initial revision of discovery info doc

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James DeFelice 2016-02-02 02:22:22 +00:00
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# Discovery
## DNS
### kube-dns
[**kube-dns**](https://github.com/kubernetes/kubernetes/blob/release-1.1/docs/admin/dns.md) is a Kubernetes add-on that works out of the box with Kubernetes-Mesos.
For details on usage see the implementation in the `cluster/mesos/docker` source tree.
kube-dns provides records both for services and pods.
### mesos-dns
**NOTE:** There is still no support for publishing Kubernetes *services* in mesos-dns.
**mesos-dns** communicates with the leading Mesos master to build a DNS record set that reflects the tasks running in a Mesos cluster as documented here: http://mesosphere.github.io/mesos-dns/docs/naming.html.
As of Kubernetes-Mesos [release v0.7.2](https://github.com/mesosphere/kubernetes/releases/tag/v0.7.2-v1.1.5) there is experimental support in the scheduler to populate a task's *discovery-info* field in order to generate alternative/more friendly record names in mesos-dns, for *pods* only.
To enable this feature, set `--mesos-generate-task-discovery=true` when launching the scheduler.
The following discovery-info fields may be set using labels (without a namespace prefix) or else `k8s.mesosphere.io/discovery-XXX` annotations:
* `visibility`: may be `framework`, `external`, or `cluster` (defaults to `cluster`)
* `environment`
* `location`
* `name` (this alters record set generation in *mesos-dns*)
* `version`
In the case where both a label as well as an annotation are supplied the value of the annotation is observed.
The interpretation of value of the `name` label (and `discovery-name` annotation) is a special case: the generated Mesos `discovery-info.name` value will be `${name}.${pod-namespace}.pod`; all other discovery-info values are passed through without modification.
#### Example 1: Use a `name` label on a pod template
```yaml
apiVersion: v1
kind: ReplicationController
metadata:
name: frontend
spec:
replicas: 3
template:
metadata:
labels:
app: guestbook
tier: frontend
name: custom-name
spec:
containers:
- name: php-redis
image: gcr.io/google_samples/gb-frontend:v3
resources:
requests:
cpu: 100m
memory: 100Mi
env:
- name: GET_HOSTS_FROM
value: dns
ports:
- containerPort: 80
```
#### Example 2: Use a `discovery-name` annotation on a pod template
```yaml
apiVersion: v1
kind: ReplicationController
metadata:
name: frontend
spec:
replicas: 3
template:
metadata:
labels:
app: guestbook
tier: frontend
annotations:
k8s.mesosphere.io/discovery-name: custom-name
spec:
containers:
- name: php-redis
image: gcr.io/google_samples/gb-frontend:v3
resources:
requests:
cpu: 100m
memory: 100Mi
env:
- name: GET_HOSTS_FROM
value: dns
ports:
- containerPort: 80
```
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