kube-promethesu调整coredns监控

K8s集群版本是二进制部署的1.20.4，kube-prometheus对应选择的版本是kube-prometheus-0.8.0

Coredns是在安装集群的时候部署的，采用的也是该版本的官方文档，kube-prometheus中也有coredns的监控配置信息，但是在prometheus的监控页面并没有发现coredns的servicemonitor.。所以我们需要一步步的去排查该问题。

先看下coredns的servicemonitor 

vim kubernetes-serviceMonitorCoreDNS.yaml

apiVersion: monitoring.coreos.com/v1
kind: ServiceMonitor
metadata:
  labels:
    app.kubernetes.io/name: coredns
  name: coredns
  namespace: monitoring
spec:
  endpoints:
  - bearerTokenFile: /var/run/secrets/kubernetes.io/serviceaccount/token
    interval: 15s
    port: metrics
  jobLabel: app.kubernetes.io/name
  namespaceSelector:
    matchNames:
    - kube-system
  selector:
    matchLabels:
      app.kubernetes.io/name: kube-dns

再来看下coredns的service配置

---
apiVersion: v1
kind: Service
metadata:
  name: kube-dns
  namespace: kube-system
  annotations:
    prometheus.io/port: "9153"
    prometheus.io/scrape: "true"
  labels:
    k8s-app: kube-dns
    kubernetes.io/cluster-service: "true"
    addonmanager.kubernetes.io/mode: Reconcile
    kubernetes.io/name: "CoreDNS"
spec:
  selector:
    k8s-app: kube-dns
  clusterIP: 10.0.0.2
  ports:
  - name: dns
    port: 53
    protocol: UDP
  - name: dns-tcp
    port: 53
    protocol: TCP
  - name: metrics
    port: 9153
    protocol: TCP

从上面两段可以看到，servicemonitor去匹配的service是

labels:

app.kubernetes.io/name: coredns

而我们创建的coredns的service的labels

labels:

    k8s-app: kube-dns

    kubernetes.io/cluster-service: "true"

    addonmanager.kubernetes.io/mode: Reconcile

    kubernetes.io/name: "CoreDNS"

两边没有对应上，所以该servicemonitor无法匹配到对应的service，所以监控不到我们的coredns.

因coredns对服务的影响比较大，我们选择去修改servicemonitor

修改labels后重新apply

Kubectl apply -f kubernetes-serviceMonitorCoreDNS.yaml

coredns就加载出来了

配置coredns的监控信息

apiVersion: monitoring.coreos.com/v1
kind: PrometheusRule
metadata:
  labels:
    app.kubernetes.io/name: kube-prometheus
    app.kubernetes.io/part-of: kube-prometheus
    prometheus: k8s
    role: alert-rules
  name: kubernetes-monitoring-coredns-rules
  namespace: monitoring

spec:
  groups:
  - name: coredns
    rules:
    - alert: CoreDNSDown
      annotations:
        message: CoreDNS has disappeared from Prometheus target discovery.
        runbook_url: https://github.com/povilasv/coredns-mixin/tree/master/runbook.md#alert-name-corednsdown
      expr: |
        absent(up{job="kube-dns"} == 1)
      for: 15m
      labels:
        severity: critical
    - alert: CoreDNS的dns请求持续时间延迟高
      annotations:
        message: CoreDNS has 99th percentile latency of {{ $value }} seconds for server
          {{ $labels.server }} zone {{ $labels.zone }} .
        runbook_url: https://github.com/povilasv/coredns-mixin/tree/master/runbook.md#alert-name-corednslatencyhigh
      expr: |
        histogram_quantile(0.99, sum(rate(coredns_dns_request_duration_seconds_bucket{job="kube-dns"}[5m])) by(server, zone, le)) > 4
      for: 10m
      labels:
        severity: critical
    - alert: CoreDNS响应错误高
      annotations:
        message: CoreDNS is returning SERVFAIL for {{ $value | humanizePercentage }} of   requests.
        runbook_url: https://github.com/povilasv/coredns-mixin/tree/master/runbook.md#alert-name-corednserorshigh
      expr: |
        sum(rate(coredns_dns_responses_total{job="kube-dns",rcode="SERVFAIL"}[5m]))
          /
        sum(rate(coredns_dns_responses_total{job="kube-dns"}[5m])) > 0.03
      for: 10m
      labels:
        severity: critical
    - alert: CoreDNS响应错误高
      annotations:
        message: CoreDNS is returning SERVFAIL for {{ $value | humanizePercentage }} of   requests.
        runbook_url: https://github.com/povilasv/coredns-mixin/tree/master/runbook.md#alert-name-corednserorshigh
      expr: |
        sum(rate(coredns_dns_responses_total{job="kube-dns",rcode="SERVFAIL"}[5m]))
          /
        sum(rate(coredns_dns_responses_total{job="kube-dns"}[5m])) > 0.01
      for: 10m
      labels:
        severity: warning

