EventBridge CloudFormation Events

It’s possible to use EventBridge event “CloudFormation Resource Status Change” to execute code when the CloudFormation stack itself is created.

AWS Infrastructure schema

This can be done describing the EventBridge event rule for a Lambda function that match the emitted event:

PostScript:
  Type: AWS::Serverless::Function
  Properties:
    FunctionName: !Sub "${AWS::StackName}-post-script"
    Runtime: nodejs16.x
    Handler: index.handler
    InlineCode: !Sub |
      exports.handler = async (event) => {
        console.log(event);
      };
    Policies:
      - AWSLambdaExecute
    Events:
      StackCreatedOrUpdated:
        Type: EventBridgeRule
        Properties:
          EventBusName: default
          Pattern:
            source:
              - aws.cloudformation
            detail-type:
              - CloudFormation Stack Status Change
            detail:
              stack-id:
                - !Ref AWS::StackId
              status-details:
                status:
                  - UPDATE_COMPLETE
                  - CREATE_COMPLETE

The event rule pattern is interpolated with AWS::StackId pseudo parameter reference. So far the only status change that is reported is CREATE_COMPLETE.

This approach can be used for executing a script when a stack resource is create, update or removed:

PostResourceScript:
  Type: AWS::Serverless::Function
  Properties:
    FunctionName: !Sub "${AWS::StackName}-post-resource-script"
    Runtime: nodejs16.x
    Handler: index.handler
    InlineCode: !Sub |
      exports.handler = async (event) => {
        console.log(event);
      };
    Policies:
      - AWSLambdaExecute
    Events:
      ResourceUpdate:
        Type: EventBridgeRule
        Properties:
          EventBusName: default
          Pattern:
            source:
              - aws.cloudformation
            detail-type:
              - CloudFormation Resource Status Change
            detail:
              stack-id:
                - !Ref AWS::StackId
              resource-type:
                - AWS::EC2::Instance
              logical-resource-id:
                - Instance

Credits: Cloudcraft.

Originally written on Oct 3, 2022.