k8s 提供了 top 命令可用于统计资源使用情况，它包含有 node 和 pod 两个⼦命令，分别显⽰ node 节点和 Pod 对象的资源使⽤信息。
kubectl top 命令依赖于 metrics 接口。k8s 系统默认未安装该接口，需要单独部署：
[root@k8s-master k8s-install]# kubectl top pod
error: Metrics API not available
安装过程
一、下载部署文件
下载 metrics 接口的部署文件components.yaml
https://github.com/kubernetes-sigs/metrics-server
wget https://github.com/kubernetes-sigs/metrics-server/releases/latest/download/components.yaml
二、修改配置
修改镜像地址
将部署文件中镜像地址修改为国内的地址。大概在部署文件的第 140 行。
原配置是：
image: k8s.gcr.io/metrics-server/metrics-server:v0.6.1
修改后的配置是：
image: registry.cn-hangzhou.aliyuncs.com/google_containers/metrics-server:v0.6.1
可使用如下命令实现修改：
sed -i 's/k8s.gcr.io\/metrics-server/registry.cn-hangzhou.aliyuncs.com\/google_containers/g' components.yaml
禁用证书
kubelet 证书需要由集群证书颁发机构签名(或者通过向 Metrics Server 传递参数 --kubelet-insecure-tls 来禁用证书验证)。
由于是测试环境，我们选择使用参数禁用证书验证，生产环境不推荐这样做！！！
在大概 139 行的位置追加参数：
spec:
containers:
- args:
- --cert-dir=/tmp
- --secure-port=4443
- --kubelet-preferred-address-types=InternalIP,ExternalIP,Hostname
- --kubelet-use-node-status-port
- --metric-resolution=15s
- --kubelet-insecure-tls
apply 部署文件：
[root@k8s-master k8s-install]# kubectl apply -f components.yaml
Warning: resource serviceaccounts/metrics-server is missing the kubectl.kubernetes.io/last-applied-configuration annotation which is required by kubectl apply. kubectl apply should only be used on resources created declaratively by either kubectl create --save-config or kubectl apply. The missing annotation will be patched automatically.
serviceaccount/metrics-server configured
Warning: resource clusterroles/system:aggregated-metrics-reader is missing the kubectl.kubernetes.io/last-applied-configuration annotation which is required by kubectl apply. kubectl apply should only be used on resources created declaratively by either kubectl create --save-config or kubectl apply. The missing annotation will be patched automatically.
clusterrole.rbac.authorization.k8s.io/system:aggregated-metrics-reader configured
Warning: resource clusterroles/system:metrics-server is missing the kubectl.kubernetes.io/last-applied-configuration annotation which is required by kubectl apply. kubectl apply should only be used on resources created declaratively by either kubectl create --save-config or kubectl apply. The missing annotation will be patched automatically.
clusterrole.rbac.authorization.k8s.io/system:metrics-server configured
Warning: resource rolebindings/metrics-server-auth-reader is missing the kubectl.kubernetes.io/last-applied-configuration annotation which is required by kubectl apply. kubectl apply should only be used on resources created declaratively by either kubectl create --save-config or kubectl apply. The missing annotation will be patched automatically.
rolebinding.rbac.authorization.k8s.io/metrics-server-auth-reader configured
Warning: resource clusterrolebindings/metrics-server:system:auth-delegator is missing the kubectl.kubernetes.io/last-applied-configuration annotation which is required by kubectl apply. kubectl apply should only be used on resources created declaratively by either kubectl create --save-config or kubectl apply. The missing annotation will be patched automatically.
clusterrolebinding.rbac.authorization.k8s.io/metrics-server:system:auth-delegator configured
Warning: resource clusterrolebindings/system:metrics-server is missing the kubectl.kubernetes.io/last-applied-configuration annotation which is required by kubectl apply. kubectl apply should only be used on resources created declaratively by either kubectl create --save-config or kubectl apply. The missing annotation will be patched automatically.
