Getting an ARN for an imported Kinesis stream - amazon-web-services

Question

I have two nested Cloudformation stacks - the first template needs to define a Kinesis stream, the second needs to use a reference to that stream's ARN, as an argument to a further nested stack.
So it seems I need to "export" the stream from the first template, and "import" it into the second (following AWS docs on importing/exporting values across stacks) -
https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/intrinsic-function-reference-importvalue.html
My export code [truncated] looks like this -
Outputs:
MyKinesisStreamOutput:
Value:
Ref: MyKinesisStream
Export:
Name: my-kinesis-stream
Resources:
MyKinesisStream:
Properties:
Name:
Ref: AppName
ShardCount: 1
Type: AWS::Kinesis::Stream
Whilst my import code [truncated] looks like this -
MyNestedStack:
Type: AWS::CloudFormation::Stack
Properties:
TemplateURL: !Sub "https://s3.${AWS::Region}.amazonaws.com/my-nested-stack.yaml"
Parameters:
AppName: my-nested-stack
KinesisStream:
Fn::GetAtt:
- Fn::ImportValue:
my-kinesis-stream
- Arn
But then I get the following Cloudformation error -
Template error: every Fn::GetAtt object requires two non-empty parameters, the resource name and the resource attribute
and suspect I am falling foul of this -
For the Fn::GetAtt logical resource name, you cannot use functions. You must specify a string that is a resource's logical ID.
https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/intrinsic-function-reference-getatt.html
Assuming I am exporting and importing the Kinesis stream correctly, how then am I supposed to get its Arn value ?

Answer 1

When you export something in Outputs, it's just a string, you can no longer GetAtt on it in the importing template.
What you need to do is to additionally export ARN:
Outputs:
MyKinesisStream:
Value: !Ref MyKinesisStream
Export:
Name: my-kinesis-stream
MyKinesisStreamArn:
Value: !GetAtt MyKinesisStream.Arn
Export:
Name: my-kinesis-stream-arn

Answer 2

I can think of two potential ways:
1) Fn::GetAtt:[!ImportValue my-kinesis-stream, Arn]
Sorry wasn't reading carefully enough
or what I would prefer
2) Directly export the required value as output: Value: !GetAtt MyKinesisStream.Arn
Hope that helps!