Interruptible Capacity Reservations for capacity owners
The capacity owner is the account that owns the source Capacity Reservation and creates the interruptible Capacity Reservation to share unused capacity with other teams while retaining control to reclaim it when needed.
This section covers how you (the capacity owner) can create, modify, reclaim, and track an interruptible Capacity Reservation.
Topics
Creating an interruptible Capacity Reservation
Create an interruptible Capacity Reservation to make unused capacity from your source reservation available for other workloads while maintaining control to reclaim it when needed.
Prerequisites
Before creating an interruptible allocation, ensure your source On-Demand Capacity Reservation meets these requirements:
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Your Capacity Reservation must be in active state with no end date set. You can't create allocations from reservations that are pending, expired, cancelled, or have scheduled end dates.
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Your Capacity Reservation must have available capacity for allocation. You can only allocate available instances (also called unused capacity).
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You can create only one interruptible allocation per source Capacity Reservation. If an allocation already exists, you must modify or cancel it before creating a new one.
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You can allocate a maximum of 1000 instances at once to an interruptible Capacity Reservation.
You can use the console or the AWS CLI to create an interruptible Capacity Reservation.
View your interruptible Capacity Reservation
After creating an interruptible Capacity Reservation, you can view the interruptible reservation in your account or from a specific resource.
View all interruptible Capacity Reservations in your account
Use the following procedure to view the interruptible Capacity Reservations in your account.
View interruptible Capacity Reservation from a specific source
Use the following procedure to view the interruptible Capacity Reservation created from a specific source Capacity Reservation.
aws ec2 describe-capacity-reservations \ --capacity-reservation-idcr-source-id
In the response, you'll find an interruptibleCapacityAllocation object that contains the interruptible
Capacity Reservation ID and allocation details. For information about the response structure, see
InterruptibleCapacityAllocation in
the Amazon EC2 API Reference.
Modifying your interruptible Capacity Reservation
Use the following procedures to edit or cancel your interruptible Capacity Reservation.
Note
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When you reduce the allocation, we first reclaim available instances, then running instances, until we meet the requested count. If we can meet the count entirely with available instances, no termination occurs. All modifications to allocated instance count are done through the source Capacity Reservation, not directly on the interruptible Capacity Reservation.
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You can only modify an interruptible Capacity Reservation by a maximum of 1000 instances at once (increase or decrease).
Edit your interruptible Capacity Reservation
Use the following procedure to edit your interruptible Capacity Reservation.
Cancel your interruptible Capacity Reservation
Use the following procedure to permanently remove the allocation and return all capacity.
Retain zero size preference
If you configured retain for the zero size preference, the interruptible Capacity Reservation stays active at zero instances. To cancel it, update the zero size preference to default, and then reduce the allocation to zero. For more information, see Retaining interruptible Capacity Reservation at zero capacity.
Retaining interruptible Capacity Reservation at zero capacity
By default, Amazon EC2 cancels the interruptible reservation when you reduce its allocation to zero instances. The reclaimed capacity returns to your source Capacity Reservation.
If you expect to share capacity again later, you can configure the interruptible reservation to remain active at zero instances. With this option, you can allocate instances to the same reservation later without recreating it.
You control this behavior with the zero size preference. You can set it when you create or edit an interruptible Capacity Reservation allocation, either in the console or with the AWS CLI.
Reclamation process and tracking
When you reclaim capacity:
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Running instances receive a 2-minute interruption warning through EventBridge events.
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After the notice period, running instances in the reclaimed capacity enter a shutting down state and get terminated.
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When terminated, the reclaimed instances become available in your source Capacity Reservation for immediate use.
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Your allocation status changes from updating to active when complete.
Complete reclamation can take a few minutes depending on instance type and shutdown time. For more information about the EventBridge notification you receive when the process is complete, see Reclamation completion.
Track reclamation status
Monitor reclamation progress by describing your source reservation:
aws ec2 describe-capacity-reservations \ --capacity-reservation-idcr-1234567890abcdef0
The response shows these fields within the interruptibleCapacityAllocation object:
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instance-count: Current allocated instances -
target-instance-count: Requested quantity after reclamation -
status: updating during reclamation and active when complete
Sharing interruptible reservations
You can share interruptible reservations only within your AWS organization using AWS Resource Access Manager (RAM).
Considerations:
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If a consumer account leaves your organization, the interruptible reservation is automatically unshared from that account.
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Any instances running in the unshared reservation are eventually terminated.
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All other sharing functionality works the same as standard Capacity Reservations.
For complete sharing procedures, see Sharing Capacity Reservations.
