Do not assume active DB when not specified

admin_interface/models.py

@@ -45,8 +45,10 @@ def pre_save_handler(instance, **kwargs):
                 pass
 
     @staticmethod
-    def get_active_theme(database="default"):
-        objs_manager = Theme.objects.using(database)
+    def get_active_theme(database=None):
+        objs_manager = (
+            Theme.objects if database is None else Theme.objects.using(database)
+        )
         objs_active_qs = objs_manager.filter(active=True)
         objs_active_ls = list(objs_active_qs)
         objs_active_count = len(objs_active_ls)

tests/routers.py

@@ -0,0 +1,45 @@
+DATABASE_APPS_MAPPING = {
+    "admin_interface": "default",
+}
+
+
+class DatabaseAppsRouter(object):
+    """
+    arouter to control all database operations on models for different
+    databases.
+
+    in case an app is not set in DATABASE_APPS_MAPPING, the router
+    will fallback to the `default` database.
+
+    Settings example:
+
+    DATABASE_APPS_MAPPING = {'app1': 'db1', 'app2': 'db2'}
+    """
+
+    def __init__(self, db_map=DATABASE_APPS_MAPPING):
+        """
+        If routers is not specified, default to DATABASE_APPS_MAPPING
+        """
+        self.db_map = db_map
+
+    def db_for_read(self, model, **hints):
+        """Point all read operations to the specific database"""
+        if model._meta.app_label in self.db_map:
+            return self.db_map[model._meta.app_label]
+
+        return None
+
+    def db_for_write(self, model, **hints):
+        """Point all write operations to the specific database"""
+        if model._meta.app_label in self.db_map:
+            return self.db_map[model._meta.app_label]
+
+        return None
+
+    def allow_relation(self, obj1, obj2, **hints):
+        """Allow any relation between apps that use the same database"""
+        return None
+
+    def allow_migrate(self, db, app_label, model_name=None, **hints):
+        """Make sure that apps only appear in the related database"""
+        return None

tests/settings.py

@@ -117,6 +117,9 @@
     "replica": database_config.get(replica_engine),
 }
 
+
+DATABASE_ROUTERS = ["tests.routers.DatabaseAppsRouter"]
+
 USE_I18N = True
 LANGUAGES = (
     ("en", "English"),

tests/test_multidb.py

@@ -0,0 +1,40 @@
+from unittest import skipIf
+
+from django import VERSION
+from django.test import TestCase
+
+from admin_interface.models import Theme
+
+from .routers import DatabaseAppsRouter
+
+
+class AdminInterfaceModelsWithDBRoutingTestCase(TestCase):
+    databases = ["replica"]
+
+    def test_standard_dbrouter(self):
+        router = DatabaseAppsRouter()
+        db_for_theme = router.db_for_read(Theme)
+        assert db_for_theme == "default"
+
+    def test_dbrouter_selects_correct_db(self):
+        DATABASE_APPS_MAPPING = {
+            "admin_interface": "replica",
+        }
+        router = DatabaseAppsRouter(db_map=DATABASE_APPS_MAPPING)
+        db_for_theme = router.db_for_read(Theme)
+        assert db_for_theme == "replica"
+
+    @skipIf(
+        VERSION[0] < 2, "TestCase does not respect database param on older versions"
+    )
+    def test_dbrouter_errors_when_fetching_from_default(self):
+        with self.assertRaises(Exception):
+            Theme.get_active_theme()
+
+    def test_dbrouter_fetches_db(self):
+        DATABASE_APPS_MAPPING = {
+            "admin_interface": "replica",
+        }
+        router = DatabaseAppsRouter(db_map=DATABASE_APPS_MAPPING)
+        with self.settings(DATABASE_ROUTERS=[router]):
+            Theme.get_active_theme()