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.
This module can be coupled with the compute-vm module which can manage instance templates, and the 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.
Stateful disks can be created directly, as shown in the last example below.
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.
module "cos-nginx" {
source = "./fabric/modules/cloud-config-container/nginx"
}
module "nginx-template" {
source = "./fabric/modules/compute-vm"
project_id = var.project_id
name = "nginx-template"
zone = "europe-west1-b"
tags = ["http-server", "ssh"]
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"
}
}
create_template = true
metadata = {
user-data = module.cos-nginx.cloud_config
}
}
module "nginx-mig" {
source = "./fabric/modules/compute-mig"
project_id = "my-project"
location = "europe-west1-b"
name = "mig-test"
target_size = 2
instance_template = module.nginx-template.template.self_link
}
# tftest modules=2 resources=2If 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:
module "cos-nginx" {
source = "./fabric/modules/cloud-config-container/nginx"
}
module "nginx-template" {
source = "./fabric/modules/compute-vm"
project_id = var.project_id
name = "nginx-template"
zone = "europe-west1-b"
tags = ["http-server", "ssh"]
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"
}
}
create_template = true
metadata = {
user-data = module.cos-nginx.cloud_config
}
}
module "nginx-mig" {
source = "./fabric/modules/compute-mig"
project_id = "my-project"
location = "europe-west1-b"
name = "mig-test"
target_size = 3
instance_template = module.nginx-template.template.self_link
versions = {
canary = {
instance_template = module.nginx-template.template.self_link
target_size = {
fixed = 1
}
}
}
}
# tftest modules=2 resources=2Autohealing policies can use an externally defined health check, or have this module auto-create one:
module "cos-nginx" {
source = "./fabric/modules/cloud-config-container/nginx"
}
module "nginx-template" {
source = "./fabric/modules/compute-vm"
project_id = var.project_id
name = "nginx-template"
zone = "europe-west1-b"
tags = ["http-server", "ssh"]
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"
}
}
create_template = true
metadata = {
user-data = module.cos-nginx.cloud_config
}
}
module "nginx-mig" {
source = "./fabric/modules/compute-mig"
project_id = "my-project"
location = "europe-west1-b"
name = "mig-test"
target_size = 3
instance_template = module.nginx-template.template.self_link
auto_healing_policies = {
initial_delay_sec = 30
}
health_check_config = {
enable_logging = true
http = {
port = 80
}
}
}
# tftest modules=2 resources=3The 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.
module "cos-nginx" {
source = "./fabric/modules/cloud-config-container/nginx"
}
module "nginx-template" {
source = "./fabric/modules/compute-vm"
project_id = var.project_id
name = "nginx-template"
zone = "europe-west1-b"
tags = ["http-server", "ssh"]
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"
}
}
create_template = true
metadata = {
user-data = module.cos-nginx.cloud_config
}
}
module "nginx-mig" {
source = "./fabric/modules/compute-mig"
project_id = "my-project"
location = "europe-west1-b"
name = "mig-test"
target_size = 3
instance_template = module.nginx-template.template.self_link
autoscaler_config = {
max_replicas = 3
min_replicas = 1
cooldown_period = 30
scaling_signals = {
cpu_utilization = {
target = 0.65
}
}
}
}
# tftest modules=2 resources=3module "cos-nginx" {
source = "./fabric/modules/cloud-config-container/nginx"
}
module "nginx-template" {
source = "./fabric/modules/compute-vm"
project_id = var.project_id
name = "nginx-template"
zone = "europe-west1-b"
tags = ["http-server", "ssh"]
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"
}
}
create_template = true
metadata = {
user-data = module.cos-nginx.cloud_config
}
}
module "nginx-mig" {
source = "./fabric/modules/compute-mig"
project_id = "my-project"
location = "europe-west1-b"
name = "mig-test"
target_size = 3
instance_template = module.nginx-template.template.self_link
update_policy = {
minimal_action = "REPLACE"
type = "PROACTIVE"
min_ready_sec = 30
max_surge = {
fixed = 1
}
}
}
# tftest modules=2 resources=2Stateful MIGs have some limitations documented here. Enforcement of these requirements is the responsibility of users of this module.
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.
An example using only the configuration at the MIG level can be seen below.
