Deleting Lambda function

We will create a Lambda function that deletes all items with the specified partition key and sort key in the DynamoDB table. And delete the image file in the S3 bucket.

  1. Open template.yaml file in fcj-book-shop folder.

  2. Add the following script at the end of the file to create a Lambda function that deletes data of DynamoDB table.

    BookDelete:
  Type: AWS::Serverless::Function
  Properties:
    CodeUri: fcj-book-shop/book_delete
    Handler: book_delete.lambda_handler
    Runtime: python3.11
    FunctionName: book_delete
    Environment:
      Variables:
        BUCKET_NAME: !Ref BookImageResizeShop
        TABLE_NAME: !Ref BooksTable
    Architectures:
      - x86_64
    Policies:
      - Statement:
          - Sid: VisualEditor0
            Effect: Allow
            Action:
              - dynamodb:DeleteItem
              - dynamodb:GetItem
              - dynamodb:Query
              - s3:DeleteObject
            Resource:
              - !Sub arn:aws:dynamodb:${AWS::Region}:${AWS::AccountId}:table/${booksTableName}
              - !Join
                - ""
                - - "arn:aws:s3:::"
                  - !Ref BookImageResizeShop
                  - /*

    LambdaDeleteFunction

  3. The directory structure is as follows.

    fcj-book-shop
├── fcj-book-shop
│   ├── books_list
│   │   └── books_list.py
│   ├── book_create
│   │   └── book_create.py
|       └── requirements.txt
│   └── book_delete
│       └── book_delete.py
└── template.yaml

    • Create book_delete folder in fcj-book-shop/fcj-book-shop/ folder.

    • Create book_delete.py file and copy the below code block to it.

      import boto3
import os

BUCKET = os.environ['BUCKET_NAME']
TABLE = os.environ['TABLE_NAME']

s3_client = boto3.client('s3')
dynamodb = boto3.resource('dynamodb')
table = dynamodb.Table(TABLE)

header_res = {
    "Content-Type": "application/json",
    "Access-Control-Allow-Origin": "*",
    "Access-Control-Allow-Methods": "OPTIONS,POST,GET,DELETE",
    "Access-Control-Allow-Headers": "Content-Type,X-Amz-Date,Authorization,X-Api-Key,X-Amz-Security-Token",
}


def lambda_handler(event, context):
    delete_id = event.get('pathParameters', {})
    delete_id['rv_id'] = 0

    try:
        # Get item from id
        try:
            delete_item = table.get_item(Key=delete_id)
            image_path = delete_item['Item'].get('image', '')
            image_name = image_path.split('/')[-1]

        except Exception as e:
            print(f"Error getting item with that {delete_id['id']}")
            raise Exception(f"Error getting item with that {delete_id['id']}")

        # Delete item in DynamoDB and s3 bucket
        try:
            items_with_same_id = table.query(
                TableName=TABLE,
                ProjectionExpression='rv_id',
                KeyConditionExpression='id = :id',
                ExpressionAttributeValues={':id': delete_id['id']}
            )

            for item in items_with_same_id['Items']:
                delete_id['rv_id'] = item['rv_id']
                table.delete_item(Key=delete_id)

            s3_client.delete_object(Bucket=BUCKET, Key=image_name)

        except Exception as e:
            print(f"Error getting item with that {delete_id['id']}")
            raise Exception(f"Error getting item with that {delete_id['id']}")

        return {
            'statusCode': 200,
            'body': 'Successfully delete item!',
            'headers': header_res
        }

    except Exception as e:
        print(f'Error deleting item: {e}')
        raise Exception(f'Error deleting item: {e}')

  4. Run the following command to deploy SAM.

    sam build
sam validate
sam deploy

    LambdaDeleteFunction

  5. Open AWS Lambda console.

    • Click book_delete function created. LambdaDeleteFunction
    • At book_delete page.
      • Click Configuration tab.
      • Select Permissions on the left menu.
      • Click on the role that the function is executing. LambdaDeleteFunction
    • At fcj-book-shop-BookDeleteRole-… page.
      • Check the permissions granted to the function. LambdaDeleteFunction