Sometimes a message is picked up twice of the SQS queue, we need to safe gaurd ourselves for that.

In this PR the id for the notification is passed in and used to created the notification, which causes a integrity error.
Normally when we get a SQLAlchemy error here we send the message to the retry queue, but if the notification already exists
we just ignore it.

tests/app/celery/test_tasks.py

@@ -806,3 +806,41 @@ def test_send_email_should_go_to_retry_queue_if_database_errors(sample_email_tem
     tasks.send_email.retry.assert_called_with(exc=expected_exception, queue='retry')
 
     assert Notification.query.count() == 0
+
+
+def test_send_email_does_not_send_duplicate_and_does_not_put_in_retry_queue(sample_notification, mocker):
+    json = _notification_json(sample_notification.template, sample_notification.to, job_id=uuid.uuid4(), row_number=1)
+    deliver_email = mocker.patch('app.celery.provider_tasks.deliver_email.apply_async')
+    retry = mocker.patch('app.celery.tasks.send_email.retry', side_effect=Exception())
+    now = datetime.utcnow()
+
+    notification_id = sample_notification.id
+
+    send_email(
+        sample_notification.service_id,
+        notification_id,
+        encryption.encrypt(json),
+        now.strftime(DATETIME_FORMAT)
+    )
+    assert Notification.query.count() == 1
+    assert not deliver_email.called
+    assert not retry.called
+
+
+def test_send_sms_does_not_send_duplicate_and_does_not_put_in_retry_queue(sample_notification, mocker):
+    json = _notification_json(sample_notification.template, sample_notification.to, job_id=uuid.uuid4(), row_number=1)
+    deliver_sms = mocker.patch('app.celery.provider_tasks.deliver_sms.apply_async')
+    retry = mocker.patch('app.celery.tasks.send_sms.retry', side_effect=Exception())
+    now = datetime.utcnow()
+
+    notification_id = sample_notification.id
+
+    send_sms(
+        sample_notification.service_id,
+        notification_id,
+        encryption.encrypt(json),
+        now.strftime(DATETIME_FORMAT)
+    )
+    assert Notification.query.count() == 1
+    assert not deliver_sms.called
+    assert not retry.called