zookeeper实战

22. zookeeper实战

官方参考sts部署：运行ZooKeeper，分布式系统协调器|Kubernetes

#这是jdk环境
root@k8s-master1:~/k8s-data/dockerfile/web/magedu/zookeeper# nerdctl pull elevy/slim_java:8
 
#然后再上传到harbor仓库
root@k8s-master1:~/k8s-data/dockerfile/web/magedu/zookeeper# nerdctl push harbor.nbrhce.com/baseimages/slim_java:8
#构建
root@k8s-master1:~/k8s-data/dockerfile/web/magedu/zookeeper# ./build-command.sh v3.4.14
#!/bin/bash
TAG=$1
#docker build -t harbor.magedu.net/magedu/zookeeper:${TAG} .
#sleep 1
#docker push  harbor.magedu.net/magedu/zookeeper:${TAG}
 
nerdctl  build -t harbor.nbrhce.com/demo/zookeeper:${TAG} .
 
nerdctl push harbor.nbrhce.com/demo/zookeeper:${TAG}
 

• Dockerfile编写

root@k8s-master1:~/k8s-data/dockerfile/web/magedu/zookeeper# cat Dockerfile 
#FROM harbor-linux38.local.com/linux38/slim_java:8 
FROM harbor.nbrhce.com/baseimages/slim_java:8
 
ENV ZK_VERSION 3.4.14
ADD repositories /etc/apk/repositories 
# Download Zookeeper
COPY zookeeper-3.4.14.tar.gz /tmp/zk.tgz
COPY zookeeper-3.4.14.tar.gz.asc /tmp/zk.tgz.asc
COPY KEYS /tmp/KEYS
RUN apk add --no-cache --virtual .build-deps \
      ca-certificates   \
      gnupg             \
      tar               \
      wget &&           \
    #
    # Install dependencies
    apk add --no-cache  \
      bash &&           \
    #
    #
    # Verify the signature
    export GNUPGHOME="$(mktemp -d)" && \
    gpg -q --batch --import /tmp/KEYS && \
    gpg -q --batch --no-auto-key-retrieve --verify /tmp/zk.tgz.asc /tmp/zk.tgz && \
    #
    # Set up directories
    #
    mkdir -p /zookeeper/data /zookeeper/wal /zookeeper/log && \
    #
    # Install
    tar -x -C /zookeeper --strip-components=1 --no-same-owner -f /tmp/zk.tgz && \
    #
    # Slim down
    cd /zookeeper && \
    cp dist-maven/zookeeper-${ZK_VERSION}.jar . && \
    rm -rf \
      *.txt \
      *.xml \
      bin/README.txt \
      bin/*.cmd \
      conf/* \
      contrib \
      dist-maven \
      docs \
      lib/*.txt \
      lib/cobertura \
      lib/jdiff \
      recipes \
      src \
      zookeeper-*.asc \
      zookeeper-*.md5 \
      zookeeper-*.sha1 && \
    #
    # Clean up
    apk del .build-deps && \
    rm -rf /tmp/* "$GNUPGHOME"
 
COPY conf /zookeeper/conf/
COPY bin/zkReady.sh /zookeeper/bin/
COPY entrypoint.sh /
 
ENV PATH=/zookeeper/bin:${PATH} \
    ZOO_LOG_DIR=/zookeeper/log \
    ZOO_LOG4J_PROP="INFO, CONSOLE, ROLLINGFILE" \
    JMXPORT=9010
 
ENTRYPOINT [ "/entrypoint.sh" ]
 
CMD [ "zkServer.sh", "start-foreground" ]
 
EXPOSE 2181 2888 3888 9010
 
#启动服务脚本
root@k8s-master1:~/k8s-data/dockerfile/web/magedu/zookeeper# cat entrypoint.sh 
#!/bin/bash
 
echo ${MYID:-1} > /zookeeper/data/myid
 
if [ -n "$SERVERS" ]; then
	IFS=\, read -a servers <<<"$SERVERS"
	for i in "${!servers[@]}"; do 
		printf "\nserver.%i=%s:2888:3888" "$((1 + $i))" "${servers[$i]}" >> /zookeeper/conf/zoo.cfg
	done
fi
 
cd /zookeeper
exec "$@"

22.1 YAML

• service

apiVersion: v1
kind: Service
metadata:
  name: zookeeper
  namespace: zookeeper
spec:
  ports:
    - name: client
      port: 2181
  selector:
    app: zookeeper
---
apiVersion: v1
kind: Service
metadata:
  name: zookeeper1
  namespace: zookeeper
spec:
  type: NodePort
  ports:
    - name: client
      port: 2181
      nodePort: 32181
    - name: followers
      port: 2888
    - name: election
      port: 3888
  selector:
    app: zookeeper
    server-id: "1"
---
apiVersion: v1
kind: Service
metadata:
  name: zookeeper2
  namespace: zookeeper
spec:
  type: NodePort
  ports:
    - name: client
      port: 2181
      nodePort: 32182
    - name: followers
      port: 2888
    - name: election
      port: 3888
  selector:
    app: zookeeper
    server-id: "2"
---
apiVersion: v1
kind: Service
metadata:
  name: zookeeper3
  namespace: zookeeper
spec:
  type: NodePort
  ports:
    - name: client
      port: 2181
      nodePort: 32183
    - name: followers
      port: 2888
    - name: election
      port: 3888
  selector:
    app: zookeeper
    server-id: "3"

