Execute Lambda Function on CloudFormation Stack delete - amazon-web-services

Question

Is there a way to trigger Lambda Function declared in the very same CFN template that was used to create a stack when the given stack is being deleted?
Preferably I'd like to implement somewhat opposite to THIS snippet (that is: a relatively simple solution that omits e.g. the need of creating SNS topics etc.).
In advance thx for any advices. Best regards! //M

Answer 1

You can achieve the desired behaviour by creating a CustomResource and hooking it up with your lambda function.
From the documentation page:
With AWS Lambda functions and custom resources, you can run custom code in response to stack events (create, update, and delete)
The lambda function needs to react to a Delete event, so it has to be written to allow for that.
Example lambda function source code
Here's an example for the AWS lambda function configuration, which needs to react to a delete event:
import cfnresponse
def lambda_handler(event, context):
response = {}
if event['RequestType'] == 'Delete':
... # do stuff
response['output'] = ' Delete event.'
cfnresponse.send(event, context, cfnresponse.SUCCESS, response)
Example lambda function
Here's a CloudFormation snippet for the lambda function:
"MyDeletionLambda": {
"Type": "AWS::Lambda::Function",
"Properties": {
"Code": {
"ZipFile": {
"Fn::Join": [
"\n",
[
"import cfnresponse",
"",
"def lambda_handler(event, context):",
" response = {}",
" if event['RequestType'] == 'Delete':",
" response['output'] = 'Delete event.'",
" cfnresponse.send(event, context, cfnresponse.SUCCESS, response)"
]
]
}
},
"Handler": "index.lambda_handler",
"Runtime": "python3.8"
}
}
}
Example custom resource
Here's a CloudFormation snippet for a custom resource:
"OnStackDeletion": {
"Type": "Custom::LambdaDependency",
"Properties": {
"ServiceToken": {
"Fn::GetAtt": [
"MyDeletionLambda",
"Arn"
]
}
}
}