毎月のアカウント利用料を通知する機能をCloudFormationで作ってみた！

AWSTemplateFormatVersion: 2010-09-09

Parameters:
  Token:
    Type: String

Resources:
  LambdaLayer:
    Type: AWS::Lambda::LayerVersion
    Properties:
      CompatibleArchitectures:
        - arm64
        - x86_64
      CompatibleRuntimes:
        - python3.9
      Content:
        S3Bucket: <任意のバケット名>
        S3Key: requests.zip
      LayerName: send-cost-layer
  LambdaFunction:
    Type: AWS::Lambda::Function
    Properties: 
      Handler: index.lambda_handler
      Code:
        ZipFile: !Sub |
          import  os
          from slack_sdk import WebClient
          import boto3
          from datetime import datetime, timedelta, date

          def get_total_billing() -> dict:
              ce = boto3.client('ce', region_name='ap-northeast-1')

              start_date = date.today().replace(day=1).isoformat()
              end_date = date.today().isoformat()

              response = ce.get_cost_and_usage(
                  TimePeriod={
                      'Start': start_date,
                      'End': end_date
                  },
                  Granularity='MONTHLY',
                  Metrics=[
                      'AmortizedCost'
                  ]
              )
              billing = '{:.2f}'.format(float(response['ResultsByTime'][0]['Total']['AmortizedCost']['Amount']))
              return billing

          def lambda_handler(event, context):
              # Web API クライアントを初期化します

              client = WebClient(os.environ["SLACK_BOT_TOKEN"])

              amount = get_total_billing()
              try:
                  # chat.postMessage API を呼び出します
                  response = client.chat_postMessage(
                      channel=f"<任意のチャンネル名>",
                      text=f"今月のサンドボックス利用料をお知らせします :hatching_chick: \n今月の利用料は{amount}USDです。",
                  )
                  print("送信に成功しました")
              except Exception as e:
                  raise e

              return 
      FunctionName: SendMonthlyCostFunction
      Runtime: python3.9
      Environment: 
        Variables:
          SLACK_BOT_TOKEN : !Sub ${Token}
      Layers:
        - !Ref LambdaLayer
      Role: !GetAtt
        - LambdaExecutionRole
        - Arn

  LambdaExecutionRole:
    Type: AWS::IAM::Role
    Properties:
      RoleName: send-cost-function-execution-role
      AssumeRolePolicyDocument:
        Version: 2012-10-17
        Statement:
          - Effect: Allow
            Principal:
              Service:
                - lambda.amazonaws.com
            Action: sts:AssumeRole
      Policies:
        - PolicyName: !Sub send-cost-function-policy
          PolicyDocument:
            Version: 2012-10-17
            Statement:
              - Resource: '*'
                Effect: Allow
                Action:
                  - logs:CreateLogGroup
                  - logs:CreateLogStream
                  - logs:PutLogEvents
                  - logs:CreateExportTask
                  - s3:*
                  - ce:GetCostAndUsage
  EventBridgeRule:
    Type: AWS::Events::Rule
    Properties: 
      EventBusName: default
      Name: send-cost-eventbridge-rule
      ScheduleExpression: cron(0 1 L * ? *)
      State: ENABLED
      Targets: 
        - Arn: !GetAtt LambdaFunction.Arn
          Id: LambdaFunction

  PermissionForEventsToInvokeLambda:
    Type: AWS::Lambda::Permission
    Properties:
      FunctionName: !Ref LambdaFunction
      Action: lambda:InvokeFunction
      Principal: events.amazonaws.com
      SourceArn: !GetAtt 'EventBridgeRule.Arn'