Enable DNS AutoScaler for CoreDNS (#3707)

* Enable AutoScaler for CoreDNS

* Only use one template for dns autoscaler

* Rename a few variables for replicas and minimum pods

* Rename a few variables for replicas and minimum pods

* Remove replicas to make autoscale work

* Cleanup kubedns-autoscaler as it has been renamed

roles/kubernetes-apps/ansible/templates/dns-autoscaler.yml.j2

@@ -0,0 +1,76 @@
+---
+# Copyright 2016 The Kubernetes Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+apiVersion: extensions/v1beta1
+kind: Deployment
+metadata:
+  name: dns-autoscaler
+  namespace: kube-system
+  labels:
+    k8s-app: dns-autoscaler
+    kubernetes.io/cluster-service: "true"
+    addonmanager.kubernetes.io/mode: Reconcile
+spec:
+  template:
+    metadata:
+      labels:
+        k8s-app: dns-autoscaler
+    spec:
+{% if kube_version is version('v1.11.1', '>=') %}
+      priorityClassName: system-cluster-critical
+{% endif %}
+      nodeSelector:
+        beta.kubernetes.io/os: linux
+      tolerations:
+        - effect: NoSchedule
+          operator: Equal
+          key: node-role.kubernetes.io/master
+      affinity:
+        podAntiAffinity:
+          requiredDuringSchedulingIgnoredDuringExecution:
+          - topologyKey: "kubernetes.io/hostname"
+            labelSelector:
+              matchLabels:
+                k8s-app: dns-autoscaler
+        nodeAffinity:
+          preferredDuringSchedulingIgnoredDuringExecution:
+          - weight: 100
+            preference:
+              matchExpressions:
+              - key: node-role.kubernetes.io/master
+                operator: In
+                values:
+                - "true"
+      containers:
+      - name: autoscaler
+        image: "{{ dnsautoscaler_image_repo }}:{{ dnsautoscaler_image_tag }}"
+        resources:
+          requests:
+            cpu: "20m"
+            memory: "10Mi"
+        command:
+        - /cluster-proportional-autoscaler
+        - --namespace=kube-system
+        - --default-params={"linear":{"nodesPerReplica":{{ dns_nodes_per_replica }},"min":{{ dns_min_replicas }}}}
+        - --logtostderr=true
+        - --v=2
+        - --configmap=dns-autoscaler
+{% if dns_mode in ['coredns', 'coredns_dual'] %}
+        - --target=Deployment/coredns{{ coredns_ordinal_suffix | default('') }}
+{% endif %}
+{% if dns_mode in ['kubedns', 'dnsmasq_kubedns'] %}
+        - --target=Deployment/kube-dns
+{% endif %}
+      serviceAccountName: cluster-proportional-autoscaler