Add validation to check that notifications dont exceed sqs msg limit

app/notifications/validators.py

@@ -52,6 +52,7 @@
     increment_todays_requested_sms_count,
 )
 from app.utils import (
+    flatten_dct,
     get_document_url,
     get_limit_reset_time_et,
     get_public_notify_type_text,
@@ -594,3 +595,19 @@ def decode_personalisation_files(json_personalisation):
                 }
             )
     return json_personalisation, errors
+
+def validate_notification_does_not_exceed_sqs_limit(notification):
+    # SQS max payload size is 256KB
+    if len(str(notification)) >= 262144:
+        # find the largest value in the payload for logging and return message
+        max_key, max_length = max(
+            ((key, len(str(value))) for key, value in flatten_dct(dict(notification)).items()),
+            key=lambda x: x[1]
+        )
+        current_app.logger.debug(
+            f"Unable to send notification {notification['id']}. Payload size exceeds SQS limit of 262144 bytes\nLikely culprit: {max_key}\nLargest value: {max_length} bytes"
+        )
+
+        raise BadRequestError(
+            message=f"Notification size cannot exceed 256Kb. Consider reducing the size of: {max_key}.", status_code=413
+        )

app/utils.py

@@ -1,6 +1,7 @@
 import os
+from collections.abc import MutableMapping
 from datetime import datetime, timedelta
-from typing import Any
+from typing import Any, List, Tuple
 
 import pytz
 from flask import current_app, url_for
@@ -142,6 +143,28 @@ def email_address_is_nhs(email_address):
     )
 
 
+def flatten_dct(dictionary: MutableMapping[Any, Any], parent_key: str = "", separator: str = ".") -> dict:
+    """Recursively flattens a nested dict structure into a single level dict structure.
+    Composite keys are generated from the nested structure keys using the specified separator
+
+    Args:
+        dictionary: The dict to flatten
+        parent_key: Root level identifier for compositing keys, defaults to the top level key of the dict
+        separator: Separator used to when compositing keys.
+
+    Returns:
+        _type_: _description_
+    """
+    items: List[Tuple[str, Any]] = []
+    for key, value in dictionary.items():
+        new_key = parent_key + separator + key if parent_key else key
+        if isinstance(value, MutableMapping):
+            items.extend(flatten_dct(value, new_key, separator=separator).items())
+        else:
+            items.append((new_key, value))
+    return dict(items)
+
+
 def update_dct_to_str(update_dct, lang):
     if lang not in ["EN", "FR"]:
         raise NotImplementedError

app/v2/notifications/post_notifications.py

@@ -2,6 +2,7 @@
 import csv
 import functools
 import uuid
+from collections.abc import MutableMapping
 from datetime import datetime
 from io import StringIO
 
@@ -83,14 +84,15 @@
     increment_email_daily_count_send_warnings_if_needed,
     increment_sms_daily_count_send_warnings_if_needed,
     validate_and_format_recipient,
+    validate_notification_does_not_exceed_sqs_limit,
     validate_template,
     validate_template_exists,
 )
 from app.schema_validation import validate
 from app.schemas import job_schema
 from app.service.utils import safelisted_members
 from app.sms_fragment_utils import fetch_todays_requested_sms_count
-from app.utils import get_delivery_queue_for_template
+from app.utils import flatten_dct, get_delivery_queue_for_template
 from app.v2.errors import BadRequestError
 from app.v2.notifications import v2_notification_blueprint
 from app.v2.notifications.create_response import (
@@ -415,6 +417,8 @@
         "reply_to_text": reply_to_text,
     }
 
+    validate_notification_does_not_exceed_sqs_limit(_notification)
+
     signed_notification_data = signer_notification.sign(_notification)
     notification = {**_notification}
     scheduled_for = form.get("scheduled_for", None)