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
     

     

2. Run the below commands.

   sam build
   sam validate
   sam deploy
   

   

Create FcjCheckOutOrder function

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

   • Add the following scripts below to create FcjCheckOutOrder 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
       

       

       FcjCheckOutOrderFunction:
         Type: AWS::Serverless::Function
         Properties:
           CodeUri: fcj-book-shop/checkout_order
           Handler: checkout_order.lambda_handler
           Runtime: python3.11
           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}"
       
       FcjCheckoutOrderResource:
         Type: AWS::ApiGateway::Resource
         Properties:
           RestApiId: !Ref BookApi
           ParentId: !Ref BookApiResource
           PathPart: !Ref checkoutPathPart
       
       FcjCheckoutOrderApiOptions:
         Type: AWS::ApiGateway::Method
         Properties:
           HttpMethod: OPTIONS
           RestApiId: !Ref BookApi
           ResourceId: !Ref FcjCheckoutOrderResource
           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
       
       FcjCheckoutOrderApi:
         Type: AWS::ApiGateway::Method
         Properties:
           HttpMethod: POST
           RestApiId: !Ref BookApi
           ResourceId: !Ref FcjCheckoutOrderResource
           AuthorizationType: NONE
           Integration:
             Type: AWS_PROXY
             IntegrationHttpMethod: POST # For Lambda integrations, you must set the integration method to POST
             Uri: !Sub >-
               arn:aws:apigateway:${AWS::Region}:lambda:path/2015-03-31/functions/${FcjCheckOutOrderFunction.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
       
       FcjCheckoutOrderApiInvokePermission:
         Type: AWS::Lambda::Permission
         Properties:
           FunctionName: !Ref FcjCheckOutOrderFunction
           Action: lambda:InvokeFunction
           Principal: apigateway.amazonaws.com
           SourceAccount: !Ref "AWS::AccountId"
       

       

2. The directory structure is as follows.

   fcj-book-shop-sam-ws3
   ├── fcj-book-shop
   │   ├── checkout_order
   │   │   └── checkout_order.py
   │   ├── ...
   │
   └── template.yaml
   

   • Create checkout_order folder in fcj-book-shop-sam-ws6/fcj-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}")
     

     

3. Uncomment this code block.

   BookApiDeployment:
     Type: AWS::ApiGateway::Deployment
     Properties:
       RestApiId: !Ref BookApi
     DependsOn:
       - BookApiGet
       - BookApiCreate
       - BookApiDelete
       - LoginApi
       - RegisterApi
       - ConfirmApi
       - FcjCheckoutOrderApi
   
   BookApiStage:
     Type: AWS::ApiGateway::Stage
     Properties:
       RestApiId: !Ref BookApi
       StageName: !Ref stage
       DeploymentId: !Ref BookApiDeployment
   

   

4. Run the below commands.

   sam build
   sam validate
   sam deploy
   

   

Check the creation

1. Open Amazon API Gateway console.

   • Click fcj-serverless-api.
   • Click Resources on the left menu.
   • Check /order just created.

2. Open Amazon Lambda console.

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