(ecs-patterns): Expose arrays of load balancers, listeners, and targetGroups as properties in ApplicationMultipleTargetGroupsFargateService and other patterns constructs

I want to utilize the construct ApplicationMultipleTargetGroupsFargateService for creating a Fargate service fronted by an Application Load Balancer. I need the Application Load Balancer to have 2 listeners and each listener to forward traffic to a distinct ApplicationTargetGroup.

The problem I run is after I instantiate the construct, and want to configure health checks for each individual target group. The ApplicationMultipleTargetGroupsFargateService provides a targetGroup property, however, according to the CDK documentation, this only contains a reference to the default Target Group. Ideally, this would contain a list of references to the different ApplicationTargetGroups configured within the construct. Is there any method for getting a reference to these additional target groups in the CDK from the construct for configuring health checks?

const service = new ApplicationMultipleTargetGroupsFargateService(this, 'ALBFargateService', {
    cluster: this.ecsALBCluster,
    taskDefinition: taskDefinition,
    desiredCount,
    assignPublicIp: true, // needed for outbound network connectivity in a public subnet
    serviceName: 'ALBFargateService',
    loadBalancers: [
        {
            name: 'ApplicationLoadBalancer',
            listeners: [
                {
                    name: 'TrafficListener',
                    port: 443,
                    protocol: ApplicationProtocol.HTTP
                },
                {
                    name: 'HealthCheckListener',
                    port: 8050,
                    protocol: ApplicationProtocol.HTTP
                }
            ]
        }
    ],
    targetGroups: [
        {
            listener: 'TrafficListener',
            containerPort: 443,
            protocol: Protocol.TCP
        },
        {
            listener: 'HealthCheckListener',
            containerPort: 8050,
            protocol: Protocol.TCP
        }
    ]
});

service.targetGroup.configureHealthCheck({
    port: '8050',
    protocol: elbv2.Protocol.HTTP,
    healthyThresholdCount: 2,
    unhealthyThresholdCount: 2,
    timeout: Duration.seconds(10),
    interval: Duration.seconds(30),
    healthyHttpCodes: '200'
});

// TODO: Configure Health Checks for second target group on port 8050

As shown above, I am configuring the service with 2 listeners and 2 target groups associated with a respective listener. Only the first target group’s reference is accessible via the targetGroup property.

[peterwoodworth]

You can work around this by using escape hatches

const lb = service.node.children[x] as ApplicationLoadBalancer
console.log(lb.listeners)

x is whatever number child your ApplicationLoadBalancer is. You can see this by doing console.log(service.node.children)

[github-actions[bot]]

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