Create checkout_order Lambda function

In this step, we will create a new checkout_order Lambda function using a SAM template.

Preparation

  1. Open template.yaml in the source code you downloaded before.

    • Comment this code block.

      # BookApiDeployment:
#   Type: AWS::ApiGateway::Deployment
#   Properties:
#     RestApiId: !Ref BookApi
#   DependsOn:
#     - BookApiGet
#     - BookApiCreate
#     - BookApiDelete
#     - LoginApi
#     - RegisterApi
#     - ConfirmApi

BookApiStage:
  Type: AWS::ApiGateway::Stage
  Properties:
    RestApiId: !Ref BookApi
    StageName: !Ref stage
#     DeploymentId: !Ref BookApiDeployment

      Comment BookApiDeployment

  2. Run the below commands.

    sam validate
sam build

    SAM validate and build

  3. Deploy the updated stack.

    sam deploy

    SAM deploy

  4. Wait for the deployment to complete.

    Deploy complete

Create FCAJCheckOutOrder function

Before adding the parameters, you need to get the SQS Queue URL and SNS Topic ARN from the AWS Console.
Open the SQS console and copy the URL of the checkout-queue.
Open the SNS console and copy the ARN of the order-notice topic.

SQS checkout-queue URL SNS order-notice ARN

  1. Open template.yaml in the source code you downloaded before.

    • Add the following scripts below to create FCAJCheckOutOrder function.

      • Change checkoutQueueUrl and orderTopicArn value to your value.

        checkoutQueueName:
  Type: String
  Default: checkout-queue

checkoutQueueUrl:
  Type: String
  Default: https://sqs.us-east-1.amazonaws.com/017820706022/checkout-queue

orderTopicName:
  Type: String
  Default: order-notice

orderTopicArn:
  Type: String
  Default: arn:aws:sns:us-east-1:017820706022:order-notice

checkoutPathPart:
  Type: String
  Default: order

        Add parameters

        FCAJCheckOutOrderFunction:
  Type: AWS::Serverless::Function
  Properties:
    CodeUri: fcaj-book-shop/checkout_order
    Handler: checkout_order.lambda_handler
    Runtime: python3.13
    FunctionName: checkout_order
    Environment:
      Variables:
        SQS_QUEUE_URL: !Ref checkoutQueueUrl
        SNS_TOPIC_ARN: !Ref orderTopicArn
    Architectures:
      - x86_64
    Policies:
      - Statement:
          - Sid: VisualEditor0
            Effect: Allow
            Action:
              - sqs:*
            Resource:
              - !Sub "arn:aws:sqs:${AWS::Region}:${AWS::AccountId}:${checkoutQueueName}"
          - Sid: VisualEditor1
            Effect: Allow
            Action:
              - sns:Publish
            Resource:
              - !Sub "arn:aws:sns:${AWS::Region}:${AWS::AccountId}:${orderTopicName}"

        Add FCAJCheckOutOrderFunction

        FCAJCheckoutOrderResource:
  Type: AWS::ApiGateway::Resource
  Properties:
    RestApiId: !Ref BookApi
    ParentId: !Ref BookApiResource
    PathPart: !Ref checkoutPathPart

FCAJCheckoutOrderApiOptions:
  Type: AWS::ApiGateway::Method
  Properties:
    HttpMethod: OPTIONS
    RestApiId: !Ref BookApi
    ResourceId: !Ref FCAJCheckoutOrderResource
    AuthorizationType: NONE
    Integration:
      Type: MOCK
      RequestTemplates:
        application/json: '{"statusCode": 200}'
      IntegrationResponses:
        - StatusCode: "200"
          ResponseParameters:
            method.response.header.Access-Control-Allow-Origin: "'*'"
            method.response.header.Access-Control-Allow-Methods: "'OPTIONS,POST,GET,DELETE'"
            method.response.header.Access-Control-Allow-Headers: "'Content-Type,X-Amz-Date,Authorization,X-Api-Key,X-Amz-Security-Token'"
    MethodResponses:
      - StatusCode: "200"
        ResponseParameters:
          method.response.header.Access-Control-Allow-Origin: true
          method.response.header.Access-Control-Allow-Methods: true
          method.response.header.Access-Control-Allow-Headers: true

