zookeeper分布式原理实战解析

来源：互联网发布：远程数据采集器编辑：程序博客网时间：2024/06/05 06:56

1.本实验基于centos7.3 +虚拟机VM+zookeeper-3.4.5.tar.gz环境下安装了三台集群测试。
安装参考：http://www.linuxidc.com/Linux/2016-09/135052.htm
启动zookeeper集群shell脚本

 #!/bin/bashcd /opt/apps/zookeeper/bin ./zkServer.sh start ssh -tt root@192.168.32.131 > /dev/null 2>&1 << remotesshcd /opt/apps/zookeeper/bin./zkServer.sh startexit remotessh ssh -tt root@192.168.32.130 > /dev/null 2>&1 << remotesshcd /opt/apps/zookeeper/bin ./zkServer.sh start exit remotessh

停止脚本：

 #!/bin/bash cd /opt/apps/zookeeper/bin ./zkServer.sh stop ssh -tt root@192.168.32.130 > /dev/null 2>&1 << remotessh cd /opt/apps/zookeeper/bin ./zkServer.sh stop exit remotessh ssh -tt root@192.168.32.131 > /dev/null 2>&1 << remotessh cd /opt/apps/zookeeper/bin ./zkServer.sh stop exit remotessh

2.zookeeper的服务上下线监听：
结构流程图：
这里写图片描述
实验测试：
服务端代码：

package com.ljt.zk.zkdist;import java.util.concurrent.CountDownLatch;import org.apache.zookeeper.CreateMode;import org.apache.zookeeper.WatchedEvent;import org.apache.zookeeper.Watcher;import org.apache.zookeeper.ZooDefs.Ids;import org.apache.zookeeper.ZooKeeper;import org.apache.zookeeper.ZooKeeper.States;/** *  * <p>Title: DistributedServer</p> * <p> 功能描述:: </p> * <p>Company: adteach </p>  * @author  刘建涛 *  * @date    2017年7月7日上午11:09:25 * @version 1.0 */public class DistributedServer {    // private static final String connectString =    // "192.168.32.129:2181,192.168.32.130:2182,192.168.32.131:2183";    private static final String connectString = "192.168.32.129:2181";    private static final int sessionTimeout = 15000;    private static final String parentNode = "/servers";    private ZooKeeper zk = null;    /**     * 创建到zk的客户端连接     *      * @throws Exception     */    public void getConnect(String agr) throws Exception {        //连接不成功等待连接        while (true) {            zk = new ZooKeeper(connectString, sessionTimeout, new Watcher() {                @Override                public void process(WatchedEvent event) {                    try {                        zk.getChildren("/servers", true);                        // 收到事件通知后的回调函数（应该是我们自己的事件处理逻辑）                        System.out.println(event.getType() + "---" + event.getPath());                        // 利用zk连接注册服务器信息                          registerServer(agr);                        // 启动业务功能                         handleBussiness(agr);                    } catch (Exception e) {                    }                }            });            if(States.CONNECTED != zk.getState()){                CountDownLatch connectedLatch = new CountDownLatch(1);                System.err.println("等待连接……");                connectedLatch.await();            }else{                System.err.println("连接成功！！！");                break;            }        }    }    /**     * 向zk集群注册服务器信息     *      * @param hostname     * @throws Exception     */    public void registerServer(String hostname) throws Exception {        String create = zk.create(parentNode + "/server", hostname.getBytes(), Ids.OPEN_ACL_UNSAFE,                CreateMode.EPHEMERAL_SEQUENTIAL);        System.out.println(hostname + "is online.." + create);    }    /**     * 业务功能     *      * @throws InterruptedException     */    public void handleBussiness(String hostname) throws InterruptedException {        System.out.println(hostname + "start working.....");        Thread.sleep(Long.MAX_VALUE);    }    public static void main(String[] args) throws Exception {        // 获取zk连接        DistributedServer server = new DistributedServer();        server.getConnect(args[0]);    }}

启动时向main函数中注入参数结果如下：
打成jar包运行命令：java -jar jar包参数
log4j:WARN No appenders could be found for logger (org.apache.zookeeper.ZooKeeper).
log4j:WARN Please initialize the log4j system properly.
等待连接……
None—null
www.ljt.cos01is online../servers/server0000000002
www.ljt.cos01start working…..

