aws lambda function that will create

This Lambda function is triggered by S3 object events and rebuilds an index.7z archive from objects in the same folder. It skips existing archive files, creates a temporary working directory, and uploads the resulting archive back to S3.

Workflow Summary

Read bucket/key from S3 event record
Resolve folder prefix from incoming object key
Download folder files to unique /tmp path
Create 7z archive via /opt/bin/7z
Upload as index.7z and cleanup temporary files

Lambda Handler (Python)

import os
import boto3
import subprocess
import shutil
import logging

# Configure logging
logging.basicConfig(level=logging.INFO)
logger = logging.getLogger()

s3_client = boto3.client('s3')

def lambda_handler(event, context):
    for record in event['Records']:
        bucket = record['s3']['bucket']['name']
        key = record['s3']['object']['key']

        # Check folder where index.zip is located
        if '/' in key:
            prefix = key.rsplit('/', 1)[0] + '/'
        else:
            prefix = ''

        # List all objects
        response = s3_client.list_objects_v2(Bucket=bucket, Prefix=prefix)
        if 'Contents' not in response:
            logger.info(f"No objects found in {prefix}")
            continue

        # Unique TMP dir
        work_dir = f"/tmp/game_folder_{context.aws_request_id}"
        if os.path.exists(work_dir):
            shutil.rmtree(work_dir)
        os.makedirs(work_dir)

        # Download files except index.zip, index.7z, and directories
        for obj in response['Contents']:
            obj_key = obj['Key']
            if (obj_key.endswith("index.zip") or
                obj_key.endswith("index.7z") or
                obj_key.endswith('/')):
                continue

            relative_path = obj_key[len(prefix):]
            local_file_path = os.path.join(work_dir, relative_path)
            local_dir = os.path.dirname(local_file_path)
            if not os.path.exists(local_dir):
                os.makedirs(local_dir)

            logger.info(f"Downloading s3://{bucket}/{obj_key} to {local_file_path}")
            try:
                s3_client.download_file(bucket, obj_key, local_file_path)
            except Exception as e:
                logger.error(f"Error downloading {obj_key}: {e}")
                raise

        # Define the path of the archive
        if not os.path.exists('/opt/bin/7z'):
            logger.error("7z binary not found at /opt/bin/7z")
            raise FileNotFoundError("7z binary missing")
        local_archive = f"/tmp/index_{context.aws_request_id}.7z"
        try:
            subprocess.check_call(
                ['/opt/bin/7z', 'a', local_archive, '.'],
                cwd=work_dir
            )
        except subprocess.CalledProcessError as e:
            logger.error(f"Error during archive creation: {e}")
            raise e

        # Upload the 7z archive to S3
        new_key = prefix + "index.7z"
        logger.info(f"Uploading archive to s3://{bucket}/{new_key}")
        s3_client.upload_file(local_archive, bucket, new_key)

        # Cleanup
        shutil.rmtree(work_dir)
        if os.path.exists(local_archive):
            os.remove(local_archive)

    return {"statusCode": 200, "body": "index.7z created and uploaded successfully."}