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examples/experimental/horizontal-pod-autoscaling/README.md
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examples/experimental/horizontal-pod-autoscaling/README.md
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<!-- BEGIN MUNGE: UNVERSIONED_WARNING -->
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<!-- BEGIN STRIP_FOR_RELEASE -->
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<img src="http://kubernetes.io/img/warning.png" alt="WARNING"
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width="25" height="25">
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<img src="http://kubernetes.io/img/warning.png" alt="WARNING"
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width="25" height="25">
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<img src="http://kubernetes.io/img/warning.png" alt="WARNING"
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width="25" height="25">
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<img src="http://kubernetes.io/img/warning.png" alt="WARNING"
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width="25" height="25">
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<img src="http://kubernetes.io/img/warning.png" alt="WARNING"
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width="25" height="25">
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<h2>PLEASE NOTE: This document applies to the HEAD of the source tree</h2>
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If you are using a released version of Kubernetes, you should
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refer to the docs that go with that version.
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<strong>
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The latest 1.0.x release of this document can be found
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[here](http://releases.k8s.io/release-1.0/examples/experimental/horizontal-pod-autoscaling/README.md).
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Documentation for other releases can be found at
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[releases.k8s.io](http://releases.k8s.io).
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</strong>
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--
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<!-- END STRIP_FOR_RELEASE -->
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<!-- END MUNGE: UNVERSIONED_WARNING -->
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# Horizontal Pod Autoscaler
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Horizontal pod autoscaling is an experimental feature in Kubernetes 1.1.
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It allows the number of pods in a replication controller or deployment to scale automatically based on observed CPU or memory usage.
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<b>Please note that the current API is tentative and will be subject to change before a stable version is released.</b>
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In this document we explain how this feature works by walking you through an example of enabling horizontal pod autoscaling with the php-apache server.
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## Prerequisites
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This example requires a running Kubernetes cluster in the version 1.1 with experimental API enabled on API server (``--runtime-config=experimental/v1alpha1=true``),
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and experimental controllers turned on in controller manager (``--enable-experimental=true``).
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This can be simply achieved on GCE by exporting ``KUBE_ENABLE_EXPERIMENTAL_API=true`` before running ```kube-up.sh``` script.
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The required version of kubectl is also 1.1.
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## Step One: Run & expose php-apache server
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To demonstrate horizontal pod autoscaler we will use a custom docker image based on php-apache server.
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The image can be found [here](image/).
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It defines [index.php](image/index.php) page which performs some CPU intensive computations.
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First, we will start a replication controller running the image and expose it as an external service:
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```console
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$ kubectl create -f ./examples/experimental/horizontal-pod-autoscaling/rc-php-apache.yaml
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replicationcontrollers/php-apache
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$ kubectl expose rc php-apache --port=80 --type=LoadBalancer
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NAME LABELS SELECTOR IP(S) PORT(S)
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php-apache run=php-apache run=php-apache 80/TCP
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```
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Now, we will wait some time and verify that both the replication controller and the service were correctly created and are running. We will also determine the IP address of the service:
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```console
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$ kubectl get pods
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NAME READY STATUS RESTARTS AGE
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php-apache-wa3t1 1/1 Running 0 12m
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$ kubectl describe services php-apache | grep "LoadBalancer Ingress"
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LoadBalancer Ingress: 146.148.24.244
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```
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We may now check that php-apache server works correctly by calling ``curl`` with the service's IP:
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```console
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$ curl http://146.148.24.244
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OK!
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```
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Please notice that when exposing the service we assumed that our cluster runs on a provider which supports load balancers (e.g.: on GCE).
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If load balancers are not supported (e.g.: on Vagrant), we can expose php-apache service as ``ClusterIP`` and connect to it using the proxy on the master:
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```console
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$ kubectl expose rc php-apache --port=80 --type=ClusterIP
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NAME LABELS SELECTOR IP(S) PORT(S)
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php-apache run=php-apache run=php-apache 80/TCP
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$ kubectl cluster-info | grep master
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Kubernetes master is running at https://146.148.6.215
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$ curl -k -u admin:password https://146.148.6.215/api/v1/proxy/namespaces/default/services/php-apache/
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OK!
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```
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## Step Two: Create horizontal pod autoscaler
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Now that the server is running, we will create a horizontal pod autoscaler for it.
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To create it, we will use the [hpa-php-apache.yaml](hpa-php-apache.yaml) file, which looks like this:
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```yaml
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apiVersion: experimental/v1alpha1
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kind: HorizontalPodAutoscaler
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metadata:
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name: php-apache
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namespace: default
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spec:
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maxReplicas: 10
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minReplicas: 1
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scaleRef:
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kind: ReplicationController
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name: php-apache
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namespace: default
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target:
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quantity: 100m
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resource: cpu
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```
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This defines a horizontal pod autoscaler that maintains between 1 and 10 replicas of the Pods
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controlled by the php-apache replication controller you created in the first step of these instructions.
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Roughly speaking, the horizontal autoscaler will increase and decrease the number of replicas
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(via the replication controller) so as to maintain an average CPU utilization across all Pods of 100 millicores.
