CloudFormation create change set fails with 'Template parameters modified by transform'

user_4839600 0
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I'm trying to create a change set for my stack, but it keeps failing with status reason Template parameters modified by transform.

I have a CodeBuild project which runs the below and then passes the template on if it's valid:

aws cloudformation validate-template --template-body file://<TEMPLATE_FILE>

I am using the CodeDeployBlueGreen transform to allow Blue/Green deployments with ECS, as per this documentation.

Transform:
  - 'AWS::CodeDeployBlueGreen'

My template does not contain any input parameters, and I removed any references to resolve::ssm....

I'm at a bit of a loss as to what's causing this issue, and I cannot find any documentation which points me in the right direction.

The template is as follows:

Template removed after answer posted for security.

amazon-cloudformation amazon-web-services
2 Answers

I hope this saves someone some headaches one day.

This is currently a known issue with CloudFormation in which you need to provide the VPC and Subnets as parameters to the stack when using AWS::CodeDeployBlueGreen Transform.

Parameters:
  VPC:
    Type: AWS::EC2::VPC::Id
  Subnet1:
    Type: AWS::EC2::Subnet::Id
  Subnet2:
    Type: AWS::EC2::Subnet::Id
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