Basic Concepts

AS Group

An AS group consists of a collection of ECS instances that apply to the same scenario. It is the basis for enabling or disabling AS policies and performing scaling actions.

AS Configuration

An AS configuration is a template specifying specifications for the ECS instances to be added to an AS group. The specifications include the ECS type, vCPUs, memory, image, and disk.

AS Policy

AS policies can trigger scaling actions to adjust the number of instances in an AS group. An AS policy defines the condition to trigger a scaling action and the operation to be performed in a scaling action. When the triggering condition is met, the system automatically triggers a scaling action.

Scaling Action

A scaling action adds instances to or removes instances from an AS group. It ensures that the expected number of instances are running in the AS group by adding or removing instances when the triggering condition is met, which improves system stability.

Cooldown Period

To prevent an alarm-based policy from being repeatedly triggered by the same event, you can set a cooldown period. A cooldown period (in seconds) is the period of time between two scaling actions. AS recounts the cooldown period after a scaling action is complete. During the cooldown period, AS denies all scaling requests triggered by alarm-based policies. Scaling requests triggered manually or by scheduled or periodic policies are not affected.

For example, if you set the cooldown period to 300 seconds (5 minutes), and there is a scaling action scheduled for 10:32, but a previous scaling action was complete at 10:30, any alarm-triggered scaling actions will be denied during the cooldown period from 10:30 to 10:35, but the scheduled scaling action will still be triggered at 10:32. If the scheduled scaling action ends at 10:36, a new cooldown period starts at 10:36 and ends at 10:41.

Bandwidth Scaling

AS automatically adjusts a bandwidth based on the scaling policies you configured.

After you configure a scaling policy as needed, when the trigger condition is met, AS automatically increases, decreases, or sets the bandwidth to a specified value based on the policy you configured. Three types of bandwidth scaling policies are available, including the alarm, scheduled, and periodic policy.