Kubernetes-在Kubernetes集群上搭建Stateful Zookeeper集群

连续花了两天时间在搭建Zookeeper集群这件事上了，碰到了N多坑，终于是搭建成功了。

准备工作

1. Zookeeper镜像，经过我的测试，在Kubernetes上搭建Zookeeper需要用Kubernetes-Zookeeper这个镜像，而不是用官方的Zookeeper镜像（后面有时间再试一试），Kubernetes-Zookeeper这个镜像在国内不好拿，我是采用docker hub构建出来的，Dockerfile如下：

FROM k8s.gcr.io/kubernetes-zookeeper:1.0-3.4.10
MAINTAINER leo.lee <lis85@163.com>

当然你也可以直接拉取我构建成功的镜像

docker pull leolee32/kubernetes-library:kubernetes-zookeeper1.0-3.4.10

1. Zookeeper集群需要用到存储，这里需要准备持久卷（PersistentVolume，简称PV），我这里以yaml文件创建3个PV，供待会儿3个Zookeeper节点创建出来的持久卷声明（PersistentVolumeClaim，简称PVC）绑定。

persistent-volume.yaml

kind: PersistentVolume
apiVersion: v1
metadata:
  name: k8s-pv-zk1
  annotations:
    volume.beta.kubernetes.io/storage-class: "anything"
  labels:
    type: local
spec:
  capacity:
    storage: 3Gi
  accessModes:
    - ReadWriteOnce
  hostPath:
    path: "/var/lib/zookeeper"
  persistentVolumeReclaimPolicy: Recycle
---
kind: PersistentVolume
apiVersion: v1
metadata:
  name: k8s-pv-zk2
  annotations:
    volume.beta.kubernetes.io/storage-class: "anything"
  labels:
    type: local
spec:
  capacity:
    storage: 3Gi
  accessModes:
    - ReadWriteOnce
  hostPath:
    path: "/var/lib/zookeeper"
  persistentVolumeReclaimPolicy: Recycle
---
kind: PersistentVolume
apiVersion: v1
metadata:
  name: k8s-pv-zk3
  annotations:
    volume.beta.kubernetes.io/storage-class: "anything"
  labels:
    type: local
spec:
  capacity:
    storage: 3Gi
  accessModes:
    - ReadWriteOnce
  hostPath:
    path: "/var/lib/zookeeper"
  persistentVolumeReclaimPolicy: Recycle

使用如下命令创建

kubectl create -f persistent-volume.yaml

create PV

查看PV

kubectl get pv -o wide

查看PV

部署Zookeeper集群

zookeeper.yaml

apiVersion: v1
kind: Service
metadata:
  name: zk-hs
  labels:
    app: zk
spec:
  ports:
  - port: 2888
    name: server
  - port: 3888
    name: leader-election
  clusterIP: None
  selector:
    app: zk
---
apiVersion: v1
kind: Service
metadata:
  name: zk-cs
  labels:
    app: zk
spec:
  ports:
  - port: 2181
    name: client
  selector:
    app: zk
---
apiVersion: policy/v1beta1
kind: PodDisruptionBudget
metadata:
  name: zk-pdb
spec:
  selector:
    matchLabels:
      app: zk
  maxUnavailable: 1
---
apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: zk
spec:
  selector:
    matchLabels:
      app: zk
  serviceName: zk-hs
  replicas: 3
  updateStrategy:
    type: RollingUpdate
  podManagementPolicy: Parallel
  template:
    metadata:
      labels:
        app: zk
    spec:
      affinity:
        podAntiAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
            - labelSelector:
                matchExpressions:
                  - key: "app"
                    operator: In
                    values:
                    - zk
              topologyKey: "kubernetes.io/hostname"
      containers:
      - name: kubernetes-zookeeper
        imagePullPolicy: Always
        image: "192.168.242.132/library/kubernetes-zookeeper:1.0-3.4.10"
        resources:
          requests:
            memory: "1Gi"
            cpu: "0.5"
        ports:
        - containerPort: 2181
          name: client
        - containerPort: 2888
          name: server
        - containerPort: 3888
          name: leader-election
        command:
        - sh
        - -c
        - "start-zookeeper \
          --servers=3 \
          --data_dir=/var/lib/zookeeper/data \
          --data_log_dir=/var/lib/zookeeper/data/log \
          --conf_dir=/opt/zookeeper/conf \
          --client_port=2181 \
          --election_port=3888 \
          --server_port=2888 \
          --tick_time=2000 \
          --init_limit=10 \
          --sync_limit=5 \
          --heap=512M \
          --max_client_cnxns=60 \
          --snap_retain_count=3 \
          --purge_interval=12 \
          --max_session_timeout=40000 \
          --min_session_timeout=4000 \
          --log_level=INFO"
        readinessProbe:
          exec:
            command:
            - sh
            - -c
            - "zookeeper-ready 2181"
          initialDelaySeconds: 10
          timeoutSeconds: 5
        livenessProbe:
          exec:
            command:
            - sh
            - -c
            - "zookeeper-ready 2181"
          initialDelaySeconds: 10
          timeoutSeconds: 5
        volumeMounts:
        - name: datadir
          mountPath: /var/lib/zookeeper
      securityContext:
        runAsUser: 1000
        fsGroup: 1000
  volumeClaimTemplates:
  - metadata:
      name: datadir
      annotations:
        volume.beta.kubernetes.io/storage-class: "anything"
    spec:
      accessModes: [ "ReadWriteOnce" ]
      resources:
        requests:
          storage: 3Gi

使用如下命令创建

kubectl create -f zookeeper.yaml

创建Zookeeper集群

创建完后会出现一个问题，就是所有的Zookeeper pod都启动不起来，查看日志发现是用户对文件夹【/var/lib/zookeeper】没有权限引起的，文件夹的权限是root用户。

image.png

这里如何通过安装解决还有待研究，目前可以先手动把文件夹【/var/lib/zookeeper】的权限修改为普通用户，Zookeeper pod就可以正常启动了。
通过命令查看pod

kubectl get pod -o wide

pods

查看PV，发现持久卷声明已经绑定上了。

kubectl get pv -o wide

PV

查看PVC

kubectl get pvc -o wide

pvc

最后来验证Zookeeper集群是否正常，查看集群节点状态

for i in 0 1 2; do kubectl exec zk-$i zkServer.sh status; done

zookeeper status

一个leader，两个follower，成功！！！