GCP Terraform script for Global TCP(proxy) LB not supporting multiple backends

Question

I created a Global(multi-region) TCP(proxy) LB on GCP console using

1. single Frontend configuration
2. Four Backend configuration of Backend type: Instance group in 4 different regions.
3. And one Health check for complete Backend configuration

Now same am unable to create with Terraform below is my full code:

Problem: The loadbalancer is not creating with name: in google_compute_target_tcp_proxy its creating with the name: only in google_compute_backend_service if only one backend is passed, If I pass multiple backends passed with count then multiple loadbalancers are creating instead of attaching all backends to one loadbalancer. Can any one suggest how to attach multiple backends to single google_compute_target_tcp_proxy ? Am new to terraform and I didnt find any details in Terraform documentation.

 provider "google" {
  credentials = file(var.credentials_file)
  project     = var.project_id
}

provider "google-beta" {
  credentials = file(var.credentials_file)
  project     = var.project_id
}


resource "google_compute_global_forwarding_rule" "default" {
  #count      = length(var.zones)
  name       = "frontend-service-mig-test" #We can have single FE IP
  #target     = google_compute_target_tcp_proxy.default[count.index].id
  target     = google_compute_target_tcp_proxy.default.id
  port_range = "443"
  load_balancing_scheme = "EXTERNAL"
}

resource "google_compute_target_tcp_proxy" "default" {
  #count       = length(var.zones)
  name            = "test-proxy" # This name wont be visible on gui.
  #backend_service = google_compute_backend_service.default[count.index].id
  backend_service = google_compute_backend_service.default.id
}

resource "google_compute_backend_service" "default" {
  count       = length(var.zones)
  name        = "mig-test-${count.index}-backend-service"
  load_balancing_scheme = "EXTERNAL"
  protocol    = "TCP"
  timeout_sec = 10
  port_name   = "https"
  health_checks = [google_compute_health_check.default.id]
  backend {
  #group       = "https://www.googleapis.com/compute/v1/projects/terraform-playground-301207/zones/northamerica-northeast1-a/instanceGroups/mig-test-0"
  group       = "https://www.googleapis.com/compute/v1/projects/terraform-playground-301207/zones/${var.zones[count.index]}/instanceGroups/mig-test-${count.index}"
  balancing_mode  = "UTILIZATION"
  capacity_scaler = 1
  max_utilization = 0.8
  }
}

resource "google_compute_health_check" "default" {
  count               = length(var.zones)
  provider            = google-beta
  name                = "health-check-mig-test-${count.index}"
  timeout_sec         = 5
  check_interval_sec  = 5
  healthy_threshold   = 2
  unhealthy_threshold = 2
  
  log_config  {
    enable = false
  }            
  tcp_health_check {
    port = "443"
  }

}

Answer 1

Solution is adding multiple backends to backend resource itself , i used dynamic feature for same.

resource "google_compute_global_forwarding_rule" "default" {
  name       = var.fe_name #We can have single FE IP
  target     = google_compute_target_tcp_proxy.default.id
  port_range = var.be_protocol_range
  load_balancing_scheme = var.lb_scheme
}

resource "google_compute_target_tcp_proxy" "default" {
  name            = var.loadbalancername # This name wont be visible on gui.
  backend_service = google_compute_backend_service.default.id
}

resource "google_compute_backend_service" "default" {
  name        = var.loadbalancername
  load_balancing_scheme = var.lb_scheme
  protocol    = var.be_protocol
  timeout_sec = var.be_timeout_sec
  port_name   = var.be_protocol_name
  health_checks = [google_compute_health_check.default.id]

  dynamic backend {
        for_each = var.zones
    content {
         group       = "https://www.googleapis.com/compute/v1/projects/terraform-playground-301207/zones/${backend.value}/instanceGroups/${var.appname}-${var.regions[backend.key]}"
         balancing_mode  = var.be_balancing_mode
         capacity_scaler = var.be_capacity_scaler
         max_utilization = var.be_max_utilization
    }
  }
}

resource "google_compute_health_check" "default" {
  provider            = google-beta
  name                = var.be_healthcheck_name
  timeout_sec         = var.be_healthcheck_timeout_sec
  check_interval_sec  = var.be_healthcheck_interval_sec
  healthy_threshold   = var.be_healthcheck_threshold
  unhealthy_threshold = var.be_unhealthycheck_threshold
  
  log_config  {
    enable = var.be_healthycheck_logconfig
  }            
  tcp_health_check {
    port = var.be_healthycheck_port
  }

}