1.什么是Metrics-Server？

Metrics-Server是集群核心监控数据的聚合器，用来替换之前的heapster。
容器相关的 Metrics 主要来自于 kubelet 内置的 cAdvisor 服务，有了MetricsServer之后，用户就可以通过标准的 Kubernetes API 来访问到这些监控数据。
Metrics API 只可以查询当前的度量数据，并不保存历史数据。
Metrics API URI 为 /apis/metrics.k8s.io/，在 k8s.io/metrics 维护。
必须部署 metrics-server 才能使用该 API，metrics-server 通过调用 Kubelet Summary API 获取数据。

Metrics Server 并不是 kube-apiserver 的一部分，而是通过 Aggregator 这种插件机制，在独立部署的情况下同 kube-apiserver 一起统一对外服务的。
kube-aggregator 其实就是一个根据 URL 选择具体的 API 后端的代理服务器。

Metrics-server属于Core metrics(核心指标)，提供API metrics.k8s.io，仅提供Node和Pod的 CPU和内存使用情况。而其他Custom Metrics(自定义指标)由Prometheus等组件来完成。

2.Metrics-Server安装部署

（1）Metrics-Server安装

[root@server2 ~]# mkdir ms
[root@server2 ~]# cd ms
[root@server2 ms]# wget https://github.com/kubernetes-sigs/metrics-server/releases/download/v0.3.6/components.yaml
--2020-07-10 08:45:51--  https://github.com/kubernetes-sigs/metrics-server/releases/download/v0.3.6/components.yaml
Resolving github.com (github.com)... 13.229.188.59
Connecting to github.com (github.com)|13.229.188.59|:443... connected.
HTTP request sent, awaiting response... 302 Found
Location: https://github-production-release-asset-2e65be.s3.amazonaws.com/92132038/cf781b00-7752-11ea-9faf-0b397e7b8445?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=AKIAIWNJYAX4CSVEH53A%2F20200710%2Fus-east-1%2Fs3%2Faws4_request&X-Amz-Date=20200710T004553Z&X-Amz-Expires=300&X-Amz-Signature=789a7d64440556513b5a85483ba5d3aac7d562fafd68c8d4e5f4dd2c7cbf81a9&X-Amz-SignedHeaders=host&actor_id=0&repo_id=92132038&response-content-disposition=attachment%3B%20filename%3Dcomponents.yaml&response-content-type=application%2Foctet-stream [following]
--2020-07-10 08:45:53--  https://github-production-release-asset-2e65be.s3.amazonaws.com/92132038/cf781b00-7752-11ea-9faf-0b397e7b8445?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=AKIAIWNJYAX4CSVEH53A%2F20200710%2Fus-east-1%2Fs3%2Faws4_request&X-Amz-Date=20200710T004553Z&X-Amz-Expires=300&X-Amz-Signature=789a7d64440556513b5a85483ba5d3aac7d562fafd68c8d4e5f4dd2c7cbf81a9&X-Amz-SignedHeaders=host&actor_id=0&repo_id=92132038&response-content-disposition=attachment%3B%20filename%3Dcomponents.yaml&response-content-type=application%2Foctet-stream
Resolving github-production-release-asset-2e65be.s3.amazonaws.com (github-production-release-asset-2e65be.s3.amazonaws.com)... 52.216.230.155
Connecting to github-production-release-asset-2e65be.s3.amazonaws.com (github-production-release-asset-2e65be.s3.amazonaws.com)|52.216.230.155|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 3335 (3.3K) [application/octet-stream]
Saving to: ‘components.yaml’

100%[=============================>] 3,335       --.-K/s   in 0s      

2020-07-10 08:45:55 (7.17 MB/s) - ‘components.yaml’ saved [3335/3335]

