CloudFormation：条件参数

Question

Building a CloudFormation stack template, I have a setup constellation where upon instantiation I want to reference either the name of another CloudFormation stack or a non-CloudFormation-managed database as a parameter.

Is there a way to represent this constellation in my template? Ie "Parameter DatabaseHost is mandatory if Parameter DatabaseStack is blank"?

Answer 1

I'm not aware of a native option in CloudFormation to make one template parameter conditional on a second template parameter.

Possible workarounds might be:

• make both optional, and tell user to supply one of them
• use two templates, one for each of the two use cases
• programmatically generate your template after asking the user for parameters

Answer 2

Maybe it wasn't possible at the time of the question, but now, you can include conditions on a CloudFormation template. See docs .

In this example, I use one value or another depending on the environment:

InfrastructurePipelineStack:
Type: AWS::CloudFormation::Stack
Properties:
  TemplateURL: !Sub "https://<masked>.yml"
  Parameters:
    ProjectName: !Ref ProjectName
    ...
    LambdaNotifications: !If [isDev, !GetAtt NotificationsStack.Outputs.LambdaNotifications, !Ref LambdaNotifications]

If the environment is Development ("isDev" condition), I use the output of other CloudFormation Stack as the value. If not, I use a provided fixed value (non-CloudFormation value).

In this case "isDev" is acting as "parameter DatabaseStack is blank" in the OP question.