Code Breakdown for AWS Lambda Function for CloudFront Invalidation.md

AWS Lambda Function for CloudFront Invalidation

Code Breakdown

1. Import Statements

import boto3
import time

• boto3: AWS SDK for Python, used to interact with AWS services
• time: Used to generate a unique caller reference for CloudFront invalidation

2. Lambda Handler Function

def lambda_handler(event, context):

• Standard AWS Lambda function signature
• Receives two parameters:
  • event: Contains trigger information (in this case, S3 event)
  • context: Runtime information about the Lambda execution

3. CloudFront Client Initialization

client = boto3.client('cloudfront')
distribution_id = 'YOUR_CLOUDFRONT_DISTRIBUTION_ID'

• Creates a boto3 client for CloudFront
• distribution_id is the unique identifier for the CloudFront distribution

4. Event Record Processing

for record in event['Records']:
    path = "/" + record['s3']['object']['key']
    print(f"Invalidating path: {path}")

• Iterates through S3 event records
• Extracts the object key and prepends a "/" to create a CloudFront path
• Logs the path being invalidated

5. CloudFront Invalidation

invalidation = client.create_invalidation(
    DistributionId=distribution_id,
    InvalidationBatch={
        'Paths': {
            'Quantity': 1,
            'Items': [path]
        },
        'CallerReference': str(time.time())
    }
)

• Creates an invalidation request for the specific CloudFront distribution
• Paths: Specifies which objects to invalidate
  • Quantity: Number of paths to invalidate
  • Items: List of paths to invalidate
• CallerReference: Unique identifier to prevent duplicate invalidations
  • Uses current timestamp as a unique reference

6. Invalidation Confirmation

print(f"Invalidation created: {invalidation['Invalidation']['Id']}")

• Logs the unique ID of the created invalidation

Use Case

This Lambda function is typically triggered by S3 object uploads/updates to automatically invalidate the corresponding CloudFront cache, ensuring immediate content updates.

Key Considerations

• Replace 'YOUR_CLOUDFRONT_DISTRIBUTION_ID' with your actual distribution ID
• Ensure Lambda has appropriate IAM permissions for CloudFront invalidation
• Be mindful of CloudFront invalidation limits and potential costs