K8S从1.8版本开始，CPU、内存等资源的metrics信息可以通过 Metrics API来获取，用户可以直接获取这些metrics信息（例如通过执行kubect top命令），HPA使用这些metics信息来实现动态伸缩。本文介绍K8S集群基于metric server的HPA。在开始之前我们需要了解一下Metrics API和Metrics Server。
Metrics API：
1、通过Metrics API我们可以获取到指定node或者pod的当前资源使用情况，API本身不存储任何信息，所以我们不可能通过API来获取资源的历史使用情况。
2、Metrics API的获取路径位于：/apis/metrics.k8s.io/
3、获取Metrics API的前提条件是metrics server要在K8S集群中成功部署
4、更多的metrics资料请参考：https://github.com/kubernetes/metrics
Metrics server：
1、Metrics server是K8S集群资源使用情况的聚合器
2、从1.8版本开始，Metrics server默认可以通过kube-up.sh 脚本以deployment的方式进行部署，也可以通过yaml文件的方式进行部署
3、Metrics server收集所有node节点的metrics信
Plan-A
[root@master49 metrics-images]# cat metrics-applaction.yaml
apiVersion: v1
kind: ServiceAccount
metadata:
name: metrics-server
namespace: kube-system
labels:
kubernetes.io/cluster-service: "true"
addonmanager.kubernetes.io/mode: Reconcile
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
name: system:metrics-server
rules:
- apiGroups:
- ""
resources:
- pods
- nodes
- nodes/stats
- namespaces
verbs:
- get
- list
- watch
- apiGroups:
- "extensions"
resources:
- deployments
verbs:
- get
- list
- watch
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
name: system:metrics-server
roleRef:
apiGroup: rbac.authorization.k8s.io
kind: ClusterRole
name: system:metrics-server
subjects:
- kind: ServiceAccount
name: metrics-server
namespace: kube-system
---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRoleBinding
metadata:
name: metrics-server:system:auth-delegator
roleRef:
apiGroup: rbac.authorization.k8s.io
kind: ClusterRole
name: system:auth-delegator
subjects:
- kind: ServiceAccount
name: metrics-server
namespace: kube-system
---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: RoleBinding
metadata:
name: metrics-server-auth-reader
namespace: kube-system
roleRef:
apiGroup: rbac.authorization.k8s.io
kind: Role
name: extension-apiserver-authentication-reader
subjects:
- kind: ServiceAccount
name: metrics-server
namespace: kube-system
---
apiVersion: apiregistration.k8s.io/v1beta1
kind: APIService
metadata:
name: v1beta1.metrics.k8s.io
spec:
service:
name: metrics-server
namespace: kube-system
group: metrics.k8s.io
version: v1beta1
insecureSkipTLSVerify: true
groupPriorityMinimum: 100
versionPriority: 100
---
apiVersion: v1
kind: Service
metadata:
name: metrics-server
namespace: kube-system
labels:
kubernetes.io/name: "Metrics-server"
spec:
selector:
k8s-app: metrics-server
ports:
- port: 443
protocol: TCP
targetPort: 443
---
apiVersion: v1
kind: ConfigMap
metadata:
name: metrics-server-config
namespace: kube-system
labels:
kubernetes.io/cluster-service: "true"
addonmanager.kubernetes.io/mode: EnsureExists
data:
NannyConfiguration: |-
apiVersion: nannyconfig/v1alpha1
kind: NannyConfiguration
---
apiVersion: apps/v1
kind: Deployment
metadata:
name: metrics-server
namespace: kube-system
labels:
k8s-app: metrics-server-v0.3.1
kubernetes.io/cluster-service: "true"
addonmanager.kubernetes.io/mode: Reconcile
version: v0.3.1
spec:
selector:
matchLabels:
k8s-app: metrics-server
version: v0.3.1
template:
metadata:
name: metrics-server
labels:
k8s-app: metrics-server
version: v0.3.1
annotations:
scheduler.alpha.kubernetes.io/critical-pod: ''
