!GetAtt not working with !Sub in cloudformation - amazon-web-services

Question

I'm trying to create some resources using Cloudformation with serverless framework, In which I need to substitute resource name from another resource. Tried to use !Sub but still I couldn't get Arn of another resource created.
Tried all the approaches in this stackoverflow question How to use Sub and GetAtt functions at the same time in CloudFormation template? to no avail.
I appreciate any help.
Resources:
BasicParameter:
Type: AWS::SSM::Parameter
Properties:
Name: /data/config-name
Type: String
Value:
Fn::Base64:
!Sub |
{
"filter_configs": [{
"stream_name": !GetAtt tpRecordDeliveryStream.Arn,
"events": [
{
"name": "event_name1",
"stream": "streamname1"
},
{
"name": "event_name2"
}
]
}]
}
Description: Configuration for stream filters
Tags:
project: projectname
team: data
owner: owner_name

Answer 1

This was resolved by using serverless-pseudo-parameters serverless plugin. Serverless framework also uses ${} placeholder and it conflicts with Cloudformation placeholders. serverless-pseudo-parameters solves that by allowing us to replace those place holders with #{} which are replaced during sls deploy with cloud formation templates
Resources:
streamConfig:
Type: AWS::SSM::Parameter
Properties:
Name: config_name
Type: String
Value:
Fn::Base64: |
{
"filter_configs": [{
"firehose_stream_arn": "#{tpRecordDeliveryStream.Arn}",
"events": [
{
"name": "config0",
"filter1": "value1"
},
{
"name": "config1"
}
]
}]
}
Description: Configuration for stream filters

Answer 2

Since you have !Sub |, instead of
"stream_name": !GetAtt tpRecordDeliveryStream.Arn,
the following should be enough
"stream_name": "${tpRecordDeliveryStream.Arn}"
The alternative using !Sub in array notation:
Value:
Fn::Base64:
!Sub
- |
{
"filter_configs": [{
"stream_name": "${tpRecordDeliveryStreamArn}",
"events": [
{
"name": "event_name1",
"stream": "streamname1"
},
{
"name": "event_name2"
}
]
}]
}
- tpRecordDeliveryStreamArn: !GetAtt tpRecordDeliveryStream.Arn