add ability for custom flags

docs/vars.md

@@ -98,6 +98,20 @@ Stack](https://github.com/kubernetes-incubator/kargo/blob/master/docs/dns-stack.
   loaded by preinstall kubernetes processes.  For example, ceph and rbd backed volumes.  Set this variable to
   true to let kubelet load kernel modules.
 
+##### Custom flags for Kube Components
+For all kube components, custom flags can be passed in. This allows for edge cases where users need changes to the default deployment that may not be applicable to all deployments. This can be done by providing a list of flags. Example:
+```
+kubelet_custom_flags:
+  - "--eviction-hard=memory.available<100Mi"
+  - "--eviction-soft-grace-period=memory.available=30s"
+  - "--eviction-soft=memory.available<300Mi"
+```
+The possible vars are:
+* *apiserver_custom_flags*
+* *controller_mgr_custom_flags*
+* *scheduler_custom_flags*
+* *kubelet_custom_flags*
+
 #### User accounts
 
 Kargo sets up two Kubernetes accounts by default: ``root`` and ``kube``. Their

roles/kubernetes/master/defaults/main.yml

@@ -51,3 +51,10 @@ kube_oidc_auth: false
 # kube_oidc_ca_file: {{ kube_cert_dir }}/ca.pem
 # kube_oidc_username_claim: sub
 # kube_oidc_groups_claim: groups
+
+##Variables for custom flags
+apiserver_custom_flags: []
+
+controller_mgr_custom_flags: []
+
+scheduler_custom_flags: []

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

@@ -81,6 +81,9 @@ spec:
 {% if kube_api_anonymous_auth is defined and kube_version | version_compare('v1.5', '>=')  %}
     - --anonymous-auth={{ kube_api_anonymous_auth }}
 {% endif %}
+{% for flag in apiserver_custom_flags %}
+    - {{ flag }}
+{% endfor %}
     livenessProbe:
       httpGet:
         host: 127.0.0.1

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

@@ -46,6 +46,9 @@ spec:
     - --configure-cloud-routes=true
     - --cluster-cidr={{ kube_pods_subnet }}
 {% endif %}
+{% for flag in controller_mgr_custom_flags %}
+    - {{ flag }}
+{% endfor %}
     livenessProbe:
       httpGet:
         host: 127.0.0.1

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

@@ -27,6 +27,9 @@ spec:
     - --leader-elect=true
     - --master={{ kube_apiserver_endpoint }}
     - --v={{ kube_log_level }}
+{% for flag in scheduler_custom_flags %}
+    - {{ flag }}
+{% endfor %}
     livenessProbe:
       httpGet:
         host: 127.0.0.1

roles/kubernetes/node/defaults/main.yml

@@ -45,3 +45,6 @@ etcd_config_dir: /etc/ssl/etcd
 kube_apiserver_node_port_range: "30000-32767"
 
 kubelet_load_modules: false
+
+##Support custom flags to be passed to kubelet
+kubelet_custom_flags: []

roles/kubernetes/node/templates/kubelet.j2

@@ -44,7 +44,7 @@ KUBELET_HOSTNAME="--hostname-override={{ ansible_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 }}"
+KUBELET_ARGS="{{ kubelet_args_base }} {{ kubelet_args_dns }} {{ kubelet_args_kubeconfig }} {{ node_labels }} {% for flag in kubelet_custom_flags %} {{flag}} {% endfor %}"
 {% 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" %}