[root@server2 ms]# ls
components.yaml
[root@server2 ms]# vim components.yaml 
[root@server2 ms]# kubectl apply -f components.yaml 
clusterrole.rbac.authorization.k8s.io/system:aggregated-metrics-reader 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
serviceaccount/metrics-server created
deployment.apps/metrics-server created
service/metrics-server created
clusterrole.rbac.authorization.k8s.io/system:metrics-server created
clusterrolebinding.rbac.authorization.k8s.io/system:metrics-server created
[root@server2 ms]# kubectl get pod -n kube-system
NAME                              READY   STATUS    RESTARTS   AGE
coredns-bd97f9cd9-8lqqc           1/1     Running   1          47h
coredns-bd97f9cd9-cdk94           1/1     Running   1          46h
etcd-server2                      1/1     Running   5          7d17h
kube-apiserver-server2            1/1     Running   5          7d17h
kube-controller-manager-server2   1/1     Running   5          7d17h
kube-flannel-ds-amd64-g8hg7       1/1     Running   5          7d16h
kube-flannel-ds-amd64-tlmh2       1/1     Running   1          46h
kube-proxy-dkr49                  1/1     Running   4          7d16h
kube-proxy-dw7lv                  1/1     Running   5          7d17h
kube-proxy-z7r6x                  1/1     Running   1          46h
kube-scheduler-server2            1/1     Running   5          7d17h
metrics-server-7cdfcc6666-ptv48   1/1     Running   0          13s
[root@server2 ms]# kubectl describe pod -n kube-system metrics-server-7cdfcc6666-ptv48
Name:         metrics-server-7cdfcc6666-ptv48
Namespace:    kube-system
Priority:     0
Node:         server4/172.25.12.4
Start Time:   Fri, 10 Jul 2020 08:56:15 +0800
Labels:       k8s-app=metrics-server
              pod-template-hash=7cdfcc6666
Annotations:  <none>
Status:       Running
IP:           10.244.2.44
IPs:
  IP:           10.244.2.44
Controlled By:  ReplicaSet/metrics-server-7cdfcc6666
Containers:
  metrics-server:
    Container ID:  docker://1f24dc0545b0150912ecb6766c4ac08f2a9a0d338642ccd28dfffa0928b5f871
    Image:         metrics-server-amd64:v0.3.6
    Image ID:      docker-pullable://metrics-server-amd64@sha256:c9c4e95068b51d6b33a9dccc61875df07dc650abbf4ac1a19d58b4628f89288b
    Port:          4443/TCP
    Host Port:     0/TCP
    Args:
      --cert-dir=/tmp
      --secure-port=4443
    State:          Running
      Started:      Fri, 10 Jul 2020 08:56:18 +0800
    Ready:          True
    Restart Count:  0
    Environment:    <none>
    Mounts:
      /tmp from tmp-dir (rw)
      /var/run/secrets/kubernetes.io/serviceaccount from metrics-server-token-8t6zs (ro)
Conditions:
  Type              Status
  Initialized       True 
  Ready             True 
  ContainersReady   True 
  PodScheduled      True 
Volumes:
  tmp-dir:
    Type:       EmptyDir (a temporary directory that shares a pod's lifetime)
    Medium:     
    SizeLimit:  <unset>
  metrics-server-token-8t6zs:
    Type:        Secret (a volume populated by a Secret)
    SecretName:  metrics-server-token-8t6zs
    Optional:    false
QoS Class:       BestEffort
Node-Selectors:  kubernetes.io/arch=amd64
                 kubernetes.io/os=linux
Tolerations:     node.kubernetes.io/not-ready:NoExecute for 300s
                 node.kubernetes.io/unreachable:NoExecute for 300s
Events:
  Type    Reason     Age   From               Message
  ----    ------     ----  ----               -------
  Normal  Scheduled  42s   default-scheduler  Successfully assigned kube-system/metrics-server-7cdfcc6666-ptv48 to server4
  Normal  Pulling    41s   kubelet, server4   Pulling image "metrics-server-amd64:v0.3.6"
  Normal  Pulled     39s   kubelet, server4   Successfully pulled image "metrics-server-amd64:v0.3.6"
  Normal  Created    39s   kubelet, server4   Created container metrics-server
  Normal  Started    39s   kubelet, server4   Started container metrics-server
[root@server2 ms]# 

下载yaml文件

下载并上传实验所需镜像metrics-server到私有仓库

应用yaml文件，metrics-server成功运行



（2）解决Metrics-server的Pod日志报错
部署后查看Metrics-server的Pod日志：
kubectl logs -n kube-system metrics-server-7cdfcc6666-ptv48
报错1：dial tcp: lookup server2 on 10.96.0.10:53: no such host
这是因为没有内网的DNS服务器，所以metrics-server无法解析节点名字。可以直接修改 coredns的configmap，将各个节点的主机名加入到hosts中，这样所有Pod都可以从 CoreDNS中解析各个节点的名字。

解决：
kubectl edit configmap coredns -n kube-system
作内部地址解析

apiVersion: v1
data:
  Corefile: |
    .:53 {
        errors
        health {
           lameduck 5s
        }
        ready
        hosts {
           172.25.12.2 server2
           172.25.12.3 server3
           172.25.12.4 server4
           fallthrough
        }

报错2：x509: certificate signed by unknown authority

Metric Server 支持一个参数 --kubelet-insecure-tls，可以跳过这一检查，然而官 方也明确说了，这种方式不推荐生产使用
解决：
启用TLS Bootstrap 证书签发(在master和各个节点中)
vim /var/lib/kubelet/config.yaml

[root@server2 ms]# vim /var/lib/kubelet/config.yaml	##添加参数
serverTLSBootstrap: true
[root@server2 ms]# systemctl restart kubelet
[root@server2 ms]# kubectl get csr
NAME        AGE   SIGNERNAME                      REQUESTOR             CONDITION
csr-57blk   13s   kubernetes.io/kubelet-serving   system:node:server2   Pending
[root@server2 ms]# kubectl certificate approve csr-57blk
certificatesigningrequest.certificates.k8s.io/csr-57blk approved
[root@server2 ms]# ubectl get csr
-bash: ubectl: command not found
[root@server2 ms]# kubectl get csr
NAME        AGE   SIGNERNAME                      REQUESTOR             CONDITION
csr-57blk   76s   kubernetes.io/kubelet-serving   system:node:server2   Approved,Issued

报错3: Error from server (ServiceUnavailable): the server is currently unable to handle the request (get nodes.metrics.k8s.io)
如果metrics-server正常启动，没有错误，应该就是网络问题。修改metricsserver的Pod 网络模式：hostNetwork: true

3. Dashboard部署

Dashboard可以给用户提供一个可视化的 Web 界面来查看当前集群的各种信息。用户可以 用 Kubernetes Dashboard 部署容器化的应用、监控应用的状态、执行故障排查任务以及管 理 Kubernetes 各种资源。
（1）下载yaml文件：

拉取并推送实验所需镜像到私有仓库




（2）应用yaml文件：



(3) 修改为NodePort类型，供外部访问
kubectl edit svc -n kubernetes-dashboard


（4）获取dashboard pod的token


访问测试https://172.25.12.2:31416

复制token值，成功登陆