I will create aws_lb and aws_lb_target_group by using Terraform, then create an ECS Service. Here are my codes:

resource "aws_lb" "my_lb" {
  name               = "my-lb"
  internal           = false
  load_balancer_type = "application"
  security_groups    = [data.aws_security_group.existing_opensearch_sg.id]
  subnets            = var.public_subnet_ids

  enable_deletion_protection = false

  tags = {
    component = "my"
    env       = terraform.workspace
    team      = "xxx"
  }
}

resource "aws_lb_target_group" "my_target_group" {
  name     = "my-target-group"
  port     = 1234
  protocol = "HTTP"
  vpc_id   = var.vpc_id
  health_check {
    path     = "/health"
    protocol = "HTTP"
  }

  tags = {
    component = "my"
    env       = terraform.workspace
    team      = "xxx"
  }

  target_type = "ip"
}

resource "aws_ecs_service" "my_service" {
  name            = "my-service"
  launch_type     = "FARGATE"
  desired_count   = 1
  cluster         = aws_ecs_cluster.my_cluster.id
  task_definition = aws_ecs_task_definition.my_task.arn

  network_configuration {
    subnets         = var.private_subnet_ids
    security_groups = [
      data.aws_security_group.existing_opensearch_sg.id
    ]
    assign_public_ip = false
  }

  load_balancer {
    target_group_arn = aws_lb_target_group.my_target_group.arn
    container_name   = "my-container"
    container_port   = 1234
  }

  tags = {
    component = "my"
    env       = terraform.workspace
    team      = "xxx"
  }
}

**When I run terraform apply, it reports an error:
**

╷
│ Error: creating ECS Service (my-service): InvalidParameterException: The target group with targetGroupArn arn:***********(I hide my arn)********* does not have an associated load balancer.
│ 
│   with aws_ecs_service.my_service,
│   on my.tf line 87, in resource "aws_ecs_service" "my_service":
│   56: resource "aws_ecs_service" "my_service" {
│ 

Then I go to AWS, it was found that both lb and target group were created, but the target group’s
Load Balance column shows “None associated”.

I’m a newbie to aws and terraform, can you all help me out?

Asked Gpt but got no reply