1. Overview
   1. The node group autoscaler automatically manages the sizes of sole-tenant node groups by increasing the size of a node group when there is insufficient capacity for another virtual machine (VM) instance on that node group
   2. After the autoscaler increases the size of the node group, the VMs are scheduled transparently
   3. Decreasing the size of a node group when there are empty nodes, avoids paying for unused sole-tenant nodes
2. Modes
   1. By default, the autoscaler is not enabled on node groups
   2. When the autoscaler is not enabled, users must manually manage the sizes of node groups
   3. When enabling autoscaler on a node group, users can specify that the autoscaler both increases and decreases the size of the node group (scales out and scales in), or that it only increases the size of the group (only scales out)
   4. In the scale out and scale in mode, the node group autoscaler both increases (scales out) and decreases (scales in) the size of node groups
   5. For this mode, specify a maximum size and a minimum size for the node group
   6. The autoscaler will not scale the size of the node group above the specified maximum or below the specified minimum
   7. The autoscaler scales out the size of a node group when there is a request to schedule a VM onto a node group that does not have capacity for another VM
   8. Conversely, the autoscaler scales in the size of a node group when there is an empty node in the node group
   9. With the only scale out mode, the autoscaler increases the size of the node group in response to requests to schedule VMs, but doesn't remove empty nodes from node groups
   10. Google recommends this mode for monotonically increasing workloads or workloads that require physical server affinity, such as BYOL workloads, which require licenses to reside on the same physical server
   11. Use the only scale out mode if node groups are configured to restart hosted VMs on minimal servers
3. Size
   1. When the autoscaler is enabled, set the size range of the node group by specifying a minimum and maximum value for the node group size
   2. If a value for the minimum size is not specified, the autoscaler sets the minimum size to zero (0)
   3. The value for the minimum size must be an integer greater than equal to 0, and it must be less than or equal to the maximum size
   4. A value for the maximum size of the node group must be specified
   5. The value must be an integer that is greater than or equal to 0 and less than or equal to 100, which is the maximum allowed size for a sole-tenant node group, and the value must be greater than or equal to the specified minimum value
   6. To accommodate workloads that might exceed the size maximum of 100 for a node group, create multiple node groups with matching affinity labels
   7. Then, schedule VMs using the affinity label, and enable autoscaling on each group to create a dynamically scaling group of node groups