Assure that the Active Task Users table is cleared out before deleting the Active Task Record.

We were depending on a cascade here, which seems to fail randomly -- apparently due to some sort of race condition.

src/spiffworkflow_backend/services/process_instance_processor.py

@@ -522,6 +522,10 @@ class ProcessInstanceProcessor:
         ).all()
         if len(active_tasks) > 0:
             for at in active_tasks:
+                active_task_users = at.active_task_users
+                for atu in active_task_users:
+                    # don't trust sqlalchemy to cascade - ran into race condition here.
+                    db.session.delete(atu)
                 db.session.delete(at)
 
         db.session.add(self.process_instance_model)

tests/spiffworkflow_backend/unit/test_active_task.py

@@ -0,0 +1,49 @@
+"""Process Model."""
+from decimal import Decimal
+
+from flask.app import Flask
+from flask_bpmn.models.db import db
+
+from spiffworkflow_backend.models.active_task import ActiveTaskModel
+from spiffworkflow_backend.models.active_task_user import ActiveTaskUserModel
+from spiffworkflow_backend.services.process_instance_processor import ProcessInstanceProcessor
+from tests.spiffworkflow_backend.helpers.base_test import BaseTest
+from tests.spiffworkflow_backend.helpers.test_data import load_test_spec
+
+from spiffworkflow_backend.models.spiff_logging import SpiffLoggingModel
+
+
+class TestActiveTask(BaseTest):
+
+    def test_can_create_and_delete_an_active_task (
+        self, app: Flask, with_db_and_bpmn_file_cleanup: None
+    ) -> None:
+        process_model = load_test_spec(
+            "call_activity_test",
+            process_model_source_directory="call_activity_same_directory",
+        )
+
+        process_instance = self.create_process_instance_from_process_model(
+            process_model
+        )
+        active_task = ActiveTaskModel(
+            process_instance_id=process_instance.id,
+            process_model_display_name="my shorts",
+            form_file_name="my_file_name",
+            ui_form_file_name="",
+            task_id="1234",
+            task_name="any old thing",
+            task_title="",
+            task_type="test type",
+            task_status="WAITING",
+            lane_assignment_id=None,
+        )
+        initiator_user = self.find_or_create_user("initiator_user")
+        db.session.add(active_task)
+        db.session.commit()
+        active_task_user = ActiveTaskUserModel(active_task_id=active_task.id, user_id=initiator_user.id)
+        db.session.add(active_task_user)
+        db.session.commit()
+        processor = ProcessInstanceProcessor(process_instance)
+        processor.save()  # This should clear out all active tasks and active task users.
+        assert(len(db.session.query(ActiveTaskModel).all()) == 0)