Move to Tasks: Core DNS Federation. (#3807)
This commit is contained in:
Steve Perry
@@ -1,10 +0,0 @@
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isClusterService: false
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serviceType: "LoadBalancer"
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middleware:
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kubernetes:
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enabled: false
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etcd:
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enabled: true
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zones:
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- "example.com."
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endpoint: "http://etcd-cluster.my-namespace:2379"
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@@ -1,126 +0,0 @@
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---
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title: Setting up CoreDNS as DNS provider for Cluster Federation
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---
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{% capture overview %}
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This page shows how to configure and deploy CoreDNS to be used as the
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DNS provider for Cluster Federation.
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{% endcapture %}
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{% capture objectives %}
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* Configure and deploy CoreDNS server
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* Bringup federation with CoreDNS as dns provider
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* Setup CoreDNS server in nameserver lookup chain
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{% endcapture %}
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{% capture prerequisites %}
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You need to have a running Kubernetes cluster (which is
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referenced as host cluster). Please see one of the
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[getting started](/docs/getting-started-guides/) guides for
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installation instructions for your platform.
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{% endcapture %}
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{% capture lessoncontent %}
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## Deploying CoreDNS and etcd charts
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CoreDNS can be deployed in various configurations. Explained below is a
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reference and can be tweaked to suit the needs of the platform and the
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cluster federation.
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To deploy CoreDNS, we shall make use of helm charts. CoreDNS will be
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deployed with [etcd](https://coreos.com/etcd) as the backend and should
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be pre-installed. etcd can also be deployed using helm charts. Shown
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below are the instructions to deploy etcd.
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helm install --namespace my-namespace --name etcd-operator stable/etcd-operator
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helm upgrade --namespace my-namespace --set cluster.enabled=true etcd-operator stable/etcd-operator
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*Note: etcd default deployment configurations can be overridden, suiting the
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host cluster.*
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After deployment succeeds, etcd can be accessed with the
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[http://etcd-cluster.my-namespace:2379](http://etcd-cluster.my-namespace:2379) endpoint within the host cluster.
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The CoreDNS default configuration should be customized to suit the federation.
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Shown below is the Values.yaml, which overrides the default
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configuration parameters on the CoreDNS chart.
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{% include code.html language="yaml" file="Values.yaml" ghlink="/docs/tutorials/federation/Values.yaml" %}
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The above configuration file needs some explanation:
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- `isClusterService` specifies whether CoreDNS should be deployed as a
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cluster-service, which is the default. You need to set it to false, so
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that CoreDNS is deployed as a Kubernetes application service.
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- `serviceType` specifies the type of Kubernetes service to be created
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for CoreDNS. You need to choose either "LoadBalancer" or "NodePort" to
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make the CoreDNS service accessible outside the Kubernetes cluster.
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- Disable `middleware.kubernetes`, which is enabled by default by
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setting `middleware.kubernetes.enabled` to false.
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- Enable `middleware.etcd` by setting `middleware.etcd.enabled` to
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true.
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- Configure the DNS zone (federation domain) for which CoreDNS is
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authoritative by setting `middleware.etcd.zones` as shown above.
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- Configure the etcd endpoint which was deployed earlier by setting
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`middleware.etcd.endpoint`
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Now deploy CoreDNS by running
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helm install --namespace my-namespace --name coredns -f Values.yaml stable/coredns
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Verify that both etcd and CoreDNS pods are running as expected.
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## Deploying Federation with CoreDNS as DNS provider
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The Federation control plane can be deployed using `kubefed init`. CoreDNS
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can be chosen as the DNS provider by specifying two additional parameters.
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--dns-provider=coredns
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--dns-provider-config=coredns-provider.conf
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coredns-provider.conf has below format:
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[Global]
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etcd-endpoints = http://etcd-cluster.my-namespace:2379
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zones = example.com.
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- `etcd-endpoints` is the endpoint to access etcd.
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- `zones` is the federation domain for which CoreDNS is authoritative and is same as --dns-zone-name flag of `kubefed init`.
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*Note: middleware.etcd.zones in CoreDNS configuration and --dns-zone-name
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flag to kubefed init should match.*
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## Setup CoreDNS server in nameserver resolv.conf chain
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Once the federation control plane is deployed and federated clusters
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are joined to the federation, you need to add the CoreDNS server to the
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pod's nameserver resolv.conf chain in all the federated clusters as this
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self hosted CoreDNS server is not discoverable publicly. This can be
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achieved by adding the below line to `dnsmasq` container's arg in
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`kube-dns` deployment.
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--server=/example.com./<CoreDNS endpoint>
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Replace `example.com` above with federation domain.
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*Note: Adding CoreDNS server to the pod's nameserver resolv.conf chain will be
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automated in subsequent releases.*
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Now the federated cluster is ready for cross-cluster service discovery!
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{% endcapture %}
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{% include templates/tutorial.md %}
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