seccomp.security.alpha.kubernetes.io/pod: 'docker/default'
spec:
priorityClassName: system-cluster-critical
serviceAccountName: metrics-server
containers:
- name: metrics-server
image: htcfive/metrics-server-amd64
command:
- /metrics-server
- --kubelet-insecure-tls
- --kubelet-preferred-address-types=InternalIP
ports:
- containerPort: 443
name: https
protocol: TCP
- name: metrics-server-nanny
image: wcollin/addon-resizer:1.8.1
resources:
limits:
cpu: 100m
memory: 300Mi
requests:
cpu: 5m
memory: 50Mi
env:
- name: MY_POD_NAME
valueFrom:
fieldRef:
fieldPath: metadata.name
- name: MY_POD_NAMESPACE
valueFrom:
fieldRef:
fieldPath: metadata.namespace
volumeMounts:
- name: metrics-server-config-volume
mountPath: /etc/config
command:
- /pod_nanny
- --cpu=40m
- --extra-cpu=0.5m
- --memory=40Mi
- --extra-memory=4Mi
- --threshold=5
- --deployment=metrics-server-v0.2.1
- --container=metrics-server
- --poll-period=300000
- --estimator=exponential
volumes:
- name: metrics-server-config-volume
configMap:
name: metrics-server-config
tolerations:
- key: "CriticalAddonsOnly"
operator: "Exists"
[root@master49 metrics-images]# kubectl apply -f metrics-applaction.yaml
serviceaccount/metrics-server created
clusterrole.rbac.authorization.k8s.io/system:metrics-server created
clusterrolebinding.rbac.authorization.k8s.io/system:metrics-server created
clusterrolebinding.rbac.authorization.k8s.io/metrics-server:system:auth-delegator created
rolebinding.rbac.authorization.k8s.io/metrics-server-auth-reader created
apiservice.apiregistration.k8s.io/v1beta1.metrics.k8s.io created
service/metrics-server created
configmap/metrics-server-config created
error: unable to recognize "metrics-applaction.yaml": no matches for kind "Deployment" in version "extensions/v1beta1"
[root@master49 metrics-images]# kubectl delete -f metrics-applaction.yaml
serviceaccount "metrics-server" deleted
clusterrole.rbac.authorization.k8s.io "system:metrics-server" deleted
clusterrolebinding.rbac.authorization.k8s.io "system:metrics-server" deleted
clusterrolebinding.rbac.authorization.k8s.io "metrics-server:system:auth-delegator" deleted
rolebinding.rbac.authorization.k8s.io "metrics-server-auth-reader" deleted
apiservice.apiregistration.k8s.io "v1beta1.metrics.k8s.io" deleted
service "metrics-server" deleted
configmap "metrics-server-config" deleted
error: unable to recognize "metrics-applaction.yaml": no matches for kind "Deployment" in version "extensions/v1beta1"
[root@master49 metrics-images]# vim metrics-applaction.yaml
[root@master49 metrics-images]# kubectl apply -f metrics-applaction.yaml
serviceaccount/metrics-server created
clusterrole.rbac.authorization.k8s.io/system:metrics-server created
clusterrolebinding.rbac.authorization.k8s.io/system:metrics-server created
clusterrolebinding.rbac.authorization.k8s.io/metrics-server:system:auth-delegator created
rolebinding.rbac.authorization.k8s.io/metrics-server-auth-reader created
apiservice.apiregistration.k8s.io/v1beta1.metrics.k8s.io created
service/metrics-server created
configmap/metrics-server-config created
deployment.apps/metrics-server created
[root@master49 metrics-images]#
[root@master49 metrics-images]# kubectl get pods -n kube-system
