Merge pull request #1884 from kfr2/0.16.x-AdditionalZoneCoreDNSConfig

[v0.16.x] Allow injection of CoreDNS configuration for non-root zones
kubernetes-retired · Jul 20, 2020 · 2260379 · 2260379
2 parents 4c8ca96 + bd0d65a
commit 2260379
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Showing 5 changed files with 49 additions and 5 deletions.
diff --git a/builtin/files/cluster.yaml.tmpl b/builtin/files/cluster.yaml.tmpl
@@ -11,7 +11,7 @@ s3URI: {{.S3URI}}
 #releaseChannel: stable
 
 # To update this to the latest AMI run the following command with the appropriate region and channel then place the resulting ID here
-#   REGION=eu-west-1 CHANNEL=stable curl -s https://$CHANNEL.release.flatcar-linux.net/amd64-usr/current/flatcar_production_ami_all.json | jq  -r ".amis[] | select(.name==\"$REGION\") .hvm
+#  REGION=eu-west-1 CHANNEL=stable curl -s https://$CHANNEL.release.flatcar-linux.net/amd64-usr/current/flatcar_production_ami_all.json | jq  -r ".amis[] | select(.name==\"$REGION\") .hvm
 amiId: "{{.AmiId}}"
 
 # Flatcar has automatic updates https://docs.flatcar-linux.org/os/update-strategies/#disable-automatic-updates-daemon. This can be a risk in certain situations and this is why is disabled by default and you can enable it by setting this param to false.
@@ -1345,9 +1345,18 @@ kubeDns:
     nodesPerReplica: 16
     min: 2
 
-  # Allows to add extra configuration into CoreDNS config map
+  # Allows addition of extra configuration into CoreDNS config map's root zone.
   # extraCoreDNSConfig: |
   #   rewrite name substring demo.app.org app.default.svc.cluster.local
+  #
+  # This configuration is injected into the CoreDNS config map after the root
+  # zone (".") and can be used to add configuration for additional zones.
+  # additionalZoneCoreDNSConfig: |
+  #  global:53 {
+  #      errors
+  #      cache 30
+  #      forward . 1.2.3.4:53
+  #  }
 
 kubeProxy:
   # Use IPVS kube-proxy mode instead of [default] iptables one (requires Kubernetes 1.9.0+ to work reliably)

diff --git a/builtin/files/userdata/cloud-config-controller b/builtin/files/userdata/cloud-config-controller
@@ -1340,7 +1340,7 @@ write_files:
       data:
         # You must set a non-zero value for Typha replicas below.
         typha_service_name: "{{- if .Kubernetes.Networking.SelfHosting.Typha }}calico-typha{{- else -}}none{{- end -}}"
-        
+
         # Configure the backend to use.
         calico_backend: "{{- if .Kubernetes.Networking.SelfHosting.CalicoConfig.VxlanMode }}vxlan{{- else -}}bird{{- end -}}"
 
@@ -4394,7 +4394,7 @@ write_files:
           - --endpoint-reconciler-type=lease
           {{- else }}
           - --apiserver-count={{if .MinControllerCount}}{{ .MinControllerCount }}{{else}}{{ .Controller.Count }}{{end}}
-          {{- end }}        
+          {{- end }}
           - --enable-admission-plugins=NamespaceLifecycle,LimitRanger,ServiceAccount,TaintNodesByCondition,Priority,DefaultTolerationSeconds,DefaultStorageClass,StorageObjectInUseProtection,PersistentVolumeClaimResize,MutatingAdmissionWebhook,ValidatingAdmissionWebhook,RuntimeClass,ResourceQuota,ExtendedResourceToleration,NodeRestriction,PodSecurityPolicy{{if .Experimental.Admission.AlwaysPullImages.Enabled}},AlwaysPullImages{{ end }}{{ if .Experimental.Admission.EventRateLimit.Enabled }},EventRateLimit{{end}}
           {{ if .Experimental.Admission.EventRateLimit.Enabled -}}
           - --admission-control-config-file=/etc/kubernetes/auth/admission-control-config.yaml
@@ -5372,6 +5372,9 @@ write_files:
               reload
               loadbalance
           }
+          {{- if and (eq .KubeDns.Provider "coredns") .KubeDns.AdditionalZoneCoreDNSConfig }}
+{{ .KubeDns.AdditionalZoneCoreDNSConfig | indent 10 }}
+          {{- end }}
 {{- else }}
   - path: /srv/kubernetes/manifests/kube-dns-sa.yaml
     content: |

diff --git a/pkg/api/cluster.go b/pkg/api/cluster.go
@@ -204,7 +204,8 @@ func NewDefaultCluster() *Cluster {
 						Cpu:    "200m",
 					},
 				},
-				ExtraCoreDNSConfig: "",
+				ExtraCoreDNSConfig:          "",
+				AdditionalZoneCoreDNSConfig: "",
 			},
 			KubeSystemNamespaceLabels: make(map[string]string),
 			Kubernetes: Kubernetes{

diff --git a/pkg/api/types.go b/pkg/api/types.go
@@ -210,6 +210,7 @@ type KubeDns struct {
 	Autoscaler                   KubeDnsAutoscaler `yaml:"autoscaler"`
 	DnsDeploymentResources       ComputeResources  `yaml:"dnsDeploymentResources,omitempty"`
 	ExtraCoreDNSConfig           string            `yaml:"extraCoreDNSConfig"`
+	AdditionalZoneCoreDNSConfig  string            `yaml:"additionalZoneCoreDNSConfig"`
 }
 
 func (c *KubeDns) MergeIfEmpty(other KubeDns) {

diff --git a/pkg/model/cluster_test.go b/pkg/model/cluster_test.go
@@ -1449,6 +1449,36 @@ kubeDns:
 				ExtraCoreDNSConfig: "rewrite name substring demo.app.org app.default.svc.cluster.local",
 			},
 		},
+		{
+			conf: `
+kubeDns:
+  provider: coredns
+  additionalZoneCoreDNSConfig: global:53 { forward . 1.2.3.4 }
+`,
+			kubeDns: api.KubeDns{
+				Provider:                     "coredns",
+				NodeLocalResolver:            false,
+				DeployToControllers:          false,
+				AntiAffinityAvailabilityZone: false,
+				TTL:                          30,
+				Autoscaler: api.KubeDnsAutoscaler{
+					CoresPerReplica: 256,
+					NodesPerReplica: 16,
+					Min:             2,
+				},
+				DnsDeploymentResources: api.ComputeResources{
+					Requests: api.ResourceQuota{
+						Memory: "70Mi",
+						Cpu:    "100m",
+					},
+					Limits: api.ResourceQuota{
+						Memory: "170Mi",
+						Cpu:    "200m",
+					},
+				},
+				AdditionalZoneCoreDNSConfig: "global:53 { forward . 1.2.3.4 }",
+			},
+		},
 	}
 
 	for _, conf := range validConfigs {