背景

边缘集群（基于 树莓派 + K3S) 需要实现基本的告警功能。

边缘集群限制

1. CPU/内存/存储 资源紧张，无法支撑至少需要 2GB 以上内存和大量存储的基于 Prometheus 的完整监控体系方案（即使是基于 Prometheus Agent, 也无法支撑） （需要避免额外的存储和计算资源消耗）
2. 网络条件，无法支撑监控体系，因为监控体系一般都需要每 1min 定时（或每时每刻）传输数据，且数据量不小；
   1. 存在 5G 收费网络的情况，且访问的目的端地址需要开通权限，且按照流量收费，且因为 5G 网络条件，网络传输能力受限，且不稳定（可能会在一段时间内离线）;

关键需求

总结下来，关键需求如下：

1. 实现对边缘集群异常的及时告警，需要知道边缘集群正在发生的异常情况；
2. 网络：网络条件情况较差，网络流量少，只只能开通极少数目的端地址，可以容忍网络不稳定（一段时间内离线）的情况；
3. 资源：需要尽量避免额外的存储和计算资源消耗

方案

综上所诉，采用如下方案实现：

基于 Kubernetes Events 的告警通知

架构图

技术方案规划

1. 从 Kubernetes 的各项资源收集 Events, 如：
   1. pod
   2. node
   3. kubelet
   4. crd
   5. ...
2. 通过 kubernetes-event-exporter 组件来实现对 Kubernetes Events 的收集；
3. 只筛选 Warning 级别 Events 供告警通知（后续，条件可以进一步定义）
4. 告警通过 飞书 webhook 等通信工具进行发送（后续，发送渠道可以增加）

实施步骤

手动方式：

在边缘集群上，执行如下操作：

1. 创建 roles

如下：

cat << _EOF_ | kubectl apply -f -
---
apiVersion: v1
kind: Namespace
metadata:
  name: monitoring
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: event-exporter-extra
rules:
  - apiGroups:
      - ""
    resources:
      - nodes
    verbs:
      - get
      - list
      - watch
---
apiVersion: v1
kind: ServiceAccount
metadata:
  namespace: monitoring
  name: event-exporter
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: event-exporter
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: view
subjects:
  - kind: ServiceAccount
    namespace: monitoring
    name: event-exporter
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: event-exporter-extra
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: event-exporter-extra
subjects:
  - kind: ServiceAccount
    namespace: kube-event-export
    name: event-exporter
_EOF_

2. 创建 kubernetes-event-exporter config

如下：

cat << _EOF_ | kubectl apply -f -
apiVersion: v1
kind: ConfigMap
metadata:
  name: event-exporter-cfg
  namespace: monitoring
data:
  config.yaml: |
    logLevel: error
    logFormat: json
    route:
      routes:
        - match:
            - receiver: "dump"      
        - drop:
            - type: "Normal"
          match:
            - receiver: "feishu"                     
    receivers:
      - name: "dump"
        stdout: {}
      - name: "feishu"
        webhook:
          endpoint: "https://open.feishu.cn/open-apis/bot/v2/hook/..."
          headers:
            Content-Type: application/json
          layout:
            msg_type: interactive
            card:
              config:
                wide_screen_mode: true
                enable_forward: true
              header:
                title:
                  tag: plain_text
                  content: XXX IoT K3S 集群告警
                template: red
              elements:
                - tag: div
                  text: 
                    tag: lark_md
                    content: "**EventType:**  {{ .Type }}\n**EventKind:**  {{ .InvolvedObject.Kind }}\n**EventReason:**  {{ .Reason }}\n**EventTime:**  {{ .LastTimestamp }}\n**EventMessage:**  {{ .Message }}"
      
_EOF_

🐾 注意：

• endpoint: "https://open.feishu.cn/open-apis/bot/v2/hook/..." 按需修改为对应的 webhook endpoint, ❌切记勿对外公布！!!
• content: XXX IoT K3S 集群告警: 按需调整为方便快速识别的名称，如："家里测试 K3S 集群告警"

3. 创建 Deployment

cat << _EOF_ | kubectl apply -f -
apiVersion: apps/v1
kind: Deployment
metadata:
  name: event-exporter
  namespace: monitoring
spec:
  replicas: 1
  selector:
    matchLabels:
      app: event-exporter
      version: v1
  template:
    metadata:
      labels:
        app: event-exporter
        version: v1
    spec:
      volumes:
        - name: cfg
          configMap:
            name: event-exporter-cfg
            defaultMode: 420
        - name: localtime
          hostPath:
            path: /etc/localtime
            type: ''
        - name: zoneinfo
          hostPath:
            path: /usr/share/zoneinfo
            type: ''
      containers:
        - name: event-exporter
          image: ghcr.io/opsgenie/kubernetes-event-exporter:v0.11
          args:
            - '-conf=/data/config.yaml'
          env:
            - name: TZ
              value: Asia/Shanghai
          volumeMounts:
            - name: cfg
              mountPath: /data
            - name: localtime
              readOnly: true
              mountPath: /etc/localtime
            - name: zoneinfo
              readOnly: true
              mountPath: /usr/share/zoneinfo
          imagePullPolicy: IfNotPresent
      serviceAccount: event-exporter
      affinity:
        nodeAffinity:
          preferredDuringSchedulingIgnoredDuringExecution:
            - weight: 100
              preference:
                matchExpressions:
                  - key: node-role.kubernetes.io/controlplane
                    operator: In
                    values:
                      - 'true'
            - weight: 100
              preference:
                matchExpressions:
                  - key: node-role.kubernetes.io/control-plane
                    operator: In
                    values:
                      - 'true'
            - weight: 100
              preference:
                matchExpressions:
                  - key: node-role.kubernetes.io/master
                    operator: In
                    values:
                      - 'true'    
      tolerations:
        - key: node-role.kubernetes.io/controlplane
          value: 'true'
          effect: NoSchedule
        - key: node-role.kubernetes.io/control-plane
          operator: Exists
          effect: NoSchedule
        - key: node-role.kubernetes.io/master
          operator: Exists
          effect: NoSchedule      
_EOF_

