Add optimistic lock in dref

Author: k9845

dref/migrations/0044_alter_dref_modified_at.py

@@ -0,0 +1,19 @@
+# Generated by Django 3.2.16 on 2022-10-18 07:32
+
+import datetime
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('dref', '0043_delete_dreffileupload'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='dref',
+            name='modified_at',
+            field=models.DateTimeField(blank=True, default=datetime.datetime.now, verbose_name='modified at'),
+        ),
+    ]

dref/models.py

@@ -1,6 +1,7 @@
 import reversion
 import os
 import copy
+from datetime import datetime
 
 from pdf2image import convert_from_bytes
 
@@ -227,7 +228,10 @@ class Status(models.IntegerChoices):
         COMPLETED = 1, _('Completed')
 
     created_at = models.DateTimeField(verbose_name=_('created at'), auto_now_add=True)
-    modified_at = models.DateTimeField(verbose_name=_('modified at'), auto_now=True)
+    modified_at = models.DateTimeField(
+        verbose_name=_('modified at'),
+        default=datetime.now, blank=True
+    )
     created_by = models.ForeignKey(
         settings.AUTH_USER_MODEL, verbose_name=_('created by'), on_delete=models.SET_NULL,
         null=True, related_name='created_by_dref'

dref/serializers.py

@@ -349,6 +349,7 @@ def create(self, validated_data):
     def update(self, instance, validated_data):
         validated_data['modified_by'] = self.context['request'].user
         is_assessment_report = validated_data.get('is_assessment_report')
+        modified_at = validated_data.get('modified_at')
         if is_assessment_report:
             # Previous Operations
             validated_data['lessons_learned'] = None
@@ -374,18 +375,21 @@ def update(self, instance, validated_data):
             dref_assessment_report = super().update(instance, validated_data)
             dref_assessment_report.needs_identified.clear()
             return dref_assessment_report
+
         # we don't send notification again to the already notified users:
         if 'users' in validated_data:
             to = {u.email for u in validated_data['users']
                   if u.email not in {t.email for t in instance.users.iterator()}}
         else:
             to = None
-        dref = super().update(instance, validated_data)
-        if to:
-            transaction.on_commit(
-                lambda: send_dref_email.delay(dref.id, list(to), 'Updated')
-            )
-        return dref
+        if modified_at and instance.modified_at and modified_at > instance.modified_at:
+            dref = super().update(instance, validated_data)
+            if to:
+                transaction.on_commit(
+                    lambda: send_dref_email.delay(dref.id, list(to), 'Updated')
+                )
+            return dref
+        return instance
 
 
 class DrefOperationalUpdateSerializer(

dref/test_views.py

@@ -1,5 +1,6 @@
 import os
 from unittest import mock
+from datetime import datetime
 
 
 from django.conf import settings
@@ -847,3 +848,27 @@ def test_dref_for_super_user(self):
         response = self.client.get(url)
         self.assertEqual(response.status_code, 200)
         self.assertEqual(len(response.data['results']), 0)
+
+    def test_dref_latest_update(self):
+        dref = DrefFactory.create(
+            title='Test Title',
+            created_by=self.user,
+            modified_at=datetime(2022, 4, 18, 2, 29, 39, 793615)
+        )
+        url = f'/api/v2/dref/{dref.id}/'
+        data = {
+            'title': "New title",
+            'modified_at': datetime(2022, 2, 18, 2, 29, 39, 793615),
+        }
+
+        self.client.force_authenticate(self.user)
+        response = self.client.patch(url, data=data)
+        self.assertEqual(response.status_code, 200)
+        # Title should be same since modified_at is less than modified_at in database
+        self.assertEqual(response.data['title'], "Test Title")
+
+        data['modified_at'] = datetime.now()
+        response = self.client.patch(url, data=data)
+        self.assertEqual(response.status_code, 200)
+        # Title should be latest since modified_at is greater than modified_at in database
+        self.assertEqual(response.data['title'], "New title")