(aws-ecs-patterns): unable to set DesiredCount to zero

The ApplicationLoadBalancedFargateService construct rejects an attempt to set a DesiredCount of zero, however this is valid and supported in the underlying AWS::ECS::Service resource.

Common use cases for this:

• I want to “suspend” a service, particularly if it’s a headless consumer with background worker tasks.
• During development of a new cluster with a new image, I want to deploy the cluster and supporting infrastructure without attempting to start the Docker image, because I don’t want a slow startup attempt, with multiple retries and a lengthly rollback of the entire cluster every time I debug an issue with the image starting up.

Environment

• CDK CLI Version : 2.0.0-rc.21 (build f35f136)

Other

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This is 🐛 Bug Report

[adrian-skybaker]

so that no one can set 0 accidentially without reading the documentation:

I’m sceptical this is actually a real problem the API needs to solve. Who is explicitly specifying zero accidentally? Or deliberately and being surprised with the result? Having used the underlying cfn resources which permit zero for many years in production, it’s never seemed remotely likely.

[dbartholomae]

I personally would also prefer to set it to 0, but this is a solution that would work for everyone and go with the design principles mentioned by the AWS team.