Terraform examples for an internal passthrough Network Load Balancer

You can use the following example to deploy a sample internal passthrough Network Load Balancer.

If you are new to using Terraform for Google Cloud, see Get started with Terraform.

Internal passthrough Network Load Balancer with no backends

You can use a Terraform module to bring up a minimal internal passthrough Network Load Balancer with a Virtual Private Cloud network, subnetwork, and all of the necessary load balancing components, but no backends. This can be useful if you already have some other script or process for creating your backends.

For information about this example and to learn how to run it, see the README in GitHub.

module "test_ilb" {
  source  = "GoogleCloudPlatform/lb-internal/google"
  version = "~> 7.0"

  project      = var.project_id
  network      = google_compute_network.test.name
  subnetwork   = google_compute_subnetwork.test.name
  region       = var.region
  name         = local.resource_name
  ports        = ["8080"]
  source_tags  = ["source-tag-foo"]
  target_tags  = ["target-tag-bar"]
  backends     = []
  health_check = local.health_check
}

Internal passthrough Network Load Balancer with managed instance group backend

You can use Terraform resources to bring up an internal passthrough Network Load Balancer with a managed instance group backend.

resource "google_compute_network" "ilb_network" {
  name                    = "l4-ilb-network"
  auto_create_subnetworks = false
}

resource "google_compute_subnetwork" "ilb_subnet" {
  name          = "l4-ilb-subnet"
  ip_cidr_range = "10.0.1.0/24"
  region        = "europe-west1"
  network       = google_compute_network.ilb_network.id
}

resource "google_compute_forwarding_rule" "google_compute_forwarding_rule" {
  name                  = "l4-ilb-forwarding-rule"
  backend_service       = google_compute_region_backend_service.default.id
  region                = "europe-west1"
  ip_protocol           = "TCP"
  load_balancing_scheme = "INTERNAL"
  all_ports             = true
  allow_global_access   = true
  network               = google_compute_network.ilb_network.id
  subnetwork            = google_compute_subnetwork.ilb_subnet.id
}

resource "google_compute_region_backend_service" "default" {
  name                  = "l4-ilb-backend-subnet"
  region                = "europe-west1"
  protocol              = "TCP"
  load_balancing_scheme = "INTERNAL"
  health_checks         = [google_compute_region_health_check.default.id]
  backend {
    group          = google_compute_region_instance_group_manager.mig.instance_group
    balancing_mode = "CONNECTION"
  }
}

resource "google_compute_instance_template" "instance_template" {
  name         = "l4-ilb-mig-template"
  machine_type = "e2-small"
  tags         = ["allow-ssh", "allow-health-check"]

  network_interface {
    network    = google_compute_network.ilb_network.id
    subnetwork = google_compute_subnetwork.ilb_subnet.id
    access_config {
      # add external ip to fetch packages
    }
  }
  disk {
    source_image = "debian-cloud/debian-12"
    auto_delete  = true
    boot         = true
  }

  # install nginx and serve a simple web page
  metadata = {
    startup-script = <<-EOF1
      #! /bin/bash
      set -euo pipefail

      export DEBIAN_FRONTEND=noninteractive
      apt-get update
      apt-get install -y nginx-light jq

      NAME=$(curl -H "Metadata-Flavor: Google" "http://metadata.google.internal/computeMetadata/v1/instance/hostname")
      IP=$(curl -H "Metadata-Flavor: Google" "http://metadata.google.internal/computeMetadata/v1/instance/network-interfaces/0/ip")
      METADATA=$(curl -f -H "Metadata-Flavor: Google" "http://metadata.google.internal/computeMetadata/v1/instance/attributes/?recursive=True" | jq 'del(.["startup-script"])')

      cat <<EOF > /var/www/html/index.html
      <pre>
      Name: $NAME
      IP: $IP
      Metadata: $METADATA
      </pre>
      EOF
    EOF1
  }
  lifecycle {
    create_before_destroy = true
  }
}

resource "google_compute_region_health_check" "default" {
  name   = "l4-ilb-hc"
  region = "europe-west1"
  http_health_check {
    port = "80"
  }
}

resource "google_compute_region_instance_group_manager" "mig" {
  name   = "l4-ilb-mig1"
  region = "europe-west1"
  version {
    instance_template = google_compute_instance_template.instance_template.id
    name              = "primary"
  }
  base_instance_name = "vm"
  target_size        = 2
}

# allow all access from health check ranges
resource "google_compute_firewall" "fw_hc" {
  name          = "l4-ilb-fw-allow-hc"
  direction     = "INGRESS"
  network       = google_compute_network.ilb_network.id
  source_ranges = ["130.211.0.0/22", "35.191.0.0/16", "35.235.240.0/20"]
  allow {
    protocol = "tcp"
  }
  target_tags = ["allow-health-check"]
}

# allow communication within the subnet
resource "google_compute_firewall" "fw_ilb_to_backends" {
  name          = "l4-ilb-fw-allow-ilb-to-backends"
  direction     = "INGRESS"
  network       = google_compute_network.ilb_network.id
  source_ranges = ["10.0.1.0/24"]
  allow {
    protocol = "tcp"
  }
  allow {
    protocol = "udp"
  }
  allow {
    protocol = "icmp"
  }
}

# allow SSH
resource "google_compute_firewall" "fw_ilb_ssh" {
  name      = "l4-ilb-fw-ssh"
  direction = "INGRESS"
  network   = google_compute_network.ilb_network.id
  allow {
    protocol = "tcp"
    ports    = ["22"]
  }
  target_tags   = ["allow-ssh"]
  source_ranges = ["0.0.0.0/0"]
}

resource "google_compute_instance" "vm_test" {
  name         = "l4-ilb-test-vm"
  tags         = ["allow-ssh"]
  zone         = "europe-west1-b"
  machine_type = "e2-small"
  network_interface {
    network    = google_compute_network.ilb_network.id
    subnetwork = google_compute_subnetwork.ilb_subnet.id
  }
  boot_disk {
    initialize_params {
      image = "debian-cloud/debian-12"
    }
  }
}