Merge pull request #1 from johnbelamaric/add-k8s-deployment

Add k8s deployment script and README

kubernetes/README.md

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+# kubernetes
+
+CoreDNS can run in place of the standard Kube-DNS in Kubernetes. Using the *kubernetes*
+middleware, CoreDNS will reading zone data from a Kubernetes cluster. It implements the
+spec defined for Kubernetes DNS-Based service discovery:
+
+   https://github.com/kubernetes/dns/blob/master/docs/specification.md
+
+## deploy.sh and coredns.yaml.sed
+
+`deploy.sh` is a convenience script to generate a manifest for running CoreDNS on a cluster
+that is currently running standard kube-dns. Using the `coredns.yaml.sed` as a template,
+it creates a ConfigMap and a CoreDNS deployment, then updates the Kube-DNS service selector
+to use the CoreDNS deployment. By re-using the existing service, there is no disruption in
+servicing requests.
+
+The script doesn't delete the kube-dns deployment or replication controller - you'll have to
+do that manually.
+
+You should examine the manifest carefully and make sure it is correct for your particular
+cluster. Depending on how you have built your cluster and the version you are running,
+some modifications to the manifest may be needed.
+
+In the best case scenario, all that's needed to replace Kube-DNS are these two commands:
+
+~~~
+$ ./deploy.sh 10.3.0.0/24 | kubectl apply -f -
+$ kubectl delete --namespace=kube-system deployment kube-dns
+~~~

kubernetes/coredns.yaml.sed

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+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: coredns
+  namespace: kube-system
+data:
+  Corefile: |
+    .:53 {
+        errors
+        log stdout
+        health
+        kubernetes CLUSTER_DOMAIN {
+          cidrs SERVICE_CIDR
+        }
+        proxy . /etc/resolv.conf
+        cache 30
+    }
+---
+apiVersion: extensions/v1beta1
+kind: Deployment
+metadata:
+  name: coredns
+  namespace: kube-system
+  labels:
+    k8s-app: coredns
+    kubernetes.io/cluster-service: "true"
+    kubernetes.io/name: "CoreDNS"
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      k8s-app: coredns
+  template:
+    metadata:
+      labels:
+        k8s-app: coredns
+      annotations:
+        scheduler.alpha.kubernetes.io/critical-pod: ''
+        scheduler.alpha.kubernetes.io/tolerations: '[{"key":"CriticalAddonsOnly", "operator":"Exists"}]'
+    spec:
+      containers:
+      - name: coredns
+        image: coredns/coredns:latest
+        imagePullPolicy: Always
+        args: [ "-conf", "/etc/coredns/Corefile" ]
+        volumeMounts:
+        - name: config-volume
+          mountPath: /etc/coredns
+        ports:
+        - containerPort: 53
+          name: dns
+          protocol: UDP
+        - containerPort: 53
+          name: dns-tcp
+          protocol: TCP
+        livenessProbe:
+          httpGet:
+            path: /health
+            port: 8080
+            scheme: HTTP
+          initialDelaySeconds: 60
+          timeoutSeconds: 5
+          successThreshold: 1
+          failureThreshold: 5
+      dnsPolicy: Default
+      volumes:
+        - name: config-volume
+          configMap:
+            name: coredns
+            items:
+            - key: Corefile
+              path: Corefile
+---
+apiVersion: v1
+kind: Service
+metadata:
+  name: kube-dns
+  namespace: kube-system
+  labels:
+    k8s-app: coredns
+    kubernetes.io/cluster-service: "true"
+    kubernetes.io/name: "CoreDNS"
+spec:
+  selector:
+    k8s-app: coredns
+  clusterIP: CLUSTER_DNS_IP
+  ports:
+  - name: dns
+    port: 53
+    protocol: UDP
+  - name: dns-tcp
+    port: 53
+    protocol: TCP

kubernetes/deploy.sh

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+#!/bin/bash
+
+# Deploys CoreDNS to a cluster currently running Kube-DNS.
+
+SERVICE_CIDR=$1
+CLUSTER_DOMAIN=${2:-cluster.local}
+YAML_TEMPLATE=${3:-`pwd`/coredns.yaml.sed}
+YAML=${4:-`pwd`/coredns.yaml}
+
+if [[ -z $SERVICE_CIDR ]]; then
+	echo "Usage: $0 SERVICE-CIDR [ CLUSTER-DOMAIN ] [ YAML-TEMPLATE ] [ YAML ]"
+	exit 1
+fi
+
+CLUSTER_DNS_IP=$(kubectl get service --namespace kube-system kube-dns -o jsonpath="{.spec.clusterIP}")
+
+sed -e s/CLUSTER_DNS_IP/$CLUSTER_DNS_IP/g -e s/CLUSTER_DOMAIN/$CLUSTER_DOMAIN/g -e s?SERVICE_CIDR?$SERVICE_CIDR?g $YAML_TEMPLATE
+
+