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Live update example

This example demonstrates the usage of Kubernetes to perform a live update on a running group of pods.

Step Zero: Prerequisites

This example assumes that you have forked the repository and turned up a Kubernetes cluster:

$ cd kubernetes
$ hack/dev-build-and-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.

$ ./cluster/kubectl.sh proxy --www=examples/update-demo/local/ &
+ ./cluster/kubectl.sh 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. You won't see anything much quite yet.

Step Two: Run the controller

Now we will turn up two replicas of an image. They all serve on internal port 80.

$ ./cluster/kubectl.sh 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 resizing the controller

Now we will increase the number of replicas from two to four:

$ ./cluster/kubectl.sh resize rc update-demo-nautilus --replicas=4

If you go back to the demo website 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.

$ ./cluster/kubectl.sh 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 with a pod template that uses the new image (gcr.io/google_containers/update-demo:kitten)
  2. Resize 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, it will update one pod every 10 seconds until all of the pods have the new image.

Step Five: Bring down the pods

$ ./cluster/kubectl.sh stop rc update-demo-kitten

This will first 'stop' the replication controller by turning the target number of replicas to 0. It'll then delete that controller.

Step Six: Cleanup

To turn down a Kubernetes cluster:

$ cd ../..  # Up to kubernetes.
$ cluster/kube-down.sh

Kill the proxy running in the background: After you are done running this demo make sure to kill it:

$ jobs
[1]+  Running                 ./cluster/kubectl.sh proxy --www=local/ &
$ kill %1
[1]+  Terminated: 15          ./cluster/kubectl.sh 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.

$ 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.