multiple_dbs_database_router.py

from django.conf import settings

# The value is the key that goes in the `DATABASES` settings.
# Ideally set in the Django settings as well, so it can be project-wide accessible
SOURCE_DB_LABEL = 'source_db'


class DatabaseRouter:
    @classmethod
    def allow_migrate(cls, db_label: str, app_label: str, **hints) -> bool:
        allow_default = db_label == 'default' and app_label != 'source_service_app'
        allow_sam_core = db_label == SOURCE_DB_LABEL and app_label in cls._get_django_apps() + ['source_service_app']
        return allow_default or allow_sam_core

    @staticmethod
    def _get_django_apps():
        return [app_label.split('.')[-1] for app_label in settings.DJANGO_APPS]