ecs: Add ability to export target group created by FargateService (EC2Service etc..)

[pitayapj]

Describe the feature

An option to export target group from FargateService.
Needed for CodeDeploy ECS blue green deployment

Use Case

I'm having trouble when create CodeDeploy EcsDeploymentGroup,
it needs to specify 2 target groups for deployment config.

One of them is a secondary target group, which could be created by new lines of code.
But one of them should be a target group that was created by FargateService.
Currently there is no option to export the target group FargateService created.

Proposed Solution

Maybe we can do this could be via property or method

const service = new cdk.aws_ecs.FargateService(this, 'fargate-cluster', {
  cluster: this.cluster,
  taskDefinition: taskDefinition,
  serviceName: "fargate-service-ex",
  deploymentController: {
    type: cdk.aws_ecs.DeploymentControllerType.CODE_DEPLOY,
  },
});

const ecsDeployGroup = new cdk.aws_codedeploy.EcsDeploymentGroup(this, 'blueGreenDG', {
  service: service,
  blueGreenDeploymentConfig: {
    blueTargetGroup: service.targetgroup, //Or service.targetgroup(), need ITargetGroup return
    greenTargetGroup: secondaryTargetGroup,
    listener: httpsListener,
  },
  deploymentConfig: cdk.aws_codedeploy.EcsDeploymentConfig.ALL_AT_ONCE,
});

Other Information

I know we can get target group of service if using ApplicationLoadBalancedFargateService.
Since ApplicationLoadBalancedFargateService doesn't have priority option. Which is important to some cases
Can we do it with FargateService as well ?

Acknowledgements

• I may be able to implement this feature request
• This feature might incur a breaking change

CDK version used

2.103.1

Environment details (OS name and version, etc.)

MacOS

[pahud]

Looks like you need to provide a elbv2.ITargetGroup but looking at the FargateService, does it always come with a target group?

[pitayapj]

@pahud yes, sorry about that.
addTargets() do return TargetGroup so I am able to config CodeDeploy now.

[github-actions]

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