Set an instance maintenance policy on your Auto Scaling group - Amazon EC2 Auto Scaling
Set an instance maintenance policyRemove an instance maintenance policy

Set an instance maintenance policy on your Auto Scaling group

You can create an instance maintenance policy when you create an Auto Scaling group. You can also create it for existing groups.

By setting an instance maintenance policy on your Auto Scaling group, you no longer have to specify values for minimum and maximum healthy percentage parameters for the instance refresh feature unless you want to override the instance maintenance policy.

In the console, Amazon EC2 Auto Scaling provides options to help you get started.

Set an instance maintenance policy

To set an instance maintenance policy on an Auto Scaling group, use one of the following methods:

Console
To set an instance maintenance policy on a new group (console)

  1. Follow the instructions in Create an Auto Scaling group using a launch template and complete each step in the procedure, up to step 11.

  2. On the Configure group size and scaling policies, for Desired capacity, enter the initial number of instances to launch.

  3. In the Scaling section, under Scaling limits, if your new value for Desired capacity is greater than Min desired capacity and Max desired capacity, the Max desired capacity is automatically increased to the new desired capacity value. You can change these limits as needed.

  4. For Automatic scaling, choose whether you want to create a target tracking scaling policy. You can also create this policy after your create your Auto Scaling group.

    If you choose Target tracking scaling policy, follow the directions in Create a target tracking scaling policy to create the policy.

  5. In the Instance maintenance policy section, choose one of the available options:

    • Launch before terminating: A new instance must be provisioned first before an existing instance can be terminated. This is a good choice for applications that favor availability over cost savings.

    • Terminate and launch: New instances are provisioned at the same time your existing instances are terminated. This is a good choice for applications that favor cost savings over availability. It's also a good choice for applications that should not launch more capacity than is currently available.

    • Custom policy: This option lets you set up your policy with a custom minimum and maximum range for the amount of capacity that you want available when replacing instances. This can help you achieve the right balance between cost and availability.

  6. For Set healthy percentage, enter values for one or both of the following fields. The enabled fields vary depending on the option that you chose in the preceding step.

    • Min: Sets the minimum healthy percentage that's required to proceed with replacing instances.

    • Max: Sets the maximum healthy percentage that's possible when replacing instances.

  7. Expand the View capacity during replacements based on your desired capacity section to confirm how the values for Min and Max apply to your group. The exact values used depend on the desired capacity value, which will change if the group scales.

  8. Continue with the steps in Create an Auto Scaling group using a launch template.

AWS CLI
To set an instance maintenance policy on a new group (AWS CLI)

Add the --instance-maintenance-policy option to the create-auto-scaling-group command. The following example set an instance maintenance policy on a new Auto Scaling group named my-asg.

aws autoscaling create-auto-scaling-group \
  --launch-template LaunchTemplateName=my-launch-template,Version='1' \
  --auto-scaling-group-name my-asg \
  --min-size 1 \
  --max-size 10 \
  --desired-capacity 5 \
  --default-instance-warmup 20 \
  --instance-maintenance-policy '{
      "MinHealthyPercentage": 90,
      "MaxHealthyPercentage": 120       
    }' \
  --vpc-zone-identifier "subnet-5e6example,subnet-613example,subnet-c93example"
Console
To set an instance maintenance policy on an existing 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. On the navigation bar at the top of the screen, choose the AWS Region that you created your Auto Scaling group 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 Details tab, choose Instance maintenance policy, Edit.

  5. To set an instance maintenance policy on the group, choose one of the available options:

    • Launch before terminating: A new instance must be provisioned first before an existing instance can be terminated. This is a good choice for applications that favor availability over cost savings.

    • Terminate and launch: New instances are provisioned at the same time your existing instances are terminated. This is a good choice for applications that favor cost savings over availability. It's also a good choice for applications that should not launch more capacity than is currently available.

    • Custom policy: This option lets you set up your policy with a custom minimum and maximum range for the amount of capacity that you want available when replacing instances. This can help you achieve the right balance between cost and availability.

  6. For Set healthy percentage, enter values for one or both of the following fields. The enabled fields vary depending on the option that you chose in the preceding step.

    • Min: Sets the minimum healthy percentage that's required to proceed with replacing instances.

    • Max: Sets the maximum healthy percentage that's possible when replacing instances.

  7. Expand the View capacity during replacements based on your desired capacity section to confirm how the values for Min and Max apply to your group. The exact values used depend on the desired capacity value, which will change if the group scales.

  8. Choose Update.

AWS CLI
To set an instance maintenance policy on an existing group (AWS CLI)

Add the --instance-maintenance-policy option to the update-auto-scaling-group command. The following example sets an instance maintenance policy on the specified Auto Scaling group.

aws autoscaling update-auto-scaling-group --auto-scaling-group-name my-asg \
  --instance-maintenance-policy '{
      "MinHealthyPercentage": 90,
      "MaxHealthyPercentage": 120       
    }'

Remove an instance maintenance policy

If you want to stop using an instance maintenance policy with your Auto Scaling group, you can remove it.

Console
To remove an instance maintenance policy (console)

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

  2. On the navigation bar at the top of the screen, choose the AWS Region that you created your Auto Scaling group 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 Details tab, choose Instance maintenance policy, Edit.

  5. Choose No instance maintenance policy.

  6. Choose Update.

AWS CLI
To remove an instance maintenance policy (AWS CLI)

Add the --instance-maintenance-policy option to the update-auto-scaling-group command. The following example removes the instance maintenance policy from the specified Auto Scaling group. 

aws autoscaling update-auto-scaling-group --auto-scaling-group-name my-asg \
  --instance-maintenance-policy '{
      "MinHealthyPercentage": -1,
      "MaxHealthyPercentage": -1       
    }'