Scheduled instance group scaling with Terraform

Written by

Yandex Cloud

Updated at March 6, 2025

Get your cloud ready
- Required paid resources
Create an infrastructure
Test instance group scaling
How to delete the resources you created

To set up scheduled scaling for an instance group using Terraform:

If you no longer need the resources you created, delete them.

Get your cloud ready

Go to the management console and log in to Yandex Cloud or create an account if you do not have one yet.
On the Yandex Cloud Billing page, make sure you have a billing account linked and it has the ACTIVE or TRIAL_ACTIVE status. If you do not have a billing account, create one.

If you have an active billing account, you can go to the cloud page to create or select a folder for your infrastructure to operate in.

Learn more about clouds and folders.

Required paid resources

The infrastructure support costs include:

Fee for disks and continuously running VMs (see Compute Cloud pricing).
Function calls, computing resources allocated to executing the function, and outgoing traffic (see Cloud Functions pricing).

With Terraform, you can quickly create a cloud infrastructure in Yandex Cloud and manage it using configuration files. These files store the infrastructure description written in HashiCorp Configuration Language (HCL). If you change the configuration files, Terraform automatically detects which part of your configuration is already deployed, and what should be added or removed.

Terraform is distributed under the Business Source License. The Yandex Cloud provider for Terraform is distributed under the MPL-2.0 license.

For more information about the provider resources, see the documentation on the Terraform website or mirror website.

Create an infrastructure with Terraform:

Install Terraform and specify the Yandex Cloud provider installation source (see Configure a provider, step 1).

Prepare your infrastructure description files:

Ready-made configuration

Manually

Clone the repository with configuration files.

git clone https://github.com/yandex-cloud-examples/yc-vm-group-scheduled-scaling

Navigate to the repository directory. Make sure it contains the following files:
- vm-scale-scheduled.tf: New infrastructure configuration.
- vm-scale-scheduled.auto.tfvars: User data file.
- vm-scale-scheduled-function.zip: Cloud Functions function code archive.

Create a folder.

In this folder, create:

vm-scale-scheduled.tf: New infrastructure configuration file:

vm-scale-scheduled.tf

# Declaring variables for confidential parameters

variable "folder_id" {
  type = string
}

variable "username" {
  type = string
}

variable "ssh_key_path" {
  type = string
}

# Configuring a provider

terraform {
  required_providers {
    yandex = {
      source  = "yandex-cloud/yandex"
      version = ">= 0.47.0"
    }
  }
}

provider "yandex" {
  folder_id = var.folder_id
}

# Creating a service account and assigning roles to it

resource "yandex_iam_service_account" "vm-scale-scheduled-sa" {
  name      = "vm-scale-scheduled-sa"
}

resource "yandex_resourcemanager_folder_iam_member" "vm-scale-scheduled-sa-role-compute" {
  folder_id = var.folder_id
  role      = "compute.editor"
  member    = "serviceAccount:${yandex_iam_service_account.vm-scale-scheduled-sa.id}"
}

resource "yandex_resourcemanager_folder_iam_member" "vm-scale-scheduled-sa-role-iam" {
  folder_id = var.folder_id
  role      = "iam.serviceAccounts.user"
  member    = "serviceAccount:${yandex_iam_service_account.vm-scale-scheduled-sa.id}"
}

resource "yandex_resourcemanager_folder_iam_member" "vm-scale-scheduled-sa-role-functions" {
  folder_id = var.folder_id
  role      = "functions.functionInvoker"
  member    = "serviceAccount:${yandex_iam_service_account.vm-scale-scheduled-sa.id}"
}

# Creating a cloud network and subnets

resource "yandex_vpc_network" "vm-scale-scheduled-network" {
  name = "vm-scale-scheduled-network"
}

resource "yandex_vpc_subnet" "vm-scale-scheduled-subnet-a" {
  name           = "vm-scale-scheduled-subnet-a"
  zone           = "ru-central1-a"
  v4_cidr_blocks = ["192.168.1.0/24"]
  network_id     = yandex_vpc_network.vm-scale-scheduled-network.id
}

resource "yandex_vpc_subnet" "vm-scale-scheduled-subnet-b" {
  name           = "vm-scale-scheduled-subnet-b"
  zone           = "ru-central1-b"
  v4_cidr_blocks = ["192.168.2.0/24"]
  network_id     = yandex_vpc_network.vm-scale-scheduled-network.id
}

