Is it possible to trigger a lambda on creation from CloudFormation template

I tried creating a set of lambdas using cloudformation. I want the lambdas to get triggered once they are created. I saw at various blogs to create a trigger to s3 or sns but none seems to be a option to trigger lambda once it has been created. Any options?

Yes, it is possible. Here are a few options:

1. Manually create an SNS Topic. Add an AWS::SNS::Subscription to your stack with the lambda function as the Endpoint and the SNS topic as the TopicArn. On stack creation/update, configure Stack Event Notifications to be sent to this SNS topic.

   • (See Setting AWS CloudFormation Stack Options for documentation on how to do this when using the AWS Console to create your stack, or use the equivalent option like --notification-arns if creating/updating your stack using the AWS CLI or other AWS SDK.)

2. Add a Custom Resource referencing a Lambda function to be called on creation.

   • If you need the Lambda function to be called after some specific Resource is created, add a DependsOn attribute on the Custom Resource referencing the Resource you want to make sure is created first before the function is called.
   • In order for the Custom Resource to create successfully (and not cause a failure/rollback in your stack), you will need to adapt your Lambda function to support the CloudFormation request/response format (see Custom Resource Reference).
   • This option will call the Lambda function while the stack status is still CREATE_IN_PROGRESS, because the Custom Resource is part of the stack itself.
   • The Lambda function will also be called again when the stack (and associated Custom Resource) is deleted. This will need to be handled by your Lambda function correctly, or your stack could get stuck in the DELETE_FAILED state.

3. Add the Lambda function reference to a Stack Output, then write a simple script that performs the stack creation and then manually invokes the Lambda function afterwards.