Amazon EC2 Auto Scaling
User Guide

Add a Scaling Policy to an Existing Auto Scaling Group

Use the console to add a scaling policy to an existing Auto Scaling group. A scaling policy is used to increase and decrease the number of running EC2 instances in the group dynamically to meet changing conditions. For more information, see Dynamic Scaling for Amazon EC2 Auto Scaling.

To update an Auto Scaling group with scaling based on metrics

  1. Open the Amazon EC2 console at https://console.aws.amazon.com/ec2/.

  2. On the navigation pane, under Auto Scaling, choose Auto Scaling Groups.

  3. Select the Auto Scaling group.

  4. On the Scaling Policies tab, choose Add policy.

    The page displays all the available resources.

  5. If you are adding a target tracking scaling policy, use the following steps. If you are using a simple or step scaling policy, skip to the next step.

    1. For Name, type a name for the policy.

    2. Choose a Metric type and specify a Target value for the metric.

    3. Specify an instance warm-up value for Instances need, which allows you to control the amount of time until a newly launched instance can contribute to the CloudWatch metrics.

    4. Check the Disable scale-in option if you only want a scale-out policy created. This allows you to create a separate scale-in policy if wanted.

    5. Choose Create.

  6. If you are using a step scaling policy, choose Create a scaling policy with steps, and then do the following:

    Note

    We recommend that you use the option to create scaling policies with steps. To use a simple scaling policy, choose Create a simple scaling policy instead. For more information about simple scaling, see Simple and Step Scaling Policies for Amazon EC2 Auto Scaling.

    1. For Name, type a name for the policy, and then choose Create new alarm.

    2. On the Create Alarm page, choose create topic. For Send a notification to, type a name for the SNS topic. For With these recipients, type one or more email addresses to receive notification. You can replace the default name for your alarm with a custom name. Next, specify the metric and the criteria for the alarm, using Whenever, Is, and For at least. Choose Create Alarm.

    3. Specify the scaling activity for the policy using Take the action. By default, the lower bound for this step adjustment is the alarm threshold and the upper bound is null (positive infinity). To add another step adjustment, choose Add step.

    4. Specify an instance warm-up value for Instances need, which allows you to control the amount of time until a newly launched instance can contribute to the CloudWatch metrics.

    5. Choose Create.