fix(idempotency): make idempotent_function decorator thread safe (#1899)

* update changelog with latest changes

* Add low level dynamodb client

* Fix black and mypy warnings

* Fix test error + add missing pytest groupings

* Simplify parallel function handler

* Rename e2e tests

* fix(idempotency): updating documentation

---------

Co-authored-by: Release bot <[email protected]>
Co-authored-by: Michal Ploski <[email protected]>
Co-authored-by: Leandro Damascena <[email protected]>

Author: 4 people

aws_lambda_powertools/event_handler/api_gateway.py

@@ -836,7 +836,6 @@ def route(
     # Override _compile_regex to exclude trailing slashes for route resolution
     @staticmethod
     def _compile_regex(rule: str, base_regex: str = _ROUTE_REGEX):
-
         return super(APIGatewayRestResolver, APIGatewayRestResolver)._compile_regex(rule, "^{}/*$")
 
 

aws_lambda_powertools/logging/utils.py

@@ -12,7 +12,6 @@ def copy_config_to_registered_loggers(
     exclude: Optional[Set[str]] = None,
     include: Optional[Set[str]] = None,
 ) -> None:
-
     """Copies source Logger level and handler to all registered loggers for consistent formatting.
 
     Parameters

aws_lambda_powertools/utilities/feature_flags/schema.py

@@ -272,7 +272,6 @@ def __init__(self, rule: Dict[str, Any], rule_name: str, logger: Optional[Union[
         self.logger = logger or logging.getLogger(__name__)
 
     def validate(self):
-
         if not self.conditions or not isinstance(self.conditions, list):
             self.logger.debug(f"Condition is empty or invalid for rule={self.rule_name}")
             raise SchemaValidationError(f"Invalid condition, rule={self.rule_name}")

aws_lambda_powertools/utilities/idempotency/persistence/base.py

@@ -37,7 +37,7 @@ class DataRecord:
 
     def __init__(
         self,
-        idempotency_key,
+        idempotency_key: str,
         status: str = "",
         expiry_timestamp: Optional[int] = None,
         in_progress_expiry_timestamp: Optional[int] = None,

aws_lambda_powertools/utilities/idempotency/persistence/dynamodb.py

@@ -4,7 +4,9 @@
 from typing import Any, Dict, Optional
 
 import boto3
+from boto3.dynamodb.types import TypeDeserializer
 from botocore.config import Config
+from botocore.exceptions import ClientError
 
 from aws_lambda_powertools.shared import constants
 from aws_lambda_powertools.utilities.idempotency import BasePersistenceLayer
@@ -79,13 +81,14 @@ def __init__(
 
         self._boto_config = boto_config or Config()
         self._boto3_session = boto3_session or boto3.session.Session()
+        self._client = self._boto3_session.client("dynamodb", config=self._boto_config)
+
         if sort_key_attr == key_attr:
             raise ValueError(f"key_attr [{key_attr}] and sort_key_attr [{sort_key_attr}] cannot be the same!")
 
         if static_pk_value is None:
             static_pk_value = f"idempotency#{os.getenv(constants.LAMBDA_FUNCTION_NAME_ENV, '')}"
 
-        self._table = None
         self.table_name = table_name
         self.key_attr = key_attr
         self.static_pk_value = static_pk_value
@@ -95,31 +98,15 @@ def __init__(
         self.status_attr = status_attr
         self.data_attr = data_attr
         self.validation_key_attr = validation_key_attr
-        super(DynamoDBPersistenceLayer, self).__init__()
 
-    @property
-    def table(self):
-        """
-        Caching property to store boto3 dynamodb Table resource
+        self._deserializer = TypeDeserializer()
 
-        """
-        if self._table:
-            return self._table
-        ddb_resource = self._boto3_session.resource("dynamodb", config=self._boto_config)
-        self._table = ddb_resource.Table(self.table_name)
-        return self._table
-
-    @table.setter
-    def table(self, table):
-        """
-        Allow table instance variable to be set directly, primarily for use in tests
-        """
-        self._table = table
+        super(DynamoDBPersistenceLayer, self).__init__()
 
     def _get_key(self, idempotency_key: str) -> dict:
         if self.sort_key_attr:
-            return {self.key_attr: self.static_pk_value, self.sort_key_attr: idempotency_key}
-        return {self.key_attr: idempotency_key}
+            return {self.key_attr: {"S": self.static_pk_value}, self.sort_key_attr: {"S": idempotency_key}}
+        return {self.key_attr: {"S": idempotency_key}}
 
     def _item_to_data_record(self, item: Dict[str, Any]) -> DataRecord:
         """
@@ -136,36 +123,39 @@ def _item_to_data_record(self, item: Dict[str, Any]) -> DataRecord:
             representation of item
 
