Trigger a lambda based on Cloudformation stack update/complete events

Question

I have this usecase where I need to trigger a lambda every time my cloudformation stack updates/deletes. Cloudformation does not emit any cloudwatch metrics. Is there a way to get the cloudformation events to trigger a lambda. Any existing examples I can refer to.

Answer 1

What you can do is add reference your lambda function within the cloudformation script as a custom resource. You can then have the custom resource run (which executes your Lambda) on every update of the stack.

Basic syntax is:

MyCustomResource: 
  Type: "Custom::TestLambdaCrossStackRef"
  Properties: 
    ServiceToken:
      !Sub arn:aws:lambda:${AWS::Region}:${AWS::AccountId}:function:${LambdaFunctionName}
    StackName: 
      Ref: "NetworkStackName"

More information here: AWS Documentation

Answer 2

Configure an SNS Topic as a Notification Option in the CFT via https://docs.aws.amazon.com/en_pv/AWSCloudFormation/latest/UserGuide/cfn-console-add-tags.html. Have your lambda be a subscriber to that topic.