Verify a scaling activity for an Auto Scaling group - Amazon EC2 Auto Scaling

Verify a scaling activity for an Auto Scaling group

In the Amazon EC2 Auto Scaling section of the Amazon EC2 console, the Activity history for an Auto Scaling group lets you view the current status of a scaling activity that is currently in progress. When the scaling activity is finished, you can see whether it succeeds or not. This is particularly useful when you are creating Auto Scaling groups or you are adding scaling conditions to existing groups.

When you add a target tracking, step, or simple scaling policy to your Auto Scaling group, Amazon EC2 Auto Scaling immediately starts evaluating the policy against the metric. The metric alarm goes to ALARM state when the metric breaches the threshold for a specified number of evaluation periods. This means that a scaling policy could result in a scaling activity soon after it's created. After Amazon EC2 Auto Scaling adjusts the desired capacity in response to a scaling policy, you can verify the scaling activity in your account. If you want to receive email notification from Amazon EC2 Auto Scaling informing you about a scaling activity, follow the instructions in Amazon SNS notification options for Amazon EC2 Auto Scaling.

Tip

In the following procedure, you look at the Activity history and Instances sections for the Auto Scaling group. In both, the named columns should already be displayed. To display hidden columns or change the number of rows shown, choose the gear icon on the top right corner of each section to open the preferences modal, update the settings as needed, and choose Confirm.

To view the scaling activities for an Auto Scaling group (console)

  1. Open the Amazon EC2 console at https://console.aws.amazon.com/ec2/, and choose Auto Scaling Groups from the navigation pane.

  2. In the navigation bar at the top of the screen, select the Region your Auto Scaling group is in.

  3. Select the check box next to the Auto Scaling group.

    A split pane opens up in the bottom of the page.

  4. On the Activity tab, under Activity history, the Status column shows whether your Auto Scaling group has successfully launched or terminated instances, or whether the scaling activity is still in progress.

  5. (Optional) If you have a lot of scaling activities, you can choose the > icon at the top edge of the activity history to see the next page of scaling activities.

  6. On the Instance management tab, under Instances, the Lifecycle column contains the state of your instances. After the instance starts and any lifecycle hooks have finished, its lifecycle state changes to InService. The Health status column shows the result of the EC2 instance health check on your instance.

To view the scaling activities for an Auto Scaling group (AWS CLI)

Use the following describe-scaling-activities command. 

aws autoscaling describe-scaling-activities --auto-scaling-group-name my-asg

The following is example output.

Scaling activities are ordered by start time. Activities still in progress are described first. 

{
  "Activities": [
    {
      "ActivityId": "5e3a1f47-2309-415c-bfd8-35aa06300799",
      "AutoScalingGroupName": "my-asg",
      "Description": "Terminating EC2 instance: i-06c4794c2499af1df",
      "Cause": "At 2020-02-11T18:34:10Z a monitor alarm TargetTracking-my-asg-AlarmLow-b9376cab-18a7-4385-920c-dfa3f7783f82 in state ALARM triggered policy my-target-tracking-policy changing the desired capacity from 3 to 2.  At 2020-02-11T18:34:31Z an instance was taken out of service in response to a difference between desired and actual capacity, shrinking the capacity from 3 to 2.  At 2020-02-11T18:34:31Z instance i-06c4794c2499af1df was selected for termination.",
      "StartTime": "2020-02-11T18:34:31.268Z",
      "EndTime": "2020-02-11T18:34:53Z",
      "StatusCode": "Successful",
      "Progress": 100,
      "Details": "{\"Subnet ID\":\"subnet-5ea0c127\",\"Availability Zone\":\"us-west-2a\"...}",
      "AutoScalingGroupARN": "arn"
    },
...
  ]
}

For a description of the fields in the output, see Activity in the Amazon EC2 Auto Scaling API Reference.

For help retrieving the scaling activities for a deleted group and for information about the types of errors that you may encounter and how to handle them, see Troubleshoot issues in Amazon EC2 Auto Scaling.