multi-database routing

README.md

@@ -17,6 +17,7 @@ Or, check out the **[documentation](https://archmonger.github.io/Conreq/)** for
 -   Customizable Core Webpages (Landing, Home, Sign In, Sign Up, Password Reset)
 -   Graphical Database Administration
 -   MySQL and SQLite Databases
+-   Automatic Multi-Database Routing
 -   Customizable Base URL
 -   [Interactive HTML via ReactPy](https://github.com/reactive-python/reactpy)
 -   [Support for Django Features](https://github.com/django/django)

conreq/_core/base/management/commands/run_conreq.py

@@ -62,7 +62,14 @@ def handle(self, *args, **options):
             cache.clear()
 
         # Migrate the database
-        call_command("migrate", "--noinput", verbosity)
+        for database in settings.DATABASES.keys():
+            call_command(
+                "migrate",
+                "--database",
+                database,
+                "--noinput",
+                verbosity,
+            )
 
         if not DEBUG:
             # Collect static files

conreq/_core/database/router.py

@@ -0,0 +1,44 @@
+from typing import Type
+
+from django.apps import apps
+from django.db.models import Model
+
+
+class DatabaseRouter:
+    """A router to control all database operations on models."""
+
+    # pylint: disable=protected-access,unused-argument
+
+    def db_for_read(self, model: Type[Model], **hints) -> None | str:
+        return getattr(model._meta, "db_for_read", "default")
+
+    def db_for_write(self, model: Type[Model], **hints) -> None | str:
+        return getattr(model._meta, "db_for_write", "default")
+
+    def allow_relation(
+        self, model_1: Type[Model], model_2: Type[Model], **hints
+    ) -> None | bool:
+        """Allow all relationships, unless either model has `allowed_relations`."""
+        rel_1: list[str] = getattr(model_1._meta, "allowed_relations", [])
+        rel_2: list[str] = getattr(model_2._meta, "allowed_relations", [])
+
+        if not rel_1 or rel_2:
+            return True
+
+        return model_2._meta.app_label in rel_1 or model_1._meta.app_label in rel_2
+
+    def allow_migrate(
+        self, db_name: str, app_label: str, model_name: str | None = None, **hints
+    ) -> None | bool:
+        """
+        Migrations only run on the `db_for_read` or `db_for_write` databases,
+        unless a list of `migration_databases` is specified.
+        """
+        if model_name is None:
+            return None
+        model = apps.get_registered_model(app_label, model_name)
+
+        if hasattr(model._meta, "migration_databases"):
+            return db_name in model._meta.migration_databases
+
+        return db_name in (self.db_for_read(model), self.db_for_write(model))

conreq/settings.py

@@ -339,6 +339,7 @@
         },
     }
 }
+DATABASE_ROUTERS = ["conreq._core.database.router.DatabaseRouter"]
 CACHE_SHARDS = min(WEBSERVER_WORKERS, 10)
 CACHES = {
     "default": {