480 lines
18 KiB
Markdown
480 lines
18 KiB
Markdown
# GCE Managed Instance Group module
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This module allows creating a managed instance group supporting one or more application versions via instance templates. Optionally, a health check and an autoscaler can be created, and the managed instance group can be configured to be stateful.
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This module can be coupled with the [`compute-vm`](../compute-vm) module which can manage instance templates, and the [`net-ilb`](../net-ilb) module to assign the MIG to a backend wired to an Internal Load Balancer. The first use case is shown in the examples below.
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Stateful disks can be created directly, as shown in the last example below.
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## Examples
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This example shows how to manage a simple MIG that leverages the `compute-vm` module to manage the underlying instance template. The following sub-examples will only show how to enable specific features of this module, and won't replicate the combined setup.
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```hcl
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module "cos-nginx" {
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source = "./modules/cloud-config-container/nginx"
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}
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module "nginx-template" {
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source = "./modules/compute-vm"
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project_id = var.project_id
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name = "nginx-template"
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zone = "europe-west1-b"
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tags = ["http-server", "ssh"]
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network_interfaces = [{
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network = var.vpc.self_link
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subnetwork = var.subnet.self_link
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nat = false
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addresses = null
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}]
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boot_disk = {
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image = "projects/cos-cloud/global/images/family/cos-stable"
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type = "pd-ssd"
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size = 10
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}
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create_template = true
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metadata = {
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user-data = module.cos-nginx.cloud_config
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}
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}
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module "nginx-mig" {
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source = "./modules/compute-mig"
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project_id = "my-project"
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location = "europe-west1-b"
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name = "mig-test"
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target_size = 2
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default_version = {
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instance_template = module.nginx-template.template.self_link
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name = "default"
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}
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}
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# tftest modules=2 resources=2
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```
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### Multiple versions
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If multiple versions are desired, use more `compute-vm` instances for the additional templates used in each version (not shown here), and reference them like this:
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```hcl
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module "cos-nginx" {
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source = "./modules/cloud-config-container/nginx"
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}
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module "nginx-template" {
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source = "./modules/compute-vm"
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project_id = var.project_id
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name = "nginx-template"
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zone = "europe-west1-b"
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tags = ["http-server", "ssh"]
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network_interfaces = [{
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network = var.vpc.self_link
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subnetwork = var.subnet.self_link
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nat = false
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addresses = null
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}]
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boot_disk = {
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image = "projects/cos-cloud/global/images/family/cos-stable"
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type = "pd-ssd"
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size = 10
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}
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create_template = true
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metadata = {
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user-data = module.cos-nginx.cloud_config
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}
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}
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module "nginx-mig" {
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source = "./modules/compute-mig"
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project_id = "my-project"
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location = "europe-west1-b"
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name = "mig-test"
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target_size = 3
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default_version = {
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instance_template = module.nginx-template.template.self_link
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name = "default"
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}
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versions = {
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canary = {
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instance_template = module.nginx-template.template.self_link
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target_type = "fixed"
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target_size = 1
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}
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}
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}
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# tftest modules=2 resources=2
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```
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### Health check and autohealing policies
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Autohealing policies can use an externally defined health check, or have this module auto-create one:
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```hcl
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module "cos-nginx" {
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source = "./modules/cloud-config-container/nginx"
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}
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module "nginx-template" {
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source = "./modules/compute-vm"
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project_id = var.project_id
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name = "nginx-template"
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zone = "europe-west1-b"
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tags = ["http-server", "ssh"]
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network_interfaces = [{
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network = var.vpc.self_link,
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subnetwork = var.subnet.self_link,
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nat = false,
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addresses = null
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}]
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boot_disk = {
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image = "projects/cos-cloud/global/images/family/cos-stable"
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type = "pd-ssd"
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size = 10
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}
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create_template = true
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metadata = {
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user-data = module.cos-nginx.cloud_config
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}
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}
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module "nginx-mig" {
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source = "./modules/compute-mig"
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project_id = "my-project"
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location = "europe-west1-b"
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name = "mig-test"
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target_size = 3
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default_version = {
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instance_template = module.nginx-template.template.self_link
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name = "default"
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}
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auto_healing_policies = {
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health_check = module.nginx-mig.health_check.self_link
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initial_delay_sec = 30
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}
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health_check_config = {
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type = "http"
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check = { port = 80 }
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config = {}
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logging = true
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}
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}
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# tftest modules=2 resources=3
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```
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### Autoscaling
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The module can create and manage an autoscaler associated with the MIG. When using autoscaling do not set the `target_size` variable or set it to `null`. Here we show a CPU utilization autoscaler, the other available modes are load balancing utilization and custom metric, like the underlying autoscaler resource.