    - alert: CoreDNS转发请求持续时间延迟高
      annotations:
        message: CoreDNS has 99th percentile latency of {{ $value }} seconds forwarding requests to {{ $labels.to }}.
        runbook_url: https://github.com/povilasv/coredns-mixin/tree/master/runbook.md#alert-name-corednsforwardlatencyhigh
      expr: |
        histogram_quantile(0.99, sum(rate(coredns_forward_request_duration_seconds_bucket{job="kube-dns"}[5m])) by(to, le)) > 4
      for: 10m
      labels:
        severity: critical
 
    - alert: CoreDNSForwardErrorsHigh
      annotations:
        message: CoreDNS is returning SERVFAIL for {{ $value | humanizePercentage }} of forward requests to {{ $labels.to }}.
        runbook_url: https://github.com/povilasv/coredns-mixin/tree/master/runbook.md#alert-name-corednsforwarderrorshigh
      expr: |
        sum(rate(coredns_forward_responses_total{job="kube-dns",rcode="SERVFAIL"}[5m]))
          /
        sum(rate(coredns_forward_responses_total{job="kube-dns"}[5m])) > 0.03
      for: 10m
      labels:
        severity: critical
 
    - alert: CoreDNSForwardErrorsHigh
      annotations:
        message: CoreDNS is returning SERVFAIL for {{ $value | humanizePercentage }} of forward requests to {{ $labels.to }}.
        runbook_url: https://github.com/povilasv/coredns-mixin/tree/master/runbook.md#alert-name-corednsforwarderrorshigh
      expr: |
        sum(rate(coredns_forward_responses_total{job="kube-dns",rcode="SERVFAIL"}[5m]))
          /
        sum(rate(coredns_forward_responses_total{job="kube-dns"}[5m])) > 0.01
      for: 10m
      labels:
        severity: warning
  
    - alert: CoreDNSForwardHealthcheckFailureCount
      annotations:
        message: CoreDNS health checks have failed to upstream server {{ $labels.to }}.
        runbook_url: https://github.com/povilasv/coredns-mixin/tree/master/runbook.md#alert-name-corednsforwardhealthcheckfailurecount
      expr: |
        sum(rate(coredns_forward_healthcheck_failures_total{job="kube-dns"}[5m])) by (to) > 0
      for: 10m
      labels:
        severity: warning
  
    - alert: CoreDNSForwardHealthcheckBrokenCount
      annotations:
        message: CoreDNS health checks have failed for all upstream servers.
        runbook_url: https://github.com/povilasv/coredns-mixin/tree/master/runbook.md#alert-name-corednsforwardhealthcheckbrokencount
      expr: |
        sum(rate(coredns_forward_healthcheck_broken_total{job="kube-dns"}[5m])) > 0
      for: 10m
      labels:
        severity: warning
    - alert: CorednsPanicCount
      expr: increase(coredns_panics_total[1m]) > 0
      for: 0m
      labels:
        severity: critical
      annotations:
        summary: CoreDNS Panic Count (instance {{ $labels.instance }})
        description: "Number of CoreDNS panics encountered\n  VALUE = {{ $value }}\n  LABELS = {{ $labels }}"