autoscaler support for CoreDNS

cluster/addons/dns-horizontal-autoscaler/dns-horizontal-autoscaler.yaml

@@ -91,7 +91,7 @@ spec:
           - --namespace=kube-system
           - --configmap=kube-dns-autoscaler
           # Should keep target in sync with cluster/addons/dns/kube-dns.yaml.base
-          - --target=Deployment/kube-dns
+          - --target={{.Target}}
           # When cluster is using large nodes(with more cores), "coresPerReplica" should dominate.
           # If using small nodes, "nodesPerReplica" should dominate.
           - --default-params={"linear":{"coresPerReplica":256,"nodesPerReplica":16,"preventSinglePointFailure":true}}

cluster/addons/dns/coredns.yaml.base

@@ -74,23 +74,26 @@ metadata:
   name: coredns
   namespace: kube-system
   labels:
-    k8s-app: coredns
+    k8s-app: kube-dns
     kubernetes.io/cluster-service: "true"
     addonmanager.kubernetes.io/mode: Reconcile
     kubernetes.io/name: "CoreDNS"
 spec:
-  replicas: 2
+  # replicas: not specified here:
+  # 1. In order to make Addon Manager do not reconcile this replicas parameter.
+  # 2. Default is 1.
+  # 3. Will be tuned in real time if DNS horizontal auto-scaling is turned on.
   strategy:
     type: RollingUpdate
     rollingUpdate:
       maxUnavailable: 1
   selector:
     matchLabels:
-      k8s-app: coredns
+      k8s-app: kube-dns
   template:
     metadata:
       labels:
-        k8s-app: coredns
+        k8s-app: kube-dns
     spec:
       serviceAccountName: coredns
       tolerations:
@@ -140,16 +143,16 @@ spec:
 apiVersion: v1
 kind: Service
 metadata:
-  name: coredns
+  name: kube-dns
   namespace: kube-system
   labels:
-    k8s-app: coredns
+    k8s-app: kube-dns
     kubernetes.io/cluster-service: "true"
     addonmanager.kubernetes.io/mode: Reconcile
     kubernetes.io/name: "CoreDNS"
 spec:
   selector:
-    k8s-app: coredns
+    k8s-app: kube-dns
   clusterIP: __PILLAR__DNS__SERVER__
   ports:
   - name: dns

cluster/addons/dns/coredns.yaml.in

@@ -74,23 +74,26 @@ metadata:
   name: coredns
   namespace: kube-system
   labels:
-    k8s-app: coredns
+    k8s-app: kube-dns
     kubernetes.io/cluster-service: "true"
     addonmanager.kubernetes.io/mode: Reconcile
     kubernetes.io/name: "CoreDNS"
 spec:
-  replicas: 2
+  # replicas: not specified here:
+  # 1. In order to make Addon Manager do not reconcile this replicas parameter.
+  # 2. Default is 1.
+  # 3. Will be tuned in real time if DNS horizontal auto-scaling is turned on.
   strategy:
     type: RollingUpdate
     rollingUpdate:
       maxUnavailable: 1
   selector:
     matchLabels:
-      k8s-app: coredns
+      k8s-app: kube-dns
   template:
     metadata:
       labels:
-        k8s-app: coredns
+        k8s-app: kube-dns
     spec:
       serviceAccountName: coredns
       tolerations:
@@ -140,16 +143,16 @@ spec:
 apiVersion: v1
 kind: Service
 metadata:
-  name: coredns
+  name: kube-dns
   namespace: kube-system
   labels:
-    k8s-app: coredns
+    k8s-app: kube-dns
     kubernetes.io/cluster-service: "true"
     addonmanager.kubernetes.io/mode: Reconcile
     kubernetes.io/name: "CoreDNS"
 spec:
   selector:
-    k8s-app: coredns
+    k8s-app: kube-dns
   clusterIP: {{ pillar['dns_server'] }}
   ports:
   - name: dns

