add check mx record

users-events/app/events/batch/chunks_into_users.py

@@ -152,7 +152,6 @@ def _create_user(rawuser: dict, context: dict) -> None:
                 'sk': f'emails#{user.email}',
                 'email_verified': False,
                 'email_primary': True,
-                'mx_record_exists': False,
                 'created_at': now_,
             }
         )

users-events/app/events/check_mx_record.py

@@ -0,0 +1,45 @@
+from aws_lambda_powertools import Logger
+from aws_lambda_powertools.utilities.data_classes import (
+    EventBridgeEvent,
+    event_source,
+)
+from aws_lambda_powertools.utilities.typing import LambdaContext
+from email_validator import EmailUndeliverableError, validate_email
+from layercake.dateutils import now
+from layercake.dynamodb import DynamoDBPersistenceLayer, KeyPair
+
+from boto3clients import dynamodb_client
+from config import USER_TABLE
+
+logger = Logger(__name__)
+dyn = DynamoDBPersistenceLayer(USER_TABLE, dynamodb_client)
+
+
+@event_source(data_class=EventBridgeEvent)
+@logger.inject_lambda_context
+def lambda_handler(event: EventBridgeEvent, context: LambdaContext) -> bool:
+    new_image = event.detail['new_image']
+    # Post-migration (users): rename `emails` to `EMAIL`
+    email = new_image['sk'].removeprefix('emails#')
+
+    return dyn.update_item(
+        key=KeyPair(
+            pk=new_image['id'],
+            sk=new_image['sk'],
+        ),
+        update_expr='SET mx_record_exists = :bool, \
+                         updated_at = :now',
+        expr_attr_values={
+            ':bool': _mx_record_exists(email),
+            ':now': now(),
+        },
+    )
+
+
+def _mx_record_exists(email: str) -> bool:
+    try:
+        validate_email(email, check_deliverability=True)
+    except EmailUndeliverableError:
+        return False
+    else:
+        return True