aws_ecs_patterns: default listener rule cannot be changed

[kcong7714]

Describe the bug

I have a my_service instantiated from aws_ecs_patterns.ApplicationLoadBalancedFargateService().

I need a custom listener rule with a host header condition so that all other traffic will not be forwarded to the container. This can be added without issue, but the default listener rule does not change despite explicitly defining it, rendering the added custom rule pointless.

Expected Behavior

Default listener rule returns HTTP 503 Service Unavailable.

Current Behavior

Default listener rule is forwarding to target group my_service.target_group.

Reproduction Steps

my_service is instantiated from aws_ecs_patterns.ApplicationLoadBalancedFargateService().

A custom listener rule is added:

aws_elbv2.ApplicationListenerRule(
    self, 'my-rule',
    listener=my_service.listener,
    priority=1,
    conditions=[aws_elbv2.ListenerCondition.host_headers([MY_DOMAIN_NAME])],
    action=elbv2.ListenerAction.forward(target_groups=[my_service.target_group]),
)

An attempt to change the default listener rule:

my_service.listener.default_action = elbv2.ListenerAction.fixed_response(
    status_code=503,
    content_type='text/plain',
    message_body='Service Unavailable',
)

Possible Solution

No response

Additional Information/Context

cdk synth sample output:

  MyServiceLBPublicListener:
    Type: AWS::ElasticLoadBalancingV2::Listener
    Properties:
      DefaultActions:
        - TargetGroupArn:
            Ref: MyServiceLBPublicListenerECSGroup
          Type: forward

CDK CLI Version

2.144.0 (build 5fb15bc)

Framework Version

No response

Node.js Version

v20.11.1

OS

Ubuntu 22.04.4 LTS

Language

Python

Language Version

3.10.12

Other information

No response

[kcong7714]

Sorry, my bad, it's not a bug. The right way to do this is:

my_service.listener.add_action(
    'DefaultAction',
    action=elbv2.ListenerAction.fixed_response(
        status_code=503,
        content_type='text/plain',
        message_body='Service Unavailable',
    )
)

When priority is not specified, it becomes the default action.

cdk synth output:

  MyServiceLBPublicListener:
    Type: AWS::ElasticLoadBalancingV2::Listener
    Properties:
      DefaultActions:
        - FixedResponseConfig:
            ContentType: text/plain
            MessageBody: Service Unavailable
            StatusCode: "503"
          Type: fixed-response

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