog':
            return 'blog'
        else:
            return None

    def db_for_write(self, model, **hints):
        if model._meta.app_label == 'discourse':
            return 'discourse'
        elif model._meta.app_label == 'blog':
            return 'blog'
        else:
            return None

    def allow_relation(self, obj1, obj2, **hints):
        return None

    def allow_migrate(self, db, app_label, model_name=None, **hints):
        if app_label == 'discourse':
            # TODO: `return False` to make production safely
            # Now is just a workaround to make testcase work on mutiple databases
            if db == 'discourse':
                return True
            else:
                return False
        elif app_label == 'blog':
            return False
        else:
            if db == 'discourse':
                return False
        return None