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: python3.9
      FunctionName: book_delete
      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/Books
                - arn:aws:s3:::book-image-resize-shop/*
    • Add the following script at the end of the file to create an S3 bucket that saves the image after resizing with CORS rule and policy settings
      BookImageResizeShop:
    Type: AWS::S3::Bucket
    Properties:
      AccessControl: PublicRead
      BucketName: book-image-resize-shop
      CorsConfiguration:
        CorsRules:
        - AllowedHeaders:
            - '*'
          AllowedMethods:
            - GET
            - PUT
            - POST
            - DELETE
          AllowedOrigins:
            - '*'

  BookImageResizeShopPolicy:
    Type: AWS::S3::BucketPolicy
    Properties:
      Bucket: !Ref BookImageResizeShop
      PolicyDocument:
        Version: 2012-10-17
        Statement:
          - Action: 
              - 's3:GetObject'
            Effect: Allow
            Principal: '*'
            Resource: !Join
              - ''
              - - 'arn:aws:s3:::'
                - !Ref BookImageResizeShop
                - /*

If you create S3 bucket names that are different from the ones in the lab, please check Policies | Resources of services and update.

LambdaDeleteFunction LambdaDeleteFunction

  1. The directory structure is as follows:

    fcj-book-shop
├── fcj-book-shop
│   ├── books_list
│   │   └── books_list.py
│   ├── book_create
│   │   └── book_create.py
│   └── 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 json

s3 = boto3.client('s3')
client = boto3.resource('dynamodb')

def get_image_name(image_path):
    str_image = image_path.split("/")
    for image_path_item in str_image:
        image_name = image_path_item

    return image_name;

def lambda_handler(event, context):
    error = None
    status = 200
    delete_id = event['pathParameters']
    delete_id['rv_id'] = 0

    table = client.Table("Books")
    image_path = ""

    try:
        data = table.get_item(Key = delete_id)
        image_path = data['Item']['image']
        image_name = get_image_name(image_path)
    except Exception as e:
        error = e

    try:
        response = table.query(
            ProjectionExpression="rv_id", 
            KeyConditionExpression="id = :id", 
            ExpressionAttributeValues={":id": delete_id['id']})

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

        print(image_name)
        s3.delete_object(Bucket='book-image-resize-shop', Key=image_name)

    except Exception as e:
        error = e

    if error is None:
        message = 'successfully deleted item!'
    else:
        message = 'delete item fail'
        status = 400

    return {
            'statusCode': status,
            'body': message,
            'headers': {
                'Content-Type': 'application/json',
                'Access-Control-Allow-Origin': '*'
            },
        }

  2. Run the following command to deploy SAM

    sam build
sam deploy

  3. Back to Lambda console

    • Click book_delete function created LambdaDeleteFunction

  4. Click Configuration tab

    • Select Permissions on the left menu
    • Click on the role that the function is executing LambdaDeleteFunction

  5. Expand the policy, see the permissions granted to the function LambdaDeleteFunction

  6. Open Amazon S3 console, the book-image-resize-shop bucket created

    • Click to this bucket LambdaDeleteFunction

  7. Click Permissions tab, see the policy added to the bucket LambdaDeleteFunction

  8. Scroll down to bottom, see Cross-origin resource sharing have been configed LambdaDeleteFunction