Scheduled scaling for Application Auto Scaling

Scaling based on a schedule allows you to set your own scaling schedule for predictable load changes. For example, every week the traffic to your web application starts to increase on Wednesday, remains high on Thursday, and starts to decrease on Friday. You can configure Application Auto Scaling to increase capacity on Wednesday and decrease capacity on Friday.

To use scheduled scaling, create scheduled actions, which tell Application Auto Scaling to perform scaling activities at specific times. When you create a scheduled action, you specify the scalable target, when the scaling activity should occur, and the minimum and maximum capacity.

At the specified time, Application Auto Scaling scales based on the new capacity values, by comparing current capacity to the specified minimum and maximum capacity.

After the scheduled action runs, the scaling policy (if any) can continue to make decisions about whether to further scale capacity. This helps you ensure that you have sufficient capacity to handle the load for your application. While your application scales to match demand, current capacity must fall within the minimum and maximum capacity that your scheduled action allows.

For a detailed example of using scheduled scaling, see the blog post Scheduling AWS Lambda Provisioned Concurrency for recurring peak usage on the AWS Compute Blog.

Considerations

When you create a scheduled action, keep the following in mind:

Register scalable target

Before you can create a scheduled action, you must register the scalable target. Use the register-scalable-target command to register a new scalable target. The following example registers the provisioned concurrency for an alias called BLUE for the Lambda function called my-function.

On local Linux, macOS, or Unix machines:

aws application-autoscaling register-scalable-target --service-namespace lambda \
  --scalable-dimension lambda:function:ProvisionedConcurrency \
  --resource-id function:my-function:BLUE \
  --min-capacity 10 --max-capacity 50

On local Windows machines:

aws application-autoscaling register-scalable-target --service-namespace lambda --scalable-dimension lambda:function:ProvisionedConcurrency --resource-id function:my-function:BLUE --min-capacity 10 --max-capacity 50

Using the AWS CLI to create or update a scheduled action

You can create and update scheduled actions that scale one time only or that scale on a recurring schedule using the put-scheduled-action command. When you specify the new capacity, you can specify a minimum capacity, a maximum capacity, or both.

Schedule actions for a one-time schedule

You can specify a one-time schedule to automatically scale your scalable target at a certain date and time, in UTC.

aws application-autoscaling put-scheduled-action --service-namespace custom-resource \
  --scalable-dimension custom-resource:ResourceType:Property \
  --resource-id file://~/custom-resource-id.txt \
  --scheduled-action-name scale-out \
  --schedule "at(2021-03-31T22:00:00)" \
  --scalable-target-action MinCapacity=3

aws application-autoscaling put-scheduled-action --service-namespace custom-resource --scalable-dimension custom-resource:ResourceType:Property --resource-id file://~/custom-resource-id.txt --scheduled-action-name scale-out --schedule "at(2021-03-31T22:00:00)" --scalable-target-action MinCapacity=3

When you specify a custom resource, the custom-resource-id.txt file specifies the API Gateway endpoint for your custom resource. For more information about configuring a custom resource, see our GitHub repository. The contents of the file may look something like this:

https://example.execute-api.region.amazonaws.com/prod/scalableTargetDimensions/1-23456789

aws application-autoscaling put-scheduled-action --service-namespace ecs \
  --scalable-dimension ecs:service:DesiredCount \
  --resource-id service/default/web-app \
  --scheduled-action-name scale-in \
  --schedule "at(2021-01-31T17:00:00)" \
  --scalable-target-action MaxCapacity=1

aws application-autoscaling put-scheduled-action --service-namespace ecs --scalable-dimension ecs:service:DesiredCount --resource-id service/default/web-app --scheduled-action-name scale-in --schedule "at(2021-01-31T17:00:00)" --scalable-target-action MaxCapacity=1

Recurring schedules using cron or rate expressions

You can set up a recurring schedule for a scheduled action using schedule expressions. Application Auto Scaling supports cron and rate formats for schedule expressions.

aws application-autoscaling put-scheduled-action --service-namespace appstream \
  --scalable-dimension appstream:fleet:DesiredCapacity \
  --resource-id fleet/sample-fleet \
  --scheduled-action-name my-recurring-action \
  --schedule "cron(0 9 * * ? *)" \
  --scalable-target-action MinCapacity=10,MaxCapacity=50

aws application-autoscaling put-scheduled-action --service-namespace appstream --scalable-dimension appstream:fleet:DesiredCapacity --resource-id fleet/sample-fleet --scheduled-action-name my-recurring-action --schedule "cron(0 9 * * ? *)" --scalable-target-action MinCapacity=10,MaxCapacity=50

aws application-autoscaling put-scheduled-action --service-namespace dynamodb \
  --scalable-dimension dynamodb:table:WriteCapacityUnits \
  --resource-id table/my-table \
  --scheduled-action-name my-recurring-action \
  --schedule "rate(5 hours)" \
  --start-time 2021-01-30T12:00:00 \
  --end-time 2021-01-31T22:00:00 \
  --scalable-target-action MinCapacity=30,MaxCapacity=100

aws application-autoscaling put-scheduled-action --service-namespace dynamodb --scalable-dimension dynamodb:table:WriteCapacityUnits --resource-id table/my-table --scheduled-action-name my-recurring-action --schedule "rate(5 hours)" --start-time 2021-01-30T12:00:00 --end-time 2021-01-31T22:00:00 --scalable-target-action MinCapacity=30,MaxCapacity=100

Describe scheduled actions

You can describe all scheduled actions for the specified service namespace using the following describe-scheduled-actions command.

aws application-autoscaling describe-scheduled-actions --service-namespace ecs

The following is example output.

{
    "ScheduledActions": [
        {
            "ScheduledActionARN": "<arn>",
            "ServiceNamespace": "ecs",
            "CreationTime": 1596319455.951,
            "ScalableDimension": "ecs:service:DesiredCount",
            "Schedule": "at(2021-01-31T17:00:00)",
            "ScalableTargetAction": {
                "MaxCapacity": 1
            },
            "ScheduledActionName": "scale-in",
            "ResourceId": "service/default/web-app"
        }
    ]
}

Delete a scheduled action

When you are finished with a scheduled action, you can delete it using the delete-scheduled-action command.

On local Linux, macOS, or Unix machines:

aws application-autoscaling delete-scheduled-action --service-namespace ec2 \
  --scalable-dimension ec2:spot-fleet-request:TargetCapacity \
  --resource-id spot-fleet-request/sfr-73fbd2ce-aa30-494c-8788-1cee4EXAMPLE \
  --scheduled-action-name my-spot-fleet-action

On local Windows machines:

aws application-autoscaling delete-scheduled-action --service-namespace ec2 --scalable-dimension ec2:spot-fleet-request:TargetCapacity --resource-id spot-fleet-request/sfr-73fbd2ce-aa30-494c-8788-1cee4EXAMPLE --scheduled-action-name my-spot-fleet-action