Serverless - Processing orders with SQS and SNS > Create API and Lambda function > Create handle_order Lambda function

Create handle_order Lambda function

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

Preparation

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
#     - FCAJCheckoutOrderApi
#     - FCAJOrderManagementApi

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

Comment BookApiDeployment

Run the below commands.
```
sam validate
sam build
```
Deploy the updated stack.
```
sam deploy
```
Review the CloudFormation changeset and confirm the deployment by typing y.
Wait for the deployment to complete.

Create FCAJHandleOrder function

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

Add the following parameter.

handleOrderPathPart:
  Type: String
  Default: handle

Add handleOrderPathPart parameter

Add the following scripts below to create FCAJHandleOrder function.

FCAJHandleOrderResource:
  Type: AWS::ApiGateway::Resource
  Properties:
    RestApiId: !Ref BookApi
    ParentId: !Ref FCAJCheckoutOrderResource
    PathPart: !Ref handleOrderPathPart

FCAJHandleOrderFunction:
  Type: AWS::Serverless::Function
  Properties:
    CodeUri: fcaj-book-shop/handle_order
    Handler: handle_order.lambda_handler
    Runtime: python3.13
    FunctionName: handle_order
    Environment:
      Variables:
        ORDER_TABLE_NAME: !Ref orderTable
        SQS_QUEUE_URL: !Ref checkoutQueueUrl
    Architectures:
      - x86_64
    Policies:
      - Statement:
          - Sid: VisualEditor0
            Effect: Allow
            Action:
              - dynamodb:PutItem
              - dynamodb:BatchWriteItem
            Resource:
              - !Sub "arn:aws:dynamodb:${AWS::Region}:${AWS::AccountId}:table/${orderTable}"
          - Sid: VisualEditor1
            Effect: Allow
            Action:
              - sqs:*
            Resource:
              - !Sub "arn:aws:sqs:${AWS::Region}:${AWS::AccountId}:${checkoutQueueName}"

Add FCAJHandleOrderResource and Function

FCAJHandleOrderApiOptions:
  Type: AWS::ApiGateway::Method
  Properties:
    HttpMethod: OPTIONS
    RestApiId: !Ref BookApi
    ResourceId: !Ref FCAJHandleOrderResource
    AuthorizationType: NONE
    Integration:
      Type: MOCK
      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 FCAJHandleOrderApiOptions

FCAJHandleOrderApi:
  Type: AWS::ApiGateway::Method
  Properties:
    HttpMethod: POST
    RestApiId: !Ref BookApi
    ResourceId: !Ref FCAJHandleOrderResource
    AuthorizationType: NONE
    Integration:
      Type: AWS_PROXY
      IntegrationHttpMethod: POST # For Lambda integrations, you must set the integration method to POST
      Uri: !Sub >-
        arn:aws:apigateway:${AWS::Region}:lambda:path/2015-03-31/functions/${FCAJHandleOrderFunction.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

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

Add FCAJHandleOrderApi and InvokePermission

The directory structure is as follows.

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

Create handle_order folder in fcaj-book-shop/fcaj-book-shop/ folder.

Create handle_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"
}

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

# Define the DynamoDB table name and SQS queue URL
table_name = os.getenv('ORDER_TABLE_NAME')
queue_url = os.getenv('SQS_QUEUE_URL')


def lambda_handler(event, context):
    # Get product body info from the event
    products = json.loads(event['body'])
    books = products['books']
    receipt_handle = products['receiptHandle']

    # Write product info to DynamoDB
    table = dynamodb.Table(table_name)
    try:
        for book in books:
            data = {
                'id': products['id'],
                'book_id': book['id'],
                'name': book['name'],
                'qty': book['qty'],
                'price': str(products['price'])
            }

            table.put_item(Item=data)

    except Exception as e:
        print(f"Error writing to DynamoDB: {e}")
        raise Exception(f"Error writing to DynamoDB: {e}")

    # Delete message from SQS
    try:
        sqs.delete_message(
            QueueUrl=queue_url,
            ReceiptHandle=receipt_handle
        )
    except Exception as e:
        print(f"Error deleting message from SQS: {e}")
        raise Exception(f"Error deleting message from SQS: {e}")

    return {
        'statusCode': 200,
        'headers': headers,
        'body': json.dumps('Successfully handled order')
    }

handle_order.py

Uncomment this code block.

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

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

Uncomment BookApiDeployment

Run the below commands.
```
sam validate
sam build
```
Deploy the updated stack.
```
sam deploy
```
Wait for the deployment to complete.

Check the creation

Open Amazon API Gateway console.
- Click fcaj-serverless-api.
- Click Resources on the left menu.
- Check /handle just created under /order.
Open Amazon Lambda console.
- Click Functions on the left menu.
- Choose handle_order function.
- At handle_order page, check the function that just created.