NAME READY STATUS RESTARTS AGE
calico-kube-controllers-75d555c48-c66ll 1/1 Running 0 18h
calico-node-4w9rr 1/1 Running 0 18h
calico-node-hrvcq 1/1 Running 0 18h
calico-node-srz5h 1/1 Running 0 18h
calico-node-xmb28 1/1 Running 0 18h
calico-node-zhrs2 1/1 Running 0 18h
coredns-7ff77c879f-46sjv 1/1 Running 0 19h
coredns-7ff77c879f-txpw9 1/1 Running 0 5h
etcd-master49 1/1 Running 6 18h
etcd-master50 1/1 Running 3 18h
etcd-master56 1/1 Running 17 18h
kube-apiserver-master49 1/1 Running 1 18h
kube-apiserver-master50 1/1 Running 0 18h
kube-apiserver-master56 1/1 Running 0 18h
kube-controller-manager-master49 1/1 Running 8 18h
kube-controller-manager-master50 1/1 Running 6 18h
kube-controller-manager-master56 1/1 Running 6 18h
kube-proxy-2gcg5 1/1 Running 0 18h
kube-proxy-4ckzn 1/1 Running 0 18h
kube-proxy-bffn9 1/1 Running 0 18h
kube-proxy-kdjtv 1/1 Running 0 18h
kube-proxy-w9xzf 1/1 Running 0 18h
kube-scheduler-master49 1/1 Running 8 18h
kube-scheduler-master50 1/1 Running 5 18h
kube-scheduler-master56 1/1 Running 7 18h
log-pilot-2d2s9 1/1 Running 0 5h1m
log-pilot-cnfvq 1/1 Running 0 5h1m
log-pilot-hgbkm 1/1 Running 0 5h1m
log-pilot-vwjtm 1/1 Running 0 5h
log-pilot-zqvnp 1/1 Running 0 5h
metrics-server-99d8bb9cc-m5lp9 2/2 Running 0 3m42s[root@master49 metrics-images]# kubectl top pods -n kube-system
NAME CPU(cores) MEMORY(bytes)
calico-kube-controllers-75d555c48-c66ll 2m 9Mi
calico-node-4w9rr 41m 25Mi
calico-node-hrvcq 44m 39Mi
calico-node-srz5h 40m 25Mi
calico-node-xmb28 41m 25Mi
calico-node-zhrs2 44m 41Mi
coredns-7ff77c879f-46sjv 8m 8Mi
coredns-7ff77c879f-txpw9 6m 8Mi
etcd-master49 64m 99Mi
etcd-master50 91m 428Mi
etcd-master56 95m 423Mi
kube-apiserver-master49 66m 471Mi
kube-apiserver-master50 61m 504Mi
kube-apiserver-master56 59m 474Mi
kube-controller-manager-master49 4m 15Mi
kube-controller-manager-master50 27m 67Mi
kube-controller-manager-master56 6m 15Mi
kube-proxy-2gcg5 1m 13Mi
kube-proxy-4ckzn 14m 14Mi
kube-proxy-bffn9 20m 14Mi
kube-proxy-kdjtv 1m 20Mi
kube-proxy-w9xzf 15m 19Mi
kube-scheduler-master49 4m 18Mi
kube-scheduler-master50 6m 24Mi
kube-scheduler-master56 4m 17Mi
log-pilot-2d2s9 3m 18Mi
log-pilot-cnfvq 3m 21Mi
log-pilot-hgbkm 3m 7Mi
log-pilot-vwjtm 4m 7Mi
log-pilot-zqvnp 3m 7Mi
metrics-server-99d8bb9cc-m5lp9 1m 28Mi
[root@master49 metrics-images]# kubectl top nodes
error: metrics not available yet
###### 别慌，等会就好了
[root@master49 metrics-images]# kubectl top nodes
NAME CPU(cores) CPU% MEMORY(bytes) MEMORY%
master49 378m 9% 1851Mi 15%
master50 498m 12% 2476Mi 20%
master56 470m 11% 2196Mi 18%
node52 2949m 12% 65802Mi 31%
node53 1285m 5% 31770Mi 15%
[root@master49 metrics-images]# ls
metrics-applaction.yaml
Plan-B
[root@master49 metrics-server]# ll
total 32
-rw-r--r--. 1 root root 304 Dec 24 13:57 auth-delegator.yaml
-rw-r--r--. 1 root root 325 Dec 24 13:57 auth-reader.yaml
-rw-r--r--. 1 root root 294 Dec 24 13:57 metrics-apiservice.yaml
-rw-r--r--. 1 root root 284 Dec 24 13:57 metrics-server-cluster-role-binding.yaml
-rw-r--r--. 1 root root 409 Dec 24 13:57 metrics-server-cluster-role.yaml
-rw-r--r--. 1 root root 585 Mar 30 14:31 metrics-server-deployment.yaml
-rw-r--r--. 1 root root 94 Dec 24 13:57 metrics-server-service-account.yaml
