Set a scheduled policy

A scheduled policy sets the number of nodes in a scale group at times you choose: one time to scale up, and one to scale down. Choose it when you know your busy hours, such as weekday mornings. To also scale on load, choose Elastic and Scheduled Policy; both policies then work within the same Minimum Node and Maximum Node. For the elastic part, see Set an elastic policy.

Before you begin

• For a new scale group, you have chosen Scheduled Policy or Elastic and Scheduled Policy under Select Policy while creating it, and your role in the current project has the create permission for Auto Scaling. See Create a scale group.
• If you are changing an existing scale group, it reads Running, and your role has the update permission for Auto Scaling.
• You have set Maximum Node to at least the upscale Cardinality you plan, and Minimum Node to at most the downscale one. To change them on a running scale group, see Change the minimum, maximum, or desired nodes.

Write the cron expressions

Each recurrence is a cron expression, read in India Standard Time (IST). A cron expression has five fields, separated by spaces: minute, hour, day of the month, month, and day of the week.

Enter the minute as a plain whole number, such as 0 or 15. If you use a step, list, or range in the minute, such as */15 9 * * *, the field says Must start with a digit. Make the rest of the expression valid cron, or the field says Invalid Cron.

For example, to run 10 nodes from 09:00 IST and three nodes from 20:00 IST, Monday to Friday:

Upscale Recurrence:   0 9 * * 1-5     Cardinality: 10
Downscale Recurrence: 0 20 * * 1-5    Cardinality: 3

For these values, set Minimum Node to 3 or fewer, and Maximum Node to 10 or more.

IST is five and a half hours ahead of UTC, so to scale at 09:00 UTC, which is 14:30 IST, enter 30 14 * * *.

The field also says This field is required. when it is empty, and Recurrences should be different. when both expressions are the same. See Troubleshooting Auto Scaling.

Set the upscale and downscale times

A scheduled policy has exactly one Upscale Recurrence and one Downscale Recurrence. Each pairs a cron expression with a Cardinality, the total number of nodes the scale group runs once that recurrence fires. The scale group starts scaling within about 20 seconds of each recurrence’s IST time.

1. Under Upscale Recurrence, enter a cron expression as Write the cron expressions describes, or pick one of the expressions the field suggests. Once the expression is valid, the page shows its schedule in words.
2. Set the upscale Cardinality, the number of nodes for your busy hours, between the downscale Cardinality and Maximum Node. It starts at 4.
3. Under Downscale Recurrence, enter the expression for when the busy hours end. Make it different from the upscale expression.
4. Set the downscale Cardinality, the number of nodes for your quiet hours, between Minimum Node and the upscale Cardinality. It starts at 2.

Before you create or update the scale group, check the times the page shows in words under each expression.

Change the schedule of a running scale group

1. In MyAccount, under Compute, click Auto Scaling, click your scale group, and open its Scale Group Details tab. There you can edit its settings, one at a time.

2. Click the edit button beside Scale group policy. Select Policy opens with the policy’s values ready to change.

3. Change the recurrences and their Cardinality values, or switch between Elastic Policy, Scheduled Policy, and Elastic and Scheduled Policy.

4. Click Update to save, or Cancel to drop the changes. After you save, you will see this message, with your scale group’s name in place of <group-name>:

   The scaling service - <group-name> - has been successfully updated.

Check the schedule

The Schedule Policy panel on Scale Group Details shows Upscale Recurrence and Downscale Recurrence in words, with Upscale Desired Nodes and Downscale Desired Nodes. When a recurrence fires, the scale group’s Audit Logs tab records the scaling; see Read the audit logs.

Your scale group now scales on its schedule. To change its minimum and maximum, see Resize, stop, or start a scale group. If the schedule is refused, see Troubleshooting Auto Scaling.