客服端代码：

package com.ljt.zk.zkdist;import java.util.ArrayList;import java.util.List;import java.util.concurrent.CountDownLatch;import org.apache.zookeeper.KeeperException;import org.apache.zookeeper.WatchedEvent;import org.apache.zookeeper.Watcher;import org.apache.zookeeper.ZooKeeper;import org.apache.zookeeper.ZooKeeper.States;/*** *  * <p>Title: DistributedClient</p> * <p> 功能描述:: </p> * <p>Company: adteach </p>  * @author  刘建涛 *  * @date    2017年7月7日上午11:12:48 * @version 1.0 */public class DistributedClient {    private static final String connectString = "192.168.32.129:2181,192.168.32.130:2182,192.168.32.131:2183";    private static final int sessionTimeout = 8000;    private static final String parentNode = "/servers";    // 注意:加volatile的意义何在？    private volatile List<String> serverList;    private ZooKeeper zk = null;    /**     * 创建到zk的客户端连接     *      * @throws Exception     */    public void getConnect() throws Exception {        zk = new ZooKeeper(connectString, sessionTimeout, new Watcher() {            @Override            public void process(WatchedEvent event) {                // 收到事件通知后的回调函数（应该是我们自己的事件处理逻辑）                try {                    // 重新更新服务器列表，并且注册了监听                    getServerList();                } catch (Exception e) {                }            }        });        CountDownLatch connectedLatch = new CountDownLatch(1);        if (States.CONNECTING == zk.getState()) {            try {                connectedLatch.await();            } catch (InterruptedException e) {                throw new IllegalStateException(e);            }        }    }    /**     * 获取服务器信息列表     *      * @throws Exception     */    public void getServerList() throws Exception {        // 获取服务器子节点信息，并且对父节点进行监听        List<String> children = zk.getChildren(parentNode, true);        // 先创建一个局部的list来存服务器信息        List<String> servers = new ArrayList<String>();        for (String child : children) {            // child只是子节点的节点名            byte[] data = zk.getData(parentNode + "/" + child, false, null);            servers.add(new String(data));        }        // 把servers赋值给成员变量serverList，已提供给各业务线程使用        serverList = servers;        // 打印服务器列表        System.out.println(serverList);    }    /**     * 业务功能     *      * @throws InterruptedException     */    public void handleBussiness() throws InterruptedException {        System.out.println("client start working.....");        Thread.sleep(Long.MAX_VALUE);    }    public static void main(String[] args) throws Exception {        // 获取zk连接        DistributedClient client = new DistributedClient();        client.getConnect();        // 获取servers的子节点信息（并监听），从中获取服务器信息列表        client.getServerList();        // 业务线程启动        client.handleBussiness();    }}

3.分布式共享锁
分布式锁结构流程图：
这里写图片描述

完整代码：

package com.ljt.zk.zklock;import java.util.Collections;import java.util.List;import java.util.Random;import org.apache.zookeeper.CreateMode;import org.apache.zookeeper.WatchedEvent;import org.apache.zookeeper.Watcher;import org.apache.zookeeper.Watcher.Event.EventType;import org.apache.zookeeper.ZooDefs.Ids;import org.apache.zookeeper.ZooKeeper;public class DistributedClientLock {    // 会话超时    private static final int SESSION_TIMEOUT = 2000;    // zookeeper集群地址    private String hosts =              "192.168.32.129:2181,192.168.32.130:2182,192.168.32.131:2183";    private String groupNode = "locks";    private String subNode = "sub";    private boolean haveLock = false;    private ZooKeeper zk;    // 记录自己创建的子节点路径    private volatile String thisPath;    /**     * 连接zookeeper     */    public void connectZookeeper() throws Exception {        zk = new ZooKeeper(hosts, SESSION_TIMEOUT, new Watcher() {            public void process(WatchedEvent event) {                try {                    // 判断事件类型，此处只处理子节点变化事件                    if (event.getType() == EventType.NodeChildrenChanged && event.getPath().equals("/" + groupNode)) {                        //获取子节点，并对父节点进行监听                        List<String> childrenNodes = zk.getChildren("/" + groupNode, true);                        String thisNode = thisPath.substring(("/" + groupNode + "/").length());                        // 去比较是否自己是最小id                        Collections.sort(childrenNodes);                        if (childrenNodes.indexOf(thisNode) == 0) {                            //访问共享资源处理业务，并且在处理完成之后删除锁                            doSomething();                            //重新注册一把新的锁                            thisPath = zk.create("/" + groupNode + "/" + subNode, null, Ids.OPEN_ACL_UNSAFE,                                    CreateMode.EPHEMERAL_SEQUENTIAL);                        }                    }                } catch (Exception e) {                    e.printStackTrace();                }            }        });        // 1、程序一进来就先注册一把锁到zk上        thisPath = zk.create("/" + groupNode + "/" + subNode, null, Ids.OPEN_ACL_UNSAFE,                CreateMode.EPHEMERAL_SEQUENTIAL);        // wait一小会，便于观察        Thread.sleep(new Random().nextInt(1000));        // 从zk的锁父目录下，获取所有子节点，并且注册对父节点的监听        List<String> childrenNodes = zk.getChildren("/" + groupNode, true);        //如果争抢资源的程序就只有自己，则可以直接去访问共享资源         if (childrenNodes.size() == 1) {            doSomething();            thisPath = zk.create("/" + groupNode + "/" + subNode, null, Ids.OPEN_ACL_UNSAFE,                    CreateMode.EPHEMERAL_SEQUENTIAL);        }    }    /**     * 处理业务逻辑，并且在最后释放锁     */    private void doSomething() throws Exception {        try {            System.out.println("gain lock: " + thisPath);            Thread.sleep(2000);            // do something        } finally {            System.out.println("finished: " + thisPath);            //  删除节点            zk.delete(this.thisPath, -1);        }    }    public static void main(String[] args) throws Exception {        DistributedClientLock dl = new DistributedClientLock();        dl.connectZookeeper();        Thread.sleep(Long.MAX_VALUE);    }}

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