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```hcl
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module "cos-nginx" {
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source = "./modules/cloud-config-container/nginx"
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}
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module "nginx-template" {
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source = "./modules/compute-vm"
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project_id = var.project_id
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name = "nginx-template"
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zone = "europe-west1-b"
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tags = ["http-server", "ssh"]
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network_interfaces = [{
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network = var.vpc.self_link
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subnetwork = var.subnet.self_link
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nat = false
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addresses = null
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}]
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boot_disk = {
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image = "projects/cos-cloud/global/images/family/cos-stable"
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type = "pd-ssd"
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size = 10
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}
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create_template = true
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metadata = {
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user-data = module.cos-nginx.cloud_config
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}
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}
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module "nginx-mig" {
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source = "./modules/compute-mig"
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project_id = "my-project"
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location = "europe-west1-b"
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name = "mig-test"
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target_size = 3
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default_version = {
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instance_template = module.nginx-template.template.self_link
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name = "default"
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}
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autoscaler_config = {
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max_replicas = 3
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min_replicas = 1
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cooldown_period = 30
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cpu_utilization_target = 0.65
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load_balancing_utilization_target = null
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metric = null
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}
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}
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# tftest modules=2 resources=3
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```
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### Update policy
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```hcl
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module "cos-nginx" {
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source = "./modules/cloud-config-container/nginx"
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}
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module "nginx-template" {
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source = "./modules/compute-vm"
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project_id = var.project_id
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name = "nginx-template"
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zone = "europe-west1-b"
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tags = ["http-server", "ssh"]
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network_interfaces = [{
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network = var.vpc.self_link
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subnetwork = var.subnet.self_link
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nat = false
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addresses = null
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}]
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boot_disk = {
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image = "projects/cos-cloud/global/images/family/cos-stable"
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type = "pd-ssd"
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size = 10
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}
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create_template = true
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metadata = {
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user-data = module.cos-nginx.cloud_config
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}
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}
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module "nginx-mig" {
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source = "./modules/compute-mig"
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project_id = "my-project"
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location = "europe-west1-b"
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name = "mig-test"
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target_size = 3
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default_version = {
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instance_template = module.nginx-template.template.self_link
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name = "default"
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}
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update_policy = {
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type = "PROACTIVE"
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minimal_action = "REPLACE"
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min_ready_sec = 30
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max_surge_type = "fixed"
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max_surge = 1
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max_unavailable_type = null
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max_unavailable = null
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}
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}
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# tftest modules=2 resources=2
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```
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### Stateful MIGs - MIG Config
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Stateful MIGs have some limitations documented [here](https://cloud.google.com/compute/docs/instance-groups/configuring-stateful-migs#limitations). Enforcement of these requirements is the responsibility of users of this module.
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You can configure a disk defined in the instance template to be stateful for all instances in the MIG by configuring in the MIG's stateful policy, using the `stateful_disk_mig` variable. Alternatively, you can also configure stateful persistent disks individually per instance of the MIG by setting the `stateful_disk_instance` variable. A discussion on these scenarios can be found in the [docs](https://cloud.google.com/compute/docs/instance-groups/configuring-stateful-disks-in-migs).
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An example using only the configuration at the MIG level can be seen below.
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Note that when referencing the stateful disk, you use `device_name` and not `disk_name`.
