Better exception handling

entity_emailer/interface.py

@@ -1,12 +1,13 @@
 import sys
+import traceback
 
 from datetime import datetime
 
 from django.core import mail
 from entity_event import context_loader
 
 from entity_emailer.models import Email
-from entity_emailer.signals import pre_send
+from entity_emailer.signals import pre_send, email_exception
 
 from entity_emailer.utils import get_medium, get_from_email_address, get_subscribed_email_addresses, \
     create_email_message, extract_email_subject_from_html_content
@@ -23,6 +24,7 @@ def send_unsent_scheduled_emails():
         Send out any scheduled emails that are unsent
         """
 
+        # Get the emails that we need to send
         current_time = datetime.utcnow()
         email_medium = get_medium()
         to_send = Email.objects.filter(
@@ -32,15 +34,30 @@ def send_unsent_scheduled_emails():
             'event__source'
         ).prefetch_related(
             'recipients'
+        ).order_by(
+            'scheduled',
+            'id'
         )
 
         # Fetch the contexts of every event so that they may be rendered
         context_loader.load_contexts_and_renderers([e.event for e in to_send], [email_medium])
 
+        # Keep track of what emails we will be sending
         emails = []
+
+        # Loop over each email and generate the recipients, and message
+        # and handle any exceptions that may occur
         for email in to_send:
+            # Compute what email addresses we actually want to send this email to
             to_email_addresses = get_subscribed_email_addresses(email)
-            if to_email_addresses:
+
+            # If there are no recipients we can just skip rendering
+            if not to_email_addresses:
+                continue
+
+            # If any exceptions occur we will catch the exception and store it as a reference
+            # As well as fire off a signal with the error and mark the email as sent and errored
+            try:
                 # Render the email
                 text_message, html_message = email.render(email_medium)
 
@@ -64,9 +81,23 @@ def send_unsent_scheduled_emails():
 
                 # Add the email to the list of emails that need to be sent
                 emails.append(message)
+            except Exception as e:
+                # Save the exception on the model
+                email.exception = traceback.format_exc()
+                email.save(update_fields=['exception'])
+
+                # Fire the email exception event
+                email_exception.send(
+                    sender=Email,
+                    email=email,
+                    exception=e
+                )
 
+        # Send all the emails that were generated properly
         connection = mail.get_connection()
         connection.send_messages(emails)
+
+        # Update the emails as sent
         to_send.update(sent=current_time)
 
     @staticmethod

entity_emailer/migrations/0003_email_exception.py

@@ -0,0 +1,18 @@
+# Generated by Django 2.2.10 on 2020-02-10 18:37
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('entity_emailer', '0002_auto_20170919_1653'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='email',
+            name='exception',
+            field=models.TextField(default=None, null=True),
+        ),
+    ]

entity_emailer/models.py

@@ -60,8 +60,13 @@ class Email(models.Model):
     # allows for a different schedule to be set (to schedule the email for some
     # time in the future), which would not be possible with an auto_add_now=True.
     scheduled = models.DateTimeField(null=True, default=datetime.utcnow)
+
+    # The time that the email was actually sent, or None if the email is still waiting to be sent
     sent = models.DateTimeField(null=True, default=None)
 
+    # Any exception that occurred when attempting to send the email last
+    exception = models.TextField(default=None, null=True)
+
     objects = EmailManager()
 
     def render(self, medium):

entity_emailer/signals.py

@@ -3,3 +3,6 @@
 
 # An event that will be fired prior to an email being sent
 pre_send = Signal(providing_args=['email', 'event', 'context', 'message'])
+
+# An event that will be fired if an exception occurs when trying to send an email
+email_exception = Signal(providing_args=['email', 'exception'])

entity_emailer/tests/interface_tests.py

@@ -412,6 +412,38 @@ def test_updates_times(self, render_mock, address_mock):
         sent_email = Email.objects.filter(sent__isnull=False)
         self.assertEqual(sent_email.count(), 1)
 
