describeCapacityReservationTopology

Describes a tree-based hierarchy that represents the physical host placement of your pending or active Capacity Reservations within an Availability Zone or Local Zone. You can use this information to determine the relative proximity of your capacity within the Amazon Web Services network before it is launched and use this information to allocate capacity together to support your tightly coupled workloads.

Capacity Reservation topology is supported for specific instance types only. For more information, see Prerequisites for Amazon EC2 instance topology in the Amazon EC2 User Guide.

The Amazon EC2 API follows an eventual consistency model due to the distributed nature of the system supporting it. As a result, when you call the DescribeCapacityReservationTopology API command immediately after launching instances, the response might return a null value for capacityBlockId because the data might not have fully propagated across all subsystems. For more information, see Eventual consistency in the Amazon EC2 API in the Amazon EC2 Developer Guide.

For more information, see Amazon EC2 topology in the Amazon EC2 User Guide.