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```hcl
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module "cos-nginx" {
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source = "./modules/cloud-config-container/nginx"
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}
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module "nginx-template" {
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source = "./modules/compute-vm"
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project_id = var.project_id
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name = "nginx-template"
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zone = "europe-west1-b"
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tags = ["http-server", "ssh"]
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network_interfaces = [{
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network = var.vpc.self_link
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subnetwork = var.subnet.self_link
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nat = false
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addresses = null
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}]
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boot_disk = {
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image = "projects/cos-cloud/global/images/family/cos-stable"
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type = "pd-ssd"
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size = 10
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}
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attached_disks = [{
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name = "repd-1"
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size = null
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source_type = "attach"
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source = "regions/${var.region}/disks/repd-test-1"
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options = {
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mode = "READ_ONLY"
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replica_zone = "${var.region}-c"
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type = "PERSISTENT"
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}
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}]
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create_template = true
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metadata = {
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user-data = module.cos-nginx.cloud_config
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}
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}
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module "nginx-mig" {
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source = "./modules/compute-mig"
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project_id = "my-project"
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location = "europe-west1-b"
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name = "mig-test"
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target_size = 3
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default_version = {
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instance_template = module.nginx-template.template.self_link
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name = "default"
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}
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autoscaler_config = {
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max_replicas = 3
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min_replicas = 1
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cooldown_period = 30
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cpu_utilization_target = 0.65
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load_balancing_utilization_target = null
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metric = null
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}
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stateful_config = {
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per_instance_config = {},
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mig_config = {
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stateful_disks = {
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persistent-disk-1 = {
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delete_rule = "NEVER"
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}
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}
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}
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}
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}
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# tftest modules=2 resources=3
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```
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### Stateful MIGs - Instance Config
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Here is an example defining the stateful config at the instance level.
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Note that you will need to know the instance name in order to use this configuration.
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```hcl
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module "cos-nginx" {
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source = "./modules/cloud-config-container/nginx"
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}
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module "nginx-template" {
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source = "./modules/compute-vm"
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project_id = var.project_id
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name = "nginx-template"
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zone = "europe-west1-b"
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tags = ["http-server", "ssh"]
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network_interfaces = [{
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network = var.vpc.self_link
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subnetwork = var.subnet.self_link
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nat = false
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addresses = null
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}]
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boot_disk = {
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image = "projects/cos-cloud/global/images/family/cos-stable"
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type = "pd-ssd"
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size = 10
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}
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attached_disks = [{
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name = "repd-1"
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size = null
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source_type = "attach"
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source = "regions/${var.region}/disks/repd-test-1"
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options = {
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mode = "READ_ONLY"
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replica_zone = "${var.region}-c"
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type = "PERSISTENT"
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}
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}]
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create_template = true
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metadata = {
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user-data = module.cos-nginx.cloud_config
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}
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}
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module "nginx-mig" {
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source = "./modules/compute-mig"
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project_id = "my-project"
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location = "europe-west1-b"
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name = "mig-test"
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target_size = 3
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default_version = {
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instance_template = module.nginx-template.template.self_link
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name = "default"
