Add feature_gates var for customizing Kubernetes feature gates (#1520)

docs/vars.md

@@ -67,6 +67,8 @@ following default cluster paramters:
   OpenStack (default is unset)
 * *kube_hostpath_dynamic_provisioner* - Required for use of PetSets type in
   Kubernetes
+* *kube_feature_gates* - A list of key=value pairs that describe feature gates for
+  alpha/experimental Kubernetes features. (defaults is `[]`)
 * *authorization_modes* - A list of [authorization mode](
 https://kubernetes.io/docs/admin/authorization/#using-flags-for-your-authorization-module)
   that the cluster should be configured for. Defaults to `[]` (i.e. no authorization).

roles/kubernetes/master/templates/manifests/kube-apiserver.manifest.j2

@@ -84,6 +84,9 @@ spec:
 {% if authorization_modes %}
     - --authorization-mode={{ authorization_modes|join(',') }}
 {% endif %}
+{% if kube_feature_gates %}
+    - --feature-gates={{ kube_feature_gates|join(',') }}
+{% endif %}
 {% if apiserver_custom_flags is string %}
     - {{ apiserver_custom_flags }}
 {% else %}

roles/kubernetes/master/templates/manifests/kube-controller-manager.manifest.j2

@@ -49,6 +49,9 @@ spec:
     - --configure-cloud-routes=true
     - --cluster-cidr={{ kube_pods_subnet }}
 {% endif %}
+{% if kube_feature_gates %}
+    - --feature-gates={{ kube_feature_gates|join(',') }}
+{% endif %}
 {% if controller_mgr_custom_flags is string %}
     - {{ controller_mgr_custom_flags }}
 {% else %}

roles/kubernetes/master/templates/manifests/kube-scheduler.manifest.j2

@@ -27,6 +27,9 @@ spec:
     - --leader-elect=true
     - --kubeconfig={{ kube_config_dir }}/kube-scheduler-kubeconfig.yaml
     - --v={{ kube_log_level }}
+{% if kube_feature_gates %}
+    - --feature-gates={{ kube_feature_gates|join(',') }}
+{% endif %}
 {% if scheduler_custom_flags is string %}
     - {{ scheduler_custom_flags }}
 {% else %}

roles/kubernetes/node/templates/kubelet.j2

@@ -55,7 +55,7 @@ KUBELET_HOSTNAME="--hostname-override={{ kube_override_hostname }}"
 {%   set node_labels %}--node-labels=node-role.kubernetes.io/node=true{% endset %}
 {% endif %}
 
-KUBELET_ARGS="{{ kubelet_args_base }} {{ kubelet_args_dns }} {{ kubelet_args_kubeconfig }} {{ node_labels }} {% if kubelet_custom_flags is string %} {{kubelet_custom_flags}} {% else %}{% for flag in kubelet_custom_flags %} {{flag}} {% endfor %}{% endif %}"
+KUBELET_ARGS="{{ kubelet_args_base }} {{ kubelet_args_dns }} {{ kubelet_args_kubeconfig }} {{ node_labels }} {% if kube_feature_gates %} --feature-gates={{ kube_feature_gates|join(',') }} {% endif %} {% if kubelet_custom_flags is string %} {{kubelet_custom_flags}} {% else %}{% for flag in kubelet_custom_flags %} {{flag}} {% endfor %}{% endif %}"
 {% if kube_network_plugin is defined and kube_network_plugin in ["calico", "weave", "canal"] %}
 KUBELET_NETWORK_PLUGIN="--network-plugin=cni --network-plugin-dir=/etc/cni/net.d --cni-bin-dir=/opt/cni/bin"
 {% elif kube_network_plugin is defined and kube_network_plugin == "weave" %}

roles/kubespray-defaults/defaults/main.yaml

@@ -131,3 +131,7 @@ openstack_lbaas_monitor_max_retries: false
 ## 'RBAC' modes are tested.
 authorization_modes: []
 rbac_enabled: "{{ 'RBAC' in authorization_modes }}"
+
+## List of key=value pairs that describe feature gates for
+## the k8s cluster.
+kube_feature_gates: []