kube-ops-view 是支援 Kubernetes 的 Monitor 工具，其特性是輕量又能簡單地查看 Cluster、Nodes 和 Pods 的分佈狀態，尤其是在 HPA, VPA, Cluster Autoscaler 作動時提供一個很容易查看的介面，雖然在 Monitor 的生態系中 Grafana + Prometheus 幾乎打死所有功能，但在比較簡單的情境下 kube-ops-view 這種簡單輕量的工具仍然提供不錯的使用場景。

Helm Install kube-ops-view

最簡單就是用 Helm 搞定，kube-ops-view 已經支援用 Helm 的方法安裝

# helm install kube-ops-view
       stable/kube-ops-view \
       --set rbac.create=true

基於安全因素，這類型的 Dashboard 都用 kubectl proxy 來訪問比較安全

# kubectl proxy --port=8001

kube-ops-view proxy access uri

http://127.0.0.1:8001/api/v1/namespaces/default/services/http:kube-ops-view:/proxy/

基於研究的角度跑一下 dry-run 看一下 kube-ops-view 到底裝了哪些東西

RBAC：Service Account、Cluster Role

kube-ops-view 需要向 Cluster 拿 nodes, pods 的資訊，所以需要建立 rbac 權限

---
# Source: kube-ops-view/templates/serviceaccount.yaml
apiVersion: v1
kind: ServiceAccount
metadata:
  name: kube-ops-view
---
# Source: kube-ops-view/templates/clusterrole.yaml
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRole
metadata:
  name: kube-ops-view
rules:
- apiGroups: [""]
  resources: ["nodes", "pods"]
  verbs: ["list"]
- apiGroups: ["metrics.k8s.io"]
  resources: ["nodes", "pods"]
---
# Source: kube-ops-view/templates/clusterrolebinding.yaml
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRoleBinding
metadata:
  name: kube-ops-view
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: kube-ops-view
subjects:
  - kind: ServiceAccount
    name: kube-ops-view
    namespace: default

Deployment：deployment、service

kube-ops-view Pod 引用 kube-ops-view 這個 service account，內建 container 內有 :8080/health 用來檢測健康狀態，和 resource limitation 限制能跑的資源，但 limit 仍然是依據有多少 Clusters、Nodes 和 Pods 決定佔用資源。

# Source: kube-ops-view/templates/deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: kube-ops-view
spec:
  replicas: 1
  selector:
    matchLabels:
      app.kubernetes.io/name: kube-ops-view
  template:
    spec:
      serviceAccountName: kube-ops-view
      containers:
      - name: kube-ops-view
        image: "hjacobs/kube-ops-view:20.4.0"
        imagePullPolicy: IfNotPresent
        env:
        ports:
        - containerPort: 8080
        livenessProbe:
          httpGet:
            path: /health
            port: 8080
        readinessProbe:
          httpGet:
            path: /health
            port: 8080
        resources:
            limits:
              cpu: 100m
              memory: 128Mi
            requests:
              cpu: 80m
              memory: 64Mi

Container 預設是聽 8080/tcp port，以 kube-ops-view 這種輕量的 Monitor 工具通常更建議跑在 Cluster or Pod 這種層級就好，更詳細的資訊採用 Grafana + Prometheus 專業的套件。

# Source: kube-ops-view/templates/service.yaml
apiVersion: v1
kind: Service
metadata:
  name: kube-ops-view
  labels:
    app.kubernetes.io/name: kube-ops-view
spec:
  type: ClusterIP
  ports:
  - port: 80
    targetPort: 8080
    protocol: TCP
  selector:
    app.kubernetes.io/name: kube-ops-view

除此之外 kube-ops-view 也支援 Multiple Cluster 這對於更大型的環境時提供 One View 有很大的幫助。

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