Leverage Terraform's Dynamic Blocks to vary the target groups attached to the ECS service

Up to five ECS services can be attached to the ALB target group, and since March of this year, the change in attach has eliminated the need to recreate the service. In order to attach a predefined number of blocks load_balancer multiple blocks must be defined, but I will introduce how it can be realized by utilizing Dynamic blocks.

main.tf

module "module" {
  services = {
    service1 = {
      container_name    = "serviceA"
      port              = 8881
    }
    service2 = {
      container_name    = "serviceB"
      port              = 8882
    }
...
  }
  services2 = {
    service6 = {
      container_name    = "serviceF"
      port              = 8886
    }
    service7 = {
      container_name    = "serviceG"
      port              = 8887
    }
...
  }
}

We can attach up to five ALB target groups, so you can only define a maximum of five services in a service. Service 2, Service 3... So, I defined as.

alb.tf

resource "aws_alb_target_group" "services" {
  for_each                      = merge(var.services, var.services2, ...)
  name                          = "${each.key}"
  port                          = lookup(each.value, "port")
}

ecs.tf

resource "aws_ecs_service" "services" {
  dynamic "load_balancer" {
    for_each = var.services
    content {
      container_name   = load_balancer.value["container_name"]
      container_port   = aws_alb_target_group.schools[load_balancer.key].port
      target_group_arn = aws_alb_target_group.schools[load_balancer.key].arn
    }
  }
}

resource "aws_ecs_service" "services2" {
  dynamic "load_balancer" {
    for_each = var.services2
    content {
      container_name   = load_balancer.value["container_name"]
      container_port   = aws_alb_target_group.schools[load_balancer.key].port
      target_group_arn = aws_alb_target_group.schools[load_balancer.key].arn
    }
  }
}

resource "aws_ecs_task_definition" "services" {
  container_definitions = jsonencode(concat(
    [
      {
        cpu               = 0
        disableNetworking = false
        name              = "nginx"
      }
    ],
    [for name, service in var.services : merge(
      {
        cpu = 0
        disableNetworking = false
        portMappings = [
          {
            containerPort = aws_alb_target_group.service[name].port
            hostPort      = aws_alb_target_group.service[name].port
            protocol      = "tcp"
          }
        ]
        environment = [
          {
            name  = "PORT"
            value = "${tostring(aws_alb_target_group.services[name].port)}"
          }
        ]
        name              = lookup(service, "container_name")
      })
    ])
  )
}

resource "aws_ecs_task_definition" "services2" {
  container_definitions = jsonencode(concat(
    [
      {
        cpu               = 0
        disableNetworking = false
        name              = "nginx"
      }
    ],
    [for name, service in var.services2 : merge(
      {
        cpu = 0
        disableNetworking = false
        portMappings = [
          {
            containerPort = aws_alb_target_group.service[name].port
            hostPort      = aws_alb_target_group.service[name].port
            protocol      = "tcp"
          }
        ]
        environment = [
          {
            name  = "PORT"
            value = "${tostring(aws_alb_target_group.services[name].port)}"
          }
        ]
        name              = lookup(service, "container_name")
      })
    ])
  )
}