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Merge pull request #15842 from piosz/hpa-example

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2015-10-22 01:19:52 -07:00
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83
examples/extensions/horizontal-pod-autoscaling/README.md
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@@ -33,20 +33,15 @@ Documentation for other releases can be found at
# Horizontal Pod Autoscaler
Horizontal pod autoscaling is an experimental feature in Kubernetes 1.1.
It allows the number of pods in a replication controller or deployment to scale automatically based on observed CPU or memory usage.
<b>Please note that the current API is tentative and will be subject to change before a stable version is released.</b>
Horizontal pod autoscaling is a [beta](../../../docs/api.md#api-versioning) feature in Kubernetes 1.1.
It allows the number of pods in a replication controller or deployment to scale automatically based on observed CPU usage.
In the future also other metrics will be supported.
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.
## Prerequisites
This example requires a running Kubernetes cluster in the version 1.1 with `extensions` API enabled on API server (``--runtime-config=extensions/v1beta1=true``),
and experimental controllers turned on in controller manager (``--enable-experimental=true``).
This can be simply achieved on GCE by exporting ``KUBE_ENABLE_EXPERIMENTAL_API=true`` before running ```kube-up.sh``` script.
The required version of kubectl is also 1.1.
This example requires a running Kubernetes cluster and kubectl in the version at least 1.1.
## Step One: Run & expose php-apache server
@@ -57,12 +52,11 @@ It defines [index.php](image/index.php) page which performs some CPU intensive c
First, we will start a replication controller running the image and expose it as an external service:
```console
$ kubectl create -f ./examples/extensions/horizontal-pod-autoscaling/rc-php-apache.yaml
$ kubectl create -f examples/extensions/horizontal-pod-autoscaling/rc-php-apache.yaml
replicationcontrollers/php-apache
$ kubectl expose rc php-apache --port=80 --type=LoadBalancer
NAME LABELS SELECTOR IP(S) PORT(S)
php-apache run=php-apache run=php-apache 80/TCP
service "php-apache" exposed
```
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:
@@ -94,7 +88,7 @@ php-apache run=php-apache run=php-apache 80/TCP
$ kubectl cluster-info | grep master
Kubernetes master is running at https://146.148.6.215
$ curl -k -u admin:password https://146.148.6.215/api/v1/proxy/namespaces/default/services/php-apache/
$ curl -k -u <admin>:<password> https://146.148.6.215/api/v1/proxy/namespaces/default/services/php-apache/
OK!
```
@@ -105,50 +99,45 @@ Now that the server is running, we will create a horizontal pod autoscaler for i
To create it, we will use the [hpa-php-apache.yaml](hpa-php-apache.yaml) file, which looks like this:
```yaml
apiVersion: extensions/v1beta1
apiVersion: extensions/v1beta1
kind: HorizontalPodAutoscaler
metadata:
name: php-apache
namespace: default
spec:
maxReplicas: 10
minReplicas: 1
scaleRef:
kind: ReplicationController
name: php-apache
namespace: default
target:
quantity: 100m
resource: cpu
minReplicas: 1
maxReplicas: 10
cpuUtilization:
targetPercentage: 50
```
This defines a horizontal pod autoscaler that maintains between 1 and 10 replicas of the Pods
controlled by the php-apache replication controller you created in the first step of these instructions.
Roughly speaking, the horizontal autoscaler will increase and decrease the number of replicas
(via the replication controller) so as to maintain an average CPU utilization across all Pods of 100 millicores.
(via the replication controller) so as to maintain an average CPU utilization across all Pods of 50%
(since each pod requests 200 milli-cores in [rc-php-apache.yaml](rc-php-apache.yaml), this means average CPU utilization of 100 milli-cores).
See [here](../../../docs/proposals/horizontal-pod-autoscaler.md#autoscaling-algorithm) for more details on the algorithm.
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.
As a general rule, the autoscaler's target should be lower than the request.
Otherwise, overloaded pods may not be able to consume more than the autoscaler's target utilization,
thereby preventing the autoscaler from seeing high enough utilization to trigger it to scale up.
We will create the autoscaler by executing the following command:
```console
$ kubectl create -f ./examples/extensions/horizontal-pod-autoscaling/hpa-php-apache.yaml
$ kubectl create -f examples/extensions/horizontal-pod-autoscaling/hpa-php-apache.yaml
horizontalpodautoscaler "php-apache" created
```
We may check the current status of autoscaler by running:
```console
$ kubectl get extensions/hpa
NAME REFERENCE TARGET CURRENT MINPODS MAXPODS AGE
php-apache ReplicationController/default/php-apache/ 100m cpu 0 cpu 1 10 4m
$ kubectl get hpa
NAME REFERENCE TARGET CURRENT MINPODS MAXPODS AGE
php-apache ReplicationController/default/php-apache/ 50% 0% 1 10 27s
```
Please note that the current CPU consumption is 0 as we are not sending any requests to the server
Please note that the current CPU consumption is 0% as we are not sending any requests to the server
(the ``CURRENT`` column shows the average across all the pods controlled by the corresponding replication controller).