         """
+        data = self._deserializer.deserialize({"M": item})
         return DataRecord(
-            idempotency_key=item[self.key_attr],
-            status=item[self.status_attr],
-            expiry_timestamp=item[self.expiry_attr],
-            in_progress_expiry_timestamp=item.get(self.in_progress_expiry_attr),
-            response_data=item.get(self.data_attr),
-            payload_hash=item.get(self.validation_key_attr),
+            idempotency_key=data[self.key_attr],
+            status=data[self.status_attr],
+            expiry_timestamp=data[self.expiry_attr],
+            in_progress_expiry_timestamp=data.get(self.in_progress_expiry_attr),
+            response_data=data.get(self.data_attr),
+            payload_hash=data.get(self.validation_key_attr),
         )
 
     def _get_record(self, idempotency_key) -> DataRecord:
-        response = self.table.get_item(Key=self._get_key(idempotency_key), ConsistentRead=True)
-
+        response = self._client.get_item(
+            TableName=self.table_name, Key=self._get_key(idempotency_key), ConsistentRead=True
+        )
         try:
             item = response["Item"]
-        except KeyError:
-            raise IdempotencyItemNotFoundError
+        except KeyError as exc:
+            raise IdempotencyItemNotFoundError from exc
         return self._item_to_data_record(item)
 
     def _put_record(self, data_record: DataRecord) -> None:
         item = {
             **self._get_key(data_record.idempotency_key),
-            self.expiry_attr: data_record.expiry_timestamp,
-            self.status_attr: data_record.status,
+            self.key_attr: {"S": data_record.idempotency_key},
+            self.expiry_attr: {"N": str(data_record.expiry_timestamp)},
+            self.status_attr: {"S": data_record.status},
         }
 
         if data_record.in_progress_expiry_timestamp is not None:
-            item[self.in_progress_expiry_attr] = data_record.in_progress_expiry_timestamp
+            item[self.in_progress_expiry_attr] = {"N": str(data_record.in_progress_expiry_timestamp)}
 
-        if self.payload_validation_enabled:
-            item[self.validation_key_attr] = data_record.payload_hash
+        if self.payload_validation_enabled and data_record.payload_hash:
+            item[self.validation_key_attr] = {"S": data_record.payload_hash}
 
         now = datetime.datetime.now()
         try:
@@ -199,8 +189,8 @@ def _put_record(self, data_record: DataRecord) -> None:
             condition_expression = (
                 f"{idempotency_key_not_exist} OR {idempotency_expiry_expired} OR ({inprogress_expiry_expired})"
             )
-
-            self.table.put_item(
+            self._client.put_item(
+                TableName=self.table_name,
                 Item=item,
                 ConditionExpression=condition_expression,
                 ExpressionAttributeNames={
@@ -210,22 +200,28 @@ def _put_record(self, data_record: DataRecord) -> None:
                     "#status": self.status_attr,
                 },
                 ExpressionAttributeValues={
-                    ":now": int(now.timestamp()),
-                    ":now_in_millis": int(now.timestamp() * 1000),
-                    ":inprogress": STATUS_CONSTANTS["INPROGRESS"],
+                    ":now": {"N": str(int(now.timestamp()))},
+                    ":now_in_millis": {"N": str(int(now.timestamp() * 1000))},
+                    ":inprogress": {"S": STATUS_CONSTANTS["INPROGRESS"]},
                 },
             )
-        except self.table.meta.client.exceptions.ConditionalCheckFailedException:
-            logger.debug(f"Failed to put record for already existing idempotency key: {data_record.idempotency_key}")
-            raise IdempotencyItemAlreadyExistsError
+        except ClientError as exc:
+            error_code = exc.response.get("Error", {}).get("Code")
+            if error_code == "ConditionalCheckFailedException":
+                logger.debug(
+                    f"Failed to put record for already existing idempotency key: {data_record.idempotency_key}"
+                )
+                raise IdempotencyItemAlreadyExistsError from exc
+            else:
+                raise
 
