Event triggers for Lambda in AWS - Mini Project: Build & Apply

Event triggers for Lambda

📖 Scenario: You are setting up a simple AWS Lambda function that runs automatically when a new file is uploaded to an S3 bucket. This helps automate tasks like image processing or data analysis without manual intervention.

🎯 Goal: Create an AWS Lambda function and configure an S3 bucket event trigger so the Lambda runs whenever a new object is created in the bucket.

📋 What You'll Learn

Create an AWS Lambda function named ProcessNewFile

Create an S3 bucket named my-upload-bucket

Configure the S3 bucket to trigger the Lambda function on ObjectCreated events

Use AWS CloudFormation YAML syntax for the infrastructure as code

💡 Why This Matters

🌍 Real World

Automating workflows by running code automatically when files are uploaded to cloud storage is common in data processing, image handling, and backups.

💼 Career

Understanding how to connect AWS Lambda with event sources like S3 is essential for cloud engineers and developers building serverless applications.

1

Create the AWS Lambda function resource

Write a CloudFormation resource named ProcessNewFile of type AWS::Lambda::Function with the following properties: FunctionName set to ProcessNewFile, Runtime set to python3.12, Handler set to index.handler, and Role set to arn:aws:iam::123456789012:role/lambda-execution-role.

AWS

# Your code here

Need a hint?

Define the Lambda function resource with the exact properties given.

2

Create the S3 bucket resource

Add a CloudFormation resource named MyUploadBucket of type AWS::S3::Bucket with the BucketName set to my-upload-bucket.

AWS

Resources:
  ProcessNewFile:
    Type: AWS::Lambda::Function
    Properties:
      FunctionName: ProcessNewFile
      Runtime: python3.12
      Handler: index.handler
      Role: arn:aws:iam::123456789012:role/lambda-execution-role

# Your code here

Need a hint?

Define the S3 bucket resource with the exact bucket name.

3

Add permission for S3 to invoke Lambda

Add a CloudFormation resource named LambdaInvokePermission of type AWS::Lambda::Permission with these properties: FunctionName set to !Ref ProcessNewFile, Action set to lambda:InvokeFunction, Principal set to s3.amazonaws.com, and SourceArn set to !GetAtt MyUploadBucket.Arn.

AWS

Resources:
  ProcessNewFile:
    Type: AWS::Lambda::Function
    Properties:
      FunctionName: ProcessNewFile
      Runtime: python3.12
      Handler: index.handler
      Role: arn:aws:iam::123456789012:role/lambda-execution-role
  MyUploadBucket:
    Type: AWS::S3::Bucket
    Properties:
      BucketName: my-upload-bucket

# Your code here

Need a hint?

Grant S3 permission to invoke the Lambda function using the exact properties.

4

Configure S3 bucket notification to trigger Lambda

Add a NotificationConfiguration property to the MyUploadBucket resource. Inside it, add a LambdaConfigurations list with one item that has Event set to s3:ObjectCreated:* and Function set to !GetAtt ProcessNewFile.Arn.

AWS

Resources:
  ProcessNewFile:
    Type: AWS::Lambda::Function
    Properties:
      FunctionName: ProcessNewFile
      Runtime: python3.12
      Handler: index.handler
      Role: arn:aws:iam::123456789012:role/lambda-execution-role
  MyUploadBucket:
    Type: AWS::S3::Bucket
    Properties:
      BucketName: my-upload-bucket

# Add NotificationConfiguration here
  LambdaInvokePermission:
    Type: AWS::Lambda::Permission
    Properties:
      FunctionName: !Ref ProcessNewFile
      Action: lambda:InvokeFunction
      Principal: s3.amazonaws.com
      SourceArn: !GetAtt MyUploadBucket.Arn

Need a hint?

Add the notification configuration exactly as described to trigger Lambda on new S3 objects.