Prometheus 使用localpv 持久化存储

Prometheus 使用localpv 持久化存储

现在我们来创建 prometheus 的 Pod 资源：

# prometheus-deploy.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: prometheus
  namespace: kube-mon
  labels:
    app: prometheus
spec:
  selector:
    matchLabels:
      app: prometheus
  template:
    metadata:
      labels:
        app: prometheus
    spec:
      serviceAccountName: prometheus
      containers:
      - image: prom/prometheus:v2.24.1
        name: prometheus
        args:
        - "--config.file=/etc/prometheus/prometheus.yml"
        - "--storage.tsdb.path=/prometheus"  # 指定tsdb数据路径
        - "--storage.tsdb.retention.time=24h"
        - "--web.enable-admin-api"  # 控制对admin HTTP API的访问，其中包括删除时间序列等功能
        - "--web.enable-lifecycle"  # 支持热更新，直接执行localhost:9090/-/reload立即生效
        ports:
        - containerPort: 9090
          name: http
        volumeMounts:
        - mountPath: "/etc/prometheus"
          name: config-volume
        - mountPath: "/prometheus"
          name: data
        resources:
          requests:
            cpu: 100m
            memory: 512Mi
          limits:
            cpu: 100m
            memory: 512Mi
      volumes:
      - name: data
        persistentVolumeClaim:
          claimName: prometheus-data
      - configMap:
          name: prometheus-config
        name: config-volume

另外为了 prometheus 的性能和数据持久化我们这里是直接将通过一个 LocalPV 来进行数据持久化的，通过 --storage.tsdb.path=/prometheus 指定数据目录，创建如下所示的一个 PVC 资源对象，注意是一个 LocalPV，和 node3 节点具有亲和性：

apiVersion: v1
kind: PersistentVolume
metadata:
  name: prometheus-local
  labels:
    app: prometheus
spec:
  accessModes:
  - ReadWriteonce
  capacity:
    storage: 20Gi
  storageClassName: local-storage
  local:
    path: /data/k8s/prometheus
  nodeAffinity:
    required:
      nodeSelectorTerms:
      - matchexpressions:
        - key: kubernetes.io/hostname
          operator: In
          values:
          - node3
  persistentVolumeReclaimPolicy: Retain
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: prometheus-data
  namespace: kube-mon
spec:
  selector:
    matchLabels:
      app: prometheus
  accessModes:
  - ReadWriteonce
  resources:
    requests:
      storage: 20Gi
  storageClassName: local-storage

现在我们就可以添加 promethues 的资源对象了：

$ kubectl apply -f prometheus-deploy.yaml 
deployment.apps/prometheus created
$ kubectl get pods -n kube-mon
NAME                         READY   STATUS             RESTARTS   AGE
prometheus-df4f47d95-vksmc   0/1     CrashLoopBackOff   3          98s
$ kubectl logs -f prometheus-df4f47d95-vksmc -n kube-mon
level=info ts=2019-12-12T03:08:49.424Z caller=main.go:332 msg="Starting Prometheus" version="(version=2.14.0, branch=HEAD, revision=edeb7a44cbf745f1d8be4ea6f215e79e651bfe19)"
level=info ts=2019-12-12T03:08:49.424Z caller=main.go:333 build_context="(go=go1.13.4, user=root@df2327081015, date=20191111-14:27:12)"
level=info ts=2019-12-12T03:08:49.425Z caller=main.go:334 host_details="(Linux 3.10.0-1062.4.1.el7.x86_64 #1 SMP Fri Oct 18 17:15:30 UTC 2019 x86_64 prometheus-df4f47d95-vksmc (none))"
level=info ts=2019-12-12T03:08:49.425Z caller=main.go:335 fd_limits="(soft=1048576, hard=1048576)"
level=info ts=2019-12-12T03:08:49.425Z caller=main.go:336 vm_limits="(soft=unlimited, hard=unlimited)"
level=error ts=2019-12-12T03:08:49.425Z caller=query_logger.go:85 component=activeQueryTracker msg="Error opening query log file" file=/prometheus/queries.active err="open /prometheus/queries.active: permission denied"
panic: Unable to create mmap-ed active query log

goroutine 1 [running]:
github.com/prometheus/prometheus/promql.NewActiveQueryTracker(0x7ffd8cf6ec5d, 0xb, 0x14, 0x2b4f400, 0xc0006f33b0, 0x2b4f400)
        /app/promql/query_logger.go:115 +0x48c
main.main()
        /app/cmd/prometheus/main.go:364 +0x5229

创建 Pod 后，我们可以看到并没有成功运行，出现了 open /prometheus/queries.active: permission denied 这样的错误信息，这是因为我们的 prometheus 的镜像中是使用的 nobody 这个用户，然后现在我们通过 LocalPV 挂载到宿主机上面的目录的 ownership 却是 root： 

$ ls -la /data/k8s
total 36
drwxr-xr-x   6 root root  4096 Dec 12 11:07 .
dr-xr-xr-x. 19 root root  4096 Nov  9 23:19 ..
drwxr-xr-x   2 root root  4096 Dec 12 11:07 prometheus

[root@master persistentvolume]# kubectl exec -it prometheus-server-5775f99578-5gm5f -n monitor  sh
kubectl exec [POD] [COMMAND] is DEPRECATED and will be removed in a future version. Use kubectl exec [POD] -- [COMMAND] instead.
/prometheus $ id
uid=65534(nobody) gid=65534(nogroup)

/prometheus $ ls -la /prometheus/
total 16
drwxr-xr-x    3 nobody   nogroup       4096 Jan 17 15:31 .
drwxr-xr-x    1 root     root          4096 Jan 17 15:31 ..
-rw-------    1 nobody   nogroup          2 Jan 17 15:31 lock
drwxr-xr-x    2 nobody   nogroup       4096 Jan 17 15:31 wal

所以当然会出现 *** 作权限问题了，这个时候我们就可以通过 securityContext 来为 Pod 设置下 volumes 的权限，通过设置 runAsUser=0 指定运行的用户为 root，也可以通过设置一个 initContainer 来修改数据目录权限：

......
initContainers:
- name: fix-permissions
  image: busybox
  command: [chown, -R, "nobody:nobody", /prometheus]
  volumeMounts:
  - name: data
    mountPath: /prometheus

这个时候我们重新更新下 prometheus：

$ kubectl apply -f prometheus-deploy.yaml
deployment.apps/prometheus configured
$ kubectl get pods -n kube-mon                              
NAME                          READY   STATUS    RESTARTS   AGE
prometheus-79b8774f68-7m8zr   1/1     Running   0          56s
$ kubectl logs -f prometheus-79b8774f68-7m8zr -n kube-mon
level=info ts=2019-12-12T03:17:44.228Z caller=main.go:332 msg="Starting Prometheus" version="(version=2.14.0, branch=HEAD, revision=edeb7a44cbf745f1d8be4ea6f215e79e651bfe19)"
......
level=info ts=2019-12-12T03:17:44.822Z caller=main.go:673 msg="TSDB started"
level=info ts=2019-12-12T03:17:44.822Z caller=main.go:743 msg="Loading configuration file" filename=/etc/prometheus/prometheus.yml
level=info ts=2019-12-12T03:17:44.827Z caller=main.go:771 msg="Completed loading of configuration file" filename=/etc/prometheus/prometheus.yml
level=info ts=2019-12-12T03:17:44.827Z caller=main.go:626 msg="Server is ready to receive web requests."