Attaches one or more EC2 instances to the specified Auto Scaling group.
When you attach instances, Amazon EC2 Auto Scaling increases the desired
capacity of the group by the number of instances being attached. If the
number of instances being attached plus the desired capacity of the
group exceeds the maximum size of the group, the operation fails.
If there is a Classic Load Balancer attached to your Auto Scaling group,
the instances are also registered with the load balancer. If there are
target groups attached to your Auto Scaling group, the instances are
also registered with the target groups.
For more information, see Attach EC2 instances to your Auto Scaling group
in the Amazon EC2 Auto Scaling User Guide.