CODEWITHSUNDEEP
amazon-web-servicesyamlaws-cloudformation
Hleb
Hleb

Reputation: 7391

How to use Sub and GetAtt functions at the same time in CloudFormation template?

I created CloudFormation yaml template and I need to use !GetAtt "TestLambda.Arn" as part of !Sub function in "AWS::ApiGateway::Method" Integration Uri:

Type: "AWS::ApiGateway::Method"
  Properties:
    RestApiId:
      Ref: "RestApi"
    ResourceId:
      Ref: "TestResource"
    HttpMethod: "GET"
    AuthorizationType: "NONE"
    Integration:
      Type: "AWS_PROXY"
      IntegrationHttpMethod: "POST"
      Uri: !Sub "arn:aws:apigateway:us-east-1:lambda:path/2015-03-31/functions/[[place where I want to use !GetAtt "TestLambda.Arn"]]/invocations"

As result I want to get a value something like that:

"arn:aws:apigateway:us-east-1:lambda:path/2015-03-31/functions/my-endpoint-lambda/invocations"

How can I use these functions together and get the desired result?

Upvotes: 79

Views: 54545

Answers (3)

Cristian Marin
Cristian Marin

Reputation: 101

I know it's an old question, but still the first result in Google:

Parameters:
  path:
    Type: String
    Default: something/script.sh
Resources:
  Bucket:
    Type: AWS::S3::Bucket
Outputs:
  ScriptUrl:
    Description: Script Url
    Value:
      Fn::Sub:
        - ${url}${the_path}
        - {url: !GetAtt Bucket.WebsiteURL, the_path: !Ref path}

Upvotes: 10

Stefano
Stefano

Reputation: 2196

You don't need to use !GetAtt here, !Sub will automatically unpack values for you if you place them within the place holder:

Uri: !Sub arn:aws:apigateway:us-east-1:lambda:path/2015-03-31/functions/${TestLambda.Arn}/invocations

This is explained in the docs:

If you specify template parameter names or resource logical IDs, such as ${InstanceTypeParameter}, AWS CloudFormation returns the same values as if you used the Ref intrinsic function. If you specify resource attributes, such as ${MyInstance.PublicIp}, AWS CloudFormation returns the same values as if you used the Fn::GetAtt intrinsic function.

Upvotes: 141

Hleb
Hleb

Reputation: 7391

We can use Fn:: for the nested intrinsic functions if using the ! short form first. So

!Sub "arn:aws:apigateway:us-east-1:lambda:path/2015-03-31/functions/$(Fn::GetAtt:[TestLambda, Arn])/invocations"

Upvotes: 8

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