Adds a generic CoreDNS chart (#785)

* CoreDNS

Adds a basic CoreDNS chart based off the project deployment
documentation

* Made CoreDNS chart generic to deploy in multiple scenarios

* Address review comments for CoreDNS chart

stable/coredns/.helmignore

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+# Patterns to ignore when building packages.
+# This supports shell glob matching, relative path matching, and
+# negation (prefixed with !). Only one pattern per line.
+.DS_Store
+# Common VCS dirs
+.git/
+.gitignore
+.bzr/
+.bzrignore
+.hg/
+.hgignore
+.svn/
+# Common backup files
+*.swp
+*.bak
+*.tmp
+*~
+# Various IDEs
+.project
+.idea/
+*.tmproj

stable/coredns/Chart.yaml

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+name: coredns
+version: 0.1.0
+description: CoreDNS is a DNS server that chains middleware and provides Kubernetes DNS Services
+keywords:
+- coredns
+- dns
+- kubedns
+home: https://coredns.io
+icon: https://raw.githubusercontent.com/coredns/logo/master/Icon/CoreDNS_Colour_Icon.svg
+sources:
+- https://github.com/coredns/coredns
+maintainers:
+- name: Acaleph
+ email: [email protected]
+- name: Shashidhara TD
+ email: [email protected]

stable/coredns/README.md

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+CoreDNS
+=======
+
+CoreDNS is a DNS server that chains middleware and provides DNS Services
+
+TL;DR;
+------
+
+```console
+$ helm install --name coredns --namespace=kube-system stable/coredns
+```
+
+Introduction
+------------
+
+This chart bootstraps a [CoreDNS](https://github.com/coredns/coredns) deployment on a [Kubernetes](http:https://kubernetes.io) cluster using the [Helm](https://helm.sh) package manager. This chart will provide DNS Services and can be deployed in multiple configuration to support various scenarios listed below:
+
+ - CoreDNS as a cluster dns service and a drop-in replacement for Kube/SkyDNS. This is the default mode and CoreDNS is deployed as cluster-service in kube-system namespace. This mode is chosen by setting `isClusterService` to true.
+ - CoreDNS as an external dns service. In this mode CoreDNS is deployed as any kubernetes app in user specified namespace. The CoreDNS service can be exposed outside the cluster by using using either the NodePort or LoadBalancer type of service. This mode is chosen by setting `isClusterService` to false.
+ - CoreDNS as an external dns provider for kubernetes federation. This is a sub case of 'external dns service' which uses etcd middleware for CoreDNS backend. This deployment mode as a dependency on `etcd-operator` chart, which needs to be pre-installed. To use this deployment mode use below configuration file to override default values.
+```
+isClusterService: false
+ serviceType: "NodePort"
+ middleware:
+ kubernetes:
+ enabled: false
+ etcd:
+ enabled: true
+ zones:
+ - "<example.io>"
+ endpoint: "http:https://<etcd-cluster>:2379"
+```
+
+Prerequisites
+-------------
+
+- Kubernetes 1.4+ with Beta APIs enabled
+
+Installing the Chart
+--------------------
+
+The chart can be installed as follows:
+
+```console
+$ helm install --name coredns --namespace=kube-system stable/coredns
+```
+
+The command deploys CoreDNS on the Kubernetes cluster in the default configuration. The [configuration](#configuration) section lists various ways to override default configuration during deployment.
+
+> **Tip**: List all releases using `helm list`
+
+Uninstalling the Chart
+----------------------
+
+To uninstall/delete the `my-release` deployment:
+
+```console
+$ helm delete coredns
+```
+
+The command removes all the Kubernetes components associated with the chart and deletes the release.
+
+Configuration
+-------------
+
+See `values.yaml` for configuration notes. Specify each parameter using the `--set key=value[,key=value]` argument to `helm install`. For example,
+
+```console
+$ helm install --name coredns \
+ --set middleware.prometheus.enabled=false \
+ stable/coredns
+```
+
+The above command disables the Prometheus middleware.
+
+Alternatively, a YAML file that specifies the values for the above parameters can be provided while installing the chart. For example,
+
+```console
+$ helm install --name coredns -f values.yaml stable/coredns
+```
+
+> **Tip**: You can use the default [values.yaml](values.yaml)

