AWS CDK Public Listener Role

A CDK construct for creating Application Load Balancer (ALB) listener rules that route traffic based on host headers to target groups.

Overview

This module provides a reusable CDK construct (AlbListenerRuleStack) that creates ALB listener rules for routing HTTP/HTTPS traffic to specific target groups based on host header conditions.

Features

• Creates ALB listener rules with host-based routing
• Configurable priority for rule evaluation order
• Integrates with existing ALB listeners via CloudFormation exports
• Outputs rule ARN and priority for cross-stack references

Installation

pip install alb-listener-rule

Usage

from alb_listener_rule.alb_listener_rule_stack import AlbListenerRuleStack

# Create listener rule in your CDK stack
listener_rule = AlbListenerRuleStack(
    self, "MyListenerRule",
    target_group_arn="arn:aws:elasticloadbalancing:region:account:targetgroup/my-tg/1234567890",
    ecs_stack_name="my-ecs-stack",
    listener_priority=100,
    host_name="api.example.com"
)

Parameters

Parameter	Type	Description
target_group_arn	str	ARN of the target group to forward traffic to
ecs_stack_name	str	Name of the ECS stack that exports the ALB listener ARN
listener_priority	int	Priority for the listener rule (1-50000, lower = higher priority)
host_name	str	Host header value to match for routing

Prerequisites

• An existing ALB with HTTPS listener that exports its ARN as ${ECSStackName}-ALBListenerHTTPS
• A target group (e.g., ECS service target group) to route traffic to

Outputs

The construct exports the following CloudFormation outputs:

• ${StackName}-AlbListenerRuleArn: ARN of the created listener rule
• ${StackName}-AlbListenerRulePriority: Priority of the created listener rule

Example Scenario

This construct is useful when you have:

1. An ECS cluster with an ALB
2. Multiple services that need different routing rules
3. Requirements to route traffic based on domain/subdomain

File Structure

aws_cdk-public-listener-role/
├── README.md
└── alb_listener_rule/