InstancesDistribution - Amazon EC2 Auto Scaling
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InstancesDistribution

Describes an instances distribution for an Auto Scaling group. You can use these parameters with the CreateAutoScalingGroup and UpdateAutoScalingGroup operations when you specify a MixedInstancesPolicy in the request. All parameters have a default value, which is the value that is used or assumed when the parameter is not specified.

The instances distribution specifies the distribution of On-Demand Instances and Spot Instances, the maximum price to pay for Spot Instances, and how the Auto Scaling group allocates instance types to fulfill On-Demand and Spot capacities.

When you modify SpotAllocationStrategy, SpotInstancePools, or SpotMaxPrice in the UpdateAutoScalingGroup API call, this update action does not deploy any changes across the running Amazon EC2 instances in the group. Your existing Spot Instances continue to run as long as the maximum price for those instances is higher than the current Spot price. When scaling out occurs, Amazon EC2 Auto Scaling launches instances based on the new settings. When scaling in occurs, Amazon EC2 Auto Scaling terminates instances according to the group's termination policies.

Contents

OnDemandAllocationStrategy

The order of the launch template overrides to use in fulfilling On-Demand capacity.

If you specify lowest-price, Amazon EC2 Auto Scaling uses price to determine the order, launching the lowest price first.

If you specify prioritized, Amazon EC2 Auto Scaling uses the priority that you assigned to each launch template override, launching the highest priority first. If all your On-Demand capacity cannot be fulfilled using your highest priority instance, then Amazon EC2 Auto Scaling launches the remaining capacity using the second priority instance type, and so on.

Default: lowest-price for Auto Scaling groups that specify InstanceRequirements in the overrides and prioritized for Auto Scaling groups that don't.

Valid values: lowest-price | prioritized

Type: String

Pattern: [\u0020-\uD7FF\uE000-\uFFFD\uD800\uDC00-\uDBFF\uDFFF\r\n\t]*

Required: No

OnDemandBaseCapacity

The minimum amount of the Auto Scaling group's capacity that must be fulfilled by On-Demand Instances. This base portion is launched first as your group scales.

If you specify weights for the instance types in the overrides, the base capacity is measured in the same unit of measurement as the instance types. If you specify InstanceRequirements in the overrides, the base capacity is measured in the same unit of measurement as your group's desired capacity.

Default: 0

Note

An update to this setting means a gradual replacement of instances to adjust the current On-Demand Instance levels. When replacing instances, Amazon EC2 Auto Scaling launches new instances before terminating the previous ones.

Type: Integer

Required: No

OnDemandPercentageAboveBaseCapacity

Controls the percentages of On-Demand Instances and Spot Instances for your additional capacity beyond OnDemandBaseCapacity. Expressed as a number (for example, 20 specifies 20% On-Demand Instances, 80% Spot Instances). If set to 100, only On-Demand Instances are used.

Default: 100

Note

An update to this setting means a gradual replacement of instances to adjust the current On-Demand and Spot Instance levels for your additional capacity higher than the base capacity. When replacing instances, Amazon EC2 Auto Scaling launches new instances before terminating the previous ones.

Type: Integer

Required: No

SpotAllocationStrategy

Indicates how to allocate instances across Spot Instance pools.

If the allocation strategy is lowest-price, the Auto Scaling group launches instances using the Spot pools with the lowest price, and evenly allocates your instances across the number of Spot pools that you specify.

If the allocation strategy is capacity-optimized (recommended), the Auto Scaling group launches instances using Spot pools that are optimally chosen based on the available Spot capacity. Alternatively, you can use capacity-optimized-prioritized and set the order of instance types in the list of launch template overrides from highest to lowest priority (from first to last in the list). Amazon EC2 Auto Scaling honors the instance type priorities on a best-effort basis but optimizes for capacity first.

Default: lowest-price

Valid values: lowest-price | capacity-optimized | capacity-optimized-prioritized

Type: String

Pattern: [\u0020-\uD7FF\uE000-\uFFFD\uD800\uDC00-\uDBFF\uDFFF\r\n\t]*

Required: No

SpotInstancePools

The number of Spot Instance pools across which to allocate your Spot Instances. The Spot pools are determined from the different instance types in the overrides. Valid only when the Spot allocation strategy is lowest-price. Value must be in the range of 1–20.

Default: 2

Type: Integer

Required: No

SpotMaxPrice

The maximum price per unit hour that you are willing to pay for a Spot Instance. If you keep the value at its default (unspecified), Amazon EC2 Auto Scaling uses the On-Demand price as the maximum Spot price. To remove a value that you previously set, include the property but specify an empty string ("") for the value.

Important

If your maximum price is lower than the Spot price for the instance types that you selected, your Spot Instances are not launched.

Valid Range: Minimum value of 0.001

Type: String

Length Constraints: Minimum length of 0. Maximum length of 255.

Required: No

See Also

For more information about using this API in one of the language-specific Amazon SDKs, see the following: