The purpose of a scaling rule varies based on its type. You can use a scaling rule to trigger a scaling activity or adjust the boundary values for a scaling group. The boundary values include the minimum number of instances that must be contained in a scaling group and the maximum number of instances that can be contained in a scaling group. This topic describes the types and limits of scaling rules. This topic also describes the operations that you can perform on scaling rules.
Scaling rule types
Auto Scaling supports the following types of scaling rules: simple scaling rules, step scaling rules, target tracking scaling rules, and predictive scaling rules. You can use simple scaling rules, step scaling rules, and target tracking scaling rules to trigger scaling activities. You can use predictive scaling rules to automatically adjust the boundary values for scaling groups. The following items describe the scaling rules based on their purposes.
Limits
The following limits apply to scaling rules:
You can create only a limited number of scaling rules for a scaling group. To view the quota of scaling rules, visit Quota Center.
If the number of instances that are in the In Service state after you execute a scaling rule is greater than the maximum number of instances or less than the minimum number of instances, Auto Scaling automatically adjusts the number of instances to ensure that the number of instances is within the allowed range. Examples:
You have a scaling group named asg-bp19ik2u5w7esjcu**** that can contain up to three instances. You also have a scaling rule named add3 that adds three instances during scale-outs. The scaling group contains two instances that are in the In Service state. If you execute the add3 scaling rule, only one instance is added to the scaling group.
You have a scaling group named asg-bp19ik2u5w7esjcu**** that must contain at least two instances. You also have a scaling rule named reduce2 that removes two instances during scale-ins. The scaling group contains three instances that are in the In Service state. If you execute the reduce2 scaling rule, only one instance is removed from the scaling group.
If you have overdue payments within your Alibaba Cloud account, you cannot execute scaling rules.
Important
To use Auto Scaling, make sure that you have sufficient balance within your Alibaba Cloud account.
Manage scaling rules
The following table describes the operations that you can perform on scaling rules and also provides the related links.
User guide | Operation | API reference |