Support dynamic kubelet config

https://kubernetes.io/blog/2018/07/11/dynamic-kubelet-configuration/

inventory/sample/group_vars/k8s-cluster/k8s-cluster.yml

@@ -154,6 +154,14 @@ k8s_image_pull_policy: IfNotPresent
 # audit log for kubernetes
 kubernetes_audit: false
 
+# dynamic kubelet configuration
+dynamic_kubelet_configuration: false
+
+# define kubelet config dir for dynamic kubelet
+#kubelet_config_dir:
+default_kubelet_config_dir: "{{ kube_config_dir }}/dynamic_kubelet_dir"
+dynamic_kubelet_configuration_dir: "{{ kubelet_config_dir | default(default_kubelet_config_dir) }}"
+
 # pod security policy (RBAC must be enabled either by having 'RBAC' in authorization_modes or kubeadm enabled)
 podsecuritypolicy_enabled: false
 

roles/kubernetes/master/templates/kubeadm-config.v1alpha2.yaml.j2

@@ -150,3 +150,7 @@ nodeRegistration:
 {% if container_manager == 'crio' %}
   criSocket: /var/run/crio/crio.sock
 {% endif %}
+{% if dynamic_kubelet_configuration %}
+featureGates:
+  DynamicKubeletConfig: true
+{% endif %}

roles/kubernetes/node/tasks/main.yml

@@ -32,6 +32,13 @@
   tags:
     - kubelet
 
+- name: Make sure dynamic kubelet configuration directory is writeable
+  file:
+    path: "{{ dynamic_kubelet_configuration_dir }}"
+    mode: 0600
+    state: directory
+  when: dynamic_kubelet_configuration
+
 - name: Write kubelet config file (kubeadm)
   template:
     src: kubelet.kubeadm.env.j2

roles/kubernetes/node/templates/kubelet.kubeadm.env.j2

@@ -48,6 +48,9 @@ KUBELET_HOSTNAME="--hostname-override={{ kube_override_hostname }}"
 {% else %}
 --fail-swap-on={{ kubelet_fail_swap_on|default(true)}} \
 {% endif %}
+{% if dynamic_kubelet_configuration %}
+--dynamic-config-dir={{ dynamic_kubelet_configuration_dir }} \
+{% endif %}
 --runtime-cgroups={{ kubelet_runtime_cgroups }} --kubelet-cgroups={{ kubelet_kubelet_cgroups }} \
 {% endset %}
 

roles/kubespray-defaults/defaults/main.yaml

@@ -136,6 +136,14 @@ kube_apiserver_port: 6443
 kube_apiserver_insecure_bind_address: 127.0.0.1
 kube_apiserver_insecure_port: 8080
 
+# dynamic kubelet configuration
+dynamic_kubelet_configuration: false
+
+# define kubelet config dir for dynamic kubelet
+#kubelet_config_dir:
+default_kubelet_config_dir: "{{ kube_config_dir }}/dynamic_kubelet_dir"
+dynamic_kubelet_configuration_dir: "{{ kubelet_config_dir | default(default_kubelet_config_dir) }}"
+
 # Aggregator
 kube_api_aggregator_routing: false
 

tests/files/gce_centos-weave-kubeadm.yml

@@ -10,5 +10,6 @@ kube_network_plugin: weave
 kubeadm_enabled: true
 deploy_netchecker: true
 kubernetes_audit: true
+dynamic_kubelet_configuration: true
 kubedns_min_replicas: 1
 cloud_provider: gce