Update Kubernetes DNS document to talk about the new Pod and Endpoint…

…s Annotations to set hostname
kubernetes · Mar 8, 2016 · 11327de · 11327de · k8s-teamcity-mesosphere · Mar 8, 2016
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commit 11327de
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diff --git a/cluster/addons/dns/README.md b/cluster/addons/dns/README.md
@@ -59,6 +59,25 @@ When enabled, pods are assigned a DNS A record in the form of `pod-ip-address.my
 
 For example, a pod with ip `1.2.3.4` in the namespace `default` with a dns name of `cluster.local` would have an entry: `1-2-3-4.default.pod.cluster.local`.
 
+
+####A Records and hostname Based on Pod Annotations - A Beta Feature in Kubernetes v1.2
+Currently when a pod is created, its hostname is the Pod's `metadata.name` value.
+With v1.2, users can specify a Pod annotation, `pod.beta.kubernetes.io/hostname`, to specify what the Pod's hostname should be.
+If the annotation is specified, the annotation value takes precendence over the Pod's name, to be the hostname of the pod.
+For example, given a Pod with annotation `pod.beta.kubernetes.io/hostname: my-pod-name`, the Pod will have its hostname set to "my-pod-name".
+
+v1.2 introduces a beta feature where the user can specify a Pod annotation, `pod.beta.kubernetes.io/subdomain`, to specify what the Pod's subdomain should be.
+If the annotation is specified, the fully qualified Pod hostname will be "<hostname>.<subdomain>.<pod namespace>.svc.<cluster domain>".
+For example, given a Pod with the hostname annotation set to "foo", and the subdomain annotation set to "bar", in namespace "my-namespace", the pod will set its own FQDN as "foo.bar.my-namespace.svc.cluster.local"
+
+If there exists a headless service in the same namespace as the pod and with the same name as the subdomain, the cluster's KubeDNS Server will also return an A record for the Pod's fully qualified hostname.
+Given a Pod with the hostname annotation set to "foo" and the subdomain annotation set to "bar", and a headless Service named "bar" in the same namespace, the pod will see it's own FQDN as "foo.bar.my-namespace.svc.cluster.local". DNS will serve an A record at that name, pointing to the Pod's IP.
+
+With v1.2, the Endpoints object also has a new annotation `endpoints.beta.kubernetes.io/hostnames-map`. Its value is the json representation of map[string(IP)][endpoints.HostRecord], for example: '{"10.245.1.6":{HostName: "my-webserver"}}'.
+If the Endpoints are for a headless service, then A records will be created with the format <hostname>.<service name>.<pod namespace>.svc.<cluster domain>
+For the example json, if endpoints are for a headless service named "bar", and one of the endpoints has IP "10.245.1.6", then a A record will be created with the name "my-webserver.bar.my-namespace.svc.cluster.local" and the A record lookup would return "10.245.1.6".
+This endpoints annotation generally does not need to be specified by end-users, but can used by the internal service controller to deliver the aforementioned feature.
+
 ## How do I find the DNS server?
 The DNS server itself runs as a Kubernetes Service.  This gives it a stable IP
 address.  When you run the SkyDNS service, you want to assign a static IP to use for