Console

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

   Go to Instance groups

2. If you have an instance group, click the name of the instance group, andthen clickEdit. On the edit instance group page, do the following:

   1. ClickGroup size & autosclaing to expand the section.
   2. ClickConfigure autoscaling.

3. If you don't have an instance group, clickCreate instance group anddo the following:

   1. In theName field, specify a name for the group.
   2. In theInstance template list, select a template.

   3. In theLocation section, depending on whether you're creating azonal or regional MIG, choose an option as follows:

      • For a zonal MIG, selectSingle zone, and then select a regionand a zone.
      • For a regional MIG, selectMultiple zones, and then select aregion and zones.

4. In theAutoscaling section, a CPU utilization autoscaling signalis added by default. You can either use the default values for the signalor do the following:

   1. Specify the minimum and the maximum numbers of instances that you wantthe autoscaler to create in this group.

   2. To edit the target CPU utilization, click the CPU utilization signalto expand the section and specify the percentage.

      1. UnderPredictive autoscaling, selectOff. To learn moreabout predictive autoscaling, and whether it is suitable for yourworkload, seeScaling based on predictions.

   3. ClickDone.

5. You can use theInitialization period to tell theautoscaler how long it takes for your application to initialize. Specifying an accurateinitialization period improves autoscaler decisions. For example, when scaling out, theautoscaler ignores data from VMs that are still initializing because those VMsmight not yet represent normal usage of your application. The default initializationperiod is 60 seconds.

6. ClickSave.

gcloud

Use theset-autoscalingsub-command to enable autoscaling for a managed instance group. For example,the following command creates an autoscaler that has a target CPUutilization of 60%. Along with the--target-cpu-utilization parameter,the--max-num-replicas parameter is also required when creating anautoscaler:

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

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

Optionally, you can enable predictive autoscaling to scale out ahead ofpredicted load. To learn whether predictive autoscaling is suitable for yourworkload, seeScaling based on predictions.

You can verify that autoscaling is successfully enabled by using theinstance-groups managed describe sub-command,which describes thecorresponding managed instance group and provides information aboutany autoscaling features for that instance group:

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

For a list of availablegcloud commands and flags, see thegcloud reference.

REST

To create an autoscaler, use theautoscalers.insert methodfor a zonal MIG or theregionAutoscalers.insert methodfor a regional MIG.

The following example creates an autoscaler for a zonal MIG:

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

Your request body must contain thename,target, andautoscalingPolicyfields.autoscalingPolicy must definecpuUtilization andmaxNumReplicas.

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

Optionally, you can enable predictive autoscaling to scale out ahead ofpredicted load. To learn whether predictive autoscaling is suitable for yourworkload, seeScaling based on predictions.

{  "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  }}