Validate queue names

Author: RealOrangeOne

README.md

@@ -81,6 +81,23 @@ The returned `TaskResult` can be interrogated to query the current state of the
 
 If the task takes arguments, these can be passed as-is to `enqueue`.
 
+### Queue names
+
+By default, tasks are enqueued onto the "default" queue. When using multiple queues, it can be useful to constrain the allowed names, so tasks aren't missed.
+
+```python
+TASKS = {
+    "default": {
+        "BACKEND": "django_tasks.backends.immediate.ImmediateBackend",
+        "QUEUES": ["default", "special"]
+    }
+}
+```
+
+Enqueueing tasks to an unknown queue name raises `InvalidTaskError`.
+
+To disable queue name validation, set `QUEUES` to `[]`.
+
 ### The database backend worker
 
 First, you'll need to add `django_tasks.backends.database`  to `INSTALLED_APPS`, and run `manage.py migrate`.

django_tasks/backends/base.py

@@ -28,7 +28,10 @@ class BaseTaskBackend(metaclass=ABCMeta):
     """Can results be retrieved after the fact (from **any** thread / process)"""
 
     def __init__(self, options: dict) -> None:
+        from django_tasks import DEFAULT_QUEUE_NAME
+
         self.alias = options["ALIAS"]
+        self.queues = set(options.get("QUEUES", [DEFAULT_QUEUE_NAME]))
 
     def validate_task(self, task: Task) -> None:
         """
@@ -51,6 +54,11 @@ def validate_task(self, task: Task) -> None:
         if task.run_after is not None and not timezone.is_aware(task.run_after):
             raise InvalidTaskError("run_after must be an aware datetime")
 
+        if self.queues and task.queue_name not in self.queues:
+            raise InvalidTaskError(
+                f"Queue '{task.queue_name}' is not valid for backend"
+            )
+
     @abstractmethod
     def enqueue(
         self, task: Task[P, T], args: P.args, kwargs: P.kwargs

tests/tests/test_database_backend.py

@@ -22,7 +22,12 @@
 
 
 @override_settings(
-    TASKS={"default": {"BACKEND": "django_tasks.backends.database.DatabaseBackend"}}
+    TASKS={
+        "default": {
+            "BACKEND": "django_tasks.backends.database.DatabaseBackend",
+            "QUEUES": ["default", "queue-1"],
+        }
+    }
 )
 class DatabaseBackendTestCase(TestCase):
     def test_using_correct_backend(self) -> None:
@@ -190,7 +195,10 @@ def test_database_backend_app_missing(self) -> None:
 
 @override_settings(
     TASKS={
-        "default": {"BACKEND": "django_tasks.backends.database.DatabaseBackend"},
+        "default": {
+            "BACKEND": "django_tasks.backends.database.DatabaseBackend",
+            "QUEUES": ["default", "queue-1"],
+        },
         "dummy": {"BACKEND": "django_tasks.backends.dummy.DummyBackend"},
     }
 )