LITE-16933 Added CQRS_NO_DB_OPERATIONS flag to support models without DB tables

dj_cqrs/controller/consumer.py

@@ -1,13 +1,13 @@
 #  Copyright © 2020 Ingram Micro Inc. All rights reserved.
 
 import logging
+from contextlib import ExitStack
 
 from django.db import close_old_connections, transaction
 
 from dj_cqrs.constants import SignalType
 from dj_cqrs.registries import ReplicaRegistry
 
-
 logger = logging.getLogger('django-cqrs')
 
 
@@ -29,26 +29,26 @@ def route_signal_to_replica_model(signal_type, cqrs_id, instance_data, previous_
     :param str cqrs_id: Replica model CQRS unique identifier.
     :param dict instance_data: Master model data.
     """
-    model_cls = ReplicaRegistry.get_model_by_cqrs_id(cqrs_id)
+    if signal_type not in (SignalType.DELETE, SignalType.SAVE, SignalType.SYNC):
+        logger.error('Bad signal type "{}" for CQRS_ID "{}".'.format(signal_type, cqrs_id))
+        return
 
+    model_cls = ReplicaRegistry.get_model_by_cqrs_id(cqrs_id)
     if model_cls:
-        close_old_connections()
+        db_is_needed = not model_cls.CQRS_NO_DB_OPERATIONS
+        if db_is_needed:
+            close_old_connections()
 
-        if signal_type == SignalType.DELETE:
-            with transaction.atomic(savepoint=False):
+        with transaction.atomic(savepoint=False) if db_is_needed else ExitStack():
+            if signal_type == SignalType.DELETE:
                 return model_cls.cqrs_delete(instance_data)
 
-        elif signal_type == SignalType.SAVE:
-            with transaction.atomic(savepoint=False):
+            elif signal_type == SignalType.SAVE:
                 return model_cls.cqrs_save(instance_data, previous_data=previous_data)
 
-        elif signal_type == SignalType.SYNC:
-            with transaction.atomic(savepoint=False):
+            elif signal_type == SignalType.SYNC:
                 return model_cls.cqrs_save(
                     instance_data,
                     previous_data=previous_data,
                     sync=True,
                 )
-
-        else:
-            logger.error('Bad signal type "{}" for CQRS_ID "{}".'.format(signal_type, cqrs_id))

dj_cqrs/mixins.py

@@ -306,6 +306,9 @@ class ReplicaMixin(Model, metaclass=ReplicaMeta):
     CQRS_SELECT_FOR_UPDATE = False
     """Set it to True to acquire lock on instance creation/update."""
 
+    CQRS_NO_DB_OPERATIONS = False
+    """Set it to True to disable any default DB operations for this model."""
+
     objects = Manager()
 
     cqrs = ReplicaManager()
@@ -328,6 +331,9 @@ def cqrs_save(cls, master_data, previous_data=None, sync=False):
         :return: Model instance.
         :rtype: django.db.models.Model
         """
+        if cls.CQRS_NO_DB_OPERATIONS:
+            raise NotImplementedError
+
         return cls.cqrs.save_instance(master_data, previous_data, sync)
 
     @classmethod
@@ -367,4 +373,7 @@ def cqrs_delete(cls, master_data):
         :return: Flag, if delete operation is successful (even if nothing was deleted).
         :rtype: bool
         """
+        if cls.CQRS_NO_DB_OPERATIONS:
+            raise NotImplementedError
+
         return cls.cqrs.delete_instance(master_data)

tests/dj_replica/models.py

@@ -55,6 +55,16 @@ class LockModelRef(ReplicaMixin, models.Model):
     id = models.IntegerField(primary_key=True)
 
 
+class NoDBModelRef(ReplicaMixin):
+    CQRS_ID = 'no_db'
+    CQRS_NO_DB_OPERATIONS = True
+
+    id = models.IntegerField(primary_key=True)
+
+    class Meta:
+        abstract = True
+
+
 class Event(models.Model):
     pid = models.IntegerField()
     cqrs_id = models.CharField(max_length=20)

tests/test_controller.py

@@ -1,6 +1,9 @@
 #  Copyright © 2020 Ingram Micro Inc. All rights reserved.
 
-from dj_cqrs.controller.consumer import consume
+import pytest
+
+from dj_cqrs.constants import SignalType
+from dj_cqrs.controller.consumer import consume, route_signal_to_replica_model
 from dj_cqrs.controller.producer import produce
 from dj_cqrs.dataclasses import TransportPayload
 
@@ -24,3 +27,14 @@ def test_consumer(mocker):
     consume(TransportPayload('a', 'b', {}, 'c', previous_data={'e': 'f'}))
 
     factory_mock.assert_called_once_with('a', 'b', {}, previous_data={'e': 'f'})
+
+
+@pytest.mark.django_db(transaction=True)
+def test_route_signal_to_replica_model_with_db(django_assert_num_queries):
+    with django_assert_num_queries(1):
+        route_signal_to_replica_model(SignalType.SAVE, 'lock', {})
+
+
+def test_route_signal_to_replica_model_without_db():
+    with pytest.raises(NotImplementedError):
+        route_signal_to_replica_model(SignalType.SAVE, 'no_db', {})

tests/test_replica/test_mixin.py

@@ -485,3 +485,12 @@ def test_select_for_update_lock(mocker):
 
     assert instance.id == 1
     m.assert_called_once()
+
+
+@pytest.mark.django_db
+def test_nodb(mocker):
+    with pytest.raises(NotImplementedError):
+        models.NoDBModelRef.cqrs_save(None)
+
+    with pytest.raises(NotImplementedError):
+        models.NoDBModelRef.cqrs_delete(None)