Created a custom POST_UPDATE_SIGNAL to save archive all updations to the Allowance object.

edx_proctoring/models.py

@@ -2,10 +2,11 @@
 Data models for the proctoring subsystem
 """
 from django.db import models
-from django.db.models.signals import post_save
-from django.dispatch import receiver
+from django.dispatch import Signal, receiver
 from model_utils.models import TimeStampedModel
 
+POST_UPDATE_SIGNAL = Signal()
+
 
 class ProctoredExam(models.Model):
     """
@@ -36,11 +37,32 @@ class ProctoredExamStudentAttempt(models.Model):
     completed_at = models.DateTimeField(null=True)
 
 
+class QuerySetWithUpdateSignal(models.query.QuerySet):
+    """
+    Custom QuerySet class to send the POST_UPDATE_SIGNAL
+    every time the object is updated.
+    """
+    def update(self, **kwargs):
+        super(QuerySetWithUpdateSignal, self).update(**kwargs)
+        POST_UPDATE_SIGNAL.send(sender=self.model, updated_obj=self.get())
+
+
+class ProctoredExamStudentAllowanceManager(models.Manager):
+    """
+    Custom manager to override with the custom queryset
+    to enable the POST_UPDATE_SIGNAL
+    """
+    def get_query_set(self):
+        return QuerySetWithUpdateSignal(self.model, using=self._db)
+
+
 class ProctoredExamStudentAllowance(TimeStampedModel):
     """
     Information about allowing a student additional time on exam.
     """
 
+    objects = ProctoredExamStudentAllowanceManager()
+
     user_id = models.IntegerField()
 
     proctored_exam = models.ForeignKey(ProctoredExam)
@@ -50,6 +72,21 @@ class ProctoredExamStudentAllowance(TimeStampedModel):
     value = models.CharField(max_length=255)
 
 
+# Hook up the custom POST_UPDATE_SIGNAL signal to record updations in the ProctoredExamStudentAllowanceHistory table.
+@receiver(POST_UPDATE_SIGNAL, sender=ProctoredExamStudentAllowance)
+def archive_allowance_updations(sender, updated_obj, **kwargs):  # pylint: disable=unused-argument
+    """
+    Archiving all changes made to the Student Allowance.
+    Will only archive on updation, and not on new entries created.
+    """
+
+    archive_object = ProctoredExamStudentAllowanceHistory()
+    updated_obj_dict = updated_obj.__dict__
+    updated_obj_dict.pop('id')
+    archive_object.__dict__.update(updated_obj_dict)
+    archive_object.save()
+
+
 class ProctoredExamStudentAllowanceHistory(TimeStampedModel):
     """
     This should be the same schema as ProctoredExamStudentAllowance
@@ -63,14 +100,3 @@ class ProctoredExamStudentAllowanceHistory(TimeStampedModel):
     key = models.CharField(max_length=255)
 
     value = models.CharField(max_length=255)
-
-
-# Hook up Django signals to record changes in the ProctoredExamStudentAllowanceHistory table.
-@receiver(post_save, sender=ProctoredExamStudentAllowance)
-def archive_deleted_user_notification(sender, instance, *args, **kwargs):  # pylint: disable=unused-argument
-    """
-    Archiving the deleted user notifications.
-    """
-    archive_object = ProctoredExamStudentAllowanceHistory()
-    archive_object.__dict__.update(instance.__dict__)
-    archive_object.save()

edx_proctoring/tests/test_models.py

@@ -21,8 +21,9 @@ class ProctoredExamModelTests(LoggedInTestCase):
 
     def test_save_proctored_exam_student_allowance_history(self):  # pylint: disable=invalid-name
         """
-        Test to Save the proctored Exam Student Allowance object
-        which also saves the entry in the History Table.
+        Test to Save and update the proctored Exam Student Allowance object.
+        Upon first save, a new entry is _not_ created in the History table
+        However, a new entry in the History table is created every time the Student Allowance entry is updated.
         """
         proctored_exam = ProctoredExam.objects.create(
             course_id='test_course',
@@ -32,8 +33,34 @@ class ProctoredExamModelTests(LoggedInTestCase):
         ProctoredExamStudentAllowance.objects.create(
             user_id=1,
             proctored_exam=proctored_exam,
-            key='test_key',
-            value='test_val'
+            key='allowance_key',
+            value='20 minutes'
         )
+        # No entry in the History table on creation of the Allowance entry.
         proctored_exam_student_history = ProctoredExamStudentAllowanceHistory.objects.filter(user_id=1)
-        self.assertEqual(len(proctored_exam_student_history), 1)
+        self.assertEqual(len(proctored_exam_student_history), 0)
+
+        # Update the allowance object twice
+        ProctoredExamStudentAllowance.objects.filter(
+            user_id=1,
+            proctored_exam=proctored_exam,
+        ).update(
+            user_id=1,
+            proctored_exam=proctored_exam,
+            key='allowance_key update 1',
+            value='10 minutes'
+        )
+
+        ProctoredExamStudentAllowance.objects.filter(
+            user_id=1,
+            proctored_exam=proctored_exam,
+        ).update(
+            user_id=1,
+            proctored_exam=proctored_exam,
+            key='allowance_key update 2',
+            value='5 minutes'
+        )
+
+        # 2 new entries are created in the History table.
+        proctored_exam_student_history = ProctoredExamStudentAllowanceHistory.objects.filter(user_id=1)
+        self.assertEqual(len(proctored_exam_student_history), 2)