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Prometheus kubernetes-cadvisor服务自动发现

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这一篇文章，通过kubernetes_sd_configs配置服务自动发现。

还原来一样，是通过kube-prometheus安装的k8s监控系统。

和之前由kubernetes-operator已经提供的yaml文件不同，这次我们需要新建一个yaml文件配置。

prometheus-additional.yaml内容如下，注意，这里自动发现的role设置为pod。通过它，将自动发现k8s集群里面所有的pod。

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- job_name: 'kubernetes-cadvisor'
  scheme: https
  tls_config:
    ca_file: /var/run/secrets/kubernetes.io/serviceaccount/ca.crt
  bearer_token_file: /var/run/secrets/kubernetes.io/serviceaccount/token
  kubernetes_sd_configs:
  - role: pod
  relabel_configs:
  - target_label: __address__
    replacement: kubernetes.default.svc:443
  - source_labels: [__meta_kubernetes_pod_node_name]
    regex: (.+)
    replacement: /api/v1/nodes/${1}/proxy/metrics/cadvisor
    target_label: __metrics_path__
  - action: labelmap
    regex: __meta_kubernetes_pod_label_(.+)

然后还需要修改prometheus-prometheus.yaml的内容，在spec项下级，serviceAccountName标签前面添加additionalScrapeConfigs标签，如下：

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spec:
  ...
  additionalScrapeConfigs:
    name: additional-configs
    key: prometheus-additional.yaml
  serviceAccountName: prometheus-k8s
  ...

删除之前的secret，如果有的话。

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# kubectl delete secret additional-configs -n monitoring
secret "additional-configs" deleted

第一次新建当然是没有的，所以直接创建secret：

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# kubectl create secret generic additional-configs --from-file=prometheus-additional.yaml -n monitoring
secret/additional-configs created

然后应用prometheus的配置，因为做过修改。

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# kubectl apply -f prometheus/prometheus-prometheus.yaml 
prometheus.monitoring.coreos.com/k8s configured

稍等片刻后，我们可以看到Prometheus Configuration设置已经变化。已经有job_name为kubernetes-cadvisor的记录了。kubernetes-cadvisor部分内容如下：

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- job_name: kubernetes-cadvisor
  honor_timestamps: true
  scrape_interval: 30s
  scrape_timeout: 10s
  metrics_path: /metrics
  scheme: https
  kubernetes_sd_configs:
  - role: pod
  bearer_token_file: /var/run/secrets/kubernetes.io/serviceaccount/token
  tls_config:
    ca_file: /var/run/secrets/kubernetes.io/serviceaccount/ca.crt
    insecure_skip_verify: false
  relabel_configs:
  - separator: ;
    regex: (.*)
    target_label: __address__
    replacement: kubernetes.default.svc:443
    action: replace
  - source_labels: [__meta_kubernetes_pod_node_name]
    separator: ;
    regex: (.+)
    target_label: __metrics_path__
    replacement: /api/v1/nodes/${1}/proxy/metrics/cadvisor
    action: replace
  - separator: ;
    regex: __meta_kubernetes_pod_label_(.+)
    replacement: $1
    action: labelmap

但奇怪的是，我们在Targets页面并没有发现kubernetes-cadvisor这个Target。

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# kubectl get po -n monitoring
NAME                                   READY   STATUS    RESTARTS   AGE
...
prometheus-k8s-0                       3/3     Running   1          77d
prometheus-k8s-1                       3/3     Running   1          77d

查看pod，未发现异常。

查看一下Pod日志。kubectl logs -f prometheus-k8s-0 prometheus -n monitoring

level=error ts=2020-03-05T02:56:36.493Z caller=klog.go:94 component=k8s_client_runtime func=ErrorDepth
msg=”/app/discovery/kubernetes/kubernetes.go:263: Failed to list v1.Endpoints: endpoints is forbidden: User \”system:serviceaccount:monitoring:prometheus-k8s\” cannot list resource \”endpoints\” in API group \”\” at the cluster scope”
level=error ts=2020-03-05T02:56:37.491Z caller=klog.go:94 component=k8s_client_runtime func=ErrorDepth msg=”/app/discovery/kubernetes/kubernetes.go:264: Failed to list v1.Service: services is forbidden: User \”system:serviceaccount:monitoring:prometheus-k8s\” cannot list resource \”services\” in API group \”\” at the cluster scope”
level=error ts=2020-03-05T02:56:37.494Z caller=klog.go:94 component=k8s_client_runtime func=ErrorDepth msg=”/app/discovery/kubernetes/kubernetes.go:265: Failed to list *v1.Pod: pods is forbidden: User \”system:serviceaccount:monitoring:prometheus-k8s\” cannot list resource \”pods\” in API group \”\” at the cluster scope”

很多出错日志，主要是上面三条的循环出现。

  1. Failed to list *v1.Endpoints: endpoints is forbidden: User \”system:serviceaccount:monitoring:prometheus-k8s\” cannot list resource \”endpoints\” in API group \”\” at the cluster scope.

  2. Failed to list *v1.Service: services is forbidden: User \”system:serviceaccount:monitoring:prometheus-k8s\” cannot list resource \”services\” in API group \”\” at the cluster scope.

