PLEASE NOTE: This document applies to the HEAD of the source
tree only. If you are using a released version of Kubernetes, you almost
certainly want the docs that go with that version.
Documentation for specific releases can be found at
[releases.k8s.io](http://releases.k8s.io).
# Live update example
This example demonstrates the usage of Kubernetes to perform a live update on a running group of [pods](../../../docs/user-guide/pods.md).
### Step Zero: Prerequisites
This example assumes that you have forked the repository and [turned up a Kubernetes cluster](../../../docs/getting-started-guides/):
```bash
$ cd kubernetes
$ ./cluster/kube-up.sh
```
### Step One: Turn up the UX for the demo
You can use bash job control to run this in the background (note that you must use the default port -- 8001 -- for the following demonstration to work properly).
This can sometimes spew to the output so you could also run it in a different terminal. You have to run `kubectl proxy` in the root of the
Kubernetes repository. Otherwise you will get "404 page not found" errors as the paths will not match. You can find more information about `kubectl proxy`
[here](https://github.com/GoogleCloudPlatform/kubernetes/blob/master/docs/kubectl_proxy.md).
```
$ kubectl proxy --www=examples/update-demo/local/ &
+ kubectl proxy --www=examples/update-demo/local/
I0218 15:18:31.623279 67480 proxy.go:36] Starting to serve on localhost:8001
```
Now visit the the [demo website](http://localhost:8001/static). You won't see anything much quite yet.
### Step Two: Run the replication controller
Now we will turn up two replicas of an image. They all serve on internal port 80.
```bash
$ kubectl create -f examples/update-demo/nautilus-rc.yaml
```
After pulling the image from the Docker Hub to your worker nodes (which may take a minute or so) you'll see a couple of squares in the UI detailing the pods that are running along with the image that they are serving up. A cute little nautilus.
### Step Three: Try scaling the replication controller
Now we will increase the number of replicas from two to four:
```bash
$ kubectl scale rc update-demo-nautilus --replicas=4
```
If you go back to the [demo website](http://localhost:8001/static/index.html) you should eventually see four boxes, one for each pod.
### Step Four: Update the docker image
We will now update the docker image to serve a different image by doing a rolling update to a new Docker image.
```bash
$ kubectl rolling-update update-demo-nautilus --update-period=10s -f examples/update-demo/kitten-rc.yaml
```
The rolling-update command in kubectl will do 2 things:
1. Create a new [replication controller](../../../docs/user-guide/replication-controller.md) with a pod template that uses the new image (`gcr.io/google_containers/update-demo:kitten`)
2. Scale the old and new replication controllers until the new controller replaces the old. This will kill the current pods one at a time, spinnning up new ones to replace them.
Watch the [demo website](http://localhost:8001/static/index.html), it will update one pod every 10 seconds until all of the pods have the new image.
### Step Five: Bring down the pods
```bash
$ kubectl stop rc update-demo-kitten
```
This first stops the replication controller by turning the target number of replicas to 0 and then deletes the controller.
### Step Six: Cleanup
To turn down a Kubernetes cluster:
```bash
$ ./cluster/kube-down.sh
```
Kill the proxy running in the background:
After you are done running this demo make sure to kill it:
```bash
$ jobs
[1]+ Running ./kubectl proxy --www=local/ &
$ kill %1
[1]+ Terminated: 15 ./kubectl proxy --www=local/
```
### Updating the Docker images
If you want to build your own docker images, you can set `$DOCKER_HUB_USER` to your Docker user id and run the included shell script. It can take a few minutes to download/upload stuff.
```bash
$ export DOCKER_HUB_USER=my-docker-id
$ ./examples/update-demo/build-images.sh
```
To use your custom docker image in the above examples, you will need to change the image name in `examples/update-demo/nautilus-rc.yaml` and `examples/update-demo/kitten-rc.yaml`.
### Image Copyright
Note that the images included here are public domain.
* [kitten](http://commons.wikimedia.org/wiki/File:Kitten-stare.jpg)
* [nautilus](http://commons.wikimedia.org/wiki/File:Nautilus_pompilius.jpg)
[]()