cluster/addons/dns/coredns.yaml.sed

@@ -74,23 +74,26 @@ metadata:
   name: coredns
   namespace: kube-system
   labels:
-    k8s-app: coredns
+    k8s-app: kube-dns
     kubernetes.io/cluster-service: "true"
     addonmanager.kubernetes.io/mode: Reconcile
     kubernetes.io/name: "CoreDNS"
 spec:
-  replicas: 2
+  # replicas: not specified here:
+  # 1. In order to make Addon Manager do not reconcile this replicas parameter.
+  # 2. Default is 1.
+  # 3. Will be tuned in real time if DNS horizontal auto-scaling is turned on.
   strategy:
     type: RollingUpdate
     rollingUpdate:
       maxUnavailable: 1
   selector:
     matchLabels:
-      k8s-app: coredns
+      k8s-app: kube-dns
   template:
     metadata:
       labels:
-        k8s-app: coredns
+        k8s-app: kube-dns
     spec:
       serviceAccountName: coredns
       tolerations:
@@ -140,16 +143,16 @@ spec:
 apiVersion: v1
 kind: Service
 metadata:
-  name: coredns
+  name: kube-dns
   namespace: kube-system
   labels:
-    k8s-app: coredns
+    k8s-app: kube-dns
     kubernetes.io/cluster-service: "true"
     addonmanager.kubernetes.io/mode: Reconcile
     kubernetes.io/name: "CoreDNS"
 spec:
   selector:
-    k8s-app: coredns
+    k8s-app: kube-dns
   clusterIP: $DNS_SERVER_IP
   ports:
   - name: dns

cluster/gce/gci/configure-helper.sh

@@ -27,6 +27,8 @@ set -o pipefail
 
 readonly UUID_MNT_PREFIX="/mnt/disks/by-uuid/google-local-ssds"
 readonly UUID_BLOCK_PREFIX="/dev/disk/by-uuid/google-local-ssds"
+readonly COREDNS_AUTOSCALER="Deployment/coredns"
+readonly KUBEDNS_AUTOSCALER="Deployment/kube-dns"
 
 # Use --retry-connrefused opt only if it's supported by curl.
 CURL_RETRY_CONNREFUSED=""
@@ -2049,6 +2051,12 @@ function setup-coredns-manifest {
   sed -i -e "s@{{ *pillar\['dns_domain'\] *}}@${DNS_DOMAIN}@g" "${coredns_file}"
   sed -i -e "s@{{ *pillar\['dns_server'\] *}}@${DNS_SERVER_IP}@g" "${coredns_file}"
   sed -i -e "s@{{ *pillar\['service_cluster_ip_range'\] *}}@${SERVICE_CLUSTER_IP_RANGE}@g" "${coredns_file}"
+
+  if [[ "${ENABLE_DNS_HORIZONTAL_AUTOSCALER:-}" == "true" ]]; then
+    setup-addon-manifests "addons" "dns-horizontal-autoscaler" "gce"
+    local -r dns_autoscaler_file="${dst_dir}/dns-horizontal-autoscaler/dns-horizontal-autoscaler.yaml"
+    sed -i'' -e "s@{{.Target}}@${COREDNS_AUTOSCALER}@g" "${dns_autoscaler_file}"
+  fi
 }
 
 # Sets up the manifests of Fluentd configmap and yamls for k8s addons.
@@ -2098,6 +2106,8 @@ EOF
 
   if [[ "${ENABLE_DNS_HORIZONTAL_AUTOSCALER:-}" == "true" ]]; then
     setup-addon-manifests "addons" "dns-horizontal-autoscaler" "gce"
+    local -r dns_autoscaler_file="${dst_dir}/dns-horizontal-autoscaler/dns-horizontal-autoscaler.yaml"
+    sed -i'' -e "s@{{.Target}}@${KUBEDNS_AUTOSCALER}@g" "${dns_autoscaler_file}"
   fi
 }