Creating an AS Policy

Scenarios

You can manage instances in an AS group through AS policies. This section describes how to create an AS policy.

Creating an Alarm Policy

  1. Log in to the management console.
  1. Click in the upper left corner to select a region and a project.
  2. Under Computing, click Auto Scaling. In the navigation pane on the left, choose Instance Scaling.
  3. Locate the row containing the target AS group and click View AS Policy in the Operation column.
  4. On the AS Policies page, click Add AS Policy.
  5. Set the parameters listed in Table 1.
    Table 1 AS policy parameters

    Parameter

    Description

    Example Value

    Policy Name

    Specifies the name of the AS policy to be created.

    as-policy-p6g5

    Policy Type

    Select Alarm.

    Alarm Policy

    Alarm Rule

    Specifies whether a new alarm rule is to be created (Create) or an existing alarm rule will be used (Use existing).

    To create an alarm rule, configure the following parameters:
    • Rule Name

      Specifies the name of the new alarm rule, for example, as-alarm-7o1u.

    • Trigger Condition

      Specifies a monitoring metric and condition for triggering a scaling action. For example, when CPU Usage becomes higher than 70%, AS automatically triggers a scaling action.

    • Monitoring Interval

      Specifies the interval (such as five minutes) at which the alarm status is updated based on the alarm rule.

    • Consecutive Occurrences

      Specifies the number of sampling points when an alarm is triggered. If Occurrences is set to n, the sampling points of the alarm rule are the sampling points in n consecutive sampling periods. Only if all the sampling points meet the threshold configured for the alarm rule will the alarm rule status be refreshed as the Alarm status.

    N/A

    Scaling Action

    Specifies an action and the number or percentage of instances.

    The following scaling action options are available:
    • Add

      Adds instances to an AS group when the scaling action is performed.

    • Reduce

      Removes instances from an AS group when the scaling action is performed.

    • Set to

      Sets the expected number of instances in an AS group to a specified value.
    • Add 1 instance
    • Add 10% instances
      The number of instances to be added is 10% of the current number of instances in the AS group. If the product of the current number of instances and the percentage is not an integer, AS automatically rounds the value up or down:
      • If the value is greater than 1, it is rounded down.
      • If the value is greater than 0 but less than 1, it is rounded up to 1.

    Cooldown Period

    To prevent an alarm policy from being repeatedly invoked by the same event, you can set a cooldown period.

    A cooldown period specifies how long any alarm-triggered scaling action will be disallowed after a previous scaling action is complete.

    The cooldown period does not apply to scheduled or periodic scaling actions. However, AS recounts the cooling duration after a scheduled or periodic scaling action is complete.

    For example, suppose that the cooldown period is set to 300 seconds (5 minutes), and a scheduled policy is specified to trigger a scaling action at 10:32, and a previous scaling action triggered by an alarm policy ends at 10:30. Any alarm-triggered scaling action will then be denied during the cooldown period from 10:30 to 10:35, but the scaling action scheduled for 10:32 will still take place. If the scheduled scaling action ends at 10:36, a new cooldown period starts at 10:36 and ends at 10:41.

    NOTE:
    • If a scaling action is triggered by an AS policy, the cooldown period is whatever configured for that AS policy.
    • If a scaling action is triggered by manually changing the expected number of instances or by other actions, the cooldown period is whatever configured for the AS group.

    300
  6. Click OK.

    The newly added AS policy is displayed on the AS Policy tab. In addition, the AS policy is in Enabled state by default.

Creating a Scheduled or Periodic Policy

  1. Log in to the management console.
  1. Click in the upper left corner to select a region and a project.
  2. Under Computing, click Auto Scaling. In the navigation pane on the left, choose Instance Scaling.
  3. Locate the row containing the target AS group and click View AS Policy in the Operation column.
  4. On the AS Policies page, click Add AS Policy.
  5. Configure the parameters listed in Table 2.
    Table 2 Parameter description

    Parameter

    Description

    Example Value

    Policy Name

    Specifies the name of the AS policy to be created.

    as-policy-p6g5

    Policy Type

    Select Scheduled or Periodic for expanding resources at a specified time.

    If you select Periodic, you are required to configure two more parameters:

    • Interval
      • One day
      • One week
      • One month
    • Time Range

      Specifies a time range during which the AS policy can be triggered.

    N/A

    Time Zone

    The default value is GMT+08:00.

    GMT+08:00 is 8:00 hours ahead of Greenwich Mean Time.

    GMT+08:00

    Triggered At

    Specifies a time at which the AS policy is triggered.

    N/A

    Scaling Action

    Specifies an action and the number of instances.

    The following scaling action options are available:
    • Add

      Adds instances to an AS group when the scaling action is performed.

    • Reduce

      Removes instances from an AS group when the scaling action is performed.

    • Set to

      Sets the expected number of instances in an AS group to a specified value.
    • Add 1 instance
    • Add 10% instances

      The number of instances to be added is 10% of the current number of instances in the AS group. If the product of the current number of instances and the percentage is not an integer, AS automatically rounds the value up or down:

      • If the value is greater than 1, it is rounded down.
      • If the value is greater than 0 but less than 1, it is rounded up to 1.

    Cooldown Period

    To prevent an alarm policy from being repeatedly invoked by the same event, you can set a cooldown period.

    Specifies how long any alarm-triggered scaling action will be disallowed after a previous scaling action is complete.

    The cooldown period does not apply to scheduled or periodic scaling actions. However, AS recounts the cooling duration after a scheduled or periodic scaling action is complete.

    For example, suppose that the cooldown period is set to 300 seconds (5 minutes), and a scheduled policy is specified to trigger a scaling action at 10:32, and a previous scaling action triggered by an alarm policy ends at 10:30. Any alarm-triggered scaling action will then be denied during the cooldown period from 10:30 to 10:35, but the scaling action scheduled for 10:32 will still take place. If the scheduled scaling action ends at 10:36, a new cooldown period starts at 10:36 and ends at 10:41.

    NOTE:
    • If a scaling action is triggered by an AS policy, the cooldown period is whatever configured for that AS policy.
    • If a scaling action is triggered by manually changing the expected number of instances or by other actions, the cooldown period is whatever configured for the AS group.

    300
  1. Click OK.

    The newly added AS policy is displayed on the AS Policy tab. In addition, the AS policy is in Enabled state by default.

If you have created scheduled or periodic AS policies that are invoked at the same time, AS will execute the one created later. This constraint does not apply to alarm-triggered AS policies.

Parent topic: AS Policy