• Deployment

root@k8s-master1:~/k8s-data/yaml/magedu/zookeeper# cat zookeeper.yaml 
kind: Deployment
#apiVersion: extensions/v1beta1
apiVersion: apps/v1
metadata:
  name: zookeeper1
  namespace: zookeeper 
spec:
  replicas: 1
  selector:
    matchLabels:
      app: zookeeper
  template:
    metadata:
      labels:
        app: zookeeper
        server-id: "1"
    spec:
      volumes:
        - name: data
          emptyDir: {}
        - name: wal
          emptyDir:
            medium: Memory
      containers:
        - name: server
          image: harbor.nbrhce.com/demo/zookeeper:v3.4.14 
          imagePullPolicy: Always
          env:
            - name: MYID
              value: "1"
            - name: SERVERS
              value: "zookeeper1,zookeeper2,zookeeper3"
            - name: JVMFLAGS
              value: "-Xmx2G"
          ports:
            - containerPort: 2181
            - containerPort: 2888
            - containerPort: 3888
          volumeMounts:
          - mountPath: "/zookeeper/data"
            name: zookeeper-datadir-pvc-1 
      volumes:
        - name: zookeeper-datadir-pvc-1 
          persistentVolumeClaim:
            claimName: zookeeper-datadir-pvc-1
---
kind: Deployment
#apiVersion: extensions/v1beta1
apiVersion: apps/v1
metadata:
  name: zookeeper2
  namespace: zookeeper
spec:
  replicas: 1
  selector:
    matchLabels:
      app: zookeeper
  template:
    metadata:
      labels:
        app: zookeeper
        server-id: "2"
    spec:
      volumes:
        - name: data
          emptyDir: {}
        - name: wal
          emptyDir:
            medium: Memory
      containers:
        - name: server
          image: harbor.nbrhce.com/demo/zookeeper:v3.4.14
          imagePullPolicy: Always
          env:
            - name: MYID
              value: "2"
            - name: SERVERS
              value: "zookeeper1,zookeeper2,zookeeper3"
            - name: JVMFLAGS
              value: "-Xmx2G"
          ports:
            - containerPort: 2181
            - containerPort: 2888
            - containerPort: 3888
          volumeMounts:
          - mountPath: "/zookeeper/data"
            name: zookeeper-datadir-pvc-2 
      volumes:
        - name: zookeeper-datadir-pvc-2
          persistentVolumeClaim:
            claimName: zookeeper-datadir-pvc-2
---
kind: Deployment
#apiVersion: extensions/v1beta1
apiVersion: apps/v1
metadata:
  name: zookeeper3
  namespace: zookeeper
spec:
  replicas: 1
  selector:
    matchLabels:
      app: zookeeper
  template:
    metadata:
      labels:
        app: zookeeper
        server-id: "3"
    spec:
      volumes:
        - name: data
          emptyDir: {}
        - name: wal
          emptyDir:
            medium: Memory
      containers:
        - name: server
          image: harbor.nbrhce.com/demo/zookeeper:v3.4.14
          imagePullPolicy: Always
          env:
            - name: MYID
              value: "3"
            - name: SERVERS
              value: "zookeeper1,zookeeper2,zookeeper3"
            - name: JVMFLAGS
              value: "-Xmx2G"
          ports:
            - containerPort: 2181
            - containerPort: 2888
            - containerPort: 3888
          volumeMounts:
          - mountPath: "/zookeeper/data"
            name: zookeeper-datadir-pvc-3
      volumes:
        - name: zookeeper-datadir-pvc-3
          persistentVolumeClaim:
           claimName: zookeeper-datadir-pvc-3

• PV

---
apiVersion: v1
kind: PersistentVolume
metadata:
  name: zookeeper-datadir-pv-1
spec:
  capacity:
    storage: 20Gi
  accessModes:
    - ReadWriteOnce
  nfs:
    server: 10.0.0.109
    path: /data/k8sdata/zookeeper-datadir-1
 
---
apiVersion: v1
kind: PersistentVolume
metadata:
  name: zookeeper-datadir-pv-2
spec:
  capacity:
    storage: 20Gi
  accessModes:
    - ReadWriteOnce
  nfs:
    server: 10.0.0.109
    path: /data/k8sdata/zookeeper-datadir-2
 