# Creating an image

resource "yandex_compute_image" "vm-scale-scheduled-image" {
  source_family = "ubuntu-2004-lts"
}

# Creating an instance group

resource "yandex_compute_instance_group" "vm-scale-scheduled-ig" {
  name               = "vm-scale-scheduled-ig"
  service_account_id = yandex_iam_service_account.vm-scale-scheduled-sa.id

  allocation_policy {
    zones = [
      "ru-central1-a",
      "ru-central1-b"
    ]
  }

  instance_template {
    boot_disk {
      mode = "READ_WRITE"
      initialize_params {
        image_id = yandex_compute_image.vm-scale-scheduled-image.id
        size     = 15
      }
    }

    platform_id = "standard-v3"
    resources {
      cores         = 2
      core_fraction = 20
      memory        = 2
    }

    network_interface {
      network_id = yandex_vpc_network.vm-scale-scheduled-network.id
      subnet_ids = [
        yandex_vpc_subnet.vm-scale-scheduled-subnet-a.id,
        yandex_vpc_subnet.vm-scale-scheduled-subnet-b.id
      ]
    }

    metadata = {
      user-data = "#cloud-config\nusers:\n  - name: ${var.username}\n    groups: sudo\n    shell: /bin/bash\n    sudo: 'ALL=(ALL) NOPASSWD:ALL'\n    ssh_authorized_keys:\n      - ${file("${var.ssh_key_path}")}"
    }
  }

  scale_policy {
    fixed_scale {
      size = 2
    }
  }

  deploy_policy {
    max_unavailable = 2
    max_creating    = 2
    max_expansion   = 2
    max_deleting    = 2
  }

  depends_on = [
    yandex_resourcemanager_folder_iam_member.vm-scale-scheduled-sa-role-compute,
    yandex_resourcemanager_folder_iam_member.vm-scale-scheduled-sa-role-iam
  ]
}

# Creating a function

resource "yandex_function" "vm-scale-scheduled-function" {
  name               = "vm-scale-scheduled-function"
  runtime            = "bash"

  user_hash          = "function-v1"
  entrypoint         = "handler.sh"
  content {
    zip_filename = "vm-scale-scheduled-function.zip"
  }

  execution_timeout  = "60"
  memory             = "128"
  service_account_id = yandex_iam_service_account.vm-scale-scheduled-sa.id

  environment = {
    IG_NAME      = yandex_compute_instance_group.vm-scale-scheduled-ig.name
    IG_BASE_SIZE = "2"
    FOLDER_ID    = var.folder_id
  }

  depends_on = [
    yandex_resourcemanager_folder_iam_member.vm-scale-scheduled-sa-role-functions
  ]
}

# Creating a trigger

resource "yandex_function_trigger" "vm-scale-scheduled-trigger" {
  name = "vm-scale-scheduled-trigger"
  timer {
    cron_expression = "*/2 * * * ? *"
  }
  function {
    id                 = yandex_function.vm-scale-scheduled-function.id
    tag                = "$latest"
    service_account_id = yandex_iam_service_account.vm-scale-scheduled-sa.id
  }

  depends_on = [
    yandex_resourcemanager_folder_iam_member.vm-scale-scheduled-sa-role-functions
  ]
}

vm-scale-scheduled.auto.tfvars: User data file:

vm-scale-scheduled.auto.tfvars

folder_id    = "<folder_ID>"
username     = "<VM_username>"
ssh_key_path = "<path_to_public_SSH_key>"

handler.sh file with the Cloud Functions function code:

handler.sh

Warning

If you are creating a file in Windows, make sure that newline characters are in \n Unix format rather than \r\n. You can replace line breaks in a text editor, such as Notepad++, or with such tools as dos2unix or Tofrodos.