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}
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autoscaler_config = {
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max_replicas = 3
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min_replicas = 1
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cooldown_period = 30
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cpu_utilization_target = 0.65
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load_balancing_utilization_target = null
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metric = null
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}
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stateful_config = {
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per_instance_config = {
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# note that this needs to be the name of an existing instance within the Managed Instance Group
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instance-1 = {
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stateful_disks = {
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persistent-disk-1 = {
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source = "test-disk",
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mode = "READ_ONLY",
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delete_rule= "NEVER",
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},
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},
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metadata = {
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foo = "bar"
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},
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update_config = {
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minimal_action = "NONE",
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most_disruptive_allowed_action = "REPLACE",
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remove_instance_state_on_destroy = false,
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},
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},
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},
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mig_config = {
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stateful_disks = {
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}
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}
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}
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}
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# tftest modules=2 resources=4
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```
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<!-- BEGIN TFDOC -->
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## Variables
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| name | description | type | required | default |
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| [default_version](variables.tf#L45) | Default application version template. Additional versions can be specified via the `versions` variable. | <code title="object({ instance_template = string name = string })">object({…})</code> | ✓ | |
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| [location](variables.tf#L64) | Compute zone, or region if `regional` is set to true. | <code>string</code> | ✓ | |
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| [name](variables.tf#L68) | Managed group name. | <code>string</code> | ✓ | |
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| [project_id](variables.tf#L79) | Project id. | <code>string</code> | ✓ | |
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| [auto_healing_policies](variables.tf#L17) | Auto-healing policies for this group. | <code title="object({ health_check = string initial_delay_sec = number })">object({…})</code> | | <code>null</code> |
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| [autoscaler_config](variables.tf#L26) | Optional autoscaler configuration. Only one of 'cpu_utilization_target' 'load_balancing_utilization_target' or 'metric' can be not null. | <code title="object({ max_replicas = number min_replicas = number cooldown_period = number cpu_utilization_target = number load_balancing_utilization_target = number metric = object({ name = string single_instance_assignment = number target = number type = string # GAUGE, DELTA_PER_SECOND, DELTA_PER_MINUTE filter = string }) })">object({…})</code> | | <code>null</code> |
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| [health_check_config](variables.tf#L53) | Optional auto-created health check configuration, use the output self-link to set it in the auto healing policy. Refer to examples for usage. | <code title="object({ type = string # http https tcp ssl http2 check = map(any) # actual health check block attributes config = map(number) # interval, thresholds, timeout logging = bool })">object({…})</code> | | <code>null</code> |
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| [named_ports](variables.tf#L73) | Named ports. | <code>map(number)</code> | | <code>null</code> |
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| [regional](variables.tf#L84) | Use regional instance group. When set, `location` should be set to the region. | <code>bool</code> | | <code>false</code> |
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| [stateful_config](variables.tf#L90) | Stateful configuration can be done by individual instances or for all instances in the MIG. They key in per_instance_config is the name of the specific instance. The key of the stateful_disks is the 'device_name' field of the resource. Please note that device_name is defined at the OS mount level, unlike the disk name. | <code title="object({ per_instance_config = map(object({ stateful_disks = map(object({ source = string mode = string # READ_WRITE | READ_ONLY delete_rule = string # NEVER | ON_PERMANENT_INSTANCE_DELETION })) metadata = map(string) update_config = object({ minimal_action = string # NONE | REPLACE | RESTART | REFRESH most_disruptive_allowed_action = string # REPLACE | RESTART | REFRESH | NONE remove_instance_state_on_destroy = bool }) })) mig_config = object({ stateful_disks = map(object({ delete_rule = string # NEVER | ON_PERMANENT_INSTANCE_DELETION })) }) })">object({…})</code> | | <code>null</code> |
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| [target_pools](variables.tf#L121) | Optional list of URLs for target pools to which new instances in the group are added. | <code>list(string)</code> | | <code>[]</code> |
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| [target_size](variables.tf#L127) | Group target size, leave null when using an autoscaler. | <code>number</code> | | <code>null</code> |
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| [update_policy](variables.tf#L133) | Update policy. Type can be 'OPPORTUNISTIC' or 'PROACTIVE', action 'REPLACE' or 'restart', surge type 'fixed' or 'percent'. | <code title="object({ type = string # OPPORTUNISTIC | PROACTIVE minimal_action = string # REPLACE | RESTART min_ready_sec = number max_surge_type = string # fixed | percent max_surge = number max_unavailable_type = string max_unavailable = number })">object({…})</code> | | <code>null</code> |
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| [versions](variables.tf#L147) | Additional application versions, target_type is either 'fixed' or 'percent'. | <code title="map(object({ instance_template = string target_type = string # fixed | percent target_size = number }))">map(object({…}))</code> | | <code>null</code> |
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| [wait_for_instances](variables.tf#L157) | Wait for all instances to be created/updated before returning. | <code>bool</code> | | <code>null</code> |
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## Outputs
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| name | description | sensitive |
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|---|---|:---:|
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| [autoscaler](outputs.tf#L17) | Auto-created autoscaler resource. | |
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| [group_manager](outputs.tf#L26) | Instance group resource. | |
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| [health_check](outputs.tf#L35) | Auto-created health-check resource. | |
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<!-- END TFDOC -->
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## TODO
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- [✓] add support for instance groups
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