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# AWS::EC2::EC2Fleet OnDemandOptionsRequest

Specifies the allocation strategy of On-Demand Instances in an EC2 Fleet.
`OnDemandOptionsRequest` is a property of the [AWS::EC2::EC2Fleet](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-ec2-ec2fleet.html) resource.
## Syntax

To declare this entity in your CloudFormation template, use the following syntax:
### JSON

```
{
 "[AllocationStrategy](#cfn-ec2-ec2fleet-ondemandoptionsrequest-allocationstrategy)" : {{String}},
 "[CapacityReservationOptions](#cfn-ec2-ec2fleet-ondemandoptionsrequest-capacityreservationoptions)" : {{CapacityReservationOptionsRequest}},
 "[MaxTotalPrice](#cfn-ec2-ec2fleet-ondemandoptionsrequest-maxtotalprice)" : {{String}},
 "[MinTargetCapacity](#cfn-ec2-ec2fleet-ondemandoptionsrequest-mintargetcapacity)" : {{Integer}},
 "[SingleAvailabilityZone](#cfn-ec2-ec2fleet-ondemandoptionsrequest-singleavailabilityzone)" : {{Boolean}},
 "[SingleInstanceType](#cfn-ec2-ec2fleet-ondemandoptionsrequest-singleinstancetype)" : {{Boolean}}
}
```
### YAML

```
 [AllocationStrategy](#cfn-ec2-ec2fleet-ondemandoptionsrequest-allocationstrategy): {{String}}
 [CapacityReservationOptions](#cfn-ec2-ec2fleet-ondemandoptionsrequest-capacityreservationoptions): {{
 CapacityReservationOptionsRequest}}
 [MaxTotalPrice](#cfn-ec2-ec2fleet-ondemandoptionsrequest-maxtotalprice): {{String}}
 [MinTargetCapacity](#cfn-ec2-ec2fleet-ondemandoptionsrequest-mintargetcapacity): {{Integer}}
 [SingleAvailabilityZone](#cfn-ec2-ec2fleet-ondemandoptionsrequest-singleavailabilityzone): {{Boolean}}
 [SingleInstanceType](#cfn-ec2-ec2fleet-ondemandoptionsrequest-singleinstancetype): {{Boolean}}
```
## Properties

`AllocationStrategy` 
The strategy that determines the order of the launch template overrides to use in fulfilling On-Demand capacity. 
`lowest-price` - EC2 Fleet uses price to determine the order, launching the lowest price first. 
`prioritized` - EC2 Fleet uses the priority that you assigned to each launch template override, launching the highest priority first. 
Default: `lowest-price` 
*Required*: No 
*Type*: String 
*Allowed values*: `lowest-price | prioritized` 
*Update requires*: [Replacement](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/using-cfn-updating-stacks-update-behaviors.html#update-replacement)
`CapacityReservationOptions` 
The strategy for using unused Capacity Reservations for fulfilling On-Demand capacity. 
Supported only for fleets of type `instant`. 
*Required*: No 
*Type*: [CapacityReservationOptionsRequest](aws-properties-ec2-ec2fleet-capacityreservationoptionsrequest.md) 
*Update requires*: [Replacement](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/using-cfn-updating-stacks-update-behaviors.html#update-replacement)
`MaxTotalPrice` 
The maximum amount per hour for On-Demand Instances that you're willing to pay. 
If your fleet includes T instances that are configured as `unlimited`, and if their average CPU usage exceeds the baseline utilization, you will incur a charge for surplus credits. The `MaxTotalPrice` does not account for surplus credits, and, if you use surplus credits, your final cost might be higher than what you specified for `MaxTotalPrice`. For more information, see [Surplus credits can incur charges](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/burstable-performance-instances-unlimited-mode-concepts.html#unlimited-mode-surplus-credits) in the *Amazon EC2 User Guide*.
*Required*: No 
*Type*: String 
*Update requires*: [Replacement](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/using-cfn-updating-stacks-update-behaviors.html#update-replacement)
`MinTargetCapacity` 
The minimum target capacity for On-Demand Instances in the fleet. If this minimum capacity isn't reached, no instances are launched. 
Constraints: Maximum value of `1000`. Supported only for fleets of type `instant`. 
At least one of the following must be specified: `SingleAvailabilityZone` \| `SingleInstanceType` 
*Required*: No 
*Type*: Integer 
*Update requires*: [Replacement](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/using-cfn-updating-stacks-update-behaviors.html#update-replacement)
`SingleAvailabilityZone` 
Indicates that the fleet launches all On-Demand Instances into a single Availability Zone. 
Supported only for fleets of type `instant`. 
*Required*: No 
*Type*: Boolean 
*Update requires*: [Replacement](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/using-cfn-updating-stacks-update-behaviors.html#update-replacement)
`SingleInstanceType` 
Indicates that the fleet uses a single instance type to launch all On-Demand Instances in the fleet. 
Supported only for fleets of type `instant`. 
*Required*: No 
*Type*: Boolean 
*Update requires*: [Replacement](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/using-cfn-updating-stacks-update-behaviors.html#update-replacement)
## See also

+ [ OnDemandOptionsRequest](https://docs.aws.amazon.com/AWSEC2/latest/APIReference/API_OnDemandOptionsRequest.html) in the *Amazon EC2 API Reference*</div><div class="naked_ctrl">
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