# Get ID and current size of the instance group
IG_SPEC=$(yc compute instance-group get --name $IG_NAME --folder-id $FOLDER_ID --format json)
IG_ID=$(jq -r ".id" <<< $IG_SPEC)
IG_SIZE=$(jq -r ".scale_policy.fixed_scale.size" <<< $IG_SPEC)

# Calculate new size for the instance group
if [ $IG_SIZE = $IG_BASE_SIZE ]; then
    IG_SIZE="$(($IG_BASE_SIZE + 1))"
else
    IG_SIZE=$IG_BASE_SIZE
fi

# Update the instance group
yc compute instance-group update --id $IG_ID --scale-policy-fixed-scale-size $IG_SIZE

In the same folder, create the vm-scale-scheduled-function.zip archive with handler.sh.

For more information about the properties of Terraform resources, see the relevant Terraform guides:

In the vm-scale-scheduled.auto.tfvars file, set the following user-defined properties:
- folder_id: Resource folder ID.
- username: VM user name.
- ssh_key_path: Path to the public SSH key required to authenticate the user on the VM. You can create a key pair by following this guide.
Create the resources:
1. In the terminal, change to the folder where you edited the configuration file.
2. Make sure the configuration file is correct using the command:
```
terraform validate
```
  If the configuration is correct, the following message is returned:
```
Success! The configuration is valid.
```
3. Run the command:
```
terraform plan
```
  The terminal will display a list of resources with parameters. No changes are made at this step. If the configuration contains errors, Terraform will point them out.
4. Apply the configuration changes:
```
terraform apply
```
5. Confirm the changes: type yes in the terminal and press Enter.

Once you created the infrastructure, test your instance group scaling.

Test instance group scaling

Management console

CLI

API

In the management console, select example-folder.
In the list of services, select Compute Cloud.
In the left-hand panel, select Instance groups.
Select the vm-scale-scheduled-ig group.
Under VM states, make sure the number of instances changes every two minutes: increases from 2 to 3, then decreases from 3 to 2, etc. You can also check if the instance group has been updated by opening the Operations tab.

Run the following command several times:

yc compute instance-group get vm-scale-scheduled-ig \
  --folder-name example-folder

Result:

id: cl1l0ljqbmkp********
folder_id: b1g9hv2loamq********
created_at: "2022-03-28T13:24:20.693Z"
...
managed_instances_state:
  target_size: "2"
  running_actual_count: "2"
...

The value of the target_size field for the group should change from 2 to 3 and back.

Get information about the vm-scale-scheduled-ig instance group multiple times using the get REST API method for the InstanceGroup resource or the InstanceGroupService/Get gRPC API call. The value of the target_size field for the group should change from 2 to 3 and back.

How to delete the resources you created

To stop paying for the resources you created:

Open the vm-scale-scheduled.tf configuration file and delete your infrastructure description from it.
Apply the changes:
1. In the terminal, change to the folder where you edited the configuration file.
2. Make sure the configuration file is correct using the command:
```
terraform validate
```
  If the configuration is correct, the following message is returned:
```
Success! The configuration is valid.
```
3. Run the command:
```
terraform plan
```
  The terminal will display a list of resources with parameters. No changes are made at this step. If the configuration contains errors, Terraform will point them out.
4. Apply the configuration changes:
```
terraform apply
```
5. Confirm the changes: type yes in the terminal and press Enter.

Scheduled instance group scaling with Terraform

Get your cloud ready

Required paid resources

Create an infrastructure

Test instance group scaling

How to delete the resources you created

See also

Was the article helpful?

Scheduled instance group scaling with Terraform

Get your cloud readyGet your cloud ready

Required paid resourcesRequired paid resources

Create an infrastructureCreate an infrastructure

Test instance group scalingTest instance group scaling

How to delete the resources you createdHow to delete the resources you created

See alsoSee also

Was the article helpful?

Get your cloud ready

Required paid resources

Create an infrastructure

Test instance group scaling

How to delete the resources you created

See also