When demand for your business resources decreases, a scaling group initiates a scale-in activity as configured. During a scale-in, the scaling group reclaims instances based on the selected Instance Reclaim Mode. This topic describes how to configure the Instance Reclaim Mode.
Instance reclaim modes
After a scale-in activity is triggered, the scaling group removes instances based on the configured Scaling Policy and Scale-In Policy. The scaling group then reclaims the removed instances based on the Instance Reclaim Mode. You can choose from the following modes:
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This setting is available only for scaling groups that contain ECS instances and use a VPC network.
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You cannot configure the Instance Reclaim Mode for scaling groups that contain ECI instances. For ECI scaling groups, the default Instance Reclaim Mode is Release.
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Release
In this mode, Auto Scaling first stops and then releases instances during a scale-in. If an instance fails to stop within the specified period, Auto Scaling forcibly releases it. No resources are retained. During a scale-out activity, Auto Scaling creates new instances and adds them to the scaling group.
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Force Release
In this mode, Auto Scaling forcibly releases instances that are in the Running (
Running) state during a scale-in. A forced release is similar to a power outage and erases all temporary data in the instance's memory and storage. This data is unrecoverable. Use this mode with caution. -
Economical Mode
In this mode, Auto Scaling stops removed ECS instances, which puts them into Economical Mode. Some resources are retained and continue to be billed. During a scale-out activity, Auto Scaling first attempts to add these stopped ECS instances to the scaling group. If more instances are needed, Auto Scaling creates and adds new ones. This mode can improve scaling efficiency. For more information, see Use the Economical Mode feature to scale instances faster.
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Force Economical Mode
In this mode, Auto Scaling forcibly shuts down instances in the Running (
Running) state during a scale-in. A forced shutdown is similar to a power outage and erases all temporary data in the instance's memory and storage. This data is unrecoverable.
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To prevent data loss, do not store application data or logs on instances that can be reclaimed.
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Stopped instances may be released in the following scenarios:
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If you manually reduce the maximum number of instances in a scaling group to trigger a scale-in, Auto Scaling prioritizes releasing stopped ECS instances.
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If an attempt to add a stopped instance to the scaling group fails due to reasons such as insufficient inventory or an overdue payment, Auto Scaling releases the instance.
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The behavior of Economical Mode is affected by the Economical Mode feature for pay-as-you-go instances. For more information, see Economical Mode.
Configure the instance reclaim mode
Existing scaling group
To modify the Instance Reclaim Mode for an existing scaling group, follow these steps.
Log on to the Auto Scaling console.
In the left-side navigation pane, click Scaling Groups.
In the top navigation bar, select the region where Auto Scaling is activated.
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On the Scaling Groups page, find the scaling group for which you want to modify the Instance Reclaim Mode. In the Actions column on the right, click Details to open the details page for the scaling group.
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Find the Instance Reclaim Mode setting and select a mode.
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Click OK to complete the configuration.
New scaling group
You can configure the Instance Reclaim Mode when creating a scaling group in the console.
The instance reclaim mode setting has four options: Release, Economical Mode, Force Release, and Force Economical Mode. This example selects Force Release.