[AKS] Autoscaling support for VMs agentpool (#9012)

Author: wenxuan0923

src/aks-preview/HISTORY.rst

@@ -13,6 +13,11 @@ Pending
 +++++++
 * Add machine command `az aks machine add` to add a machine to an existing machine pool.
 
+18.0.0b37
++++++++
+* Enable autoscaler support for the VirtualMachines agent pool type.
+* Add `--node-vm-size` to `az aks update` to allow changing the VM size for VirtualMachines node pools.
+
 18.0.0b36
 +++++++
 * Add option `AzureLinux3` to `--os-sku` for `az aks nodepool add` and `az aks nodepool update`.

src/aks-preview/azext_aks_preview/_help.py

@@ -2251,6 +2251,9 @@
         - name: --localdns-config
           type: string
           short-summary: Set the localDNS Profile for a nodepool with a JSON config file.
+        - name: --node-vm-size -s
+          type: string
+          short-summary: VM size for Kubernetes nodes. Only configurable when updating the autoscale settings of a VirtualMachines node pool.
     examples:
       - name: Reconcile the nodepool back to its current state.
         text: az aks nodepool update -g MyResourceGroup -n nodepool1 --cluster-name MyManagedCluster
@@ -2262,6 +2265,8 @@
         text: az aks nodepool update --update-cluster-autoscaler --min-count 1 --max-count 10 -g MyResourceGroup -n nodepool1 --cluster-name MyManagedCluster
       - name: Change a node pool to system mode
         text: az aks nodepool update --mode System -g MyResourceGroup -n nodepool1 --cluster-name MyManagedCluster
+      - name: Update cluster autoscaler vm size, min-count and max-count for virtual machines node pool
+        text: az aks nodepool update -g MyResourceGroup -n nodepool1 --cluster-name MyManagedCluster --update-cluster-autoscaler --node-vm-size "Standard_D2s_v3" --min-count 2 --max-count 4
 """
 
 helps['aks nodepool get-upgrades'] = """

src/aks-preview/azext_aks_preview/_params.py

@@ -1891,6 +1891,11 @@ def load_arguments(self, _):
             'localdns_config',
             help='Path to a JSON file to configure the local DNS profile for an existing nodepool.',
         )
+        c.argument(
+            "node_vm_size",
+            options_list=["--node-vm-size", "-s"],
+            completer=get_vm_size_completion_list,
+        )
 
     with self.argument_context("aks nodepool upgrade") as c:
         c.argument("max_surge", validator=validate_max_surge)