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Getting the public IP a container is supposed to use is O(hard), and usually involves ugly gyrations in python or with interfaces. Using the downward API means that the IP Kube is announcing to other endpoints is also visible inside the container for pods to identify themselves. |
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| dapi-pod.yaml | ||
| README.md | ||
PLEASE NOTE: This document applies to the HEAD of the source tree
If you are using a released version of Kubernetes, you should refer to the docs that go with that version.
The latest 1.0.x release of this document can be found [here](http://releases.k8s.io/release-1.0/docs/user-guide/downward-api/README.md).Documentation for other releases can be found at releases.k8s.io.
Downward API example
Following this example, you will create a pod with a containers that consumes the pod's name and namespace using the downward API.
Step Zero: Prerequisites
This example assumes you have a Kubernetes cluster installed and running, and that you have
installed the kubectl command line tool somewhere in your path. Please see the getting
started for installation instructions for your platform.
Step One: Create the pod
Containers consume the downward API using environment variables. The downward API allows containers to be injected with the name and namespace of the pod the container is in.
Use the examples/downward-api/dapi-pod.yaml file to create a Pod with a container that consumes the
downward API.
$ kubectl create -f docs/user-guide/downward-api/dapi-pod.yaml
Examine the logs
This pod runs the env command in a container that consumes the downward API. You can grep
through the pod logs to see that the pod was injected with the correct values:
$ kubectl logs dapi-test-pod | grep POD_
2015-04-30T20:22:18.568024817Z MY_POD_NAME=dapi-test-pod
2015-04-30T20:22:18.568087688Z MY_POD_NAMESPACE=default
2015-04-30T20:22:18.568092435Z MY_POD_IP=10.0.1.6