Minor cleanups of CoreDNS issues and CI job (#4719)

* Minor cleanups

* Add comment in docs that nodelocaldns cache is enabled by default

docs/dns-stack.md

@@ -114,10 +114,12 @@ The only exception is that ``hostNetwork: true`` PODs and non-k8s managed contai
 cluster service names.
 
 ## Nodelocal DNS cache
-Setting ``enable_nodelocaldns`` to ``true`` will make pods reach out to the dns (core-dns) caching agent running on the same node, thereby avoiding iptables DNAT rules and connection tracking. The local caching agent will query kube-dns / core-dns (depending on what main DNS plugin is configured in your cluster) for cache misses of cluster hostnames(cluster.local suffix by default).
+Setting ``enable_nodelocaldns`` to ``true`` will make pods reach out to the dns (core-dns) caching agent running on the same node, thereby avoiding iptables DNAT rules and connection tracking. The local caching agent will query core-dns (depending on what main DNS plugin is configured in your cluster) for cache misses of cluster hostnames(cluster.local suffix by default).
 
 More information on the rationale behind this implementation can be found [here](https://github.com/kubernetes/enhancements/blob/master/keps/sig-network/0030-nodelocal-dns-cache.md).
 
+**As per the 2.10 release, Nodelocal DNS cache is enabled by default.**
+
 
 Limitations
 -----------
@@ -129,9 +131,7 @@ Limitations
 
 * There is
   [no way to specify a custom value](https://github.com/kubernetes/kubernetes/issues/33554)
-  for the SkyDNS ``ndots`` param via an
+  for the SkyDNS ``ndots`` param.
-  [option for KubeDNS](https://github.com/kubernetes/kubernetes/blob/master/cmd/kube-dns/app/options/options.go)
-  add-on, while SkyDNS supports it though.
 
 * the ``searchdomains`` have a limitation of a 6 names and 256 chars
   length. Due to default ``svc, default.svc`` subdomains, the actual

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

@@ -94,7 +94,7 @@ ingress_nginx_enabled: false
 # ingress_nginx_configmap_tcp_services:
 #   9000: "default/example-go:8080"
 # ingress_nginx_configmap_udp_services:
-#   53: "kube-system/kube-dns:53"
+#   53: "kube-system/coredns:53"
 
 # Cert manager deployment
 cert_manager_enabled: false

roles/kubernetes-apps/ansible/tasks/cleanup_dns.yml

@@ -7,6 +7,16 @@
     resource: "deploy"
     state: absent
   when:
-    - kubeadm_init is defined
+    - dns_mode in ['coredns', 'coredns_dual']
-    - kubeadm_init.changed|default(false)
+    - inventory_hostname == groups['kube-master'][0]
+
+- name: Kubernetes Apps | Delete kubeadm Kube-DNS service
+  kube:
+    name: "kube-dns"
+    namespace: "kube-system"
+    kubectl: "{{ bin_dir }}/kubectl"
+    resource: "svc"
+    state: absent
+  when:
+    - dns_mode in ['coredns', 'coredns_dual']
     - inventory_hostname == groups['kube-master'][0]

roles/kubernetes-apps/rotate_tokens/tasks/main.yml

@@ -34,7 +34,7 @@
     {{ bin_dir }}/kubectl --kubeconfig /etc/kubernetes/admin.conf get secrets --all-namespaces
     -o 'jsonpath={range .items[*]}{"\n"}{.metadata.namespace}{" "}{.metadata.name}{" "}{.type}{end}'
     | grep kubernetes.io/service-account-token
-    | egrep 'default-token|kube-proxy|kube-dns|netchecker|weave|calico|canal|flannel|dashboard|cluster-proportional-autoscaler|tiller|local-volume-provisioner'
+    | egrep 'default-token|kube-proxy|coredns|netchecker|weave|calico|canal|flannel|dashboard|cluster-proportional-autoscaler|tiller|local-volume-provisioner'
   register: tokens_to_delete
   when: needs_rotation
 

tests/files/packet_centos7-flannel-addons.yml

@@ -18,7 +18,8 @@ dns_min_replicas: 1
 kube_encrypt_secret_data: true
 ingress_nginx_enabled: true
 cert_manager_enabled: true
-metrics_server_enabled: true
+# Disable as health checks are still unstable and slow to respond.
+metrics_server_enabled: false
 metrics_server_kubelet_insecure_tls: true
 kube_token_auth: true
 kube_basic_auth: true