Note that when referencing the stateful disk, you use device_name and not disk_name.
module "cos-nginx" {
source = "./fabric/modules/cloud-config-container/nginx"
}
module "nginx-template" {
source = "./fabric/modules/compute-vm"
project_id = var.project_id
name = "nginx-template"
zone = "europe-west1-b"
tags = ["http-server", "ssh"]
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"
}
}
attached_disks = [{
name = "repd-1"
size = null
source_type = "attach"
source = "regions/${var.region}/disks/repd-test-1"
options = {
mode = "READ_ONLY"
replica_zone = "${var.region}-c"
type = "PERSISTENT"
}
}]
create_template = true
metadata = {
user-data = module.cos-nginx.cloud_config
}
}
module "nginx-mig" {
source = "./fabric/modules/compute-mig"
project_id = "my-project"
location = "europe-west1-b"
name = "mig-test"
target_size = 3
instance_template = module.nginx-template.template.self_link
autoscaler_config = {
max_replicas = 3
min_replicas = 1
cooldown_period = 30
scaling_signals = {
cpu_utilization = {
target = 0.65
}
}
}
stateful_disks = {
repd-1 = false
}
}
# tftest modules=2 resources=3
Here is an example defining the stateful config at the instance level.
Note that you will need to know the instance name in order to use this configuration.
module "cos-nginx" {
source = "./fabric/modules/cloud-config-container/nginx"
}
module "nginx-template" {
source = "./fabric/modules/compute-vm"
project_id = var.project_id
name = "nginx-template"
zone = "europe-west1-b"
tags = ["http-server", "ssh"]
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"
}
}
attached_disks = [{
name = "repd-1"
size = null
source_type = "attach"
source = "regions/${var.region}/disks/repd-test-1"
options = {
mode = "READ_ONLY"
replica_zone = "${var.region}-c"
type = "PERSISTENT"
}
}]
create_template = true
metadata = {
user-data = module.cos-nginx.cloud_config
}
}
module "nginx-mig" {
source = "./fabric/modules/compute-mig"
project_id = "my-project"
location = "europe-west1-b"
name = "mig-test"
target_size = 3
instance_template = module.nginx-template.template.self_link
autoscaler_config = {
max_replicas = 3
min_replicas = 1
cooldown_period = 30
scaling_signals = {
cpu_utilization = {
target = 0.65
}
}
}
stateful_config = {
# name needs to match a MIG instance name
instance-1 = {
minimal_action = "NONE",
most_disruptive_allowed_action = "REPLACE"
preserved_state = {
disks = {
persistent-disk-1 = {
source = "test-disk",
}
}
metadata = {
foo = "bar"
}
}
}
}
}
# tftest modules=2 resources=4
| name | description | type | required | default |
|---|---|---|---|---|
| instance_template | Instance template for the default version. | string |
✓ | |
| location | Compute zone or region. | string |
✓ | |
| name | Managed group name. | string |
✓ | |
| project_id | Project id. | string |
✓ | |
| all_instances_config | Metadata and labels set to all instances in the group. | object({…}) |
null |
|
| auto_healing_policies | Auto-healing policies for this group. | object({…}) |
null |
|
| autoscaler_config | Optional autoscaler configuration. | object({…}) |
null |
|
| default_version_name | Name used for the default version. | string |
"default" |
|
| description | Optional description used for all resources managed by this module. | string |
"Terraform managed." |
|
| distribution_policy | DIstribution policy for regional MIG. | object({…}) |
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({…}) |
null |
|
| named_ports | Named ports. | map(number) |
null |
|
| stateful_config | Stateful configuration for individual instances. | map(object({…})) |
{} |
|
| stateful_disks | Stateful disk configuration applied at the MIG level to all instances, in device name => on permanent instance delete rule as boolean. | map(bool) |
{} |
|
| target_pools | Optional list of URLs for target pools to which new instances in the group are added. | list(string) |
[] |
|
| target_size | Group target size, leave null when using an autoscaler. | number |
null |
|
| update_policy | Update policy. Minimal action and type are required. | object({…}) |
null |
|
| versions | Additional application versions, target_size is optional. | map(object({…})) |
{} |
|
| wait_for_instances | Wait for all instances to be created/updated before returning. | object({…}) |
null |
| name | description | sensitive |
|---|---|---|
| autoscaler | Auto-created autoscaler resource. | |
| group_manager | Instance group resource. | |
| health_check | Auto-created health-check resource. |