## Step Three: Increase load
@@ -163,18 +152,18 @@ $ while true; do curl http://146.148.6.244; done
We may examine, how CPU load was increased (the results should be visible after about 2 minutes) by executing:
```console
$ kubectl get extensions/hpa
NAME REFERENCE TARGET CURRENT MINPODS MAXPODS AGE
php-apache ReplicationController/default/php-apache/ 100m cpu 471m cpu 1 10 10m
$ kubectl get hpa
NAME REFERENCE TARGET CURRENT MINPODS MAXPODS AGE
php-apache ReplicationController/default/php-apache/ 50% 305% 1 10 4m
```
In the case presented here, it bumped CPU consumption to 471 milli-cores.
As a result, the replication controller was resized to 5 replicas:
In the case presented here, it bumped CPU consumption to 305% of the request.
As a result, the replication controller was resized to 7 replicas:
```console
$ kubectl get rc
CONTROLLER CONTAINER(S) IMAGE(S) SELECTOR REPLICAS AGE
php-apache php-apache gcr.io/dev-jsz/php-apache run=php-apache 5 26m
CONTROLLER CONTAINER(S) IMAGE(S) SELECTOR REPLICAS AGE
php-apache php-apache gcr.io/google_containers/hpa-example run=php-apache 7 18m
```
Now, we may increase the load even more by running yet another infinite loop of queries (in yet another terminal):
@@ -186,13 +175,13 @@ $ while true; do curl http://146.148.6.244; done
In the case presented here, it increased the number of serving pods to 10:
```console
$ kubectl get extensions/hpa
NAME REFERENCE TARGET CURRENT MINPODS MAXPODS AGE
php-apache ReplicationController/default/php-apache/ 100m cpu 133m cpu 1 10 15m
$ kubectl get hpa
NAME REFERENCE TARGET CURRENT MINPODS MAXPODS AGE
php-apache ReplicationController/default/php-apache/ 50% 65% 1 10 14m
$ kubectl get rc
CONTROLLER CONTAINER(S) IMAGE(S) SELECTOR REPLICAS AGE
php-apache php-apache gcr.io/dev-jsz/php-apache run=php-apache 10 31m
CONTROLLER CONTAINER(S) IMAGE(S) SELECTOR REPLICAS AGE
php-apache php-apache gcr.io/google_containers/hpa-example run=php-apache 10 24m
```
## Step Four: Stop load
@@ -201,13 +190,13 @@ We will finish our example by stopping the user load.
We will terminate both infinite ``while`` loops sending requests to the server and verify the result state:
```console
$ kubectl get extensions/hpa
NAME REFERENCE TARGET CURRENT MINPODS MAXPODS AGE
php-apache ReplicationController/default/php-apache/ 100m cpu 0 cpu 1 10 26m
$ kubectl get hpa
NAME REFERENCE TARGET CURRENT MINPODS MAXPODS AGE
php-apache ReplicationController/default/php-apache/ 50% 0% 1 10 21m
$ kubectl get rc
CONTROLLER CONTAINER(S) IMAGE(S) SELECTOR REPLICAS AGE
php-apache php-apache gcr.io/dev-jsz/php-apache run=php-apache 1 42m
CONTROLLER CONTAINER(S) IMAGE(S) SELECTOR REPLICAS AGE
php-apache php-apache gcr.io/google_containers/hpa-example run=php-apache 1 31m
```
As we see, in the presented case CPU utilization dropped to 0, and the number of replicas dropped to 1.

11
examples/extensions/horizontal-pod-autoscaling/hpa-php-apache.yaml
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@@ -1,15 +1,14 @@
apiVersion: experimental/v1alpha1
apiVersion: extensions/v1beta1
kind: HorizontalPodAutoscaler
metadata:
name: php-apache
namespace: default
spec:
maxReplicas: 10
minReplicas: 1
scaleRef:
kind: ReplicationController
name: php-apache
namespace: default
target:
quantity: 100m
resource: cpu
minReplicas: 1
maxReplicas: 10
cpuUtilization:
targetPercentage: 50

2
examples/extensions/horizontal-pod-autoscaling/image/Dockerfile
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@@ -1,3 +1,5 @@
FROM php:5-apache
ADD index.php /var/www/html/index.php
RUN chmod a+rx index.php

2
examples/extensions/horizontal-pod-autoscaling/rc-php-apache.yaml
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@@ -15,7 +15,7 @@ spec:
run: php-apache
spec:
containers:
- image: gcr.io/dev-jsz/php-apache
- image: gcr.io/google_containers/hpa-example
name: php-apache
resources:
requests: