alb_application_load_balancer.tf

...

resource "aws_alb_target_group" "http" {
  name     = "${var.project_name}-alb-tg-http"
  port     = 80
  protocol = "HTTP"

  vpc_id = "${var.vpc_id}"

  health_check {
      path = "/"
      matcher = "200-299"
      port = 80 # or "traffic-port" (default)
      protocol = "HTTP" # default

      interval = 20
      timeout = 10
      healthy_threshold = 2
      unhealthy_threshold = 3
  }
}

...