使用zk实现主从选举

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使用zookeeper实现主从选举
package cn.julong;import org.apache.zookeeper.*;import org.apache.zookeeper.ZooDefs.Ids;import java.io.IOException;import java.util.ArrayList;import java.util.List;/** * Hello world! */public class LeaderElection {    public static void main(String[] args) throws Exception {        String connectString = "dpnode05:2181";        new Master(connectString, connectString.substring(0, connectString.indexOf(":"))).start();    }    static class Master extends Thread{        //心跳时间间隔        private static final int heartbeatTime = 3000;        private static final int sessionTimeOut = 10000;        //等待上次作为leader的Master重连之前抢战leader前时间，可以防止网络波动导致leader频繁切换        private static final int scrambleWaitTime = 5000;        private static final String rootPath = "/wcm2";        private static final String leaderPath = rootPath + "/leader";        private ZooKeeper zk;        private String learder;        private String self;        private Watcher watcher;        private volatile boolean leaderDeadForever = true;        private volatile boolean watcherConsumed = true;        @Override        public void run() {            List<String> children = new ArrayList<>();            while (true) {                try {                    //检测是否需要执行等待原来主节点重连                    if (!leaderDeadForever && !learder.equals(self)) {                        System.out.println("检测到主节点挂掉，等待" +(scrambleWaitTime/1000)+ "秒！...");                        try { Thread.sleep(scrambleWaitTime); } catch (InterruptedException e1) { e1.printStackTrace(); }                        leaderDeadForever = true;                    }                    //如果注册的监听器被消费，则从新注册监听器                    if (watcherConsumed) {                        //1. 注册监听器，坚挺根节点删除事件，如果坚挺到事件，立即进入第2条，并从新注册监听                        zk.getChildren(rootPath, watcher).size();                        watcherConsumed = false;                    }                    heartbeatAction();                    //心跳结束，则输出本次主从状态                    System.out.println(this.toString());                    Thread.sleep(heartbeatTime);                } catch (Exception e){                    e.printStackTrace();                }finally {                }            }        }        private void heartbeatAction() {            while (true) {                try {                    //2. 尝试在根节点创建leader节点，创建成功，则写入自己的信息，心跳结束                    zk.create(leaderPath, self.getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);                    this.learder = self;                    break;                }catch (KeeperException.NodeExistsException e) {                    //3. 创建失败，读取节点信息，读取成功，则记录leader节点信息，心跳结束                    try {                        byte[] leaderData = zk.getData(leaderPath, true, null);                        learder = new String(leaderData);                        break;                    } catch (KeeperException.NoNodeException ee) {                        //4. 读取失败，则立即返回第2条                        if (null != learder && !learder.equals(self)) {                            System.out.println("检测到主节点挂掉，等待" +(scrambleWaitTime/1000)+ "秒！...");                            try { Thread.sleep(scrambleWaitTime); } catch (InterruptedException e1) { e1.printStackTrace(); }                        }                        continue;                    } catch (Exception ee) {                        ee.printStackTrace();                    }                } catch (Exception e) {                    e.printStackTrace();                }            }        }        public Master(String connectString, String self) {            super(self);            this.learder = self;            this.self = self;            Thread thisThread = this;            try {                zk = new ZooKeeper(connectString, sessionTimeOut, null);                watcher = new Watcher() {                    @Override                    public void process(WatchedEvent event) {                        try {                            if (event.getType() == Event.EventType.NodeChildrenChanged) {                                if (zk.getChildren(rootPath, watcher).size() == 0) {                                    leaderDeadForever = false;                                    watcherConsumed = true;                                }                            }                        } catch (Exception e) {                            e.printStackTrace();                        }                    }                };            } catch (IOException e) {                e.printStackTrace();            }        }        @Override        public String toString() {            return "Server{" +                    "learder='" + learder + '\'' +                    ", self='" + self + '\'' +                    '}';        }    }}
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