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Internal Passthrough Network Load Balancer Module

This module allows managing a GCE Internal Load Balancer and integrates the forwarding rule, regional backend, and optional health check resources. It's designed to be a simple match for the compute-vm module, which can be used to manage instance templates and instance groups.

Examples

Referencing existing MIGs

This example shows how to reference existing Managed Infrastructure Groups (MIGs).

module "instance_template" {
  source          = "./fabric/modules/compute-vm"
  project_id      = var.project_id
  zone            = "europe-west1-b"
  name            = "vm-test"
  create_template = true
  service_account = {
    auto_create = true
  }
  network_interfaces = [
    {
      network    = var.vpc.self_link
      subnetwork = var.subnet.self_link
    }
  ]
  tags = [
    "http-server"
  ]
}

module "mig" {
  source            = "./fabric/modules/compute-mig"
  project_id        = var.project_id
  location          = "europe-west1"
  name              = "mig-test"
  target_size       = 1
  instance_template = module.instance_template.template.self_link
}

module "ilb" {
  source        = "./fabric/modules/net-lb-int"
  project_id    = var.project_id
  region        = "europe-west1"
  name          = "ilb-test"
  service_label = "ilb-test"
  vpc_config = {
    network    = var.vpc.self_link
    subnetwork = var.subnet.self_link
  }
  backends = [{
    group = module.mig.group_manager.instance_group
  }]
  health_check_config = {
    http = {
      port = 80
    }
  }
}
# tftest modules=3 resources=6

Externally managed instances

This examples shows how to create an ILB by combining externally managed instances (in a custom module or even outside of the current root module) in an unmanaged group. When using internally managed groups, remember to run terraform apply each time group instances change.

module "ilb" {
  source        = "./fabric/modules/net-lb-int"
  project_id    = var.project_id
  region        = "europe-west1"
  name          = "ilb-test"
  service_label = "ilb-test"
  vpc_config = {
    network    = var.vpc.self_link
    subnetwork = var.subnet.self_link
  }
  group_configs = {
    my-group = {
      zone = "europe-west1-b"
      instances = [
        "instance-1-self-link",
        "instance-2-self-link"
      ]
    }
  }
  backends = [{
    group = module.ilb.groups.my-group.self_link
  }]
  health_check_config = {
    http = {
      port = 80
    }
  }
}
# tftest modules=1 resources=4

Passing multiple protocols through the load balancers

The example shows how to send multiple protocols through the same internal network passthrough load balancer.

module "ilb" {
  source        = "./fabric/modules/net-lb-int"
  project_id    = var.project_id
  region        = "europe-west1"
  name          = "ilb-test"
  service_label = "ilb-test"
  vpc_config = {
    network    = var.vpc.self_link
    subnetwork = var.subnet.self_link
  }
  forwarding_rules_config = {
    "" = {
      protocol = "L3_DEFAULT"
    }
  }
  group_configs = {
    my-group = {
      zone = "europe-west1-b"
      instances = [
        "instance-1-self-link",
        "instance-2-self-link"
      ]
    }
  }
  backends = [{
    group = module.ilb.groups.my-group.self_link
  }]
}
# tftest modules=1 resources=4

Multiple forwarding rules

You can add more forwarding rules to your load balancer and override some forwarding rules defaults, including the global access policy, the IP protocol, the IP version and ports.

The example adds two forwarding rules:

  • the first one, called ilb-test-vip-one exposes an IPv4 address, it listens on all ports, and allows connections from any region.
  • the second one, called ilb-test-vip-two exposes an IPv4 address, it listens on port 80 and allows connections from the same region only.
module "ilb" {
  source        = "./fabric/modules/net-lb-int"
  project_id    = var.project_id
  region        = "europe-west1"
  name          = "ilb-test"
  service_label = "ilb-test"
  vpc_config = {
    network    = var.vpc.self_link
    subnetwork = var.subnet.self_link
  }
  forwarding_rules_config = {
    vip-one = {}
    vip-two = {
      global_access = false
      ports         = [80]
    }
  }
  group_configs = {
    my-group = {
      zone = "europe-west1-b"
      instances = [
        "instance-1-self-link",
        "instance-2-self-link"
      ]
    }
  }
  backends = [{
    group = module.ilb.groups.my-group.self_link
  }]
}
# tftest modules=1 resources=5

Dual stack (IPv4 and IPv6)

Your load balancer can use a combination of either or both IPv4 and IPv6 forwarding rules. In this example we set the load balancer to work as dual stack, meaning it exposes both an IPv4 and an IPv6 address.

module "ilb" {
  source        = "./fabric/modules/net-lb-int"
  project_id    = var.project_id
  region        = "europe-west1"
  name          = "ilb-test"
  service_label = "ilb-test"
  vpc_config = {
    network    = var.vpc.self_link
    subnetwork = var.subnet.self_link
  }
  forwarding_rules_config = {
    ipv4 = {
      version = "IPV4"
    }
    ipv6 = {
      version = "IPV6"
    }
  }
  group_configs = {
    my-group = {
      zone = "europe-west1-b"
      instances = [
        "instance-1-self-link",
        "instance-2-self-link"
      ]
    }
  }
  backends = [{
    group = module.ilb.groups.my-group.self_link
  }]
}
# tftest modules=1 resources=5

