feat: example using S3 trigger for Lambda (#106)

Author: pubudusj

README.md

@@ -92,6 +92,7 @@ $ cdk destroy
 | [fargate-load-balanced-service](https://github.com/aws-samples/aws-cdk-examples/tree/master/python/ecs/fargate-load-balanced-service/) | Starting a container fronted by a load balancer on Fargate |
 | [fargate-service-with-autoscaling](https://github.com/aws-samples/aws-cdk-examples/tree/master/python/ecs/fargate-service-with-autoscaling/) | Starting an ECS service of FARGATE launch type that auto scales based on average CPU Utilization |
 | [lambda-cron](https://github.com/aws-samples/aws-cdk-examples/tree/master/python/lambda-cron/) | Running a Lambda on a schedule |
+| [lambda-s3-trigger](https://github.com/aws-samples/aws-cdk-examples/tree/master/python/lambda-s3-trigger/) | S3 trigger for Lambda |
 | [stepfunctions](https://github.com/aws-samples/aws-cdk-examples/tree/master/python/stepfunctions/) | A simple StepFunctions workflow |
 | [url-shortner](https://github.com/aws-samples/aws-cdk-examples/tree/master/python/url-shortener) | Demo from the [Infrastructure ***is*** Code with the AWS CDK](https://youtu.be/ZWCvNFUN-sU) AWS Online Tech Talk |
 

python/lambda-s3-trigger/app.py

@@ -0,0 +1,10 @@
+#!/usr/bin/env python3
+
+from aws_cdk import core
+
+from s3trigger.s3trigger_stack import S3TriggerStack
+
+app = core.App()
+S3TriggerStack(app, "s3trigger")
+
+app.synth()

python/lambda-s3-trigger/cdk.json

@@ -0,0 +1,3 @@
+{
+  "app": "python3 app.py"
+}

python/lambda-s3-trigger/lambda/lambda-handler.py

@@ -0,0 +1,8 @@
+def main(event, context):
+    # save event to logs
+    print(event)
+
+    return {
+        'statusCode': 200,
+        'body': event
+    }

python/lambda-s3-trigger/requirements.txt

@@ -0,0 +1,5 @@
+aws-cdk.core
+
+aws-cdk.aws-s3
+aws-cdk.aws-lambda
+aws-cdk.aws_s3_notifications

python/lambda-s3-trigger/s3trigger/__init__.py

@@ -0,0 +1,26 @@
+from aws_cdk import (
+    aws_lambda as _lambda,
+    aws_s3 as _s3,
+    aws_s3_notifications,
+    core
+)
+
+
+class S3TriggerStack(core.Stack):
+
+    def __init__(self, scope: core.Construct, id: str, **kwargs) -> None:
+        super().__init__(scope, id, **kwargs)
+
+        # create lambda function
+        function = _lambda.Function(self, "lambda_function",
+                                    runtime=_lambda.Runtime.PYTHON_3_7,
+                                    handler="lambda-handler.main",
+                                    code=_lambda.Code.asset("./lambda"))
+        # create s3 bucket
+        s3 = _s3.Bucket(self, "s3bucket")
+
+        # create s3 notification for lambda function
+        notification = aws_s3_notifications.LambdaDestination(function)
+
+        # assign notification for the s3 event type (ex: OBJECT_CREATED)
+        s3.add_event_notification(_s3.EventType.OBJECT_CREATED, notification)