Now that we have discovered that the catch all Exception handler doesn't work, I've created a custom exception (SendNotificationQueueError) that handles this case and an error handler for it.

Talked these through with @becca as an approach.

app/errors.py

@@ -6,6 +6,7 @@ from sqlalchemy.exc import SQLAlchemyError, DataError
 from sqlalchemy.orm.exc import NoResultFound
 from marshmallow import ValidationError
 from app.authentication.auth import AuthError
+from app.notifications import SendNotificationToQueueError
 
 
 class InvalidRequest(Exception):
@@ -83,6 +84,11 @@ def register_errors(blueprint):
         current_app.logger.exception(e)
         return jsonify(result='error', message="No result found"), 404
 
+    @blueprint.errorhandler(SendNotificationToQueueError)
+    def failed_to_create_notification(e):
+        current_app.logger.exception(e)
+        return jsonify(result='error', message=e.message), 500
+
     @blueprint.errorhandler(SQLAlchemyError)
     def db_error(e):
         current_app.logger.exception(e)

app/notifications/__init__.py

@@ -0,0 +1,7 @@
+
+
+class SendNotificationToQueueError(Exception):
+    status_code = 500
+
+    def __init__(self):
+        self.message = "Failed to create the notification"

app/notifications/process_notifications.py

@@ -9,7 +9,7 @@ from app.celery import provider_tasks
 from app.dao.notifications_dao import dao_create_notification, dao_delete_notifications_and_history_by_id
 from app.models import SMS_TYPE, Notification, KEY_TYPE_TEST, EMAIL_TYPE
 from app.notifications.validators import check_sms_content_char_count
-from app.v2.errors import BadRequestError
+from app.v2.errors import BadRequestError, SendNotificationToQueueError
 
 
 def create_content_for_notification(template, personalisation):
@@ -78,9 +78,9 @@ def send_notification_to_queue(notification, research_mode):
                 queue='send-email' if not research_mode else 'research-mode'
             )
     except Exception as e:
-        current_app.logger.exception("Failed to send to SQS exception")
+        current_app.logger.exception(e)
         dao_delete_notifications_and_history_by_id(notification.id)
-        raise e
+        raise SendNotificationToQueueError()
 
     current_app.logger.info(
         "{} {} created at {}".format(notification.notification_type, notification.id, notification.created_at)

app/notifications/rest.py

@@ -242,10 +242,7 @@ def send_notification(notification_type):
                                                   notification_type=notification_type,
                                                   api_key_id=api_user.id,
                                                   key_type=api_user.key_type)
-        try:
-            send_notification_to_queue(saved_notification, service.research_mode)
-        except Exception as e:
-            return jsonify(result='error', message="Internal server error"), 500
+        send_notification_to_queue(saved_notification, service.research_mode)
 
     notification_id = create_uuid() if saved_notification is None else saved_notification.id
     notification.update({"template_version": template.version})

app/v2/errors.py

@@ -5,6 +5,7 @@ from sqlalchemy.exc import DataError
 from sqlalchemy.orm.exc import NoResultFound
 from app.authentication.auth import AuthError
 from app.errors import InvalidRequest
+from app.notifications import SendNotificationToQueueError
 
 
 class TooManyRequestsError(InvalidRequest):
@@ -47,6 +48,13 @@ def register_errors(blueprint):
     def auth_error(error):
         return jsonify(error.to_dict_v2()), error.code
 
+    @blueprint.errorhandler(SendNotificationToQueueError)
+    def failed_to_create_notification(error):
+        current_app.logger.exception(error)
+        return jsonify(
+            status_code=500,
+            errors=[{"error": error.__class__.__name__, "message": error.message}]), 500
+
     @blueprint.errorhandler(Exception)
     def internal_server_error(error):
         current_app.logger.exception(error)