stable/coredns

Chart version: 1.13.8
Api version: v1
App version: 1.7.1
DEPRECATED CoreDNS is a DNS server that chains plugins and prov...
application
Chart Type
DEPRECATED
Status
Unknown
License
6638
Downloads
https://kubernetes-charts.storage.googleapis.com
Set me up:
helm repo add center https://repo.chartcenter.io
Install Chart:
helm install coredns center/stable/coredns
Versions (0)

⚠️ Repo Archive Notice

As of Nov 13, 2020, charts in this repo will no longer be updated. For more information, see the Helm Charts Deprecation and Archive Notice, and Update.

CoreDNS

CoreDNS is a DNS server that chains plugins and provides DNS Services

DEPRECATION NOTICE

This chart is deprecated and no longer supported.

TL;DR;

$ helm install --name coredns --namespace=kube-system stable/coredns

Introduction

This chart bootstraps a CoreDNS deployment on a Kubernetes cluster using the Helm 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 plugin for CoreDNS backend. This deployment mode as a dependency on etcd-operator chart, which needs to be pre-installed.

Prerequisites

  • Kubernetes 1.10 or later

Installing the Chart

The chart can be installed as follows:

$ helm install --name coredns --namespace=kube-system stable/coredns

The command deploys CoreDNS on the Kubernetes cluster in the default configuration. The 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:

$ helm delete coredns

The command removes all the Kubernetes components associated with the chart and deletes the release.

Configuration

Parameter Description Default
image.repository The image repository to pull from coredns/coredns
image.tag The image tag to pull from v1.7.1
image.pullPolicy Image pull policy IfNotPresent
replicaCount Number of replicas 1
resources.limits.cpu Container maximum CPU 100m
resources.limits.memory Container maximum memory 128Mi
resources.requests.cpu Container requested CPU 100m
resources.requests.memory Container requested memory 128Mi
serviceType Kubernetes Service type ClusterIP
prometheus.service.enabled Set this to true to create Service for Prometheus metrics false
prometheus.service.annotations Annotations to add to the metrics Service {prometheus.io/scrape: "true", prometheus.io/port: "9153"}
prometheus.monitor.enabled Set this to true to create ServiceMonitor for Prometheus operator false
prometheus.monitor.additionalLabels Additional labels that can be used so ServiceMonitor will be discovered by Prometheus {}
prometheus.monitor.namespace Selector to select which namespaces the Endpoints objects are discovered from. ""
service.clusterIP IP address to assign to service ""
service.loadBalancerIP IP address to assign to load balancer (if supported) ""
service.externalIPs External IP addresses []
service.externalTrafficPolicy Enable client source IP preservation []
service.annotations Annotations to add to service {}
serviceAccount.create If true, create & use serviceAccount false
serviceAccount.name If not set & create is true, use template fullname
rbac.create If true, create & use RBAC resources true
rbac.pspEnable Specifies whether a PodSecurityPolicy should be created. false
isClusterService Specifies whether chart should be deployed as cluster-service or normal k8s app. true
priorityClassName Name of Priority Class to assign pods ""
servers Configuration for CoreDNS and plugins See values.yml
affinity Affinity settings for pod assignment {}
nodeSelector Node labels for pod assignment {}
tolerations Tolerations for pod assignment []
zoneFiles Configure custom Zone files []
extraVolumes Optional array of volumes to create []
extraVolumeMounts Optional array of volumes to mount inside the CoreDNS container []
extraSecrets Optional array of secrets to mount inside the CoreDNS container []
customLabels Optional labels for Deployment(s), Pod, Service, ServiceMonitor objects {}
rollingUpdate.maxUnavailable Maximum number of unavailable replicas during rolling update 1
rollingUpdate.maxSurge Maximum number of pods created above desired number of pods 25%
podDisruptionBudget Optional PodDisruptionBudget {}
podAnnotations Optional Pod only Annotations {}
terminationGracePeriodSeconds Optional duration in seconds the pod needs to terminate gracefully. 30
preStopSleep Definition of Kubernetes preStop hook executed before Pod termination {}
hpa.enabled Enable Hpa autoscaler instead of proportional one false
hpa.minReplicas Hpa minimum number of CoreDNS replicas 1
hpa.maxReplicas Hpa maximum number of CoreDNS replicas 2
hpa.metrics Metrics definitions used by Hpa to scale up and down {}
autoscaler.enabled Optionally enabled a cluster-proportional-autoscaler for CoreDNS false
autoscaler.coresPerReplica Number of cores in the cluster per CoreDNS replica 256
autoscaler.nodesPerReplica Number of nodes in the cluster per CoreDNS replica 16
autoscaler.min Min size of replicaCount 0
autoscaler.max Max size of replicaCount 0 (aka no max)
autoscaler.includeUnschedulableNodes Should the replicas scale based on the total number or only schedulable nodes false
autoscaler.preventSinglePointFailure If true does not allow single points of failure to form true
autoscaler.image.repository The image repository to pull autoscaler from k8s.gcr.io/cluster-proportional-autoscaler-amd64
autoscaler.image.tag The image tag to pull autoscaler from 1.7.1
autoscaler.image.pullPolicy Image pull policy for the autoscaler IfNotPresent
autoscaler.priorityClassName Optional priority class for the autoscaler pod. priorityClassName used if not set. ""
autoscaler.affinity Affinity settings for pod assignment for autoscaler {}
autoscaler.nodeSelector Node labels for pod assignment for autoscaler {}
autoscaler.tolerations Tolerations for pod assignment for autoscaler []
autoscaler.resources.limits.cpu Container maximum CPU for cluster-proportional-autoscaler 20m
autoscaler.resources.limits.memory Container maximum memory for cluster-proportional-autoscaler 10Mi
autoscaler.resources.requests.cpu Container requested CPU for cluster-proportional-autoscaler 20m
autoscaler.resources.requests.memory Container requested memory for cluster-proportional-autoscaler 10Mi
autoscaler.configmap.annotations Annotations to add to autoscaler config map. For example to stop CI renaming them {}

See values.yaml for configuration notes. Specify each parameter using the --set key=value[,key=value] argument to helm install. For example,

$ helm install --name coredns \
  --set rbac.create=false \
    stable/coredns

The above command disables automatic creation of RBAC rules.

Alternatively, a YAML file that specifies the values for the above parameters can be provided while installing the chart. For example,

$ helm install --name coredns -f values.yaml stable/coredns

Tip: You can use the default values.yaml

Caveats

The chart will automatically determine which protocols to listen on based on the protocols you define in your zones. This means that you could potentially use both “TCP” and “UDP” on a single port. Some cloud environments like “GCE” or “Azure container service” cannot create external loadbalancers with both “TCP” and “UDP” protocols. So When deploying CoreDNS with serviceType="LoadBalancer" on such cloud environments, make sure you do not attempt to use both protocols at the same time.

Autoscaling

By setting autoscaler.enabled = true a cluster-proportional-autoscaler will be deployed. This will default to a coredns replica for every 256 cores, or 16 nodes in the cluster. These can be changed with autoscaler.coresPerReplica and autoscaler.nodesPerReplica. When cluster is using large nodes (with more cores), coresPerReplica should dominate. If using small nodes, nodesPerReplica should dominate.

This also creates a ServiceAccount, ClusterRole, and ClusterRoleBinding for the autoscaler deployment.

replicaCount is ignored if this is enabled.

By setting hpa.enabled = true a Horizontal Pod Autoscaler is enabled for Coredns deployment. This can scale number of replicas based on meitrics like CpuUtilization, MemoryUtilization or Custom ones.