Merge pull request #164 from jaap3/retry-limit

Retry limit

CHANGES.rst

@@ -7,6 +7,9 @@ Change log
 * Add fix for email address that is a NoneType
 * Stop testing on unsupported Python (<3.7) and Django (<2.2) versions
 * Start testing on Python 3.11 and Django 4.1/4.2
+* Add setting to limit the amount of retries for deferred messages
+  (``MAILER_EMAIL_MAX_RETRIES``), defaults to ``None`` (unlimited)
+  (See Issue `#161 <https://github.com/pinax/django-mailer/issues/161>`_)
 
 2.2 - 2022-03-11
 ----------------

docs/usage.rst

@@ -185,6 +185,12 @@ value more suitable for you. This value, which defaults to ``None``, will be pas
 `Django's bulk_create method <https://docs.djangoproject.com/en/stable/ref/models/querysets/#bulk-create>`_
 as the ``batch_size`` parameter.
 
+To limit the amount of times a deferred message is retried, you can set
+``MAILER_EMAIL_MAX_RETRIES`` to an integer value. The default is ``None``, which means
+that the message will be retried indefinitely. If you set this to a value of ``0``,
+the message will not be retried at all, any number greater than ``0`` will be the
+maximum number of retries (excluding the initial attempt).
+
 Using the DontSendEntry table
 =============================
 

src/mailer/admin.py

@@ -22,7 +22,7 @@ def plain_text_body(self, instance):
 
 class MessageAdmin(MessageAdminMixin, admin.ModelAdmin):
 
-    list_display = ["id", show_to, "subject", "when_added", "priority"]
+    list_display = ["id", show_to, "subject", "when_added", "priority", "retry_count"]
     readonly_fields = ['plain_text_body']
     date_hierarchy = "when_added"
 

src/mailer/migrations/0006_message_retry_count.py

@@ -0,0 +1,18 @@
+# Generated by Django 4.2.1 on 2023-05-25 13:45
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('mailer', '0005_id_bigautofield'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='message',
+            name='retry_count',
+            field=models.IntegerField(default=0),
+        ),
+    ]

src/mailer/models.py

@@ -7,6 +7,8 @@
 
 import six
 
+from django.conf import settings
+
 try:
     from django.utils.encoding import python_2_unicode_compatible
 except ImportError:
@@ -89,7 +91,10 @@ def deferred(self):
         return self.filter(priority=PRIORITY_DEFERRED)
 
     def retry_deferred(self, new_priority=PRIORITY_MEDIUM):
-        return self.deferred().update(priority=new_priority)
+        qs = self.deferred()
+        if getattr(settings, 'MAILER_EMAIL_MAX_RETRIES', None) is not None:
+            qs = qs.filter(retry_count__lt=settings.MAILER_EMAIL_MAX_RETRIES)
+        return qs.update(priority=new_priority, retry_count=models.F('retry_count') + 1)
 
 
 base64_encode = base64.encodebytes if hasattr(base64, 'encodebytes') else base64.encodestring
@@ -133,6 +138,7 @@ class Message(BigAutoModel):
     message_data = models.TextField()
     when_added = models.DateTimeField(default=datetime_now)
     priority = models.PositiveSmallIntegerField(choices=PRIORITIES, default=PRIORITY_MEDIUM)
+    retry_count = models.IntegerField(default=0)
 
     objects = MessageManager()
 

tests/test_mailer.py

@@ -88,6 +88,54 @@ def test_retry_deferred(self):
             engine.send_all()
             self.assertEqual(len(mail.outbox), 1)
             self.assertEqual(Message.objects.count(), 0)
+            self.assertEqual(MessageLog.objects.count(), 2)
+
+    def test_max_retry_deferred(self):
+        with self.settings(MAILER_EMAIL_BACKEND="tests.FailingMailerEmailBackend", MAILER_EMAIL_MAX_RETRIES=2):  # noqa
+            mailer.send_mail("Subject", "Body", "[email protected]", ["[email protected]"])
+            engine.send_all()
+            # First try fails, message is deferred
+            self.assertEqual(Message.objects.count(), 1)
+            self.assertEqual(MessageLog.objects.count(), 1)
+            self.assertEqual(Message.objects.deferred().count(), 1)
+            for n in range(4):
+                with self.subTest(tries=n):
+                    # Re-que the deferred message
+                    Message.objects.retry_deferred()
+                    # Retry count is updated, unless the max is reached
+                    self.assertEqual(
+                        Message.objects.values_list('retry_count', flat=True).get(),
+                        n + 1 if n < 2 else 2,
+                        msg="Expected retry_count to be at most 2, got %d" % n
+                    )
+                    # Send all messages
+                    engine.send_all()
+                    # Message is retried (log entry is added), unless the max is reached
+                    self.assertEqual(
+                        MessageLog.objects.count(), 1 + (n + 1) if n < 2 else 3,
+                        msg="Expected at most 3 attempts (log entries), got %d" % n
+                    )
+                    # Message remain deferred
+                    self.assertEqual(Message.objects.deferred().count(), 1)
+
+    def test_max_retry_zero(self):
+        with self.settings(MAILER_EMAIL_BACKEND="tests.FailingMailerEmailBackend", MAILER_EMAIL_MAX_RETRIES=0):  # noqa
+            mailer.send_mail("Subject", "Body", "[email protected]", ["[email protected]"])
+            engine.send_all()
+            # First try fails, message is deferred
+            self.assertEqual(Message.objects.count(), 1)
+            self.assertEqual(MessageLog.objects.count(), 1)
+            self.assertEqual(Message.objects.deferred().count(), 1)
+            # Re-que the deferred message
+            Message.objects.retry_deferred()
+            # Retry count remains at 0, the message is not retried
+            self.assertEqual(Message.objects.values_list('retry_count', flat=True).get(), 0)
+            # Send all messages
+            engine.send_all()
+            # Message is not retried (log entry is not added)
+            self.assertEqual(MessageLog.objects.count(), 1)
+            # Message remain deferred
+            self.assertEqual(Message.objects.deferred().count(), 1)
 
     def test_purge_old_entries(self):