+    @patch('entity_emailer.interface.email_exception')
+    @patch('entity_emailer.interface.get_subscribed_email_addresses')
+    @patch.object(Event, 'render', spec_set=True)
+    def test_exceptions(self, render_mock, address_mock, mock_email_exception):
+        """
+        Test that we properly handle when an exception occurs
+        """
+
+        # Mock the render method to raise an exception that we should properly catch
+        render_mock.side_effect = [
+            Exception('test'),
+            ['<p>This is a test html email.</p>', 'This is a test text email.']
+        ]
+        address_mock.return_value = ['test1@example.com', 'test2@example.com']
+
+        # Create a test emails to send
+        g_email(context={}, scheduled=datetime.min)
+        g_email(context={
+            'test': 'test'
+        }, scheduled=datetime.min)
+
+        # Send the emails
+        EntityEmailerInterface.send_unsent_scheduled_emails()
+
+        # Assert that both emails were marked as sent
+        self.assertEqual(Email.objects.filter(sent__isnull=False).count(), 2)
+
+        # Assert that one email raised an exception
+        exception_email = Email.objects.get(sent__isnull=False, exception__isnull=False)
+        self.assertIsNotNone(exception_email)
+        self.assertTrue('Exception: test' in exception_email.exception)
+
 
 class CreateEmailObjectTest(TestCase):
     def test_no_html(self):

entity_emailer/version.py

@@ -1 +1 @@
-__version__ = '1.1.1'
+__version__ = '1.1.2'

release_notes.rst

@@ -1,6 +1,12 @@
 Release Notes
 =============
 
+v1.1.2
+------
+* Handle email render exceptions
+* Add `exception` field
+* Add `email_exception` signal
+
 v1.1.1
 ------
 * Add `pre_send` signal

requirements/requirements-testing.txt

@@ -1,5 +1,5 @@
 coverage
-django-dynamic-fixture
+django-dynamic-fixture<=2.0.0
 django-nose
 flake8
 freezegun

requirements/requirements.txt

@@ -1,5 +1,5 @@
 beautifulsoup4>=4.3.2
-Django>=2.0
+Django>=2.0,<3.0
 django-db-mutex>=1.2.0
 django-entity>=4.2.0
 django-entity-event>=1.2.0

settings.py

@@ -17,10 +17,13 @@ def configure_settings():
         if test_db is None:
             db_config = {
                 'ENGINE': 'django.db.backends.postgresql_psycopg2',
-                'NAME': 'ambition_test',
+                'NAME': 'ambition',
                 'USER': 'postgres',
                 'PASSWORD': '',
                 'HOST': 'db',
+                'TEST': {
+                    'NAME': 'test_entity_emailer'
+                }
             }
         elif test_db == 'postgres':
             db_config = {
@@ -32,30 +35,39 @@ def configure_settings():
             raise RuntimeError('Unsupported test DB {0}'.format(test_db))
 
         settings.configure(
-            MIDDLEWARE_CLASSES=(),
             DATABASES={
                 'default': db_config,
             },
             INSTALLED_APPS=(
                 'db_mutex',
+                'django.contrib.admin',
                 'django.contrib.auth',
                 'django.contrib.contenttypes',
+                'django.contrib.messages',
                 'django.contrib.sessions',
-                'django.contrib.admin',
                 'entity',
                 'entity_event',
                 'entity_emailer',
                 'entity_emailer.tests',
             ),
+            MIDDLEWARE=(
+                'django.contrib.sessions.middleware.SessionMiddleware',
+                'django.contrib.auth.middleware.AuthenticationMiddleware',
+                'django.contrib.messages.middleware.MessageMiddleware',
+            ),
             ROOT_URLCONF='entity_emailer.urls',
             DEFAULT_FROM_EMAIL='test@example.com',
             DEBUG=False,
+            TEMPLATES=[{
+                'BACKEND': 'django.template.backends.django.DjangoTemplates',
+                'APP_DIRS': True,
+                'OPTIONS': {
+                    'context_processors': [
+                        'django.contrib.auth.context_processors.auth',
+                        'django.contrib.messages.context_processors.messages'
+                    ]
+                }
+            }],
             TEST_RUNNER='django_nose.NoseTestSuiteRunner',
             NOSE_ARGS=['--nocapture', '--nologcapture', '--verbosity=1'],
-            TEMPLATES=[
-                {
-                    'BACKEND': 'django.template.backends.django.DjangoTemplates',
-                    'APP_DIRS': True,
-                },
-            ]
         )