(aws-ecs): Can't enable both Fargate and ASG capacity providers

[hnrc]

According to the ECS Cluster Capacity Providers docs it should be possible to have both Fargate and ASG powered capacity providers associated with a ECS cluster.

A cluster may contain a mix of both Auto Scaling group capacity providers and Fargate capacity providers, however a capacity provider strategy may only contain one or the other but not both.

This seem to not be the case with CDK. Cloudformation fails with a "The cluster already contains capacity provider associations" message when trying to provision a cluster that have both enableFargateCapacityProviders set to true and an ASG provided through addAsgCapacityProvider(...).

Reproduction Steps

const cluster = new Cluster(this, 'EcsCluster', {
  vpc,
  clusterName: props.clusterName,
  enableFargateCapacityProviders: true,
});

const autoScalingGroup = new AutoScalingGroup(this, 'Asg', {
  vpc,
  machineImage: EcsOptimizedImage.amazonLinux2(),
  instanceType: new InstanceType('t3.micro'),
  minCapacity: 1,
  maxCapacity: 100,
});

const capacityProvider = new AsgCapacityProvider(
  this,
  'AsgCapacityProvider',
  {
    autoScalingGroup,
    capacityProviderName: props.clusterName,
  },
);
cluster.addAsgCapacityProvider(capacityProvider);

What did you expect to happen?

The CF stack to finish successfully and for the cluster to be associated with both Fargate and ASG capacity providers, thus allowing for a service to decide if it should run on EC2 or Fargate, in the same ECS cluster.

What actually happened?

Resource handler returned message: "The cluster already contains capacity provider associations" (RequestToken: 5c5f5982-c7d4-37ae-535a-92833ee7bef6, HandlerErrorCode: AlreadyExists)

Environment

• CDK CLI Version: 1.104.0
• Framework Version: 1.104.0
• Node.js Version: 14.16.1
• OS: MacOS 10.15.7
• Language (Version): Typescript 4.2.4

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This is 🐛 Bug Report

[SoManyHs]

The issue here is that we are specifying the FARGATE and FARGATE_SPOT capacity providers as a member of the Cluster resource, but creating ClusterCapacityProviderAssociations for the ASG capacity providers. In order for this to work with cloudformation, all of the capacity providers need to be specified either in the Cluster.CapacityProviders field OR on the ClusterCapacityProviderAssocitations.CapacityProvider field. Since specifying an ASG Capacity Provider in CFN requires specifying the latter in order to avoid a circular dependency issue, we need to change the Fargate CPs to also create a ClusterCPAssociation. Working on a fix!

[github-actions]

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