Lambda Troubleshooting

AWS Services

• AWS Lambda
• Amazon S3

Summary

You have been provided with an existing simple Lambda function that is not working as expected. It is supposed to list various objects in an S3 bucket, but it is failing to do so. You are required to troubleshoot the Lambda function and fix the issue. You should also ensure that the function is correctly configured and that it has the necessary permissions to access the S3 bucket.

Task

A client has reported that their Lambda function is failing to list objects in an S3 bucket. Your goal is to identify and resolve the issue.

1. Inspect the Lambda function’s configuration and code for errors.
2. Verify that the Lambda function has the required IAM role and permissions:
   • Ensure the role includes s3:ListBucket for the bucket in question.
   • Ensure the role includes s3:GetObject for objects within the bucket.
3. Test the Lambda function by invoking it and confirming that it lists the objects as expected.

Verification:

• Confirm that the Lambda function successfully lists the objects in the S3 bucket.
• Verify the logs in CloudWatch for any remaining errors or warnings.

Hints:

• Check the Lambda execution role in the IAM console to ensure it is correctly attached and has the necessary policies.
• Use the AWS Lambda test interface to invoke the function with different input payloads if required.
• Review the function’s logs in CloudWatch to identify and debug any runtime issues.

Example Code:

import boto3
import os

def lambda_handler(event, context):
    # Initialize the S3 client
    s3 = boto3.client('s3')

    # Specify the S3 bucket name (can be hardcoded or passed via the event)
    bucket_name = os.environ.get('BUCKET_NAME', 'your-bucket-name')

    try:
        # List objects in the bucket
        response = s3.list_objects_v2(Bucket=bucket_name)
        if 'Contents' in response:
            files = [obj['Key'] for obj in response['Contents']]
            return {
                'statusCode': 200,
                'body': f"Objects in bucket '{bucket_name}': {files}"
            }
        else:
            return {
                'statusCode': 200,
                'body': f"No objects found in bucket '{bucket_name}'."
            }
    except Exception as e:
        return {
            'statusCode': 500,
            'body': f"Error accessing bucket '{bucket_name}': {str(e)}"
        }