stable/coredns/templates/NOTES.txt

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+{{- if .Values.isClusterService }}
+CoreDNS is now running in the cluster as a cluster-service.
+{{- else }}
+CoreDNS is now running in the cluster.
+It can be accessed using the below endpoint
+{{- if contains "NodePort" .Values.serviceType }}
+ export NODE_PORT=$(kubectl get --namespace {{ .Release.Namespace }} -o jsonpath="{.spec.ports[0].nodePort}" services {{ template "fullname" . }})
+ export NODE_IP=$(kubectl get nodes --namespace {{ .Release.Namespace }} -o jsonpath="{.items[0].status.addresses[0].address}")
+ echo "$NODE_IP:$NODE_PORT"
+{{- else if contains "LoadBalancer" .Values.serviceType }}
+ NOTE: It may take a few minutes for the LoadBalancer IP to be available.
+ You can watch the status of by running 'kubectl get svc -w {{ template "fullname" . }}'
+
+ export SERVICE_IP=$(kubectl get svc --namespace {{ .Release.Namespace }} {{ template "fullname" . }} -o jsonpath='{.status.loadBalancer.ingress[0].ip}')
+ echo $SERVICE_IP
+{{- else if contains "ClusterIP" .Values.serviceType }}
+ "{{ template "fullname" . }}.{{ .Release.Namespace }}.svc.cluster.local"
+ from within the cluster
+{{- end }}
+{{- end }}
+
+It can be tested with the following:
+
+1. Launch a Pod with DNS tools:
+
+kubectl run -it --rm --restart=Never --image=infoblox/dnstools:latest dnstools
+
+2. Query the DNS server:
+
+/ # host kubernetes

stable/coredns/templates/_helpers.tpl

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+{{/* vim: set filetype=mustache: */}}
+{{/*
+Expand the name of the chart.
+*/}}
+{{- define "name" -}}
+{{- default .Chart.Name .Values.nameOverride | trunc 63 | trimSuffix "-" -}}
+{{- end -}}
+
+{{/*
+Create a default fully qualified app name.
+We truncate at 63 chars because some Kubernetes name fields are limited to this (by the DNS naming spec).
+*/}}
+{{- define "fullname" -}}
+{{- $name := default .Chart.Name .Values.nameOverride -}}
+{{- printf "%s-%s" .Release.Name $name | trunc 63 | trimSuffix "-" -}}
+{{- end -}}

stable/coredns/templates/configmap.yaml

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+apiVersion: v1
+kind: ConfigMap
+metadata:
+ name: {{ template "fullname" . }}
+data:
+ Corefile: |-
+ .:53 {
+ {{- range $key, $middleware := .Values.middleware }}
+ {{- if $middleware.enabled }}
+ {{- if eq "kubernetes" $key }}
+ kubernetes {{ $middleware.clusterDomain }} {
+ cidrs {{ $middleware.clusterCidr }}
+ }
+ {{- end }}
+ {{- if eq "etcd" $key }}
+ etcd {{ range $middleware.zones }}{{ . }} {{ end }}{
+ {{ if $middleware.path }}path {{ $middleware.path }}{{ end }}
+ endpoint {{ $middleware.endpoint }}
+ }
+ {{- end }}
+ {{- if eq "loadbalance" $key }}
+ loadbalance {{ default "round_robin" $middleware.policy }}
+ {{- end }}
+ {{- if eq "log" $key }}
+ log {{ default "stdout" $middleware.file }}
+ {{- end }}
+ {{- if eq "errors" $key }}
+ errors {{ default "stderr" $middleware.file }}
+ {{- end }}
+ {{- if eq "health" $key }}
+ health
+ {{- end }}
+ {{- if eq "prometheus" $key }}
+ prometheus localhost:{{ $middleware.port }}
+ {{- end }}
+ {{- if eq "proxy" $key }}
+ proxy . /etc/resolv.conf
+ {{- end }}
+ {{- if eq "cache" $key }}
+ cache 30
+ {{- end }}
+ {{- end }}
+ {{- end }}
+ }

