Creating a Fargate service on existing Fargate cluster causes recreation of VPC resources

[richarddowner]

Hello,

I am having troubles understanding why my Fargate service keeps trying to re-create existing resources such as VPC/Cluster etc when referencing cluster and vpc of an existing stack.

I am referencing the cluster and vpc using the respective Vpc.fromLookup and Cluster.fromClusterAttributes methods.

Fargate service code as follows:

const vpc = ec2.Vpc.fromLookup(this, 'Vpc', {
    vpcId: ssm.StringParameter.valueFromLookup(this, `${this.props.vpcLookupSSMParam}`),
});        

const cluster = ecs.Cluster.fromClusterAttributes(this, 'Cluster', {
    clusterName: cdk.Fn.importValue(this.props.clusterName),            
    vpc: vpc,
    securityGroups: []
});

const containerImage = ecs.ContainerImage.fromEcrRepository(this.props.repository, this.props.stage);        

const httpListenerArn = ssm.StringParameter.valueFromLookup(this, `${this.props.httpListenerArnSSMParam}`);
const httpListener = elb.ApplicationListener.fromLookup(this, 'Listener', {
    listenerArn: httpListenerArn
});

const taskDefinition = new ecs.TaskDefinition(this, 'TaskDefinition', {
    compatibility: ecs.Compatibility.FARGATE,
    cpu: '256',
    memoryMiB: '512',
    networkMode: ecs.NetworkMode.AWS_VPC,
    family: `${this.props.service}-${this.props.stage}`    
});

taskDefinition.addToExecutionRolePolicy(
    new iam.PolicyStatement({
        actions: ['ecr:*'],
        resources: ['*']
}));

taskDefinition.addContainer(`${this.props.service}-${this.props.stage}-container`, {
    image: containerImage,    
    portMappings: [{
        containerPort: 80
    }]        
});    

const targetGroup = new elb.ApplicationTargetGroup(this, 'TargetGroup', {
    port: 80,
    protocol: elb.ApplicationProtocol.HTTP,
    healthCheck: {
        interval: cdk.Duration.seconds(10),
        path: '/',
        protocol: elb.Protocol.HTTP,
        timeout: cdk.Duration.seconds(5),
        healthyThresholdCount: 2,
        unhealthyThresholdCount: 2,
        healthyHttpCodes: "200",
    },
    targetType: elb.TargetType.IP,               
    vpc: vpc   
});         

const service = new ecs.FargateService(this, 'FargateService', {
    cluster: cluster,
    taskDefinition: taskDefinition,            
});

service.attachToApplicationTargetGroup(targetGroup);       

new elb.ApplicationListenerRule(this, 'ListenerRule', {
    listener: httpListener,
    priority: 10,
    targetGroups: [targetGroup],
    conditions: [
        //elb.ListenerCondition.hostHeaders(['example.com']),
        elb.ListenerCondition.pathPatterns([`/${this.props.stage}`]) 
    ]            
});

Not sure what I'm doing wrong, another pair of eyes would be greatly appreciated.
Thanks

[richarddowner]

As per this answered solution, I have also tried passing the VPC and Cluster through to the fargate stack via props.

The solution linked above did not work either, it also created a new VPC and Cluster instead of using the existing ones provided as below:

Props interface:

export interface FargateServiceStackProps extends cdk.StackProps {
    vpc: ec2.IVpc
    cluster: ecs.ICluster
}

Target group and cluster referencing props:

const targetGroup = new elb.ApplicationTargetGroup(this, 'TargetGroup', {
    port: 80,
    protocol: elb.ApplicationProtocol.HTTP,
    healthCheck: {
        interval: cdk.Duration.seconds(10),
        path: '/',
        protocol: elb.Protocol.HTTP,
        timeout: cdk.Duration.seconds(5),
        healthyThresholdCount: 2,
        unhealthyThresholdCount: 2,
        healthyHttpCodes: "200",
    },
    targetType: elb.TargetType.IP,               
    vpc: props.vpc   
});         

const service = new ecs.FargateService(this, 'FargateService', {
    cluster: props.cluster,
    taskDefinition: taskDefinition,            
});

Cluster stack export:

export class AppStack extends cdk.Stack {
    private props: AppStackProps;
    public readonly vpc: ec2.IVpc;
    public readonly cluster: ecs.ICluster;
    .
    .
    .

Cluster stack vpc and cluster creation:

constructor(scope: Construct, id: string, props: AppStackProps) {
        super(scope, id, props);
        this.props = props;    

        this.vpc = new ec2.Vpc(this, "Vpc", {
            maxAzs: 3
        });

       this.cluster = new ecs.Cluster(this, "FargateCluster", {
            vpc: this.vpc
        });
       .
       .
       .