makes notify-restaurant function idempotent

Author: sv3ndk

README.md

@@ -28,6 +28,9 @@ Status: Week 3 in progress
       * allows users to register or sign in to the Cognito user pool, using SRP
       * uses the Cognito JWT token to send requests from the browser to `/restaurants/search`
 
+* [Lambda Power Tools](https://docs.powertools.aws.dev/lambda/python/latest/) is used for logging, idempotency and
+  event sourced event parsing.
+
 * database: DynamoDB
 
 * Tests: 

cdk/app.py

@@ -32,6 +32,7 @@
     construct_id=f"Event{feature_name}",
     service_name=service_name,
     maturity_level=maturity_level,
+    idempotency_table=db_stack.idempotency_table,
 )
 
 ApiStack(

cdk/db_stack.py

@@ -13,14 +13,26 @@ def __init__(self, scope: Construct, construct_id: str, **kwargs) -> None:
 
         self.table = aws_dynamodb.Table(
             scope=self,
-            id=f"restaurants",
+            id="restaurants",
             partition_key=aws_dynamodb.Attribute(
                 name="name",
                 type=aws_dynamodb.AttributeType.STRING
             ),
             billing_mode=aws_dynamodb.BillingMode.PAY_PER_REQUEST
         )
 
+        self.idempotency_table = aws_dynamodb.Table(
+            scope=self,
+            id="idempotency",
+            partition_key=aws_dynamodb.Attribute(
+                name="id",
+                type=aws_dynamodb.AttributeType.STRING
+            ),
+            # name of the attribute that stores the time-to-live value:
+            time_to_live_attribute="exiration",
+            billing_mode=aws_dynamodb.BillingMode.PAY_PER_REQUEST
+        )
+
         CfnOutput(
             scope=self,
             id="restaurants_table_name",

cdk/event_stack.py

@@ -3,6 +3,7 @@
     aws_events,
     aws_sns, aws_lambda_python_alpha, Duration, aws_lambda, aws_events_targets, CfnOutput
 )
+from aws_cdk.aws_dynamodb import Table
 from aws_cdk.aws_events import EventPattern
 from constructs import Construct
 
@@ -16,6 +17,7 @@ def __init__(
 
             service_name: str,
             maturity_level: str,
+            idempotency_table: Table,
 
             **kwargs) -> None:
         super().__init__(scope, construct_id, **kwargs)
@@ -42,11 +44,13 @@ def __init__(
                 "POWERTOOLS_SERVICE_NAME": service_name,
                 "MATURITY_LEVEL": maturity_level,
                 "EVENT_BUS_NAME": self.event_bus.event_bus_name,
-                "TOPIC_ARN": self.topic.topic_arn
+                "TOPIC_ARN": self.topic.topic_arn,
+                "IDEMPOTENCY_TABLE_NAME": idempotency_table.table_name
             }
         )
         self.event_bus.grant_put_events_to(notify_restaurant_fn)
         self.topic.grant_publish(notify_restaurant_fn)
+        idempotency_table.grant_read_write_data(notify_restaurant_fn)
 
         rule = aws_events.Rule(
             scope=self,

src/functions/notify_restaurant/notify_restaurant.py

@@ -3,13 +3,18 @@
 import boto3
 from aws_lambda_powertools.logging import Logger
 from aws_lambda_powertools.utilities.data_classes import event_source, EventBridgeEvent
+from aws_lambda_powertools.utilities.idempotency import DynamoDBPersistenceLayer, idempotent, IdempotencyConfig
 
 logger = Logger(log_uncaught_exceptions=True)
 
 bus_name = os.getenv("EVENT_BUS_NAME")
 if not bus_name:
     raise ValueError("EVENT_BUS_NAME environment variable is not set")
 
+idempotency_table = os.getenv("IDEMPOTENCY_TABLE_NAME")
+if not bus_name:
+    raise ValueError("IDEMPOTENCY_TABLE_NAME environment variable is not set")
+
 topic_ARN = os.getenv("TOPIC_ARN")
 if not bus_name:
     raise ValueError("TOPIC_ARN environment variable is not set")
@@ -18,6 +23,10 @@
 sns_client = boto3.client("sns")
 
 @event_source(data_class=EventBridgeEvent)
+@idempotent(
+    persistence_store=DynamoDBPersistenceLayer(table_name=idempotency_table),
+    config=IdempotencyConfig(event_key_jmespath='detail.orderId')
+)
 def handler(event: EventBridgeEvent, context):
 
     order = event.detail