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117 lines
4.4 KiB
Markdown
117 lines
4.4 KiB
Markdown
<!--
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Copyright 2014 Google Inc. All rights reserved.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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-->
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# Live update example
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This example demonstrates the usage of Kubernetes to perform a live update on a running group of pods.
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### Step Zero: Prerequisites
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This example assumes that you have forked the repository and [turned up a Kubernetes cluster](https://github.com/GoogleCloudPlatform/kubernetes-new#contents):
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```bash
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$ cd kubernetes
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$ hack/dev-build-and-up.sh
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```
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### Step One: Turn up the UX for the demo
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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.
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```
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$ ./cluster/kubectl.sh proxy --www=examples/update-demo/local/ &
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+ ./cluster/kubectl.sh proxy --www=examples/update-demo/local/
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I0218 15:18:31.623279 67480 proxy.go:36] Starting to serve on localhost:8001
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```
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Now visit the the [demo website](http://localhost:8001/static). You won't see anything much quite yet.
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### Step Two: Run the controller
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Now we will turn up two replicas of an image. They all serve on internal port 80.
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```bash
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$ ./cluster/kubectl.sh create -f examples/update-demo/nautilus-rc.yaml
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```
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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.
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### Step Three: Try resizing the controller
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Now we will increase the number of replicas from two to four:
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```bash
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$ ./cluster/kubectl.sh resize rc update-demo-nautilus --replicas=4
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```
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If you go back to the [demo website](http://localhost:8001/static/index.html) you should eventually see four boxes, one for each pod.
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### Step Four: Update the docker image
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We will now update the docker image to serve a different image by doing a rolling update to a new Docker image.
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```bash
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$ ./cluster/kubectl.sh rolling-update update-demo-nautilus --update-period=10s -f examples/update-demo/kitten-rc.yaml
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```
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The rolling-update command in kubectl will do 2 things:
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1. Create a new replication controller with a pod template that uses the new image (`gcr.io/google_containers/update-demo:kitten`)
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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.
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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.
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### Step Five: Bring down the pods
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```bash
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$ ./cluster/kubectl.sh stop rc update-demo-kitten
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```
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This will first 'stop' the replication controller by turning the target number of replicas to 0. It'll then delete that controller.
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### Step Six: Cleanup
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To turn down a Kubernetes cluster:
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```bash
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$ cd ../.. # Up to kubernetes.
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$ cluster/kube-down.sh
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```
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Kill the proxy running in the background:
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After you are done running this demo make sure to kill it:
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```bash
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$ jobs
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[1]+ Running ./cluster/kubectl.sh proxy --www=local/ &
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$ kill %1
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[1]+ Terminated: 15 ./cluster/kubectl.sh proxy --www=local/
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```
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### Updating the Docker images
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If you want to build your own docker images, you can set `$DOCKER_HUB_USER` to your Docker user id and run the included shell script. It can take a few minutes to download/upload stuff.
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```bash
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$ export DOCKER_HUB_USER=my-docker-id
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$ ./examples/update-demo/build-images.sh
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```
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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`.
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### Image Copyright
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Note that the images included here are public domain.
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* [kitten](http://commons.wikimedia.org/wiki/File:Kitten-stare.jpg)
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* [nautilus](http://commons.wikimedia.org/wiki/File:Nautilus_pompilius.jpg)
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