clusterrolebinding.rbac.authorization.k8s.io/system:metrics-server configured
Warning: resource services/metrics-server is missing the kubectl.kubernetes.io/last-applied-configuration annotation which is required by kubectl apply. kubectl apply should only be used on resources created declaratively by either kubectl create --save-config or kubectl apply. The missing annotation will be patched automatically.
service/metrics-server configured
Warning: resource deployments/metrics-server is missing the kubectl.kubernetes.io/last-applied-configuration annotation which is required by kubectl apply. kubectl apply should only be used on resources created declaratively by either kubectl create --save-config or kubectl apply. The missing annotation will be patched automatically.
deployment.apps/metrics-server configured
Warning: resource apiservices/v1beta1.metrics.k8s.io is missing the kubectl.kubernetes.io/last-applied-configuration annotation which is required by kubectl apply. kubectl apply should only be used on resources created declaratively by either kubectl create --save-config or kubectl apply. The missing annotation will be patched automatically.
apiservice.apiregistration.k8s.io/v1beta1.metrics.k8s.io configured
metrics pod 已经正常运行：
[root@k8s-master k8s-install]# kubectl get pod -A | grep metrics
kube-system metrics-server-fd9598766-8zphn 1/1 Running 0
三、部署 metrics 接口
[root@k8s-master k8s-install]# kubectl create -f components.yaml
serviceaccount/metrics-server created
clusterrole.rbac.authorization.k8s.io/system:aggregated-metrics-reader created
clusterrole.rbac.authorization.k8s.io/system:metrics-server created
rolebinding.rbac.authorization.k8s.io/metrics-server-auth-reader created
clusterrolebinding.rbac.authorization.k8s.io/metrics-server:system:auth-delegator created
clusterrolebinding.rbac.authorization.k8s.io/system:metrics-server created
service/metrics-server created
deployment.apps/metrics-server created
apiservice.apiregistration.k8s.io/v1beta1.metrics.k8s.io created
查看该 metric pod 的运行情况：
[root@k8s-master k8s-install]# kubectl get pods --all-namespaces | grep metrics
kube-system metrics-server-6ffc8966f5-84hbb 0/1 Running 0 2m23s
四、验证
kubectl top 命令成功：
[root@k8s-master k8s-install]# kubectl top pod
NAME CPU(cores) MEMORY(bytes)
front-end-59bc6df748-699vb 0m 3Mi
front-end-59bc6df748-r7pkr 0m 3Mi
kucc4 1m 2Mi
legacy-app 1m 1Mi
my-demo-nginx-998bbf8f5-9t9pw 0m 0Mi
my-demo-nginx-998bbf8f5-lfgvw 0m 0Mi
my-demo-nginx-998bbf8f5-nfn7r 1m 0Mi
nginx-kusc00401 0m 3Mi
[root@k8s-master k8s-install]#
[root@k8s-master k8s-install]# kubectl top node
NAME CPU(cores) CPU% MEMORY(bytes) MEMORY%
k8s-master 232m 5% 1708Mi 46%
k8s-slave1 29m 1% 594Mi 34%
k8s-slave2 25m 1% 556Mi 32%
五、报错解决
kubectl top nodes 报错 Error from server (ServiceUnavailable): the server is currently unable to handle the request (get nodes.metrics.k8s.io)
1、添加hostNetwork=true
apiVersion: apps/v1
kind: Deployment
metadata:
labels:
k8s-app: metrics-server
name: metrics-server
namespace: kube-system
spec:
selector:
matchLabels:
k8s-app: metrics-server
strategy:
rollingUpdate:
maxUnavailable: 0
template:
metadata:
labels:
k8s-app: metrics-server
spec:
hostNetwork: true # 添加这个
2、重启kubeapi pod和 kubelet
kubectl delete pod kube-apiserver-k8s-master -n kube-system
systemctl restart kubelet