PSC service attachments

The optional service_attachments variable allows publishing Private Service Connect services by configuring up to one service attachment for each of the forwarding rules.

module "ilb" {
  source        = "./fabric/modules/net-lb-int"
  project_id    = var.project_id
  region        = "europe-west1"
  name          = "ilb-test"
  service_label = "ilb-test"
  vpc_config = {
    network    = var.vpc.self_link
    subnetwork = var.subnet.self_link
  }
  forwarding_rules_config = {
    vip-one = {}
    vip-two = {
      global_access = false
      ports         = [80]
    }
  }
  group_configs = {
    my-group = {
      zone = "europe-west1-b"
      instances = [
        "instance-1-self-link",
        "instance-2-self-link"
      ]
    }
  }
  backends = [{
    group = module.ilb.groups.my-group.self_link
  }]
  service_attachments = {
    vip-one = {
      nat_subnets          = [var.subnet_psc_1.self_link]
      automatic_connection = true
    }
    vip-two = {
      nat_subnets          = [var.subnet_psc_2.self_link]
      automatic_connection = true
    }
  }
}
# tftest modules=1 resources=7

End to end example

This example spins up a simple HTTP server and combines four modules:

  • nginx from the cloud-config-container collection, to manage instance configuration
  • compute-vm to manage the instance template and unmanaged instance group
  • this module to create an Internal Load Balancer in front of the managed instance group

Note that the example uses the GCE default service account. You might want to create an ad-hoc service account by combining the iam-service-account module, or by having the GCE VM module create one for you. In both cases, remember to set at least logging write permissions for the service account, or the container on the instances won't be able to start.

module "cos-nginx" {
  source = "./fabric/modules/cloud-config-container/nginx"
}

module "instance-group" {
  source     = "./fabric/modules/compute-vm"
  for_each   = toset(["b", "c"])
  project_id = var.project_id
  zone       = "${var.region}-${each.key}"
  name       = "ilb-test-${each.key}"
  network_interfaces = [{
    network    = var.vpc.self_link
    subnetwork = var.subnet.self_link
    nat        = false
    addresses  = null
  }]
  boot_disk = {
    initialize_params = {
      image = "projects/cos-cloud/global/images/family/cos-stable"
      type  = "pd-ssd"
      size  = 10
    }
  }
  tags = ["http-server", "ssh"]
  metadata = {
    user-data = module.cos-nginx.cloud_config
  }
  group = { named_ports = {} }
}

module "ilb" {
  source        = "./fabric/modules/net-lb-int"
  project_id    = var.project_id
  region        = var.region
  name          = "ilb-test"
  service_label = "ilb-test"
  vpc_config = {
    network    = var.vpc.self_link
    subnetwork = var.subnet.self_link
  }
  forwarding_rules_config = {
    "" = {
      ports = [80]
    }
  }
  backends = [
    for z, mod in module.instance-group : {
      group = mod.group.self_link
    }
  ]
  health_check_config = {
    http = {
      port = 80
    }
  }
}
# tftest modules=3 resources=7 e2e

Deploying changes to load balancer configurations

For deploying changes to load balancer configuration please refer to net-lb-app-ext README.md

Issues

There are some corner cases where Terraform raises a cycle error on apply, for example when using the entire ILB module as a value in for_each counts used to create static routes in the VPC module. These are easily fixed by using forwarding rule ids instead of modules as values in the for_each loop.

Variables

name description type required default
name Name used for all resources. string ✓
project_id Project id where resources will be created. string ✓
region GCP region. string ✓
vpc_config VPC-level configuration. object({…}) ✓
backend_service_config Backend service level configuration. object({…}) {}
backends Load balancer backends. list(object({…})) []
description Optional description used for resources. string "Terraform managed."
forwarding_rules_config The optional forwarding rules configuration. map(object({…})) {…}
group_configs Optional unmanaged groups to create. Can be referenced in backends via outputs. map(object({…})) {}
health_check Name of existing health check to use, disables auto-created health check. string null
health_check_config Optional auto-created health check configuration, use the output self-link to set it in the auto healing policy. Refer to examples for usage. object({…}) {…}
labels Labels set on resources. map(string) {}
service_attachments PSC service attachments, keyed by forwarding rule. map(object({…})) null
service_label Optional prefix of the fully qualified forwarding rule name. string null

Outputs

name description sensitive
backend_service Backend resource. ✓
backend_service_id Backend id.
backend_service_self_link Backend self link.
forwarding_rule_addresses Forwarding rule address.
forwarding_rule_self_links Forwarding rule self links.
forwarding_rules Forwarding rule resources.
group_self_links Optional unmanaged instance group self links.
groups Optional unmanaged instance group resources.
health_check Auto-created health-check resource.
health_check_id Auto-created health-check id.
health_check_self_link Auto-created health-check self link.
id Fully qualified forwarding rule ids.
service_attachment_ids Service attachment ids.