# alb — Application Load Balancer (load balancer + target group + listener)

> **Module kind:** L1 primitive  |  **Version:** 1.0.0

An Application Load Balancer with a target group and a listener. This is
a multi-resource module: it creates a load balancer, a target group, and
a listener that forwards traffic to the target group. The target group
is what `ecs-service` registers its tasks with.

## Resources

| Resource | Type | Purpose |
|----------|------|---------|
| load_balancer | `aws_lb` | Application load balancer in the VPC subnets |
| target_group | `aws_lb_target_group` | Target group for the ECS service tasks |
| listener | `aws_lb_listener` | Listener forwarding the LB port to the target group |

## Inputs

| Name | Type | Required | Default | Description |
|------|------|----------|---------|-------------|
| `name` | string | yes | — | Name tag for the load balancer and child resources |
| `subnets` | string | yes | — | Comma-separated subnet ids (from `vpc`) |
| `security_group` | string | yes | — | Security group id for the load balancer |
| `port` | number | no | 80 | Listener port |
| `protocol` | string | no | `HTTP` | Listener protocol |
| `region` | string | yes | — | AWS region the load balancer is created in |

## Outputs

| Name | Type | Description |
|------|------|-------------|
| `lb_arn` | arn | The load balancer ARN |
| `listener_arn` | arn | The listener ARN |
| `target_group_arn` | arn | The target group ARN |

## Usage

```json
{
  "id": "alb",
  "type": "aws:elbv2:loadbalancer",
  "module": "alb@1.0.0",
  "inputs": {
    "name": "acdl-microservice",
    "subnets": "ref:vpc.subnet_ids",
    "security_group": "ref:roles.role_arn",
    "port": 8080,
    "protocol": "HTTP",
    "region": "us-east-1"
  }
}
```

The `target_group_arn` output is referenced by `ecs-service` as its
`lb_target_group_arn` input to wire the service to the ALB.

## Compliance extension points

- **TLS / HTTPS listener** — add `aws_acm_certificate` + `ssl_policy` + `certificate_arn` for encryption in transit (SOC2 CC6.1, PCI-DSS 4.1, HIPAA §164.312(e)(1), GDPR Art.32).
- **Access logs** — add `access_logs { bucket = ..., prefix = ... }` to the load balancer (SOX, SOC2 CC7.2, DORA ICT audit trail).
- **Security group rules** — add ingress/egress rules restricting traffic to known sources (SOC2 CC6.6, PCI-DSS 1.2).
- **Health check** — add a `health_check` block to the target group (SOC2 CC7.3 monitoring, DORA operational resilience).
- **WAF** — add `aws_wafv2_web_acl_association` for application-layer protection (SOC2 CC7.6, PCI-DSS 6.5, DORA ICT risk).
- **Deregistration delay** — add `deregistration_delay` for graceful draining (SOC2 CC9.1 resilience).

## Versioning

`1.0.0` — interface MAJOR, behavior MINOR, lifecycle PATCH. MAJOR bumps
require a new registry entry (immutable publication); old entries enter
a 12-month deprecation window.