Prometheus监控CoreDNS

一、监控方案说明

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K8s中的域名解析的主流方案是CoreDNS，部署完成K8s集群之后，我们都会部署CoreDNS服务实现集群内部域名解析访问，而且CoreDNS有默认提供监控metrics的接口，这里我们prometheus的用的是kube-prometheus，通过serviceMontor来监控CoreDNS的Service。

二、创建监控接口SVC

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默认部署的coredns，会自动创建一个kube-dns的Service，业务pod内就是通过访问这个Service来用coredns进行域名的解析。CoreDNS默认用9153端口提供了metrics接口，因此我们还需要新建一个Service，用来暴露CoreDNS的9153端口。

[root@k8s-master1 coredns]# vim coredns-svc.yaml
apiVersion: v1
kind: Service
metadata:
  name: coredns-metrics
  namespace: kube-system
  labels:
    app: cordns  
spec:
  ports:
  - name: croedns-metrics
    port: 9153
    protocol: TCP
    targetPort: 9153
  selector:
    k8s-app: kube-dns
  sessionAffinity: None
  type: ClusterIP

[root@k8s-master1 coredns]# kubectl apply -f coredns-svc.yaml
[root@k8s-master1 coredns]# kubectl get svc -n kube-system

三、配置Prometheus采集监控数据

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[root@k8s-master1 discovery]# vim prometheus-additional-configs.yaml
apiVersion: v1
kind: Secret
metadata:
  name: additional-scrape-configs
  namespace: monitoring
type: Opaque
stringData:
  additional-scrape-configs.yaml: |
……
    - job_name: coredns-metrics
      honor_labels: true
      honor_timestamps: true
      scrape_interval: 15s
      metrics_path: /metrics
      scheme: http
      kubernetes_sd_configs:
      - role: endpoints
        namespaces:
          names:
          - kube-system
      relabel_configs:
      - source_labels: [__config_type]
        separator: ;
        regex: service
        target_label: __config_type
        replacement: $1
        action: replace
      - source_labels: [__meta_kubernetes_endpoint_port_name]
        separator: ;
        regex: 9153-9153-tcp
        replacement: $1
        action: keep
      - source_labels: [__meta_kubernetes_service_name]
        separator: ;
        regex: coredns-metrics
        replacement: $1
        action: keep
      - source_labels: [__meta_kubernetes_pod_node_name]
        separator: ;
        regex: (.*)
        target_label: node
        replacement: $1
        action: replace
      - source_labels: [__meta_kubernetes_namespace]
        separator: ;
        regex: (.*)
        target_label: namespace
        replacement: $1
        action: replace
      - source_labels: [__meta_kubernetes_service_name]
        separator: ;
        regex: (.*)
        target_label: service
        replacement: $1
        action: replace
      - source_labels: [__meta_kubernetes_pod_name]
        separator: ;
        regex: (.*)
        target_label: pod
        replacement: $1
        action: replace
      - source_labels: [__meta_kubernetes_endpoint_port_name]
        separator: ;
        regex: (.*)
        target_label: endpoint
        replacement: $1
        action: replace

四、检查Prometheus Targets

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五、添加Grafan监控面板

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