[root@master C]# kubectl explain hpa
KIND: HorizontalPodAutoscaler
VERSION: autoscaling/v1 #可以看到使用的默認版本是v1DESCRIPTION:configuration of a horizontal pod autoscaler.FIELDS:apiVersion <string>APIVersion defines the versioned schema of this representation of anobject. Servers should convert recognized schemas to the latest internalvalue, and may reject unrecognized values. More info:https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#resourceskind <string>Kind is a string value representing the REST resource this objectrepresents. Servers may infer this from the endpoint the client submitsrequests to. Cannot be updated. In CamelCase. More info:https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#types-kindsmetadata <Object>Standard object metadata. More info:https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#metadataspec <Object>behaviour of autoscaler. More info:https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#spec-and-status.status <Object>current information about the autoscaler.
指定使用版本，這里并不是修改，相當于執行這條命令時，指定了下版本
[root@master C]# kubectl explain hpa --api-version=autoscaling/v2beta1
KIND: HorizontalPodAutoscaler
VERSION: autoscaling/v2beta1DESCRIPTION:HorizontalPodAutoscaler is the configuration for a horizontal podautoscaler, which automatically manages the replica count of any resourceimplementing the scale subresource based on the metrics specified.FIELDS:apiVersion <string>APIVersion defines the versioned schema of this representation of anobject. Servers should convert recognized schemas to the latest internalvalue, and may reject unrecognized values. More info:https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#resourceskind <string>Kind is a string value representing the REST resource this objectrepresents. Servers may infer this from the endpoint the client submitsrequests to. Cannot be updated. In CamelCase. More info:https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#types-kindsmetadata <Object>metadata is the standard object metadata. More info:https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#metadataspec <Object>spec is the specification for the behaviour of the autoscaler. More info:https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#spec-and-status.status <Object>status is the current information about the autoscaler.
4.2、 HPA部署
（1）部署metrics-server
[root@master kube-system]# kubectl top nodes #查看節點狀態，因為沒有安裝，所以會報錯
Error from server (NotFound): the server could not find the requested resource (get services http:heapster:)
[root@master test]# kubectl get pods -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
nginx-9cb8d65b5-tq9v4 1/1 Running 0 14m 10.244.1.22 node <none> <none>
[root@master test]# kubectl get svc nginx
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
nginx ClusterIP 172.16.169.27 <none> 80/TCP 15m
[root@master test]# kubectl describe svc nginx
Name: nginx
Namespace: default
Labels: run=nginx
Annotations: Selector: run=nginx
Type: ClusterIP
IP: 172.16.169.27
Port: <unset> 80/TCP
TargetPort: 80/TCP
Endpoints: 10.244.1.22:80
Session Affinity: None
Events: <none>
[root@node test]# curl 172.16.169.27 #訪問成功
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>body {width: 35em;margin: 0 auto;font-family: Tahoma, Verdana, Arial, sans-serif;}
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p><p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p><p><em>Thank you for using nginx.</em></p>
</body>
</html>
（3）基于CPU創建HPA
#創建一個cpu利用率達到20，最大10個pod，最小1個，這里沒有指定版本所以默認是v1版本，而v1版本只能以CPU為標準
[root@master test]# kubectl autoscale deployment nginx --cpu-percent=20 --min=1 --max=10
horizontalpodautoscaler.autoscaling/nginx autoscaled#TARGETS可以看到使用率
[root@master test]# kubectl get hpa
NAME REFERENCE TARGETS MINPODS MAXPODS REPLICAS AGE
nginx Deployment/nginx 0%/20% 1 10 1 86s#創建一個測試pod增加負載，訪問地址要和pod的svc地址相同
[root@master ~]# kubectl run busybox -it --image=busybox -- /bin/sh -c 'while true; do wget -q -O- http://10.244.1.22; done'#過一分鐘后看hap的使用率，REPLICAS是當前pod的數量
[root@master test]# kubectl get hpa
NAME REFERENCE TARGETS MINPODS MAXPODS REPLICAS AGE
nginx Deployment/nginx 27%/20% 1 10 5 54m[root@master test]# kubectl get pods #再看pod數量，發現已經增加到了5個
NAME READY STATUS RESTARTS AGE
bustbox 1/1 Running 0 119s
nginx-9cb8d65b5-24dg2 1/1 Running 0 57s
nginx-9cb8d65b5-c6n98 1/1 Running 0 87s
nginx-9cb8d65b5-ksjzv 1/1 Running 0 57s
nginx-9cb8d65b5-n77fm 1/1 Running 0 87s
nginx-9cb8d65b5-tq9v4 1/1 Running 0 84m
[root@master test]# kubectl get deployments.apps
NAME READY UP-TO-DATE AVAILABLE AGE
nginx 5/5 5 5 84m#此時，停止壓測，過好幾分鐘后再次查看pod數量和使用率
[root@master test]# kubectl delete pod busybox #終止后，刪除pod
[root@master test]# kubectl get hpa #雖然使用率已經降到0了，但是可以看到當前REPLICAS的數量還5，這個需要等一會就會縮容
NAME REFERENCE TARGETS MINPODS MAXPODS REPLICAS AGE
nginx Deployment/nginx 0%/20% 1 10 5 58m#過了幾分鐘后，可以看到pod數量已經回到了1
[root@master test]# kubectl get hpa
NAME REFERENCE TARGETS MINPODS MAXPODS REPLICAS AGE
nginx Deployment/nginx 0%/20% 1 10 1 64m
[root@master test]# kubectl get pods
NAME READY STATUS RESTARTS AGE
nginx-9cb8d65b5-tq9v4 1/1 Running 0 95m