     def _update_record(self, data_record: DataRecord):
         logger.debug(f"Updating record for idempotency key: {data_record.idempotency_key}")
         update_expression = "SET #response_data = :response_data, #expiry = :expiry, " "#status = :status"
         expression_attr_values = {
-            ":expiry": data_record.expiry_timestamp,
-            ":response_data": data_record.response_data,
-            ":status": data_record.status,
+            ":expiry": {"N": str(data_record.expiry_timestamp)},
+            ":response_data": {"S": data_record.response_data},
+            ":status": {"S": data_record.status},
         }
         expression_attr_names = {
             "#expiry": self.expiry_attr,
@@ -235,7 +231,7 @@ def _update_record(self, data_record: DataRecord):
 
         if self.payload_validation_enabled:
             update_expression += ", #validation_key = :validation_key"
-            expression_attr_values[":validation_key"] = data_record.payload_hash
+            expression_attr_values[":validation_key"] = {"S": data_record.payload_hash}
             expression_attr_names["#validation_key"] = self.validation_key_attr
 
         kwargs = {
@@ -245,8 +241,8 @@ def _update_record(self, data_record: DataRecord):
             "ExpressionAttributeNames": expression_attr_names,
         }
 
-        self.table.update_item(**kwargs)
+        self._client.update_item(TableName=self.table_name, **kwargs)
 
     def _delete_record(self, data_record: DataRecord) -> None:
         logger.debug(f"Deleting record for idempotency key: {data_record.idempotency_key}")
-        self.table.delete_item(Key=self._get_key(data_record.idempotency_key))
+        self._client.delete_item(TableName=self.table_name, Key={**self._get_key(data_record.idempotency_key)})

docs/utilities/idempotency.md

@@ -132,13 +132,9 @@ When using `idempotent_function`, you must tell us which keyword parameter in yo
 
 !!! info "We support JSON serializable data, [Python Dataclasses](https://docs.python.org/3.7/library/dataclasses.html){target="_blank"}, [Parser/Pydantic Models](parser.md){target="_blank"}, and our [Event Source Data Classes](./data_classes.md){target="_blank"}."
 
-???+ warning "Limitations"
+???+ warning "Limitation"
     Make sure to call your decorated function using keyword arguments.
 
-    Decorated functions with `idempotent_function` are not thread-safe, if the caller uses threading, not the function computation itself.
-
-    DynamoDB Persistency layer uses a Resource client [which is not thread-safe](https://boto3.amazonaws.com/v1/documentation/api/latest/guide/resources.html?highlight=multithreading#multithreading-or-multiprocessing-with-resources){target="_blank"}.
-
 === "dataclass_sample.py"
 
     ```python hl_lines="3-4 23 33"

mypy.ini

@@ -29,6 +29,9 @@ ignore_missing_imports = True
 [mypy-boto3.dynamodb.conditions]
 ignore_missing_imports = True
 
+[mypy-boto3.dynamodb.types]
+ignore_missing_imports = True
+
 [mypy-botocore.config]
 ignore_missing_imports = True
 
@@ -58,3 +61,5 @@ ignore_missing_imports = True
 
 [mypy-ijson]
 ignore_missing_imports = True
+
+

tests/e2e/idempotency/handlers/function_thread_safety_handler.py

@@ -0,0 +1,29 @@
+import os
+import time
+from concurrent.futures import ThreadPoolExecutor, as_completed
+from threading import current_thread
+
+from aws_lambda_powertools.utilities.idempotency import (
+    DynamoDBPersistenceLayer,
+    idempotent_function,
+)
+
+TABLE_NAME = os.getenv("IdempotencyTable", "")
+persistence_layer = DynamoDBPersistenceLayer(table_name=TABLE_NAME)
+threads_count = 2
+
+
+@idempotent_function(persistence_store=persistence_layer, data_keyword_argument="record")
+def record_handler(record):
+    time_now = time.time()
+    return {"thread_name": current_thread().name, "time": str(time_now)}
+
+
+def lambda_handler(event, context):
+    with ThreadPoolExecutor(max_workers=threads_count) as executor:
+        futures = [executor.submit(record_handler, **{"record": event}) for _ in range(threads_count)]
+
+    return [
+        {"state": future._state, "exception": future.exception(), "output": future.result()}
+        for future in as_completed(futures)
+    ]

tests/e2e/idempotency/handlers/parallel_execution_handler.py

@@ -12,7 +12,6 @@
 
 @idempotent(persistence_store=persistence_layer)
 def lambda_handler(event, context):
-
     time.sleep(5)
 