  3. Failed to list *v1.Pod: pods is forbidden: User \”system:serviceaccount:monitoring:prometheus-k8s\” cannot list resource \”pods\” in API group \”\” at the cluster scope.

endpoints/services/pods is forbidden，说明是RBAC权限问题，namespace: monitoring下的serviceaccount: prometheus-k8s这个用户没有权限。

查看prometheus-prometheus.yaml内容，可以看到Prometheus绑定了一个名为prometheus-k8s的serviceAccount对象。

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apiVersion: monitoring.coreos.com/v1
kind: Prometheus
metadata:
  labels:
    prometheus: k8s
  name: k8s
  namespace: monitoring
spec:
  ...
  serviceAccountName: prometheus-k8s
  ...

通过查看prometheus-clusterRole.yaml得知，名为prometheus-k8s的serviceAccount对象绑定的是一个名为prometheus-k8s的ClusterRole。

绑定关系在prometheus-clusterRoleBinding.yaml这个文件。

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apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: prometheus-k8s
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: prometheus-k8s
subjects:
- kind: ServiceAccount
  name: prometheus-k8s
  namespace: monitoring

查看这个Role：

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apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: prometheus-k8s
rules:
- apiGroups:
  - ""
  resources:
  - nodes/metrics
  verbs:
  - get
- nonResourceURLs:
  - /metrics
  verbs:
  - get

在上面的权限规则中，并未发现对endpoints/services/pods的list权限。所以做如下修改：

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apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: prometheus-k8s
rules:
- apiGroups:
  - ""
  resources:
  - nodes/metrics
  - configmaps
  verbs:
  - get
- nonResourceURLs:
  - /metrics
  verbs:
  - get
# new apiGroups
- apiGroups:
  - ""
  resources:
  - nodes
  - services
  - endpoints
  - pods
  - nodes/proxy
  verbs:
  - get
  - list
  - watch

应用一下

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# kubectl apply -f prometheus-clusterRole.yaml 
clusterrole.rbac.authorization.k8s.io/prometheus-k8s configured

这时就可以看到Targets了。

我们分析一下第二个Endpoint为：https://kubernetes.default.svc:443/api/v1/nodes/k8s-node1/proxy/metrics/cadvisor

在node节点上是无法解析kubernetes.default.svc的，所以我们先获取这个域名的真实地址。

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kubectl get svc
NAME               TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)        AGE
kubernetes         ClusterIP   10.96.0.1      <none>        443/TCP        62d

再通过secret获取到token，就可以访问url以获取指标了。

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# curl -k https://10.96.0.1:443/api/v1/nodes/k8s-node1/proxy/metrics/cadvisor -H "Authorization: Bearer 
eyJhbGciOiJSUzI1NiIsImtpZCI6IiJ9.eyJpc3MiOiJrdWJlcm5ldGVzL3NlcnZpY2VhY2NvdW50Iiwia3ViZXJuZXRlcy5pby9zZXJ2aWNlYWNjb3VudC9uYW1lc3BhY2UiOiJtb25pdG9yaW5nIiwia3ViZXJuZXRlcy5pby9zZXJ2aWNlYWNjb3VudC9zZWNyZXQubmFtZSI6InByb21ldGhldXMtazhzLXRva2VuLXNtNmdkIiwia3ViZXJuZXRlcy5pby9zZXJ2aWNlYWNjb3VudC9zZXJ2aWNlLWFjY291bnQubmFtZSI6InByb21ldGhldXMtazhzIiwia3ViZXJuZXRlcy5pby9zZXJ2aWNlYWNjb3VudC9zZXJ2aWNlLWFjY291bnQudWlkIjoiMTk2OTkyOTItNDY2Yi00NWQ4LWJmYmYtYzkyZjIwNjczOWY3Iiwic3ViIjoic3lzdGVtOnNlcnZpY2VhY2NvdW50Om1vbml0b3Jpbmc6cHJvbWV0aGV1cy1rOHMifQ.iggZ4ZxmD0y04OQfDlo4P6zRgzn0ryVhcdhlgncpnBY5BJ39Xz0a2AA51ePa78R2njFDjPcecgDJRcqPv76X3o-C-G7EZvN_Ru8zSdB51YxqlLNoIW5hy6Jr27aw74lMslg1MYX_31kkRTqD9DxVn6lq6Uqf4Djebj_E-2maiwl863GCeNRfS1X6KM8idsVknLlpdVINbM8U_l1Yuw-auNzelAk1NQlBdbJqsm1CZKIg_YBsT-KbiyTsbjX2v0uL1D6-Q5Xs9NZMLEAa7dfwz_EOYMDnIGbv-eyhD-924H4_pGOIoQ0dCBP01cxFm7pLJPGouwLaEwPs5BRS0B6u-w"

指标以container_开始。和我们之前讨论的kubelet/1的指标完全一样。Prometheus monitoring/kubelet监控指标

所以其实是可以通过修改kubelet/1的配置来达到新增这个Target的目的。但kubelet/1的目的主要是监控kubelet的情况，其他的Pod它不监控，Target是没有被keep的。如下图：

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relabel_configs:
- source_labels: [__meta_kubernetes_service_label_k8s_app]
  separator: ;
  regex: kubelet
  replacement: $1
  action: keep

我将指标存入kubernetes-cadvisor-1.txt 点击查看，供下载查看。

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