Managing Scaling Policies

A scaling policy specifies the conditions for triggering a scaling action as well as the triggered operation. If the conditions are met, a scaling action is triggered to perform the required operation. This section describes how to manage AS policies, including creating, modifying, enabling, disabling, immediately executing, and deleting an AS policy.

A policy can be of Alarm, Scheduled, or Periodic type.

Alarm: AS automatically increases or decreases the number of instances in an AS group or sets the number of instances to the configured value when Cloud Eye generates an alarm for a configured metric, such as high CPU usage.
Periodic: AS automatically increases or decreases the number of instances in an AS group or sets the number of instances to the configured value at a configured interval, such as daily, weekly, or monthly.
Scheduled: AS automatically increases or decreases the number of instances in an AS group or sets the number of instances to the configured value at a specified time.

For example, the instance utilization in an AS group is generally low during the off-peak hours from 00:00 to 08:00. To maximize resource utilization, you can configure two AS policies to enable AS to automatically remove an instance at 00:00 and add one at 08:00 every day.

Create an AS Policy

For details, see sections Dynamically Expanding Resources and Expanding Resources as Planned.

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

Modify an AS Policy

Modify parameter settings of an AS policy if it cannot meet service requirements.

Log in to the management console.
Under Computing, click Auto Scaling. Then, on the Auto Scaling page, click the AS Group tab.
Locate the row containing the target AS group and click View AS Policy in the Operation column. On the displayed page, locate the row containing the target AS policy and choose More > Modify in the Operation column.
In the displayed Modify AS Policy dialog box, modify the parameters and click OK.

Enable an AS Policy

An AS policy can trigger scaling actions only when it and the AS group are both enabled. Enable one or multiple AS policies for an AS group as required.

Before enabling multiple AS policies, ensure that the AS policies do not conflict with one another.
An AS policy can be enabled only when its status is Disabled.

Locate the row containing the target AS group and click View AS Policy in the Operation column. On the displayed page, locate the row containing the target AS policy and click Enable in the Operation column.

Disable an AS Policy

Disable a specified AS policy if you do not want it to trigger any scaling action within a specified period of time.

If all AS policies of an AS group are disabled, no scaling action will be triggered for this AS group. However, if you manually change the value of Expected Instances, a scaling action will still be triggered.
You can disable an AS policy only when its status is Enabled.

Manually Execute an AS policy

Perform this operation to make the number of instances in an AS group reach the expected number of instances immediately.

You can manually execute an AS policy if the scaling conditions configured in the AS policy are not met.
You can manually execute an AS policy only when the AS group and AS policy are both in Enabled state.
Locate the row containing the target AS group and click View AS Policy in the Operation column. On the displayed page, locate the row containing the target AS policy and click Execute Now in the Operation column.

Delete an AS Policy

Delete an AS policy that will not be used for triggering scaling actions.

An AS policy can be deleted even when the scaling action triggered based on the AS policy is in progress. Deleting the AS policy does not adversely affect the in-progress scaling action.

Locate the row containing the target AS group and click View AS Policy in the Operation column. On the displayed page, locate the row containing the target AS policy and choose More > Delete in the Operation column.

Parent topic: Scaling Actions