Listing Lambda function

We will create a Lambda function that reads all the data in the DynamoDB table.

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

  2. Add the following script at the end of the file.

    BooksList:
  Type: AWS::Serverless::Function
  Properties:
    CodeUri: fcj-book-shop/books_list
    Handler: books_list.lambda_handler
    Runtime: python3.11
    FunctionName: books_list
    Environment:
      Variables:
        TABLE_NAME: !Ref BooksTable
    Architectures:
      - x86_64
    Policies:
      - Statement:
          - Sid: ReadDynamoDB
            Effect: Allow
            Action:
              - dynamodb:Scan
              - dynamodb:Query
            Resource:
              - !Sub arn:aws:dynamodb:${AWS::Region}:${AWS::AccountId}:table/${booksTableName}

    LambdaListFunction

  3. The directory structure is as follows.

    fcj-book-shop
├── fcj-book-shop
│   ├── books_list
│       └── books_list.py
└── template.yaml

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

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

      import boto3
import os
import simplejson as json

TABLE = os.environ['TABLE_NAME']

# Get the service resource
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",
}

secondary_index = "name-index"


def lambda_handler(event, context):
    try:
        books_data = table.scan(
            TableName=TABLE,
            IndexName=secondary_index
        )

        books = books_data.get('Items', [])

        for book in books:
            data_comment = table.query(
                TableName=TABLE,
                KeyConditionExpression="id = :id AND rv_id > :rv_id",
                ExpressionAttributeValues={
                    ":id": book['id'],
                    ":rv_id": 0
                }
            )

            book['comments'] = data_comment['Items']

        return {
            "statusCode": 200,
            "headers": header_res,
            "body": json.dumps(books, use_decimal=True)
        }
    except Exception as e:
        print(f'Error getting items: {e}')
        raise Exception(f'Error getting items: {e}')

  4. Run the following command to deploy SAM.

    If you have issues with Python version, following this instruction for setting up an virtual Python environment: pyenv Github page.

    sam build
sam validate
sam deploy

    LambdaListFunction

  5. Open AWS Lambda console.

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