Setting of Automatic Horizontal Scaling of Working Load
Introduction to HPA (Horizontal Pod Autoscaling)
HPA can automatically scale the number of pods in a deployment or replica set according to CPU utilization or metrics provided by some applications, which can better deal with scenarios such as burst traffic.
This article introduces how to use HPA to automatically expand and shrink applications in Cloud Container Engine (CCE).
Verify HPA
To demonstrate HPA, this article uses a custom Docker image based on php-apache image. The image includes an index.php page, which contains some code that can run CPU intensive computing tasks. The example Dockerfile is as follows:
FROM php:5-apache
ADD index.php /var/www/html/index.php
RUN chmod a+rx index.php The example index.php file is as follows:
<?php
$x = 0.0001;
for ($i = 0; $i<= 1000000; $i++) {
$x += sqrt($x);
}
echo "OK!";
?> Precondition
1.A Kubernetes cluster has been deployed through CCE.
2.Kubectl has been configured to access the Kubernetes cluster locally.
1.Deployment and Operation
First, deploy a Deployment to run the above Docker image and expose it as a Kubernetes service.
kubectl run php-apache --image=hpa-example --requests=cpu=200m --expose --port=80
service "php-apache" created
deployment "php-apache" created 2.Create HPA
kubectl autoscale deployment php-apache --cpu-percent=50 --min=1 --max=10
deployment "php-apache" autoscaled
After creation, the current monitoring value is unknown. After step 3, wait for 1-2 minutes, and then it will become normal percentage
[root@instance-2tpjy37t ~]# kubectl get hpa
NAME REFERENCE TARGETS MINPODS MAXPODS REPLICAS AGE
php-apache Deployment/php-apache <unknown>/50% 1 10 1 5s The corresponding YAML is as follows:
apiVersion: autoscaling/v2alpha1
kind: HorizontalPodAutoscaler
metadata:
name: php-apache
namespace: default
spec:
scaleTargetRef:
apiVersion: apps/v1beta1
kind: Deployment
name: php-apache
minReplicas: 1
maxReplicas: 10
metrics:
- type: Resource
resource:
name: cpu
targetAverageUtilization: 50 Field Explanation:
- scaleTargetRef : target object of HPA autoscaling
- minReplicas : Minimum Pod quantity
- maxReplicas : Maximum number of pods allowed
- metrics : Metrics
- targetAverageUtilization: That is, the set resource utilization rate, which triggers horizontal expansion when exceeding the set value
HPA currently supports three types of metrics. For details, please see Kubernetes Horizontal Pod Autoscaler:
- Predefined metrics: CPU and memory usage of Pod (built-in support).
- Custom Pod metrics: Monitoring indicators provided by the application (monitoring shall be deployed and metric server shall be customized).
- Custom Object indicator: Monitoring indicators of other resources in the same namespace as Pod (need to deploy monitoring and customize metric server).
3.Add Load to php-apache Service and Verify Automatic Scale-up/down
Start a container and send infinite query requests to the php-apache server through a loop (run the following command on another terminal).
kubectl run -i --tty load-generator --image=busybox /bin/sh
Hit enter for command prompt
$ while true; do wget -q -O- http://php-apache.default.svc.cluster.local; done
Output:
OK!OK!OK!OK!OK!OK!OK!OK!OK!OK!OK!OK!OK!OK!OK!OK!OK!OK!OK!OK!OK!OK!OK!OK!OK!OK!OK!OK!!OK!OK!OK!OK 4.Observe the Change of HPA
As the load increases, the number of replicas in the Deployment begins to increase.
[root@instance-2tpjy37t ~]# kubectl get hpa
NAME REFERENCE TARGETS MINPODS MAXPODS REPLICAS AGE
php-apache Deployment/php-apache 332%/50% 1 10 7 19m
[root@instance-2tpjy37t ~]# kubectl get deployment php-apache
NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
php-apache 7 7 7 7 19m 5.Stop the Load
In the terminal of the container generating the load, input <Ctrl>+c to terminate the load generation.
Then check the load status again (wait a few minutes).
[root@instance-2tpjy37t ~]# kubectl get hpa
NAME REFERENCE TARGET MINPODS MAXPODS REPLICAS AGE
php-apache Deployment/php-apache/scale 0%50% 1 10 1 11m
# As the load decreases, so does the number of pods
[root@instance-2tpjy37t ~]# kubectl get deployment php-apache
NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
php-apache 1 1 1 1 27m