Some pseudo code and notes of how to implement a check for the letter acknowledgement file.

app/celery/scheduled_tasks.py

@@ -447,3 +447,22 @@ def daily_stats_template_usage_by_month():
                 result.year,
                 result.count
             )
+
+
+@notify_celery.task(name='raise-alert-if-no-letter-ack-file')
+@statsd(namespace="tasks")
+def raise_alert_if_no_letter_ack_file():
+    """
+    Get all files sent "today"
+    list_of_zip_files => get file names s3.get_s3_bucket_objects() look in the folder with todays date
+
+    list_of_ack_files => Get all files sent today with name containing ack.txt from a diff bucket
+
+    For filename in list_of_zip_files:
+        for ack_file in list_of_ack_files if name= file.strip("NOTIFY.", ".ZIP")
+        IF no ack_file
+            raise NoAckFileReceived(status=500, message="No ack file received for {filename}")
+
+    """
+
+    pass

app/config.py

@@ -249,6 +249,11 @@ class Config(object):
             'schedule': crontab(hour=17, minute=50),
             'options': {'queue': QueueNames.PERIODIC}
         },
+        'raise-alert-if-no-letter-ack-file': {
+            'task': 'raise-alert-if-no-letter-ack-file',
+            'schedule': crontab(hour=19, minute=00),
+            'options': {'queue': QueueNames.PERIODIC}
+        },
         'run-letter-api-notifications': {
             'task': 'run-letter-api-notifications',
             'schedule': crontab(hour=17, minute=40),

app/notifications/notifications_letter_callback.py

@@ -53,6 +53,7 @@ def process_letter_response():
         message = json.loads(req_json['Message'])
         filename = message['Records'][0]['s3']['object']['key']
         current_app.logger.info('Received file from DVLA: {}'.format(filename))
+        # IF file name contains .rs.txt THEN continue ELSE log message with file name. and return
         current_app.logger.info('DVLA callback: Calling task to update letter notifications')
         update_letter_notifications_statuses.apply_async([filename], queue=QueueNames.NOTIFY)