In CloudFormation, how do I target a Lambda alias in Events::Rule - aws-lambda

Question

I'm trying to trigger a Lambda:alias (the alias is key here) on a schedule. The following code errors out with
"SampleLambdaLiveAlias is not valid. Reason: Provided Arn is not in
correct format. (Service: AmazonCloudWatchEvents; Status Code: 400;
Error Code: ValidationException;"
How do I properly target the lambda:alias in CloudFormation? I've tried !Ref, !Sub and just the logical name.
My custom-resource approach to retrieving the latest lambda version appears to be a necessary evil of setting up the "live" alias because AWS maintains old lambda versions, even after you delete the lambda and stack AND a valid version is required for a new alias. If anyone knows a more elegant approach to that problem, please see: how-to-use-sam-deploy-to-get-a-lambda-with-autopublishalias-and-additional-alises
SampleLambdaFunction:
Type: AWS::Serverless::Function
Properties:
FunctionName: SampleLambda
AutoPublishAlias: staging
CodeUri: src/
Handler: SampleLambda.handler
MemorySize: 512
Runtime: nodejs12.x
Role: !GetAtt SampleLambdaRole.Arn
SampleLambdaLiveAlias:
Type: AWS::Lambda::Alias
Properties:
FunctionName: !Ref SampleLambdaFunction
FunctionVersion: !GetAtt SampleLambdaGetMaxVersionFunction.version
Name: live
SampleLambdaFunctionScheduledEvent:
Type: AWS::Events::Rule
Properties:
State: ENABLED
ScheduleExpression: rate(1 minute) # same as cron(0/1 * * * ? *)
Description: Run SampleLambdaFunction once every 5 minutes.
Targets:
- Id: EventSampleLambda
Arn: SampleLambdaLiveAlias

Answer 1

Your error is in the last line of the piece of configuration you shared. In order to get the resource ARN you need to use Ref intrinsic function such as, !Ref SampleLambdaLiveAlias:
SampleLambdaFunctionScheduledEvent:
Type: AWS::Events::Rule
Properties:
State: ENABLED
ScheduleExpression: rate(1 minute) # same as cron(0/1 * * * ? *)
Description: Run SampleLambdaFunction once every 5 minutes.
Targets:
- Id: EventSampleLambda
Arn: !Ref SampleLambdaLiveAlias
Be aware that Ref intrinsic function may return different things for different types of resources. For Lambda alias it returns the ARN, just what you need.
You can check the official documentation for more detail.