📝 说明：

1. event-exporter-cfg 相关配置，是用于加载以 ConfigMap 形式保存的配置文件；
2. localtime zoneinfo TZ 相关配置，是用于修改该 pod 的时区为Asia/Shanghai, 以使得终显示的通知效果为 CST 时区；
3. affinity tolerations 相关配置，是为了确保：无论如何，优先调度到 master node 上去，按需调整，此处是因为 master 往往在边缘集群中作为网关存在，配置较高，且在线时间较长；

自动化部署

效果：安装 K3S 时就自动部署

在 K3S server 所在节点，/var/lib/rancher/k3s/server/manifests/ 目录（如果没有该目录就先创建）下，创建 event-exporter.yaml

---
apiVersion: v1
kind: Namespace
metadata:
  name: monitoring
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: event-exporter-extra
rules:
  - apiGroups:
      - ""
    resources:
      - nodes
    verbs:
      - get
      - list
      - watch
---
apiVersion: v1
kind: ServiceAccount
metadata:
  namespace: monitoring
  name: event-exporter
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: event-exporter
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: view
subjects:
  - kind: ServiceAccount
    namespace: monitoring
    name: event-exporter
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: event-exporter-extra
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: event-exporter-extra
subjects:
  - kind: ServiceAccount
    namespace: kube-event-export
    name: event-exporter
---
apiVersion: v1
kind: ConfigMap
metadata:
  name: event-exporter-cfg
  namespace: monitoring
data:
  config.yaml: |
    logLevel: error
    logFormat: json
    route:
      routes:
        - match:
            - receiver: "dump"      
        - drop:
            - type: "Normal"
          match:
            - receiver: "feishu"                     
    receivers:
      - name: "dump"
        stdout: {}
      - name: "feishu"
        webhook:
          endpoint: "https://open.feishu.cn/open-apis/bot/v2/hook/dc4fd384-996b-4d20-87cf-45b3518869ec"
          headers:
            Content-Type: application/json
          layout:
            msg_type: interactive
            card:
              config:
                wide_screen_mode: true
                enable_forward: true
              header:
                title:
                  tag: plain_text
                  content: xxxK3S集群告警
                template: red
              elements:
                - tag: div
                  text: 
                    tag: lark_md
                    content: "**EventType:**  {{ .Type }}\n**EventKind:**  {{ .InvolvedObject.Kind }}\n**EventReason:**  {{ .Reason }}\n**EventTime:**  {{ .LastTimestamp }}\n**EventMessage:**  {{ .Message }}"
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: event-exporter
  namespace: monitoring
spec:
  replicas: 1
  selector:
    matchLabels:
      app: event-exporter
      version: v1
  template:
    metadata:
      labels:
        app: event-exporter
        version: v1
    spec:
      volumes:
        - name: cfg
          configMap:
            name: event-exporter-cfg
            defaultMode: 420
        - name: localtime
          hostPath:
            path: /etc/localtime
            type: ''
        - name: zoneinfo
          hostPath:
            path: /usr/share/zoneinfo
            type: ''
      containers:
        - name: event-exporter
          image: ghcr.io/opsgenie/kubernetes-event-exporter:v0.11
          args:
            - '-conf=/data/config.yaml'
          env:
            - name: TZ
              value: Asia/Shanghai
          volumeMounts:
            - name: cfg
              mountPath: /data
            - name: localtime
              readOnly: true
              mountPath: /etc/localtime
            - name: zoneinfo
              readOnly: true
              mountPath: /usr/share/zoneinfo
          imagePullPolicy: IfNotPresent
      serviceAccount: event-exporter
      affinity:
        nodeAffinity:
          preferredDuringSchedulingIgnoredDuringExecution:
            - weight: 100
              preference:
                matchExpressions:
                  - key: node-role.kubernetes.io/controlplane
                    operator: In
                    values:
                      - 'true'
            - weight: 100
              preference:
                matchExpressions:
                  - key: node-role.kubernetes.io/control-plane
                    operator: In
                    values:
                      - 'true'
            - weight: 100
              preference:
                matchExpressions:
                  - key: node-role.kubernetes.io/master
                    operator: In
                    values:
                      - 'true'    
      tolerations:
        - key: node-role.kubernetes.io/controlplane
          value: 'true'
          effect: NoSchedule
        - key: node-role.kubernetes.io/control-plane
          operator: Exists
          effect: NoSchedule
        - key: node-role.kubernetes.io/master
          operator: Exists
          effect: NoSchedule  

之后启动 K3S 就会自动部署。

📚️Reference:
自动部署 manifests 和 Helm charts | Rancher 文档

终效果

如下图：

📚️参考文档

• opsgenie/kubernetes-event-exporter: Export Kubernetes events to multiple destinations with routing and filtering (github.com)
• AliyunContainerService/kube-eventer: kube-eventer emit kubernetes events to sinks (github.com)
• kubesphere/kube-events: K8s Event Exporting, Filtering and Alerting in Multi-Tenant Environment (github.com)
• kubesphere/notification-manager: K8s native notification management with multi-tenancy support (github.com)