        Add FCAJCheckoutOrderResource and ApiOptions

        FCAJCheckoutOrderApi:
  Type: AWS::ApiGateway::Method
  Properties:
    HttpMethod: POST
    RestApiId: !Ref BookApi
    ResourceId: !Ref FCAJCheckoutOrderResource
    AuthorizationType: NONE
    Integration:
      Type: AWS_PROXY
      IntegrationHttpMethod: POST # For Lambda integrations, you must set the integration method to POST
      Uri: !Sub >-
        arn:aws:apigateway:${AWS::Region}:lambda:path/2015-03-31/functions/${FCAJCheckOutOrderFunction.Arn}/invocations
    MethodResponses:
      - StatusCode: "200"
        ResponseParameters:
          method.response.header.Access-Control-Allow-Origin: true
          method.response.header.Access-Control-Allow-Methods: true
          method.response.header.Access-Control-Allow-Headers: true

        Add FCAJCheckoutOrderApi

        FCAJCheckoutOrderApiInvokePermission:
  Type: AWS::Lambda::Permission
  Properties:
    FunctionName: !Ref FCAJCheckOutOrderFunction
    Action: lambda:InvokeFunction
    Principal: apigateway.amazonaws.com
    SourceAccount: !Ref "AWS::AccountId"

        Add FCAJCheckoutOrderApiInvokePermission

  2. The directory structure is as follows.

    fcaj-book-shop
├── fcaj-book-shop
│   ├── checkout_order
│   │   └── checkout_order.py
│   ├── ...
│
└── template.yaml

    • Create checkout_order folder in fcaj-book-shop/fcaj-book-shop/ folder.

    • Create checkout_order.py file and copy the following code to it.

      import json
import boto3
import os

headers = {
    "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):
    sqs = boto3.client('sqs')
    sns = boto3.client('sns')

    sqs_queue_url = os.environ['SQS_QUEUE_URL']
    sns_topic_arn = os.environ['SNS_TOPIC_ARN']
    sns_topic_subject = "New order received. Please process."

    try:
        body = json.loads(event['body'])

        print(f"body: {body}")

        # Send to SQS
        sqs_response = sqs.send_message(
            QueueUrl=sqs_queue_url,
            MessageBody=json.dumps(body)
        )

        # Send to SNS
        sns_response = sns.publish(
            TopicArn=sns_topic_arn,
            Message=f"New order received: {json.dumps(body)}",
            Subject=sns_topic_subject
        )

        return {
            'statusCode': 200,
            'headers': headers,
            'body': json.dumps({
                'message': 'Order processed successfully',
                'sqs_message_id': sqs_response['MessageId'],
                'sns_message_id': sns_response['MessageId']
            })
        }

    except Exception as e:
        print(f"Error processing order: {e}")
        raise Exception(f"Error processing order: {e}")

      checkout_order.py

  3. Uncomment this code block.

    BookApiDeployment:
  Type: AWS::ApiGateway::Deployment
  Properties:
    RestApiId: !Ref BookApi
  DependsOn:
    - BookApiGet
    - BookApiCreate
    - BookApiDelete
    - LoginApi
    - RegisterApi
    - ConfirmApi
    - FCAJCheckoutOrderApi

BookApiStage:
  Type: AWS::ApiGateway::Stage
  Properties:
    RestApiId: !Ref BookApi
    StageName: !Ref stage
    DeploymentId: !Ref BookApiDeployment

    Uncomment BookApiDeployment

  4. Run the below commands.

    sam validate
sam build

    SAM validate and build

  5. Deploy the updated stack.

    sam deploy

    SAM deploy with FCAJCheckoutOrder

  6. Wait for the deployment to complete.

    Deploy complete

Check the creation

  1. Open Amazon API Gateway console.

    • Click fcaj-serverless-api. API Gateway list
    • Click Resources on the left menu.
    • Check /order just created. API Gateway Resources

  2. Open Amazon Lambda console.

    • Click Functions on the left menu.
    • Choose checkout_order function. Lambda Functions list
    • At checkout_order page, check the function that just created. checkout_order function detail