Autoscaling an Instance Group with Custom Cloud Monitoring Metrics

Create bucket and download application files

1. Create a GCS bucket

   export PROJECT_ID=$(gcloud info --format='value(config.project)')
   gsutil mb gs://$PROJECT_ID

2. Copy application files from Google managed project bucket

   gsutil cp -r gs://spls/gsp087/* gs://$PROJECT_ID

Creating an instance template

1. In the Cloud Console, go to Navigation menu > Compute Engine > Instance templates.
2. Click Create Instance Template at the top of the page.
3. Name the instance template autoscaling-instance01.
4. Scroll down, click NETWORKING, DISKS, SECURITY, MANAGEMENT, SOLE-TENANCY to expand the input options.
5. In the Metadata section of the Management tab, enter these metadata keys and values, clicking the + Add item button to add each one. Remember to substitute your bucket name for the [YOUR_BUCKET_NAME] placeholder:
   startup-script-url: gs://[YOUR_BUCKET_NAME]/startup.sh
   gcs-bucket: gs://[YOUR_BUCKET_NAME]
6. Click Create.

Creating the instance group

1. In the left pane, click Instance groups.
   
2. Click Create instance group at the top of the page.
   Name: autoscaling-instance-group-1.
   For Instance template: select the instance template you just created.
   Set Autoscaling mode to Off: do not auto scale. 

    

    

    

3. Click Create.
4. Verify application is running by checking the logs in Cloud Logging
   

Configure autoscaling for the instance group

1. In the Cloud Console, go to Compute Engine > Instance groups.
2. Click the autoscaling-instance-group-1 group.
3. Under Autoscaling click Configure.
4. Set Autoscaling mode to On: add and remove instances to the group.
5. Under Autoscaling metrics click ADD METRIC to edit metric. Set the following fields, leave all others at the default value.
   1. Metric type: Cloud Monitoring metric
   2. Metric export scope: Time series per instance
   3. Metric identifier: custom.googleapis.com/appdemo_queue_depth_01
   4. Utilization target: 150
   5. Utilization target type: Gauge
   6. Minimum number of instances: 1
   7. Maximum number of instances: 3
6. Click Save

Watching the instance group perform autoscaling

1. In the left pane, click Instance groups.
2. Click the builtin-igm instance group in the list.
3. Click the Monitoring tab.
4. Enable Auto Refresh.