Merge pull request #37730 from MrHohn/dns-deployment-maxUnavailable

Automatic merge from submit-queue

Set strategy spec for kube-dns to support zero downtime rolling update

From #37728 and coreos/kube-aws#111.

Set `maxUnavailable` to 0 to prevent DNS service outage during update when the replica number is only 1.

Also keeps all kube-dns yaml files in sync.

@bowei @thockin

cluster/addons/dns/skydns-rc.yaml.base

@@ -31,6 +31,10 @@ spec:
   # 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:
+    rollingUpdate:
+      maxSurge: 10%
+      maxUnavailable: 0
   selector:
     matchLabels:
       k8s-app: kube-dns

cluster/addons/dns/skydns-rc.yaml.in

@@ -31,6 +31,10 @@ spec:
   # 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:
+    rollingUpdate:
+      maxSurge: 10%
+      maxUnavailable: 0
   selector:
     matchLabels:
       k8s-app: kube-dns

cluster/addons/dns/skydns-rc.yaml.sed

@@ -31,6 +31,10 @@ spec:
   # 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:
+    rollingUpdate:
+      maxSurge: 10%
+      maxUnavailable: 0
   selector:
     matchLabels:
       k8s-app: kube-dns