This topic describes instance management in Auto Scaling.

Instance management operations

In Auto Scaling, you can manually add or remove instances of Alibaba Cloud services, set instance status such as Protected and Standby in a scaling group, and query instances.

Impacts of instance interruption

Auto Scaling uses instances of other Alibaba Cloud services. You can manage these instances in their consoles. For example, you can delete Elastic Compute Service (ECS) instances that Auto Scaling automatically created in the ECS console. However, the deletion operation interrupts the instances. If instances are interrupted due to operations or system failures, Auto Scaling responds to the instance interruption as described in the following table.

Resource Instance management operation Processing method
ECS A user deletes an ECS instance from a scaling group by using the ECS console or calling API operations. If the Health Check feature is enabled, Auto Scaling checks whether an ECS instance is healthy based on the status of the ECS instance. Auto Scaling removes the ECS instance if the ECS instance is considered unhealthy. The internal IP address of the ECS instance that is removed from the scaling group cannot be automatically deleted from the whitelist of the associated ApsaraDB RDS instance. If the difference between the total number of ECS instances that is specified by Total Capacity and the number of ECS instances that you determine to remove is less than the value of the MinSize parameter, Auto Scaling automatically creates ECS instances to maintain the required minimum number in the scaling group. For more information about the Health Check feature, see Instance health check.
ECS A user revokes the ECS API permissions granted to Auto Scaling. Auto Scaling rejects all scaling activity requests.
SLB A user manually removes an ECS instance from a Server Load Balancer (SLB) instance by using the SLB console or calling API operations. Auto Scaling does not automatically detect this operation or handle this exception. The ECS instance remains in the scaling group. When a scale-in activity is triggered, Auto Scaling releases the ECS instance if the instance meets the removal policy.
SLB A user manually deletes an SLB instance or disables the Health Check feature for an SLB instance by using the SLB console or calling API operations. Auto Scaling does not add ECS instances to the scaling group that is associated with the SLB instance. Auto Scaling removes ECS instances from the scaling group if a scaling task triggers a scale-in rule or the ECS instances are considered unhealthy after a health check is performed.
SLB An SLB instance becomes unavailable due to reasons such as overdue payments or system failures. All scaling activities fail except for scale-in activities that are manually executed.
SLB A user revokes the SLB API permissions granted to Auto Scaling. Auto Scaling rejects all scaling activity requests for the scaling group that is associated with the SLB instance.
ApsaraDB RDS A user manually removes the IP address of an ECS instance from the whitelist of the associated ApsaraDB RDS instance by using the ApsaraDB RDS console or calling API operations. Auto Scaling does not automatically detect this operation or handle this exception. The ECS instance remains in the scaling group. When a scale-in activity is triggered, Auto Scaling releases the ECS instance if the instance meets the removal policy.
ApsaraDB RDS A user manually deletes an ApsaraDB RDS instance by using the ApsaraDB RDS console or calling API operations. Auto Scaling does not add ECS instances to the scaling group that is associated with the ApsaraDB RDS instance. Auto Scaling removes ECS instances from the scaling group if a scaling task triggers a scale-in rule or the ECS instances are considered unhealthy after a health check is performed.
ApsaraDB RDS An ApsaraDB RDS instance becomes unavailable due to reasons such as overdue payments or system failures. All scaling activities fail except for scale-in activities that are manually executed.
ApsaraDB RDS A user revokes the ApsaraDB RDS API permissions granted to Auto Scaling. Auto Scaling rejects all scaling activity requests for the scaling group that is associated with the ApsaraDB RDS instance.