---
apiVersion: v1
kind: PersistentVolume
metadata:
  name: zookeeper-datadir-pv-3
spec:
  capacity:
    storage: 20Gi
  accessModes:
    - ReadWriteOnce
  nfs:
    server: 10.0.0.109
    path: /data/k8sdata/zookeeper-datadir-3

• PVC

---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: zookeeper-datadir-pvc-1
  namespace: zookeeper
spec:
  accessModes:
    - ReadWriteOnce
  volumeName: zookeeper-datadir-pv-1
  resources:
    requests:
      storage: 10Gi
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: zookeeper-datadir-pvc-2
  namespace: zookeeper
spec:
  accessModes:
    - ReadWriteOnce
  volumeName: zookeeper-datadir-pv-2
  resources:
    requests:
      storage: 10Gi
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: zookeeper-datadir-pvc-3
  namespace: zookeeper
spec:
  accessModes:
    - ReadWriteOnce
  volumeName: zookeeper-datadir-pv-3
  resources:
    requests:
      storage: 10Gi

22.2 Zookeeper选举机制

• 选举不同阶段的状态

Leader 选举可以分为两个不同的阶段，第一个是我们提到的 Leader 宕机需要重新选举，第二则是当 Zookeeper 启动时需要进行系统的 Leader 初始化选举。下面是zkserver的几种状态：
 
LOOKING 不确定Leader状态。该状态下的服务器认为当前集群中没有Leader，会发起Leader选举。
FOLLOWING 跟随者状态。表明当前服务器角色是Follower，并且它知道Leader是谁。
LEADING 领导者状态。表明当前服务器角色是Leader，它会维护与Follower间的心跳。
OBSERVING 观察者状态。表明当前服务器角色是Observer，与Folower唯一的不同在于不参与选举，也不参与集群写操作时的投票。

22.3 初始化Leader选举

• 服务第一次运行的选举

假设我们集群中有3台机器，那也就意味着我们需要2台同意（超过半数）。这里假设服务器1~3的myid分别为1,2,3，初始化Leader选举过程如下：
 
服务器 1 启动，发起一次选举。它会首先 投票给自己 ，投票内容为(myid, ZXID)，因为初始化所以 ZXID 都为0，此时 server1 发出的投票为(1, 0)，即myid为1， ZXID为0。此时服务器 1 票数一票，不够半数以上，选举无法完成，服务器 1 状态保持为 LOOKING。
服务器 2 启动，再发起一次选举。服务器2首先也会将投票选给自己(2, 0)，并将投票信息广播出去（server1也会，只是它那时没有其他的服务器了），server1 在收到 server2 的投票信息后会将投票信息与自己的作比较。首先它会比较 ZXID ，ZXID 大的优先为 Leader，如果相同则比较 myid，myid 大的优先作为 Leader。所以，此时server1 发现 server2 更适合做 Leader，它就会将自己的投票信息更改为(2, 0)然后再广播出去，之后server2 收到之后发现和自己的一样无需做更改。此时，服务器1票数0票，服务器2票数2票，投票已经超过半数，确定 server2 为 Leader。服务器 1更改状态为 FOLLOWING，服务器 2 更改状态为 LEADING。
服务器 3 启动，发起一次选举。此时服务器 1，2已经不是 LOOKING 状态，它会直接以 FOLLOWING 的身份加入集群

• 运行时Leader选举

运行时候如果Leader节点崩溃了会走崩溃恢复模式，新Leader选出前会暂停对外服务，大致可以分为四个阶段：选举、发现、同步、广播（见4.5节），此时Leader选举流程如下：
 
Leader挂掉，剩下的两个 Follower 会将自己的状态 从 Following 变为 Looking 状态 ，每个Server会发出一个投票，第一次都是投自己，其中投票内容为(myid, ZXID)，注意这里的 zxid 可能不是0了
收集来自各个服务器的投票
处理投票，处理逻辑：优先比较ZXID，然后比较myid
统计投票，只要超过半数的机器接收到同样的投票信息，就可以确定leader
改变服务器状态Looking变为Following或Leading
然后依次进入发现、同步、广播阶段
举个例子来说明，假设集群有三台服务器，Leader (server2)挂掉了，只剩下server1和server3。 server1 给自己投票为(1,99)，然后广播给其他 server，server3 首先也会给自己投票(3,95)，然后也广播给其他 server。server1 和 server3 此时会收到彼此的投票信息，和一开始选举一样，他们也会比较自己的投票和收到的投票（zxid 大的优先，如果相同那么就 myid 大的优先）。这个时候 server1 收到了 server3 的投票发现没自己的合适故不变，server3 收到 server1 的投票结果后发现比自己的合适于是更改投票为(1,99)然后广播出去，最后 server1 收到了发现自己的投票已经超过半数就把自己设为 Leader，server3 也随之变为 Follower。