Defined in github.com/aws/aws-sdk-go/service/ec2/api.go
The user-specified name for a logical grouping of bids.
When you specify an Availability Zone group in a Spot Instance request, all Spot instances in the request are launched in the same Availability Zone. Instance proximity is maintained with this parameter, but the choice of Availability Zone is not. The group applies only to bids for Spot Instances of the same instance type. Any additional Spot instance requests that are specified with the same Availability Zone group name are launched in that same Availability Zone, as long as at least one instance from the group is still active.
If there is no active instance running in the Availability Zone group that you specify for a new Spot instance request (all instances are terminated, the bid is expired, or the bid falls below current market), then Amazon EC2 launches the instance in any Availability Zone where the constraint can be met. Consequently, the subsequent set of Spot instances could be placed in a different zone from the original request, even if you specified the same Availability Zone group.
Default: Instances are launched in any available Availability Zone.