stable/coredns/templates/deployment.yaml

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+apiVersion: extensions/v1beta1
+kind: Deployment
+metadata:
+ name: {{ template "fullname" . }}
+ labels:
+ heritage: {{ .Release.Service | quote }}
+ release: {{ .Release.Name | quote }}
+ chart: "{{ .Chart.Name }}-{{ .Chart.Version | replace "+" "_" }}"
+ {{- if .Values.isClusterService }}
+ k8s-app: {{ .Chart.Name | quote }}
+ kubernetes.io/cluster-service: "true"
+ kubernetes.io/name: "CoreDNS"
+ {{- else }}
+ app: {{ template "fullname" . }}
+ {{- end }}
+spec:
+ replicas: {{ .Values.replicaCount }}
+ selector:
+ matchLabels:
+ {{- if .Values.isClusterService }}
+ k8s-app: {{ .Chart.Name | quote }}
+ {{- else }}
+ app: {{ template "fullname" . }}
+ {{- end }}
+ template:
+ metadata:
+ labels:
+ {{- if .Values.isClusterService }}
+ k8s-app: {{ .Chart.Name | quote }}
+ {{- else }}
+ app: {{ template "fullname" . }}
+ {{- end }}
+ release: {{ .Release.Name | quote }}
+ annotations:
+ {{- if .Values.isClusterService }}
+ scheduler.alpha.kubernetes.io/critical-pod: ''
+ scheduler.alpha.kubernetes.io/tolerations: '[{"key":"CriticalAddonsOnly", "operator":"Exists"}]'
+ {{- end }}
+ spec:
+ containers:
+ - name: "coredns"
+ image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"
+ imagePullPolicy: {{ .Values.image.pullPolicy }}
+ args: [ "-conf", "/etc/coredns/Corefile" ]
+ volumeMounts:
+ - name: config-volume
+ mountPath: /etc/coredns
+ resources:
+{{ toYaml .Values.resources | indent 10 }}
+ 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
+ volumes:
+ - name: config-volume
+ configMap:
+ name: {{ template "fullname" . }}
+ items:
+ - key: Corefile
+ path: Corefile

stable/coredns/templates/service.yaml

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+apiVersion: v1
+kind: Service
+metadata:
+ name: {{ template "fullname" . }}
+ labels:
+ heritage: {{ .Release.Service | quote }}
+ release: {{ .Release.Name | quote }}
+ chart: "{{ .Chart.Name }}-{{ .Chart.Version | replace "+" "_" }}"
+ {{- if .Values.isClusterService }}
+ k8s-app: {{ .Chart.Name | quote }}
+ kubernetes.io/cluster-service: "true"
+ kubernetes.io/name: "CoreDNS"
+ {{- else }}
+ app: {{ template "fullname" . }}
+ {{- end }}
+ annotations:
+ {{- if .Values.middleware.prometheus.enabled }}
+ prometheus.io/scrape: "true"
+ prometheus.io/port: {{ .Values.middleware.prometheus.port | quote }}
+ {{- end }}
+spec:
+ selector:
+ {{- if .Values.isClusterService }}
+ k8s-app: {{ .Chart.Name | quote }}
+ {{- else }}
+ app: {{ template "fullname" . }}
+ {{- end }}
+ {{- if .Values.isClusterService }}
+ clusterIP: {{ .Values.middleware.kubernetes.clusterIP }}
+ {{- end }}
+ ports:
+ - name: dns
+ port: 53
+ protocol: UDP
+ - name: dns-tcp
+ port: 53
+ protocol: TCP
+ type: {{ default "ClusterIP" .Values.serviceType }}

stable/coredns/values.yaml

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+# Default values for coredns.
+# This is a YAML-formatted file.
+# Declare variables to be passed into your templates.
+
+replicaCount: 1
+
+image:
+ repository: coredns/coredns
+ tag: "006"
+ pullPolicy: IfNotPresent
+
+resources:
+ limits:
+ cpu: 100m
+ memory: 128Mi
+ requests:
+ cpu: 100m
+ memory: 128Mi
+
+# isClusterService specifies whether chart should be deployed as cluster-service or normal k8s app.
+isClusterService: true
+
+# serviceType specifies type of service to be created for this chart.
+serviceType: "ClusterIP"
+
+# middleware configuration of CoreDNS refer to https://github.com/coredns/coredns/tree/master/middleware
+# for all specific details. set enabled to true/false to enable/disable a middleware.
+middleware:
+ kubernetes:
+ enabled: true
+ clusterCidr: "10.3.0.0/24"
+ clusterDomain: "cluster.local"
+ clusterIP:
+ prometheus:
+ enabled: true
+ port: "9153"
+ errors:
+ enabled: true
+ file: "stderr"
+ log:
+ enabled: false
+ file: "stdout"
+ health:
+ enabled: true
+ proxy:
+ enabled: true
+ cache:
+ enabled: true
+ loadbalance:
+ enabled: true
+ policy: "round_robin"
+ etcd:
+ enabled: false
+ zones:
+ - "k8s.io"
+ path: "/skydns"
+ endpoint: "http:https://localhost:2379"