-rw-r--r--. 1 root root 245 Dec 24 13:57 metrics-server-service.yaml
[root@master49 metrics-server]# ll|awk '{print $9}'
auth-delegator.yaml
auth-reader.yaml
metrics-apiservice.yaml
metrics-server-cluster-role-binding.yaml
metrics-server-cluster-role.yaml
metrics-server-deployment.yaml
metrics-server-service-account.yaml
metrics-server-service.yaml
[root@master49 metrics-server]# ll|awk '{print $9}' | xargs cat
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRoleBinding
metadata:
name: metrics-server:system:auth-delegator
roleRef:
apiGroup: rbac.authorization.k8s.io
kind: ClusterRole
name: system:auth-delegator
subjects:
- kind: ServiceAccount
name: metrics-server
namespace: kube-system
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: RoleBinding
metadata:
name: metrics-server-auth-reader
namespace: kube-system
roleRef:
apiGroup: rbac.authorization.k8s.io
kind: Role
name: extension-apiserver-authentication-reader
subjects:
- kind: ServiceAccount
name: metrics-server
namespace: kube-system
apiVersion: apiregistration.k8s.io/v1beta1
kind: APIService
metadata:
name: v1beta1.metrics.k8s.io
spec:
service:
name: metrics-server
namespace: kube-system
group: metrics.k8s.io
version: v1beta1
insecureSkipTLSVerify: true
groupPriorityMinimum: 100
versionPriority: 100
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
name: system:metrics-server
roleRef:
apiGroup: rbac.authorization.k8s.io
kind: ClusterRole
name: system:metrics-server
subjects:
- kind: ServiceAccount
name: metrics-server
namespace: kube-system
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
name: system:metrics-server
rules:
- apiGroups:
- ""
resources:
- pods
- nodes
- nodes/stats
- namespaces
verbs:
- get
- list
- watch
- apiGroups:
- "apps"
resources:
- deployments
verbs:
- get
- list
- watch
- apiGroups:
- "extensions"
resources:
- deployments
verbs:
- get
- list
- watch
apiVersion: apps/v1
kind: Deployment
metadata:
name: metrics-server
namespace: kube-system
labels:
k8s-app: metrics-server
spec:
selector:
matchLabels:
k8s-app: metrics-server
template:
metadata:
name: metrics-server
labels:
k8s-app: metrics-server
spec:
serviceAccountName: metrics-server
containers:
- name: metrics-server
image: docker.io/carlziess/metrics-server-amd64-v0.2.1:latest
imagePullPolicy: Always
command:
- /metrics-server
- --source=kubernetes.summary_api:''
apiVersion: v1
kind: ServiceAccount
metadata:
name: metrics-server
namespace: kube-system
apiVersion: v1
kind: Service
metadata:
name: metrics-server
namespace: kube-system
labels:
kubernetes.io/name: "Metrics-server"
spec:
selector:
k8s-app: metrics-server
ports:
- port: 443
protocol: TCP
targetPort: 443
[root@master49 metrics-server]# kubectl apply -f .
clusterrolebinding.rbac.authorization.k8s.io/metrics-server:system:auth-delegator created
rolebinding.rbac.authorization.k8s.io/metrics-server-auth-reader created
apiservice.apiregistration.k8s.io/v1beta1.metrics.k8s.io created
clusterrolebinding.rbac.authorization.k8s.io/system:metrics-server created
clusterrole.rbac.authorization.k8s.io/system:metrics-server created
deployment.apps/metrics-server created
serviceaccount/metrics-server created
service/metrics-server created