Fix(idempotency): Log nested exception message (#1813)

Co-authored-by: Release bot <aws-devax-open-source@amazon.com>
Co-authored-by: Michal Ploski <mploski@amazon.com>

Author: 3 people

aws_lambda_powertools/utilities/idempotency/base.py

@@ -113,7 +113,9 @@ def _process_idempotency(self):
             record = self._get_idempotency_record()
             return self._handle_for_status(record)
         except Exception as exc:
-            raise IdempotencyPersistenceLayerError("Failed to save in progress record to idempotency store") from exc
+            raise IdempotencyPersistenceLayerError(
+                "Failed to save in progress record to idempotency store", exc
+            ) from exc
 
         return self._get_function_response()
 
@@ -161,7 +163,7 @@ def _get_idempotency_record(self) -> DataRecord:
         # Wrap remaining unhandled exceptions with IdempotencyPersistenceLayerError to ease exception handling for
         # clients
         except Exception as exc:
-            raise IdempotencyPersistenceLayerError("Failed to get record from idempotency store") from exc
+            raise IdempotencyPersistenceLayerError("Failed to get record from idempotency store", exc) from exc
 
         return data_record
 
@@ -214,7 +216,7 @@ def _get_function_response(self):
                 self.persistence_store.delete_record(data=self.data, exception=handler_exception)
             except Exception as delete_exception:
                 raise IdempotencyPersistenceLayerError(
-                    "Failed to delete record from idempotency store"
+                    "Failed to delete record from idempotency store", delete_exception
                 ) from delete_exception
             raise
 
@@ -223,7 +225,7 @@ def _get_function_response(self):
                 self.persistence_store.save_success(data=self.data, result=response)
             except Exception as save_exception:
                 raise IdempotencyPersistenceLayerError(
-                    "Failed to update record state to success in idempotency store"
+                    "Failed to update record state to success in idempotency store", save_exception
                 ) from save_exception
 
         return response

aws_lambda_powertools/utilities/idempotency/exceptions.py

@@ -3,49 +3,71 @@
 """
 
 
-class IdempotencyItemAlreadyExistsError(Exception):
+from typing import Optional, Union
+
+
+class BaseError(Exception):
+    """
+    Base error class that overwrites the way exception and extra information is printed.
+    See https://github.com/awslabs/aws-lambda-powertools-python/issues/1772
+    """
+
+    def __init__(self, *args: Optional[Union[str, Exception]]):
+        self.message = str(args[0]) if args else ""
+        self.details = "".join(str(arg) for arg in args[1:]) if args[1:] else None
+
+    def __str__(self):
+        """
+        Return all arguments formatted or original message
+        """
+        if self.message and self.details:
+            return f"{self.message} - ({self.details})"
+        return self.message
+
+
+class IdempotencyItemAlreadyExistsError(BaseError):
     """
     Item attempting to be inserted into persistence store already exists and is not expired
     """
 
 
-class IdempotencyItemNotFoundError(Exception):
+class IdempotencyItemNotFoundError(BaseError):
     """
     Item does not exist in persistence store
     """
 
 
-class IdempotencyAlreadyInProgressError(Exception):
+class IdempotencyAlreadyInProgressError(BaseError):
     """
     Execution with idempotency key is already in progress
     """
 
 
-class IdempotencyInvalidStatusError(Exception):
+class IdempotencyInvalidStatusError(BaseError):
     """
     An invalid status was provided
     """
 
 
-class IdempotencyValidationError(Exception):
+class IdempotencyValidationError(BaseError):
     """
     Payload does not match stored idempotency record
     """
 
 
-class IdempotencyInconsistentStateError(Exception):
+class IdempotencyInconsistentStateError(BaseError):
     """
     State is inconsistent across multiple requests to persistence store
     """
 
 
-class IdempotencyPersistenceLayerError(Exception):
+class IdempotencyPersistenceLayerError(BaseError):
     """
     Unrecoverable error from the data store
     """
 
 
-class IdempotencyKeyError(Exception):
+class IdempotencyKeyError(BaseError):
     """
     Payload does not contain an idempotent key
     """

tests/functional/idempotency/test_idempotency.py

@@ -1070,7 +1070,19 @@ def test_idempotent_lambda_save_inprogress_error(persistence_store: DynamoDBPers
     # GIVEN a miss configured persistence layer
     # like no table was created for the idempotency persistence layer
     stubber = stub.Stubber(persistence_store.table.meta.client)
-    stubber.add_client_error("put_item", "ResourceNotFoundException")
+    service_error_code = "ResourceNotFoundException"
+    service_message = "Custom message"
+
+    exception_message = "Failed to save in progress record to idempotency store"
+    exception_details = (
+        f"An error occurred ({service_error_code}) when calling the PutItem operation: {service_message}"
+    )
+
+    stubber.add_client_error(
+        "put_item",
+        service_error_code,
+        service_message,
+    )
     stubber.activate()
 
     @idempotent(persistence_store=persistence_store)
@@ -1083,9 +1095,13 @@ def lambda_handler(event, context):
         lambda_handler({}, lambda_context)
 
     # THEN idempotent should raise an IdempotencyPersistenceLayerError
+    # AND append downstream exception details
     stubber.assert_no_pending_responses()
     stubber.deactivate()
-    assert "Failed to save in progress record to idempotency store" == e.value.args[0]
+    assert exception_message == e.value.args[0]
+    assert isinstance(e.value.args[1], Exception)
+    assert exception_details in e.value.args[1].args
+    assert f"{exception_message} - ({exception_details})" in str(e.value)
 
 
 def test_handler_raise_idempotency_key_error(persistence_store: DynamoDBPersistenceLayer, lambda_context):