     return event

tests/e2e/idempotency/handlers/ttl_cache_expiration_handler.py

@@ -14,7 +14,6 @@
 
 @idempotent(config=config, persistence_store=persistence_layer)
 def lambda_handler(event, context):
-
     time_now = time.time()
 
     return {"time": str(time_now)}

tests/e2e/idempotency/handlers/ttl_cache_timeout_handler.py

@@ -14,7 +14,6 @@
 
 @idempotent(config=config, persistence_store=persistence_layer)
 def lambda_handler(event, context):
-
     sleep_time: int = event.get("sleep") or 0
     time.sleep(sleep_time)
 

tests/e2e/idempotency/infrastructure.py

@@ -15,6 +15,7 @@ def create_resources(self):
         table.grant_read_write_data(functions["TtlCacheExpirationHandler"])
         table.grant_read_write_data(functions["TtlCacheTimeoutHandler"])
         table.grant_read_write_data(functions["ParallelExecutionHandler"])
+        table.grant_read_write_data(functions["FunctionThreadSafetyHandler"])
 
     def _create_dynamodb_table(self) -> Table:
         table = dynamodb.Table(

tests/e2e/idempotency/test_idempotency_dynamodb.py

@@ -22,6 +22,11 @@ def parallel_execution_handler_fn_arn(infrastructure: dict) -> str:
     return infrastructure.get("ParallelExecutionHandlerArn", "")
 
 
+@pytest.fixture
+def function_thread_safety_handler_fn_arn(infrastructure: dict) -> str:
+    return infrastructure.get("FunctionThreadSafetyHandlerArn", "")
+
+
 @pytest.fixture
 def idempotency_table_name(infrastructure: dict) -> str:
     return infrastructure.get("DynamoDBTable", "")
@@ -97,3 +102,32 @@ def test_parallel_execution_idempotency(parallel_execution_handler_fn_arn: str):
     # THEN
     assert "Execution already in progress with idempotency key" in error_idempotency_execution_response
     assert "Task timed out after" in timeout_execution_response
+
+
+@pytest.mark.xdist_group(name="idempotency")
+def test_idempotent_function_thread_safety(function_thread_safety_handler_fn_arn: str):
+    # GIVEN
+    payload = json.dumps({"message": "Lambda Powertools - Idempotent function thread safety check"})
+
+    # WHEN
+    # first execution
+    first_execution, _ = data_fetcher.get_lambda_response(
+        lambda_arn=function_thread_safety_handler_fn_arn, payload=payload
+    )
+    first_execution_response = first_execution["Payload"].read().decode("utf-8")
+
+    # the second execution should return the same response as the first execution
+    second_execution, _ = data_fetcher.get_lambda_response(
+        lambda_arn=function_thread_safety_handler_fn_arn, payload=payload
+    )
+    second_execution_response = second_execution["Payload"].read().decode("utf-8")
+
+    # THEN
+    # Function threads finished without exception AND
+    # first and second execution is the same
+    for function_thread in json.loads(first_execution_response):
+        assert function_thread["state"] == "FINISHED"
+        assert function_thread["exception"] is None
+        assert function_thread["output"] is not None
+
+    assert first_execution_response == second_execution_response

tests/e2e/parameters/infrastructure.py

@@ -34,7 +34,6 @@ def create_resources(self):
         )
 
     def _create_app_config(self, function: Function):
-
         service_name = build_service_name()
 
         cfn_application = appconfig.CfnApplication(
@@ -82,7 +81,6 @@ def _create_app_config_freeform(
         function: Function,
         service_name: str,
     ):
-
         cfn_configuration_profile = appconfig.CfnConfigurationProfile(
             self.stack,
             "appconfig-profile",

tests/functional/feature_flags/test_feature_flags.py

@@ -315,6 +315,7 @@ def test_flags_conditions_rule_match_multiple_actions_multiple_rules_multiple_co
 
 # check a case where the feature exists but the rule doesn't match so we revert to the default value of the feature
 
+
 # Check IN/NOT_IN/KEY_IN_VALUE/KEY_NOT_IN_VALUE/VALUE_IN_KEY/VALUE_NOT_IN_KEY conditions
 def test_flags_match_rule_with_in_action(mocker, config):
     expected_value = True
@@ -775,6 +776,7 @@ def test_get_configuration_with_envelope_and_raw(mocker, config):
 ## Inequality test cases
 ##
 
+
 # Test not equals
 def test_flags_not_equal_no_match(mocker, config):
     expected_value = False