Create a MIG with autoscaling enabled

Console

1. In the console, go to the Instance groups page.

   Go to Instance groups

   The remaining steps appear in the Google Cloud console.

2. If you have an instance group, select it and click Edit. If you don't have an instance group, click Create instance group.
3. For a new instance group, assign a name, then choose an instance template for the instance group or create a new one.
4. If no autoscaling configuration exists, under Autoscaling, click Configure autoscaling.
5. Under Autoscaling mode, select On: add and remove instances to the group to enable autoscaling.
6. Specify the minimum and maximum numbers of instances that you want the autoscaler to create in this group.
7. In the Autoscaling metrics section, if an existing CPU utilization metric does not yet exist, add one:
   1. Click Add metric.
   2. Under Metric type, select CPU utilization.
   3. Enter the Target CPU utilization that you want. This value is treated as a percentage. For example, for 75% CPU utilization, enter 75.
   4. Under Predictive autoscaling, select Off. To learn more about predictive autoscaling, and whether it is suitable for your workload, see Scaling based on predictions.
   5. Click Done.
8. You can use the Initialization period to set the initialization period, which tells the autoscaler how long it takes for your application to initialize. Specifying an accurate initialization period improves autoscaler decisions. For example, when scaling out, the autoscaler ignores data from VMs that are still initializing because those VMs might not yet represent normal usage of your application. The default initialization period is 60 seconds.
9. To create the MIG, click Create.

gcloud

Before you can enable autoscaling, you must create a MIG. Follow the instructions to create a MIG with VMs confined to a single zone or create a MIG with VMs spread across multiple zones in a region.

Then use the set-autoscaling sub-command to enable autoscaling for the group. For example, the following command creates an autoscaler that has a target CPU utilization of 60%. Along with the --target-cpu-utilization parameter, the --max-num-replicas parameter is also required when creating an autoscaler.

Optionally, you can set the --min-num-replicas indicating the minimum number of VMs that you want in the group. If you don't set the minimum, by default, MIG sets this value to 2.

You can use the --cool-down-period flag to set the initialization period, which tells the autoscaler how long it takes for your application to initialize. Specifying an accurate initialization period improves autoscaler decisions. For example, when scaling out, the autoscaler ignores data from VMs that are still initializing because those VMs might not yet represent normal usage of your application. The default initialization period is 60 seconds.

gcloud compute instance-groups managed set-autoscaling example-managed-instance-group \
  --max-num-replicas 20 \
  --target-cpu-utilization 0.60 \
  --cool-down-period 90

If you want, you can enable predictive autoscaling to scale out ahead of predicted load. To learn whether predictive autoscaling is suitable for your workload, see Scaling based on predictions.

You can verify that autoscaling is successfully enabled by using the instance-groups managed describe command, which describes the corresponding MIG and provides information about any autoscaling features for that group:

gcloud compute instance-groups managed describe example-managed-instance-group

Terraform

Before you can enable autoscaling, you must create a MIG. Follow the instructions to create a MIG with VMs confined to a single zone or create a MIG with VMs spread across multiple zones in a region.

To configure autoscaling in a MIG, you can use the google_compute_autoscaler resource.

The following sample configures autoscaling based on CPU utilization in a zonal MIG.

resource "google_compute_autoscaler" "default" {
  name   = "example-autoscaler"
  zone   = "us-central1-f"
  target = google_compute_instance_group_manager.default.id

  autoscaling_policy {
    max_replicas    = 20
    min_replicas    = 0
    cooldown_period = 90

    cpu_utilization {
      target = 0.60
    }
  }
}

To learn how to apply or remove a Terraform configuration, see Basic Terraform commands.

REST

Before you can enable autoscaling, you must create a MIG with VMs confined to a single zone or create a MIG with VMs spread across multiple zones in a region.

If you have a zonal MIG, make a POST request to the autoscalers.insert method. If you have a regional MIG, use the regionAutoscalers.insert method.

For example:

POST https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/zones/ZONE/autoscalers/

Your request body must contain the name, target, and autoscalingPolicy fields. The autoscalingPolicy field must define your target cpuUtilization value and maxNumReplicas value.

Optionally, you can set the minNumReplicas indicating the minimum number of VMs that you want in the group. If you don't set the minimum, by default, MIG sets this value to 2.

You can use the coolDownPeriodSec field to set the initialization period, which tells the autoscaler how long it takes for your application to initialize. Specifying an accurate initialization period improves autoscaler decisions. For example, when scaling out, the autoscaler ignores data from VMs that are still initializing because those VMs might not yet represent normal usage of your application. The default initialization period is 60 seconds.

{
  "name": "example-autoscaler",
  "target": "https://www.googleapis.com/compute/v1/projects/myproject/zones/us-central1-f/instanceGroupManagers/example-managed-instance-group",
  "autoscalingPolicy": {
    "maxNumReplicas": 10,
    "cpuUtilization": {
      "utilizationTarget": 0.6
    },
    "coolDownPeriodSec": 90
  }
}

If you want, you can enable predictive autoscaling to scale out ahead of predicted load. To learn whether predictive autoscaling is suitable for your workload, see Scaling based on predictions.