When the workload on your resources decreases, the scaling group initiates a scale-in activity based on your configuration. During a scale-in, the scaling group reclaims removed instances based on the preset Instance Reclamation Mode. This topic describes how to configure the Instance Reclamation Mode.
Instance reclamation modes
After a scale-in activity is triggered, the scaling group removes instances based on the configured Scaling Policy and Scale-in Policy. The removed instances are then reclaimed based on the Instance Reclamation Mode. The following instance reclamation modes are supported.
You can configure this setting only when the scaling group type is ECS and the network type is VPC.
If the scaling group type is ECI, you cannot configure the Instance Reclamation Mode. For ECI scaling groups, the default Instance Reclamation Mode is Release Mode.
Release Mode
In this mode, Auto Scaling stops the instances during a scale-in activity. After the instances are stopped, they are released. If an instance fails to stop within the timeout period, it is forcibly released. No resources are retained. During a scale-out, Auto Scaling creates new instances and adds them to the scaling group.
Forced Release Mode
In this mode, Auto Scaling forcibly releases instances that are in the Running (
Running) state during a scale-in activity. Forcibly releasing an instance is similar to a power outage. This action erases temporary data in the instance's memory and storage. This data cannot be recovered. Use this mode with caution.Stop And Reclaim Mode
In this mode, removed ECS instances are stopped, which enables the economical mode. Some resources are retained, and you are billed for them. During a scale-out, Auto Scaling prioritizes adding the stopped ECS instances to the scaling group before it creates new instances. This mode improves the efficiency of scaling activities. For more information, see Improve scaling efficiency using the economical mode.
Forced Stop And Reclaim Mode
In this mode, instances that are in the Running (
Running) state are forcibly stopped during a scale-in activity. A forced stop is similar to a power outage. This action erases temporary data in the instance's memory and storage. This data cannot be recovered.
Do not store application data or logs on instances to prevent data loss after the instances are reclaimed.
Stopped instances may be released in the following situations:
If you manually decrease the maximum number of instances in a scaling group to trigger a scale-in, Auto Scaling releases the stopped ECS instances first.
A stopped instance may fail to be added to a scaling group due to insufficient inventory or an overdue payment. If the instance cannot be added, it is released.
The Stop and Reclaim Mode is affected by the economical mode for pay-as-you-go instances. For more information, see Economical mode.
Configure an instance reclamation mode
Modify the instance reclamation mode of an existing scaling group
To modify the Instance Reclamation Mode for an existing scaling group, perform the following 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.
On the Scaling Groups page, find the scaling group whose Instance Reclamation Mode you want to modify. In the Actions column, click Details. On the details page, find the scaling configuration section and click the
icon. The Modify Scaling Configuration window appears.Set Instance Reclamation Mode to the desired mode.
Click OK.
Configure the instance reclamation mode when you create a scaling group
When you create a scaling group, you can configure the Instance Reclamation Mode on the creation page, as shown in the following figure.
