Allow to enable scale down in kube-up for gce

cluster/gce/config-default.sh

@@ -121,6 +121,7 @@ ENABLE_NODE_AUTOSCALER="${KUBE_ENABLE_NODE_AUTOSCALER:-false}"
 if [[ "${ENABLE_NODE_AUTOSCALER}" == "true" ]]; then
   AUTOSCALER_MIN_NODES="${KUBE_AUTOSCALER_MIN_NODES:-}"
   AUTOSCALER_MAX_NODES="${KUBE_AUTOSCALER_MAX_NODES:-}"
+  AUTOSCALER_ENABLE_SCALE_DOWN="${KUBE_AUTOSCALER_ENABLE_SCALE_DOWN:-false}"
 fi
 
 # Admission Controllers to invoke prior to persisting objects in cluster

cluster/gce/config-test.sh

@@ -135,6 +135,7 @@ ENABLE_NODE_AUTOSCALER="${KUBE_ENABLE_NODE_AUTOSCALER:-false}"
 if [[ "${ENABLE_NODE_AUTOSCALER}" == "true" ]]; then
   AUTOSCALER_MIN_NODES="${KUBE_AUTOSCALER_MIN_NODES:-}"
   AUTOSCALER_MAX_NODES="${KUBE_AUTOSCALER_MAX_NODES:-}"
+  AUTOSCALER_ENABLE_SCALE_DOWN="${KUBE_AUTOSCALER_ENABLE_SCALE_DOWN:-false}"
 fi
 
 # If we included ResourceQuota, we should keep it at the end of the list to prevent incremeting quota usage prematurely.

cluster/gce/util.sh

@@ -837,6 +837,8 @@ function create-cluster-autoscaler-mig-config() {
     local mig_url="https://www.googleapis.com/compute/v1/projects/${PROJECT}/zones/${ZONE}/instanceGroups/${group_name}"
     AUTOSCALER_MIG_CONFIG="${AUTOSCALER_MIG_CONFIG} --nodes=${this_mig_min}:${this_mig_max}:${mig_url}"
   done
+
+  AUTOSCALER_MIG_CONFIG="{AUTOSCALER_MIG_CONFIG} --experimental-scale-down-enabled=${AUTOSCALER_ENABLE_SCALE_DOWN}"
 }
 
 # Assumes: