AWS云表单任务定义条件命令

Question

Let say I have an app that has the ability to run in a dry run mode, set by a flag on the command line; myapp --dryrun , and the CloudForm for its task definition is:

MyTaskDefinition
  Type: AWS::ECS::TaskDefinition
  Properties:
    ContainerDefinitions:
    - Name: myApp
      Image: user/myapp:latest
      Command:
      - ./myapp
      - --dryrun
      Environment:
      - Name: SOME_ENV_VAR
        Value: !Ref SomeEnvVar

I am trying to create a single CloudForm template for a Task Definition that can be used in a development and production environment, where the dry run flag is set only for the development environment.

Is there some way to set conditional command, or am I going to resort to a hacky string that I pass in like:

      Command:
      - ./myapp
      - !Ref DryRun

Answer 1

The neatest solution was to use an If function, which sets the flag when true, and uses AWS::NoValue if false.

AWS::NoValue will remove the property completely, meaning the command for true is ["./myapp", "--dryrun"] and the command when false is ["./myapp"] .

Unfortunately, there is no Bool type for CloudForm parameters, and so you have to pass this in as a String , and then use a Condition to convert from the String to a Bool .

MyTaskDefinition
  Type: AWS::ECS::TaskDefinition
  Properties:
    ContainerDefinitions:
    - Name: myApp
      Image: user/myapp:latest
      Command:
      - ./myapp
      - Fn::If:
        - UseDryRun
        - --dryrun
        - Ref: AWS::NoValue

Parameters:
  DryRun:
    Type: String
    AllowedValues: # No bool parameter in CFN
    - true
    - false

Conditions:
  UseDryRun: !Equals [ !Ref DryRun, true ]