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See [here](../../../docs/proposals/horizontal-pod-autoscaler.md#autoscaling-algorithm) for more details on the algorithm.
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Please be aware that this configuration sets the target CPU consumption to 100 milli-cores, while in [rc-php-apache.yaml](rc-php-apache.yaml) each pod requests 200 milli-cores.
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As a general rule, the autoscaler's target should be lower than the request.
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Otherwise, overloaded pods may not be able to consume more than the autoscaler's target utilization,
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thereby preventing the autoscaler from seeing high enough utilization to trigger it to scale up.
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We will create the autoscaler by executing the following command:
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```console
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$ kubectl create -f ./examples/experimental/horizontal-pod-autoscaling/hpa-php-apache.yaml
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horizontalpodautoscaler "php-apache" created
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```
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We may check the current status of autoscaler by running:
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```console
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$ kubectl get experimental/hpa
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NAME REFERENCE TARGET CURRENT MINPODS MAXPODS AGE
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php-apache ReplicationController/default/php-apache/ 100m cpu 0 cpu 1 10 4m
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```
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Please note that the current CPU consumption is 0 as we are not sending any requests to the server
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(the ``CURRENT`` column shows the average across all the pods controlled by the corresponding replication controller).
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## Step Three: Increase load
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Now, we will see how the autoscaler reacts on the increased load of the server.
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We will start an infinite loop of queries to our server (please run it in a different terminal):
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```console
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$ while true; do curl http://146.148.6.244; done
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```
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We may examine, how CPU load was increased (the results should be visible after about 2 minutes) by executing:
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```console
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$ kubectl get experimental/hpa
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NAME REFERENCE TARGET CURRENT MINPODS MAXPODS AGE
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php-apache ReplicationController/default/php-apache/ 100m cpu 471m cpu 1 10 10m
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```
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In the case presented here, it bumped CPU consumption to 471 milli-cores.
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As a result, the replication controller was resized to 5 replicas:
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```console
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$ kubectl get rc
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CONTROLLER CONTAINER(S) IMAGE(S) SELECTOR REPLICAS AGE
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php-apache php-apache gcr.io/dev-jsz/php-apache run=php-apache 5 26m
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```
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Now, we may increase the load even more by running yet another infinite loop of queries (in yet another terminal):
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```console
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$ while true; do curl http://146.148.6.244; done
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```
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In the case presented here, it increased the number of serving pods to 10:
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```console
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$ kubectl get experimental/hpa
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NAME REFERENCE TARGET CURRENT MINPODS MAXPODS AGE
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php-apache ReplicationController/default/php-apache/ 100m cpu 133m cpu 1 10 15m
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$ kubectl get rc
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CONTROLLER CONTAINER(S) IMAGE(S) SELECTOR REPLICAS AGE
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php-apache php-apache gcr.io/dev-jsz/php-apache run=php-apache 10 31m
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```
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## Step Four: Stop load
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We will finish our example by stopping the user load.
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We will terminate both infinite ``while`` loops sending requests to the server and verify the result state:
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```console
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$ kubectl get experimental/hpa
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NAME REFERENCE TARGET CURRENT MINPODS MAXPODS AGE
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php-apache ReplicationController/default/php-apache/ 100m cpu 0 cpu 1 10 26m
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$ kubectl get rc
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CONTROLLER CONTAINER(S) IMAGE(S) SELECTOR REPLICAS AGE
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php-apache php-apache gcr.io/dev-jsz/php-apache run=php-apache 1 42m
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```
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As we see, in the presented case CPU utilization dropped to 0, and the number of replicas dropped to 1.
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<!-- BEGIN MUNGE: GENERATED_ANALYTICS -->
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[]()
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<!-- END MUNGE: GENERATED_ANALYTICS -->
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@ -0,0 +1,15 @@
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apiVersion: experimental/v1alpha1
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kind: HorizontalPodAutoscaler
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metadata:
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name: php-apache
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namespace: default
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spec:
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maxReplicas: 10
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minReplicas: 1
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scaleRef:
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kind: ReplicationController
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name: php-apache
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namespace: default
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target:
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quantity: 100m
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resource: cpu
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FROM php:5-apache
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ADD index.php /var/www/html/index.php
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7
examples/experimental/horizontal-pod-autoscaling/image/index.php
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7
examples/experimental/horizontal-pod-autoscaling/image/index.php
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<?php
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$x = 0.0001;
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for ($i = 0; $i <= 1000000; $i++) {
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$x += sqrt($x);
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}
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echo "OK!";
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?>
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apiVersion: v1
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kind: ReplicationController
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metadata:
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labels:
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run: php-apache
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name: php-apache
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namespace: default
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spec:
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replicas: 1
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selector:
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run: php-apache
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template:
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metadata:
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labels:
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run: php-apache
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spec:
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containers:
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- image: gcr.io/dev-jsz/php-apache
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name: php-apache
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resources:
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requests:
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cpu: 200m
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restartPolicy: Always
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